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. 2021 Apr 15;19:eRW5704. doi: 10.31744/einstein_journal/2021RW5704
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Overview of miRNAs for the non-invasive diagnosis of endometriosis: evidence, challenges and strategies. A systematic review

Vitor Ulisses Monnaka 1, Camila Hernandes 2, Debora Heller 2, Sérgio Podgaec 2
PMCID: PMC8054530  PMID: 33909757

ABSTRACT

Objective

The aim of the study was to assess the evidence on miRNAs as biomarkers for the diagnosis of endometriosis, as well as to provide insights into the challenges and strategies associated with the use of these molecules as accessible tools in clinical practice.

Methods

Systematic review conducted on PubMed®, Latin American and Caribbean Health Sciences Literature (LILACS), MEDLINE® and Web of Science databases using the search terms endometriosis (all fields) AND miRNA (all fields), evaluating all publication up to May 2019.

Results

Most miRNAs found to be dysregulated in this study were harvested from tissue samples, which precludes their use as a non-invasive diagnostic test. However, differential expression of 62 miRNAs was reported in samples that may be used for non-invasive diagnosis of endometriosis, such as blood, serum and plasma.

Conclusion

Despite the identification of several candidates, studies are investigatory in nature and have been conducted with small number of samples. Also, no particular miRNA has been validated for diagnostic purposes so far. Studies based primarily on biological samples and applicable to translational research are warranted. Large databases comprising information on sample type and the use of saliva and vaginal fluid for miRNAs identification may prove essential to overcome current barriers to diagnosis of endometriosis.

Keywords: Biomarkers, Saliva, Serum, Vaginal fluid, Body fluids banks, MicroRNAs, Endometriosis/diagnosis

INTRODUCTION

Endometriosis is a common disease that affects up to 10% of women of reproductive age(1,2) and is characterized by the presence of endometrial cells outside the uterine cavity. The disease has been the focus of many studies, however, the diagnosis is still very difficult. Clinical presentation varies widely, ranging from asymptomatic to severe, and no diagnostic biomarkers have been approved for routine clinical diagnosis of endometriosis to date.(1,3)

Diagnostic imaging tests such as pelvic ultrasonography and magnetic resonance have been used, especially in deep endometriosis. However, examiner expertise has a strong impact on imaging findings,(4-7) which ultimately makes the diagnosis difficult. In cases with no positive imaging findings, a final diagnosis of superficial endometriosis can only be made through histological analysis of the lesion, usually in samples obtained by laparoscopic surgery.(8,9) However, this procedure is invasive and requires general anesthesia.

The complexity of the disease, combined with the lack of precise and less invasive diagnostic methods, contributes to delayed diagnosis, which can take up to 11 years.(5,10,11) Therefore, there is great demand for accurate and less invasive diagnostic tests for endometriosis.(12-16)

Different research groups have investigated the role of miRNAs (microRNAs or miR) in the regulation of known genes, given their association with processes involved in disease pathogenesis and progression. miRNAs are a class of small endogenous, non-coding RNA molecules involved in post-transcriptional regulation of gene expression.(17) These small molecules have also been found in peripheral blood and may therefore be potential diagnostic biomarkers for endometriosis.(18,19)

This literature search was conducted to determine how close miRNAs are to being used as biomarkers for endometriosis. Findings of this review are expected to guide the next steps towards overcoming challenges associated with the use of miRNAs in clinical practice.

OBJECTIVE

To determine which miRNAs are applicable to the diagnosis of endometriosis and to outline the challenges and strategies involved in the use of these molecules as accessible diagnostic tools in clinical settings.

METHODS

To identify research articles addressing associations between endometriosis and miRNA, a search was conducted in PubMed®, Latin American and Caribbean Health Sciences Literature (LILACS), MEDLINE® and Web of Science databases using the search terms endometriosis (all fields) AND miRNA (all fields).

All publications listed up to May 2019 (automatically selected) were manually curated, and only those involving miRNA expression patterns, validated by polymerase chain reaction (PCR) in clinical samples of endometriosis, were discussed in this review. Articles published in languages other than English or based on cell culture, retracted articles and articles published in conference proceedings or inaccessible were excluded. Reports listed in more than one database were included only once in the pool of publications.

This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement for systematic reviews adopted by Hospital Israelita Albert Einstein (HIAE), located in São Paulo (SP), Brazil. Data were extracted in duplicate and independently by two different investigators, then compared for confirmation. miRNAs and their respective expression levels in different types of samples and patient populations were examined. Studies were also analyzed according to year and country of publication.

RESULTS

Overview of publications on miRNA and endometriosis

A total of 449 research articles addressing associations between endometriosis and miRNA were found in databases selected for this review. Most (185) were retrieved from PubMed®, followed by LILACS and MEDLINE® (158) and Web of Science (106). Out of this publication pool, 46 matched final selection criteria and were selected for further discussion in this review (Figure 1).

Figure 1. Summarized results of database screening for publications addressing associations between endometriosis and miRNAs.

Figure 1

SNP: single-nucleotide polymorphisms; LncRNAs: long non-coding ribonucleic acids; circRNAs: circular ribonucleic acids; PCR: polymerase chain reaction.

The number of publications investigating dysregulated miRNAs in women with endometriosis increased sharply since 2009, with approximately half of selected articles (23) published in the last 3 years. China and the United States were the countries with the largest number of publications (21 and 9 articles, respectively).

Within this pool of 46 studies, 43 investigated miRNAs found to be dysregulated in the ectopic (EC) relative to the eutopic endometrium of control patients (EN), 25 were detected in the EC relative to the eutopic endometrium (EU) of women with endometriosis and 23 were detected in the EU compared to the EN group. Furthermore, 27 were detected in the serum, 18 in the plasma, 30 in the blood and six in the peritoneal fluid of women with endometriosis compared to the Control Group. Blood seems to be the most widely investigated type of sample regarding potential applicability to non-invasive diagnosis. The summary of dysregulated miRNA found in selected published articles are listed in table 1A-1G .

Table 1A. miRNAs differentially expressed in eutopic endometrium of endometriosis patients compared with eutopic endometrium of control patients.

miRNA Regulation Endometriosis n Control n References
miR-126 DR 31 27 Liu et al.(20)
miR-1281 UR 38 38 Yang et al.(21)
miR-142-5p UR 38 38 Yang et al.(21)
miR-145 UR 11 22 Zheng et al.(22)
miR-146a-5p UR 38 38 Yang et al.(21)
miR-183-5p DR N/A N/A Shi et al.(23)
miR-199a DR 12 12 Dai et al.(24)
miR-202-3p DR 51 32 Braza-Boïls et al.(25)
miR-204 DR 38 9 Haikalis et al.(26)
miR-29c DR 20 10 Long et al.(27)
miR-30d-5p UR 21 25 Laudanski et al.(28)
miR-3152-5p UR 21 25 Laudanski et al.(28)
miR-34b DR 4 3 Burney et al.(29)
miR-34c-5p DR 4 3 Burney et al.(29)
miR-424-5p DR 51 32 Braza-Boils et al.(25)
miR-4634 UR 38 38 Yang et al.(21)
miR-483-5p DR 21 25 Laudanski et al.(30)
miR-5187-3p UR 21 25 Laudansk et al.(28)
miR-543 DR 38 38 Yang et al.(21)
miR-556-3p DR 51 32 Braza-Boïls et al.(25)
miR-629* DR 21 25 Laudanski et al.(30)
miR-9 DR 4 3 Burney et al.(29)
miR-940 UR 38 38 Yang et al.(21)

miRNA: microRNA; DR: downregulated; UR: upregulated; N/A: not available.

Table 1B. miRNAs differentially expressed in ectopic endometrium of endometriosis patients and eutopic endometrium of control patients.

miRNA Regulation Endometriosis n Control n References
let-7g UR N/A N/A Wright et al.(31)
miR-100 UR N/A N/A Wright et al.(31)
miR-1304-3p UR 14 10 Xu et al.(32)
miR-133a-3p UR 33 17 Braicu et al.(33)
miR-138 UR 51 32 Braza-Boïls et al.(25)
miR-141 UR 22 24 Saare et al.(34)
miR-143 UR 11 22 Zheng et al.(22)
miR-145 UR 11 22 Zheng et al.(22)
miR-148a UR N/A N/A Wright et al.(31)
miR-183-5p DR N/A N/A Shi et al.(23)
miR-191 UR 12 12 Dong et al.(35)
miR-199a DR 12 12 Dai et al.(24)
miR-200a UR 22 24 Saare et al.(34)
miR-200b UR 22 24 Saare et al.(34)
miR-200c DR 27 12 Liang et al.(36)
miR-202-3p UR 51 32 Braza-Boïls et al.(25)
miR-205-5p DR 14 10 Xu et al.(32)
miR-20a UR 40 20 Zhao et al.(37)
miR-21-3p UR 7 7 Qi et al.(38)
miR-223-3p UR 7 7 Qi et al.(38)
miR-29a UR N/A N/A Wright et al.(31)
miR-29c DR 20 10 Long et al.(27)
miR-29c UR 51 32 Braza-Boïls et al.(25)
miR-29c UR 15 11 Joshi et al.(39)
miR-325 UR 33 17 Braicu et al.(33)
miR-33b DR 20 15 Yang et al.(40)
miR-34c UR 22 24 Saare et al.(34)
miR-3663-3p UR 7 7 Qi et al.(38)
miR-3684 UR 14 10 Xu et al.(32)
miR-373-3p UR 51 32 Braza-Boïls et al.(25)
miR-3935 DR 14 10 Xu et al.(32)
miR-411-5p UR 51 32 Braza-Boïls et al.(25)
miR-4427 DR 14 10 Xu et al.(32)
miR-449a UR 22 24 Saare et al.(34)
miR-450a-5p DR 7 7 Qi et al.(38)
miR-451 UR 30 0 Graham et al.(41)
miR-4683 UR 14 10 Xu et al.(32)
miR-492 UR 33 17 Braicu et al.(33)
miR-494-5p UR 14 10 Xu et al.(32)
miR-503-5p DR 7 7 Qi et al.(38)
miR-520e UR 33 17 Braicu et al.(33)
miR-544b UR 14 10 Xu et al.(32)
miR-5481 DR N/A N/A Wright et al.(31)
miR-652-5p DR 14 10 Xu et al.(32)
miR-6747-3p UR 14 10 Xu et al.(32)

miRNA: microRNA; DR: downregulated; N/A: not available; UR: upregulated.

Table 1C. miRNAs differentially expressed in the ectopic and eutopic endometrium of endometriosis patients.

miRNA Regulation Endometriosis n Control n References
miR-106a-5p DR 22 0 Zhao et al.(42)
miR-106b-5p UR 32 19 Yang et al.(43)
miR-10a DR 38 38 Haikalis et al.(26)
miR-125a UR 58 38 Ramón et al.(44)
miR-126 DR 31 27 Liu et al.(20)
miR-126 UR 8 N/A Ohlsson Teague et al.(45)
miR-141 DR 8 N/A Ohlsson Teague et al.(45)
miR-145 UR 8 N/A Ohlsson Teague et al.(45)
miR-145-5p UR 32 19 Yang et al.(43)
miR-146a-5p DR 32 19 Yang et al.(43)
miR-15a-5p DR 32 19 Yang et al.(43)
miR-16-5p UR 32 19 Yang et al.(43)
miR-182 DR 16 N/A Filigheddu et al.(46)
miR-182-5p DR 22 0 Zhao et al.(42)
miR-19b-1-5p DR 32 19 Yang et al.(43)
miR-200a DR 16 N/A Filigheddu et al.(46)
miR-200a-3p DR 22 0 Zhao et al.(42)
miR-200b DR 16 N/A Filigheddu et al.(46)
miR-200b DR 8 N/A Ohlsson Teague et al.(45)
miR-200b DR 32 19 Yang et al.(43)
miR-200c DR 16 N/A Filigheddu et al.(46)
miR-200c DR 32 19 Yang et al.(43)
miR-202 UR 16 N/A Filigheddu et al.(46)
miR-21 DR 38 38 Haikalis et al.(26)
miR-222 UR 58 38 Ramón et al.(44)
miR-34c DR 22 0 Zhao et al.(42)
miR-424 DR 8 N/A Ohlsson Teague et al.(45)
miR-424 DR 38 38 Haikalis et al.(26)
miR-449b DR 51 32 Braza-Boïls et al.(25)
miR-449b DR 22 0 Zhao et al.(42)
miR-451a UR 41 40 Nothnick et al.(47)
miR-615 UR 22 0 Zhao et al.(42)
miR-9 DR 38 38 Haikalis et al.(26)
miR-99a UR 8 N/A Ohlsson Teague et al.(45)

miRNA: microRNA; DR: downregulated; UR: upregulated; N/A: not available.

Table 1D. miRNAs differentially expressed in the serum of endometriosis and control patients.

miRNA Regulation Endometriosis n Control n References
let-7b DR 24 24 Cho et al.(48)
let-7b-5p DR 20 26 Nematian et al.(49)
miR-122 UR 60 25 Wang et al.(19)
miR-122 UR 45 35 Maged et al.(50)
miR-125b-5p UR 24 24 Cosar et al.(51)
miR-125b UR 20 26 Nematian et al.(49)
miR-127-3p DR 30 20 Wang et al.(52)
miR-135a DR 24 24 Cosar et al.(51)
miR-141 DR 60 25 Wang et al.(19)
miR-143-3p UR 24 24 Cosar et al.(51)
miR-145 DR 60 25 Wang et al.(19)
miR-145-5p UR 24 24 Cosar et al.(51)
miR-150-5p UR 24 24 Cosar et al.(51)
miR-15b-5p DR 30 20 Wang et al.(52)
miR-17 DR 80 60 Wang et al.(53)
miR-185-5p UR 30 20 Wang et al.(52)
miR-18a-5p UR 24 24 Cosar et al.(51)
miR-191 UR 12 12 Dong et al.(35)
miR-199a UR 60 25 Wang et al.(19)
miR-199a UR 45 35 Maged et al.(50)
miR-199a-5p DR 40 25 Hsu et al.(54)
miR-20a-5p DR 30 20 Wang et al.(52)
miR-30c-5p DR 30 20 Wang et al.(52)
miR-342-3p UR 24 24 Cosar et al.(51)
miR-3613-5p DR 24 24 Cosar et al.(51)
miR-370 DR 20 26 Hu et al.(55)
miR-424-3p UR 30 20 Wang et al.(52)
miR-451a UR 41 40 Nothnick et al.(47)
miR-451a UR 24 24 Cosar et al.(51)
miR-500a-3p UR 24 24 Cosar et al.(51)
miR-542-3p DR 60 25 Wang et al.(19)
miR-6755-3p DR 24 24 Cosar et al.(51)
miR-9 DR 60 25 Wang et al.(19)
miR-99b-5p DR 30 20 Wang et al.(52)

miRNA: microRNA; DR: downregulated; UR: upregulated.

Table 1E. miRNAs differentially expressed in the plasma of endometriosis and control patients.

miRNA Regulation Endometriosis n Control n References
miR-139 DR 80 39 Nisenblat et al.(56)
miR-141 DR 61 65 Rekker et al.(57)
miR-145 UR 55 23 Bashti et al.(58)
miR-154-5p DR 51 41 Pateisky et al.(59)
miR-155 DR 80 39 Nisenblat et al.(56)
miR-16 UR 33 20 Suryawanshi et al.(60)
miR-17-5p DR 23 23 Jia et al.(61)
miR-191 UR 33 20 Suryawanshi et al.(60)
miR-195 UR 33 20 Suryawanshi et al.(60)
miR-196b DR 51 41 Pateisky et al.(59)
miR-200a DR 61 65 Rekker et al.(57)
miR-200b DR 61 65 Rekker et al.(57)
miR-20a DR 23 23 Jia et al.(61)
miR-22 DR 23 23 Jia et al.(61)
miR-31 DR 55 23 Bashti et al.(58)
miR-33a UR 51 41 Pateisky et al.(59)
miR-378a DR 51 41 Pateisky et al.(59)
miR-574 DR 80 39 Nisenblat et al.(56)

miRNA: microRNA; DR: downregulated; UR: upregulated.

Table 1F. miRNAs differentially expressed in the blood of endometriosis and control patients.

miRNA Regulation Endometriosis n Control n References
let-3c DR 4 3 Azmy et al.(62)
let-7e DR 4 3 Azmy et al.(62)
let-7f DR 5 3 Azmy et al.(62)
let-7g DR 4 3 Azmy et al.(62)
miR-103 DR 4 3 Azmy et al.(62)
miR-106b DR 4 3 Azmy et al.(62)
miR-125a-5p DR 4 3 Azmy et al.(62)
miR-126 DR 4 3 Azmy et al.(62)
miR-15b DR 4 3 Azmy et al.(62)
miR-16 DR 4 3 Azmy et al.(62)
miR-17 DR 4 3 Azmy et al.(62)
miR-181b DR 4 3 Azmy et al.(62)
miR-18a DR 4 3 Azmy et al.(62)
miR-194 DR 4 3 Azmy et al.(62)
miR-195 DR 4 3 Azmy et al.(62)
miR-19a DR 4 3 Azmy et al.(62)
miR-19b DR 4 3 Azmy et al.(62)
miR-20a DR 4 3 Azmy et al.(62)
miR-21 DR 4 3 Azmy et al.(62)
miR-22 DR 4 3 Azmy et al.(62)
miR-26a DR 4 3 Azmy et al.(62)
miR-26b DR 4 3 Azmy et al.(62)
miR-27a DR 4 3 Azmy et al.(62)
miR-27b DR 4 3 Azmy et al.(62)
miR-30a DR 4 3 Azmy et al.(62)
miR-374a DR 4 3 Azmy et al.(62)
miR-374b DR 4 3 Azmy et al.(62)
miR-424 DR 4 3 Azmy et al.(62)
miR-7 DR 4 3 Azmy et al.(62)
miR-93 DR 4 3 Azmy et al.(62)

miRNA: microRNA; DR: downregulated.

Table 1G. miRNAs differentially expressed in the peritoneal fluid of endometriosis and control patients.

miRNA Regulation Endometriosis n Control n References
miR-106b-3p UR 126 45 Marí-Alexandre et al.(63)
miR-122 UR 45 35 Maged et al.(50)
miR-130b UR 6 3 Chen et al.(64)
miR-199a UR 45 35 Maged et al.(50)
miR-451a UR 126 45 Marí-Alexandre et al.(63)
miR-486-5p UR 126 45 Marí-Alexandre et al.(63)

miRNA: microRNA; UR: upregulated.

A total of 33 miRNAs were examined in more than one study. Of these, 13 miRNAs were analyzed in the same types of samples. miRNAs identified in more than one study and body fluid are described in table 2.

Table 2. Summary of miRNA dysregulated identified in more than one study in different samples.

Total EU versus EN EC versus EN EC versus EU Plasma Serum Blood PF References
6 miR-145 miR-145 miR-145 miR-145 miR-145     Wang et al.,(19) Zheng et al.,(22) Yang et al.,(43) Ohlsson Teague et al.,(45) Cosar et al.(51) and Bashti et al.(58)
5   miR-200b miR-200b miR-200b       Saare et al.,(34) Yang et al.,(43) Ohlsson Teague et al.,(45) Filigheddu et al.(46) and Rekker et al.(57)
5 miR-424   miR-424   miR-424 miR-424   Braza-Boils et al.,(25) Haikalis et al.,(26) Ohlsson Teague et al.,(45) Wang et al.(52) and Azmy et al.(62)
4 miR-199a miR-199a     miR-199a   miR-199a Wang et al.,(19) Dai et al.,(24) Maged et al.(50) and Hsu et al.(54)
4   miR-141 miR-141 miR-141 miR-141     Wang et al.,(19) Saare et al.,(34) Ohlsson Teague et al.(45) and Rekker et al.(57)
4   miR-20a   miR-20a miR-20a miR-20a   Zhao et al.,(37) Wang et al.,(52) Jia et al.(61) and Azmy et al.(62)
4   miR-200a miR-200a miR-200a       Saare et al.,(34) Zhao et al.,(42) Filigheddu et al.(46) and Rekker et al.(57)
3 miR-29c miR-29c miR-29c         Braza-Boils et al.,(25) Long et al.(27) and Joshi et al.(39)
3 miR-34c miR-34c miR-34c         Braza-Boïls et al.,(25) Saare et al.(34) and Joshi et al.(39)
3   miR-200c miR-200c         Liang et al.,(36) Yang et al.(43) and Filigheddu et al.(46)
3   miR-21 miR-21     miR-21   Haikalis et al.,(26) Qi et al.(38) and Azmy et al.(62)
3 miR-126   miR-126     miR-126   Liu et al.,(20) Ohlsson Teague et al.(45) and Azmy et al.(62)
3     miR-16 miR-16   miR-16   Yang et al.,(43) Suryawanshi et al.(60) and Azmy et al.(62)
3     miR-451a   miR-451a   miR-451a Nothnick et al.,(47) Cosar et al.(51) and Marí-Alexandre et al.(63)
3 miR-9   miR-9   miR-9     Wang et al.,(19) Haikalis et al.(26) and Burney et al.(29)
3     miR-106b     miR-106b miR-106b Yang et al.,(43) Azmy et al.(62) and Marí-Alexandre et al.(63)
3       miR-17 miR-17 miR-17   Wang et al.,(53) Jia et al.(61) and Azmy et al.(62)
2         miR-122   miR-122 Wang et al.(19) and Maged et al.(50)
2     miR-449b         Braza-Boïls et al.(25) and Zhao et al.(42)
2   miR-191   miR-191 miR-191     Dong et al.(35) and Suryawanshi et al.(60)
2 miR-202 miR-202 miR-202         Braza-Boïls et al.(25) and Filigheddu et al.(46)
2   miR-143     miR-143     Zheng et al.(22) and Cosar et al.(51)
2       miR-22   miR-22   Jia et al.(61) and Azmy et al.(62)
2   miR let-7g       miR let-7g   Wright et al.(31) and Azmy et al.(62)
2         miR-15b miR-15b   Wanget al.(52) and Azmy et al.(62)
2     miR-125a     miR-125a   Ramón et al.(44) and Azmy et al.(62)
2       miR-195   miR-195   Suryawanshi et al.(60) and Azmy et al.(62)
2         miR-18a miR-18a   Cosar et al.(51) and Azmy et al.(62)
2     miR-19b     miR-19b   Yanget al.(43) and Azmy et al.(62)
2 miR-146a   miR-146a         Yang et al.(21) and Yang et al.(43)
2     miR-182         Zhao et al.(42) and Filigheddu et al.(46)
2         miR-125b     Nematian et al.(49) and Cosar et al.(51)
2         miR-let-7b     Cho et al.(48) and Nematian et al.(49)

EU: eutopic endometrium of women with endometriosis; EN: eutopic endometrium of control patients; EC: ectopic endometrium; PF: peritoneal fluid.

Twenty out of 62 miRNAs identified in samples with potential applicability to minimally invasive diagnosis of endometriosis, such as blood, serum, and plasma, were also found to be dysregulated in other types of tissue, such as EC and eutopic endometrium, and in the peritoneal fluid. Of these, 35% were detected in the same type of tissue in more than one study, including miR-200b, miR-145, miR-199a, miR-424, miR-200a, miR-126, and miR-451a. Thirteen miRNAs were found to be up or downregulated, as follows: miR-125b, miR-let-7b, miR-122, miR-451a and miR-199a in serum; miR-29c in the EC relative to the EN Group; and miR-145, miR-200b, miR-424, miR-200a, miR-200c, miR-449b and miR-182 in the EC relative to the EC of women with endometriosis (Table 3).

Table 3. Characterization of miRNAs expression for upregulation and downregulation in different samples.

miRNA n EU versus EN EC versus EN EC versus EU Plasma Serum Blood PF
EU EN EC EN EC EU
miR-145 6 ↑ (1) ↓ (1) ↑ (1) ↓ (1) ↑ (2) ↓ (2) ↑ (1) ↑ (1) /↓ (1)    
miR-200b 5     ↑ (1) ↓ (1) ↓ (3) ↑ (3) ↓ (1)      
miR-424 5 ↓ (1) ↑ (1)     ↓ (2) ↑ (2)   ↑ (1) ↓ (1)  
miR-199a 4 ↓ (1) ↑ (1) ↓ (1) ↑ (1)     ↑ (1) ↑ (2)/↓ (1)   ↑ (1)
miR-141 4     ↑ (1) ↓ (1) ↓ (1) ↑ (1) ↓ (1) ↓ (1)    
miR-20a 4     ↑ (1) ↓ (1)     ↓ (1) ↓ (1) ↓ (1)  
miR-200a 4     ↑ (1) ↓ (1) ↓ (2) ↑ (2) ↓ (1)      
miR-29c 3 ↓ (1) ↑ (1) ↑ (2) /↓ (1) ↓ (2) / ↑(1) ↓ (1) ↑ (1)        
miR-34c 3 ↓ (1) ↑ (1) ↑ (1) ↓ (1) ↓ (1) ↑ (1)        
miR-200c 3     ↓ (1) ↑ (1) ↓ (2) ↑ (2)        
miR-21 3     ↑ (1) ↓ (1) ↓ (1) ↑ (1)     ↓ (1)  
miR-126 3 ↓ (1) ↑ (1)     ↑ (1)/↓ (1) ↓ (1)/↑ (1)     ↓ (1)  
miR-16 3         ↑ (1) ↓ (1) ↑ (1)   ↓ (1)  
miR-451a 3         ↑ (1) ↓ (1)   ↑ (2)   ↑ (1)
miR-9 3 ↓ (1) ↑ (1)     ↓ (1) ↑ (1)   ↓ (1)    
miR-106b 3         ↑ (1) ↓ (1)     ↓ (1) ↑ (1)
miR-17 3             ↓ (1) ↓ (1) ↓ (1)  
miR-122 2               ↑ (2)   ↑ (1)
miR-449b 2         ↓ (2) ↑ (2)        
miR-191 2     ↑ (1) ↓ (1)     ↑ (1) ↑ (1)    
miR-202 2 ↓ (1) ↑ (1) ↑ (1) ↓ (1) ↑ (1) ↓ (1)        
miR-143 2     ↑ (1) ↓ (1)       ↑ (1)    
miR-22 2             ↓ (1)   ↓ (1)  
miR let-7g 2     ↑ (1) ↓ (1)         ↓ (1)  
miR-15b 2               ↓ (1) ↓ (1)  
miR-125a 2         ↑ (1) ↓ (1)     ↓ (1)  
miR-195 2             ↑ (1)   ↓ (1)  
miR-18a 2               ↑ (1) ↓ (1)  
miR-19b 2         ↓ (1) ↑ (1)     ↓ (1)  
miR-146a 2 ↑ (1) ↓ (1)     ↓ (1) ↑ (1)        
miR-182 2         ↓ (2) ↑ (2)        
miR-125b 2               ↑ (2)    
miR-let-7b 2               ↓ (2)    

↑ upregulation; ↓ downregulation.

miRNA: microRNA; EU: eutopic endometrium of women with endometriosis; EN: eutopic endometrium of control patients; EC: ectopic endometrium; PF: peritoneal fluid.

DISCUSSION

Endometriosis can be a debilitating disease and may lead to poor quality of life.(65) The disease is associated with dysmenorrhea, deep dyspareunia, chronic pelvic pain and infertility(66,67) and is considered a public health concern, given the impact on patient physical and psychological health, and the socioeconomic impact of diagnosis, treatment and clinical control costs.(68)

The final diagnosis of endometriosis is currently based on histological analysis of the lesion, usually in samples obtained by laparoscopic surgery.(69) However, imaging modalities are important non-invasive diagnostic alternatives for ovarian and deep endometriosis. Both surgical and non-surgical approaches require considerable professional skill and availability of specific data, which may represent a huge economic and health burden in developing countries.(4-9)

In the last three decades, researchers worldwide have tried to identify a non-invasive test that could shorten the turnaround time for diagnosis of endometriosis. CA-125 can be detected in blood or peritoneal fluid and is one of the best studied biomarkers. In some case studies, measurement of CA-125 levels was deemed promising, especially for diagnosis of more invasive endometriosis, provided measurements are made in the beginning of the menstrual cycle.(70-72)

In spite of conflicting results regarding the value of CA-125 as a final and important biomarker reported in recent reviews, according to Socolov et al., CA-125 is still the most recommended biomarker for endometriosis diagnosis and monitoring.(73) In a more recent Cochrane review published in 2016, Nisenblat et al. compared the accuracy of any combination of non-invasive diagnostic tests to surgical diagnosis of pelvic endometriosis, using randomized controlled trials or cross-sectional studies published until early 2015 as a reference standard. Authors concluded that none of the biomarkers investigated (including CA-125) could be duly evaluated due to insufficient or poor-quality evidence, given the high heterogeneity and risk of bias in selected studies.(15)

CA-125 is most elevated in advanced stages of endometriosis. Therefore, the sensitivity of this marker is limited. Its specificity is also thought to be poor, since it is upregulated in other gynecological conditions.(74) In this context, the search for novel and effective noninvasive biomarkers capable of improving endometriosis diagnosis, management and monitoring remains high on the priority list.

Circulating miRNAs, first identified as non-invasive serological markers of tumors in 2008,(75-77) are promising alternative candidates. The high stability of circulating miRNAs in human plasma and their resistance to multiple sample handling procedures has been emphasized in these pioneer studies.

These same studies also established the concept of disease diagnosis based on specific cell-free miRNA signatures. Since then, miRNAs have been validated as noninvasive diagnostic markers for several diseases, including oncologic, inflammatory, cardiovascular, metabolic and reproductive disorders. miRNAs proved to be ideal diagnostic markers in oncology, as shown by differential circulating miRNA expression patterns in lung, ovarian, colorectal, prostate and breast cancer patients relative to healthy controls.(78)

In the female reproductive system in particular, dysregulated miRNA expression has been studied in uterine leiomyomata, in several gynecologic cancers (including adenocarcinomas), and in pregnancy disorders, such as preeclampsia and preterm birth.(79-83) These small noncoding molecules associated with several diseases have been proposed as useful diagnostic candidates for endometriosis.(84)

In this review, miR-145 was the miRNA found to be differentially expressed in the largest number of studies (six articles). In the 46 studies analyzed, most miRNAs found to be dysregulated in endometriosis were harvested from tissue samples. Bodily fluids were seldom investigated, even though they may be used as non- or minimally invasive diagnostic tools. Also, most studies compared miRNA expression differences between the eutopic and EC of patients with endometriosis and only a few compared the endometrium of patients with endometriosis, suggesting that examinations based endometrial biopsies are difficult.

As regards dysregulated miRNAs in endometriosis patients compared in this review, 30 were found in the blood, 27 in the serum and 18 in the plasma of women with endometriosis relative to control populations. Differences in the molecular composition of serum and plasma have been well-documented.(85,86)

When comparing the miRNA spectrum between serum and plasma, Wang et al.,(19) detected several differences in RNA levels driven by the release of certain miRNAs and other RNAs during the coagulation process, and suggested that use of plasma as the sample of choice for studying circulating miRNAs, since RNAs released during coagulation may alter the true repertoire of circulating miRNAs.

Differential expression of six miRNAs was detected in the peritoneal fluid of endometriosis patients relative to non-affected women. Hence, some miRNAs found in peritoneal fluid may play a role in the pathogenesis of endometriosis. However, given the nature of this fluid, its use is limited by the need for surgical (i.e., invasive) collection.

Some points are worthy of note and should be emphasized in these studies: conflicting results. They have been reported in studies investigating miR-145, -424, -199a, -29c, -126, -16, -195 and -18a expression in the same type of sample. Major characteristics of these studies are described below.

Upregulation of miR-145 was found in the serum, in a study with 24 stages III and IV endometriosis and 24 control patients,(51) and in plasma, in a study with 55 stages I and II endometriosis and 23 control patients.(58) In contrast, the same miRNA was found to be downregulated in the serum in a study including 60 cases and 25 controls,(19) in which disease stage was not reported.

miR-424 was downregulated in blood in a study with four patients with mild endometriosis and three controls.(62) However, it was also found to be upregulated in the serum of 30 patients with minimal-mild endometriosis relative to 20 control individuals.(52)

miR-199a was upregulated in the serum of patients with endometriosis in two studies, one with 60 stages III and IV endometriosis and 25 control patients,(19) and another with 45 endometriosis and 35 control patients.(50) However, the same miRNA was found to be downregulated in the serum in a different study with 40 endometriosis and 25 control patients.(54)

A study with 15 clinical cases and 11 controls revealed miR-29c upregulation in the EC of women with endometriosis relative to the eutopic endometrium in the Control Group.(39) This finding was further confirmed in a study including 51 women with endometriosis and 32 control women,(25) in the proliferative and secretory phases of the menstrual cycle. However, conflicting results suggesting miR-29c downregulation in the EC of 20 women with endometriosis relative to the eutopic endometrium of ten control patients,(27) all of them in the proliferative phase of the cycle, have been reported by a different researcher.

miR-126 was found to be upregulated in the ectopic compared to the eutopic endometrium of eight women with stages III to IV endometriosis(45) in the proliferative and secretory phases of the menstrual cycle. However, miR-126 downregulation was reported in the ectopic compared to the eutopic endometrium in 31 women with stages III to IV endometriosis,(20) all of them in the secretory phase of the menstrual cycle.

miR-16 and miR-195 were found to be upregulated in plasma of 33 women with endometriosis relative to 20 control patients.(60) However, another study identified both downregulated in the blood of four patients with mild endometriosis relative to three controls.(62)

miR-18a was upregulated in serum of 24 women with stage III and IV endometriosis compared to 24 control patients.(51) However, it was found to be downregulated in the blood of four patients with mild endometriosis compared to three controls.(62)

Conflicting results emphasize the relevance of criteria such as menstrual cycle phase, disease stage, type of sample and type of test procedure, and the need for studies with larger sample size to develop novel diagnostic tests for endometriosis.

The second objective of this review was to provide new directions for future studies aimed to identify a miRNA which may be used as a reliable biomarker and an accurate diagnostic tool for endometriosis. Sadly, according to this critical literature review no particular miRNA or miRNA combination has been validated for improved diagnosis of endometriosis to date. This may reflect the heterogeneity of the disease and resultant differences in tissue composition.(87) Thus, we support the World Endometriosis Research Foundation (WERF) and Endometriosis Phenome and Biobanking Harmonization Project (EPHect) initiatives. Endometriosis research teams worldwide must join forces in order to develop large databases comprising data derived from samples obtained from patients with well-characterized endometriosis.

This is an important tool for identification and validation of biomarkers and may play a key role in biomarker investigation in future endometriosis studies.(88) The inclusion of a large global pool of clinical samples collected from endometriosis patients is vital for the advancement of medical knowledge, and could be a key factor in the implementation of targeted therapies, which may enhance treatment effectiveness and improve the quality of life of endometriosis patients.

No studies investigating miRNA expression profile in the vaginal fluid were found in this literature review. This body fluid can be easily collected during gynecological examinations and, in spite of high rates of bacterial colonization, appears to be a promising source of diagnostic material.(89,90) The value of differential miRNA expression in vaginal fluid as potential screening test for HPV has been examined, with interesting results.(91-95)

Likewise, none of the papers examined investigated miRNAs in saliva. To date, there are no scientifically proven salivary biomarkers for endometriosis. Saliva is a suitable and desirable medium for biomarker detection(96,97) and its applicability to the diagnosis of endometriosis has been explored previously.(98,99) Saliva is widely available and can be easily collected in a non-invasive manner, at low cost and with minimal discomfort. Therefore, it is an ideal fluid for biomarker investigation and is attracting great interest in the public health sector. The use of saliva for miRNA identification could be a potential non-invasive solution to overcome current barriers to the diagnosis of endometriosis.

This study has some limitations. When evaluating papers with contrasting results, it was not possible to tease out the factors underlying such different outcomes. Reasons explaining miRNA heterogeneity were also not found.

In this review, different studies investigating miRNA expression in endometriosis patients were discussed. Most of these studies were based on pooled or small samples. Large, well-designed clinical trials aimed to validate endometriosis-related miRNAs are needed in order to develop accurate, low-invasiveness diagnostic methods for endometriosis. The clinical impact of scientifically proven miRNA biomarkers for endometriosis will translate into better access to care and less health disparities, with potential impacts on global health. The diagnosis of endometriosis at earlier stages of the disease may lead to dramatic reduction in health costs and provide significant benefits for patients through improved health and quality of life.

CONCLUSION

Differential miR-145 expression was reported in the largest number of studies (six articles). Most dysregulated miRNAs were harvested from tissue samples.

No particular miRNA or miRNA combination has been validated for improved diagnosis of endometriosis to date. This may have reflected the heterogeneity of the disease and resultant differences in tissue composition. Large databases comprising data derived from samples collected from patients with well-characterized endometriosis may play a key role in biomarker investigation in future studies. The use of saliva and vaginal fluid samples for miRNA identification could be a potential non-invasive solution to overcome current barriers to the diagnosis of endometriosis.

ACKNOWLEDGEMENTS

To Carlos Augusto Cardim de Oliveira for his instructions about the best practices for a good systematic review.

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Einstein (Sao Paulo). 2021 Apr 15;19:eRW5704. [Article in Portuguese]

Visão geral de miRNAs como diagnóstico não invasivo de endometriose: evidências, desafios e estratégias. Uma revisão sistemática

Vitor Ulisses Monnaka 1, Camila Hernandes 2, Debora Heller 2, Sérgio Podgaec 2

RESUMO

Objetivo

O objetivo do estudo foi analisar as evidências sobre miRNAs como biomarcadores para o diagnóstico de endometriose, bem como levantar informações sobre os desafios e as estratégias necessárias para tornar essas moléculas ferramentas acessíveis para uso na prática clínica.

Métodos

Revisão sistemática conduzida nos bancos de dados PubMed®, Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS), MEDLINE® e Web of Science utilizando os termos de pesquisa “endometriosis” (todos os campos) ANDmiRNA” (todos os campos), avaliando todas as publicações até maio de 2019.

Resultados

A maioria dos miRNAs desregulados foram analisados a partir de amostras de tecido, o que inviabiliza seu uso como teste diagnóstico não invasivo. Todavia, 62 miRNAs foram identificados como diferencialmente expressos em amostras que poderiam ser usadas para o diagnóstico pouco invasivo de endometriose, como sangue, soro e plasma.

Conclusão

Apesar de todos esses candidatos, os trabalhos são exploratórios, realizados com números pequenos de amostras, sem miRNAs específicos validados para fins diagnósticos. Estudos envolvendo principalmente amostras biológicas, visando à pesquisa translacional, deveriam ser mais explorados. O desenvolvimento de grandes bancos de dados sobre amostras, bem como o uso de saliva e fluido vaginal para identificação de miRNAs, poderia servir como recursos essenciais para as barreiras atuais no diagnóstico da endometriose.

Keywords: Biomarcadores, Saliva, Soro, Fluido vaginal, Bancos de fluidos corpóreos, MicroRNAs, Endometriose/diagnóstico

INTRODUÇÃO

A endometriose é uma doença comum, que afeta até 10% das mulheres em idade reprodutiva(1,2) e se caracteriza pela presença de células endometriais fora da cavidade uterina. Apesar de ter sido alvo de muitos estudos, o diagnóstico da doença segue um desafio. As apresentações clínicas variam, indo desde quadros assintomáticos até com sintomatologia grave, e faltam biomarcadores diagnósticos cientificamente aprovados para o diagnóstico clínico de rotina.(1,3)

Exames de imagem, como a ultrassonografia pélvica e a ressonância magnética, são utilizados, principalmente em lesões profundas, porém o resultado é altamente influenciado pela experiência do examinador,(4-7) o que dificulta o diagnóstico. Nos casos sem achados positivos de imagem, o diagnóstico definitivo da endometriose superficial só pode ser fechado por análise histológica da lesão em amostras geralmente coletadas por cirurgia laparoscópica.(8,9) Entretanto, esse procedimento é invasivo e requer anestesia geral.

A complexidade da doença, aliada à falta de métodos diagnósticos precisos e menos invasivos, contribui para o atraso no diagnóstico, que pode levar até 11 anos.(5,10,11) Consequentemente, é enorme a demanda por testes diagnósticos de alta acurácia e pouco invasivos para o diagnóstico da endometriose.(12-16)

Diferentes grupos de pesquisa investigaram o papel dos miRNAs (microRNA ou miR) na regulação de genes conhecidos, dada a sua associação com processos envolvidos na patogênese e na evolução dessa doença. Os miRNAs são uma classe de pequenas moléculas endógenas de RNA não codificante, envolvidas na regulação pós-transcricional da expressão gênica.(17) Essas pequenas moléculas foram observadas na circulação sanguínea periférica e podem constituir biomarcadores em potencial para o diagnóstico da endometriose.(18,19)

A fim de determinar a real possibilidade de se empregar os miRNAs como biomarcadores para endometriose, realizamos um levantamento de todos os estudos publicados, na esperança de direcionar os passos futuros necessários para vencer os desafios associados ao uso de miRNAs na prática clínica.

OBJETIVO

Determinar quais miRNAs têm aplicabilidade diagnóstica na endometriose e delinear os desafios e estratégias envolvidos na transformação dessas moléculas em ferramentas diagnósticas acessíveis para uso na clínica.

MÉTODOS

A fim de identificar artigos científicos abordando associações entre endometriose e miRNA, foi realizada uma busca nas bases de dados PubMed®, Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS), MEDLINE® e Web of Science, empregando-se os unitermos endometriosis (todos os campos) AND miRNA (todos os campos).

Todas as publicações listadas até maio de 2019 (automaticamente selecionadas) foram manualmente analisadas, e somente as que envolviam padrões de expressão de miRNA validados por reação em cadeia da polimerase (PCR) em amostras clínicas de endometriose foram discutidas nesta revisão. Artigos publicados em idiomas que não o inglês, artigos baseados em cultura de células e artigos retratados, publicados em anais ou inacessíveis foram excluídos. Relatos que figuravam em mais de uma base de dados foram incluídos uma única vez no total de publicações.

Este estudo foi conduzido de acordo com a recomendação Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) para revisões sistemáticas, adotada pelo Hospital Israelita Albert Einstein (HIAE), localizado em São Paulo (SP). A extração de dados foi realizada em duplicata e de forma independente por dois pesquisadores, sendo, então, comparada para confirmação. Os miRNAs e seus respectivos níveis de expressão foram avaliados em amostras e populações de pacientes diferentes, assim como por ano e país de publicação.

RESULTADOS

Visão geral das publicações abordando miRNA e endometriose

No total, 449 artigos científicos abordando associações entre endometriose e miRNA foram encontrados nas bases de dados selecionadas para esta revisão. A maioria dos artigos (185) foi recuperada da base de dados PubMed®, seguida da LILACS e da MEDLINE® (158) e finalmente da Web of Science (106). Desse conjunto de publicações, 46 se enquadraram nos critérios finais de seleção e foram selecionados para discussão nesta revisão (Figura 1).

Figura 1. Resultados resumidos da triagem de publicações abordando associações entre endometriose e miRNAs.

Figura 1

SNP: polimorfismo de nucleotídeo único; LncRNAs: ácidos ribonucleicos longos não codificantes; circRNAs: ácidos ribonucleicos circulares; PCR: reação em cadeia de polimerase.

O número de publicações investigando miRNAs desregulados em mulheres com endometrioses aumentou rapidamente desde 2009, tendo aproximadamente a metade do número total de artigos (23) sido publicada nos últimos 3 anos. China e Estados Unidos foram os países com o maior número de publicações (21 e 9 artigos, respectivamente).

Nesta amostra de 46 estudos, 43 investigaram miRNAs desregulados no endométrio ectópico (EC) comparativamente ao endométrio eutópico de pacientes controle (EN), 25 foram identificados no EC comparativamente ao endométrio eutópico de mulheres com endometriose (EU), e 23 foram identificados no grupo EU comparativamente ao Grupo EN. Além disso, 27 foram identificados no soro, 18 no plasma, 30 no sangue e seis no líquido peritoneal de mulheres com endometriose em relação ao Grupo Controle. Dentre os tipos de amostras analisados, o sangue parece ser o material mais bem estudado em termos de potencial de aplicação no diagnóstico não invasivo. O resumo dos miRNAs desregulados encontrados em artigos publicados selecionados está listado em tabela 1A-1G .

Tabela 1A. miRNAs diferencialmente expressos em endométrio eutópico de pacientes com endometriose comparados ao endométrio eutópico de pacientes controle.

miRNA Regulação Endometriose n Controle n Referências
miR-126 RN 31 27 Liu et al.(20)
miR-1281 RP 38 38 Yang et al.(21)
miR-142-5p RP 38 38 Yang et al.(21)
miR-145 RP 11 22 Zheng et al.(22)
miR-146a-5p RP 38 38 Yang et al.(21)
miR-183-5p RN N/D N/D Shi et al.(23)
miR-199a RN 12 12 Dai et al.(24)
miR-202-3p RN 51 32 Braza-Boïls et al.(25)
miR-204 RN 38 9 Haikalis et al.(26)
miR-29c RN 20 10 Long et al.(27)
miR-30d-5p RP 21 25 Laudanski et al.(28)
miR-3152-5p RP 21 25 Laudanski et al.(28)
miR-34b RN 4 3 Burney et al.(29)
miR-34c-5p RN 4 3 Burney et al.(29)
miR-424-5p RN 51 32 Braza-Boils et al.(25)
miR-4634 RP 38 38 Yang et al.(21)
miR-483-5p RN 21 25 Laudanski et al.(30)
miR-5187-3p RP 21 25 Laudansk et al.(28)
miR-543 RN 38 38 Yang et al.(21)
miR-556-3p RN 51 32 Braza-Boïls et al.(25)
miR-629* RN 21 25 Laudanski et al.(30)
miR-9 RN 4 3 Burney et al.(29)
miR-940 RP 38 38 Yang et al.(21)

miRNA: microRNA; RN: regulação negativa; RP: regulação positiva; N/D: não disponível.

Tabela 1B. miRNAs diferencialmente expressos em endométrio ectópico de pacientes com endometriose e endométrio eutópico de pacientes controle.

miRNA Regulação Endometriose n Controle n Referências
let-7g RP N/D N/D Wright et al.(31)
miR-100 RP N/D N/D Wright et al.(31)
miR-1304-3p RP 14 10 Xu et al.(32)
miR-133a-3p RP 33 17 Braicu et al.(33)
miR-138 RP 51 32 Braza-Boïls et al.(25)
miR-141 RP 22 24 Saare et al.(34)
miR-143 RP 11 22 Zheng et al.(22)
miR-145 RP 11 22 Zheng et al.(22)
miR-148a RP N/D N/D Wright et al.(31)
miR-183-5p RN N/D N/D Shi et al.(23)
miR-191 RP 12 12 Dong et al.(35)
miR-199a RN 12 12 Dai et al.(24)
miR-200a RP 22 24 Saare et al.(34)
miR-200b RP 22 24 Saare et al.(34)
miR-200c RN 27 12 Liang et al.(36)
miR-202-3p RP 51 32 Braza-Boïls et al.(25)
miR-205-5p RN 14 10 Xu et al.(32)
miR-20a RP 40 20 Zhao et al.(37)
miR-21-3p RP 7 7 Qi et al.(38)
miR-223-3p RP 7 7 Qi et al.(38)
miR-29a RP N/D N/D Wright et al.(31)
miR-29c RN 20 10 Long et al.(27)
miR-29c RP 51 32 Braza-Boïls et al.(25)
miR-29c RP 15 11 Joshi et al.(39)
miR-325 RP 33 17 Braicu et al.(33)
miR-33b RN 20 15 Yang et al.(40)
miR-34c RP 22 24 Saare et al.(34)
miR-3663-3p RP 7 7 Qi et al.(38)
miR-3684 RP 14 10 Xu et al.(32)
miR-373-3p RP 51 32 Braza-Boïls et al.(25)
miR-3935 RN 14 10 Xu et al.(32)
miR-411-5p RP 51 32 Braza-Boïls et al.(25)
miR-4427 RN 14 10 Xu et al.(32)
miR-449a RP 22 24 Saare et al.(34)
miR-450a-5p RN 7 7 Qi et al.(38)
miR-451 RP 30 0 Graham et al.(41)
miR-4683 RP 14 10 Xu et al.(32)
miR-492 RP 33 17 Braicu et al.(33)
miR-494-5p RP 14 10 Xu et al.(32)
miR-503-5p RN 7 7 Qi et al.(38)
miR-520e RP 33 17 Braicu et al.(33)
miR-544b RP 14 10 Xu et al.(32)
miR-5481 RN N/D N/D Wright et al.(31)
miR-652-5p RN 14 10 Xu et al.(32)
miR-6747-3p RP 14 10 Xu et al.(32)

miRNA: microRNA; RN: regulação negativa; N/D: não disponível; RP: regulação positiva.

Tabela 1C. miRNAs diferencialmente expressos em endométrio ectópico e eutópico de pacientes com endometriose.

miRNA Regulação Endometriose n Controle n Referências
miR-106a-5p RN 22 0 Zhao et al.(42)
miR-106b-5p RP 32 19 Yang et al.(43)
miR-10a RN 38 38 Haikalis et al.(26)
miR-125a RP 58 38 Ramón et al.(44)
miR-126 RN 31 27 Liu et al.(20)
miR-126 RP 8 N/D Ohlsson Teague et al.(45)
miR-141 RN 8 N/D Ohlsson Teague et al.(45)
miR-145 RP 8 N/D Ohlsson Teague et al.(45)
miR-145-5p RP 32 19 Yang et al.(43)
miR-146a-5p RN 32 19 Yang et al.(43)
miR-15a-5p RN 32 19 Yang et al.(43)
miR-16-5p RP 32 19 Yang et al.(43)
miR-182 RN 16 N/D Filigheddu et al.(46)
miR-182-5p RN 22 0 Zhao et al.(42)
miR-19b-1-5p RN 32 19 Yang et al.(43)
miR-200a RN 16 N/D Filigheddu et al.(46)
miR-200a-3p RN 22 0 Zhao et al.(42)
miR-200b RN 16 N/D Filigheddu et al.(46)
miR-200b RN 8 N/D Ohlsson Teague et al.(45)
miR-200b RN 32 19 Yang et al.(43)
miR-200c RN 16 N/D Filigheddu et al.(46)
miR-200c RN 32 19 Yang et al.(43)
miR-202 RP 16 N/D Filigheddu et al.(46)
miR-21 RN 38 38 Haikalis et al.(26)
miR-222 RP 58 38 Ramón et al.(44)
miR-34c RN 22 0 Zhao et al.(42)
miR-424 RN 8 N/D Ohlsson Teague et al.(45)
miR-424 RN 38 38 Haikalis et al.(26)
miR-449b RN 51 32 Braza-Boïls et al.(25)
miR-449b RN 22 0 Zhao et al.(42)
miR-451a RP 41 40 Nothnick et al.(47)
miR-615 RP 22 0 Zhao et al.(42)
miR-9 RN 38 38 Haikalis et al.(26)
miR-99a RP 8 N/D Ohlsson Teague et al.(45)

miRNA: microRNA; RN: regulação negativa; RP: regulação positiva; N/D: não disponível.

Tabela 1D. miRNAs diferencialmente expressos no soro de pacientes com endometriose e pacientes controle.

miRNA Regulação Endometriose n Controle n Referências
let-7b RN 24 24 Cho et al.(48)
let-7b-5p RN 20 26 Nematian et al.(49)
miR-122 RP 60 25 Wang et al.(19)
miR-122 RP 45 35 Maged et al.(50)
miR-125b-5p RP 24 24 Cosar et al.(51)
miR-125b RP 20 26 Nematian et al.(49)
miR-127-3p RN 30 20 Wang et al.(52)
miR-135a RN 24 24 Cosar et al.(51)
miR-141 RN 60 25 Wang et al.(19)
miR-143-3p RP 24 24 Cosar et al.(51)
miR-145 RN 60 25 Wang et al.(19)
miR-145-5p RP 24 24 Cosar et al.(51)
miR-150-5p RP 24 24 Cosar et al.(51)
miR-15b-5p RN 30 20 Wang et al.(52)
miR-17 RN 80 60 Wang et al.(53)
miR-185-5p RP 30 20 Wang et al.(52)
miR-18a-5p RP 24 24 Cosar et al.(51)
miR-191 RP 12 12 Dong et al.(35)
miR-199a RP 60 25 Wang et al.(19)
miR-199a RP 45 35 Maged et al.(50)
miR-199a-5p RN 40 25 Hsu et al.(54)
miR-20a-5p RN 30 20 Wang et al.(52)
miR-30c-5p RN 30 20 Wang et al.(52)
miR-342-3p RP 24 24 Cosar et al.(51)
miR-3613-5p RN 24 24 Cosar et al.(51)
miR-370 RN 20 26 Hu et al.(55)
miR-424-3p RP 30 20 Wang et al.(52)
miR-451a RP 41 40 Nothnick et al.(47)
miR-451a RP 24 24 Cosar et al.(51)
miR-500a-3p RP 24 24 Cosar et al.(51)
miR-542-3p RN 60 25 Wang et al.(19)
miR-6755-3p RN 24 24 Cosar et al.(51)
miR-9 RN 60 25 Wang et al.(19)
miR-99b-5p RN 30 20 Wang et al.(52)

miRNA: microRNA; RN: regulação negativa; RP: regulação positiva.

Tabela 1E. miRNAs diferencialmente expressos no plasma de pacientes com endometriose e pacientes controle.

miRNA Regulação Endometriose n Controle n Referências
miR-139 RN 80 39 Nisenblat et al.(56)
miR-141 RN 61 65 Rekker et al.(57)
miR-145 RP 55 23 Bashti et al.(58)
miR-154-5p RN 51 41 Pateisky et al.(59)
miR-155 RN 80 39 Nisenblat et al.(56)
miR-16 RP 33 20 Suryawanshi et al.(60)
miR-17-5p RN 23 23 Jia et al.(61)
miR-191 RP 33 20 Suryawanshi et al.(60)
miR-195 RP 33 20 Suryawanshi et al.(60)
miR-196b RN 51 41 Pateisky et al.(59)
miR-200a RN 61 65 Rekker et al.(57)
miR-200b RN 61 65 Rekker et al.(57)
miR-20a RN 23 23 Jia et al.(61)
miR-22 RN 23 23 Jia et al.(61)
miR-31 RN 55 23 Bashti et al.(58)
miR-33a RP 51 41 Pateisky et al.(59)
miR-378a RN 51 41 Pateisky et al.(59)
miR-574 RN 80 39 Nisenblat et al.(56)

miRNA: microRNA; RN: regulação negativa; RP: regulação positiva.

Tabela 1F. miRNAs diferencialmente expressos no sangue de pacientes com endometriose e pacientes controle.

miRNA Regulação Endometriose n Controle n Referências
let-3c RN 4 3 Azmy et al.(62)
let-7e RN 4 3 Azmy et al.(62)
let-7f RN 5 3 Azmy et al.(62)
let-7g RN 4 3 Azmy et al.(62)
miR-103 RN 4 3 Azmy et al.(62)
miR-106b RN 4 3 Azmy et al.(62)
miR-125a-5p RN 4 3 Azmy et al.(62)
miR-126 RN 4 3 Azmy et al.(62)
miR-15b RN 4 3 Azmy et al.(62)
miR-16 RN 4 3 Azmy et al.(62)
miR-17 RN 4 3 Azmy et al.(62)
miR-181b RN 4 3 Azmy et al.(62)
miR-18a RN 4 3 Azmy et al.(62)
miR-194 RN 4 3 Azmy et al.(62)
miR-195 RN 4 3 Azmy et al.(62)
miR-19a RN 4 3 Azmy et al.(62)
miR-19b RN 4 3 Azmy et al.(62)
miR-20a RN 4 3 Azmy et al.(62)
miR-21 RN 4 3 Azmy et al.(62)
miR-22 RN 4 3 Azmy et al.(62)
miR-26a RN 4 3 Azmy et al.(62)
miR-26b RN 4 3 Azmy et al.(62)
miR-27a RN 4 3 Azmy et al.(62)
miR-27b RN 4 3 Azmy et al.(62)
miR-30a RN 4 3 Azmy et al.(62)
miR-374a RN 4 3 Azmy et al.(62)
miR-374b RN 4 3 Azmy et al.(62)
miR-424 RN 4 3 Azmy et al.(62)
miR-7 RN 4 3 Azmy et al.(62)
miR-93 RN 4 3 Azmy et al.(62)

miRNA: microRNA; RN: regulação negativa.

Tabela 1G. miRNAs diferencialmente expressos no líquido peritoneal de pacientes com endometriose e pacientes controle.

miRNA Regulação Endometriose n Controle n Referências
miR-106b-3p RP 126 45 Marí-Alexandre et al.(63)
miR-122 RP 45 35 Maged et al.(50)
miR-130b RP 6 3 Chen et al.(64)
miR-199a RP 45 35 Maged et al.(50)
miR-451a RP 126 45 Marí-Alexandre et al.(63)
miR-486-5p RP 126 45 Marí-Alexandre et al.(63)

miRNA: microRNA; RP: regulação positiva.

Ao todo, 33 miRNAs foram analisados em mais de um estudo. Destes, 13 foram analisados em amostras do mesmo tipo. Os miRNAs identificados em mais de um estudo e fluido corporal encontram-se descritos na tabela 2.

Tabela 2. Resumo dos miRNAs desregulados identificados em mais de um estudo em diferentes amostras.

Total EU versus EN EC versus EN EC versus EU Plasma Soro Sangue LP Referências
6 miR-145 miR-145 miR-145 miR-145 miR-145     Wang et al.,(19) Zheng et al.,(22) Yang et al.,(43) Ohlsson Teague et al.,(45) Cosar et al.(51) e Bashti et al.(58)
5   miR-200b miR-200b miR-200b       Saare et al.,(34) Yang et al.,(43) Ohlsson Teague et al.,(45) Filigheddu et al.(46) e Rekker et al.(57)
5 miR-424   miR-424   miR-424 miR-424   Braza-Boils et al.,(25) Haikalis et al.,(26) Ohlsson Teague et al.,(45) Wang et al.(52) e Azmy et al.(62)
4 miR-199a miR-199a     miR-199a   miR-199a Wang et al.,(19) Dai et al.,(24) Maged et al.(50) e Hsu et al.(54)
4   miR-141 miR-141 miR-141 miR-141     Wang et al.,(19) Saare et al.,(34) Ohlsson Teague et al.(45) e Rekker et al.(57)
4   miR-20a   miR-20a miR-20a miR-20a   Zhao et al.,(37) Wang et al.,(52) Jia et al.(61) e Azmy et al.(62)
4   miR-200a miR-200a miR-200a       Saare et al.,(34) Zhao et al.,(42) Filigheddu et al.(46) e Rekker et al.(57)
3 miR-29c miR-29c miR-29c         Braza-Boils et al.,(25) Long et al.(27) e Joshi et al.(39)
3 miR-34c miR-34c miR-34c         Braza-Boïls et al.,(25) Saare et al.(34) e Joshi et al.(39)
3   miR-200c miR-200c         Liang et al.,(36) Yang et al.(43) e Filigheddu et al.(46)
3   miR-21 miR-21     miR-21   Haikalis et al.,(26) Qi et al.(38) e Azmy et al.(62)
3 miR-126   miR-126     miR-126   Liu et al.,(20) Ohlsson Teague et al.(45) e Azmy et al.(62)
3     miR-16 miR-16   miR-16   Yang et al.,(43) Suryawanshi et al.(60) e Azmy et al.(62)
3     miR-451a   miR-451a   miR-451a Nothnick et al.,(47) Cosar et al.(51) e Marí-Alexandre et al.(63)
3 miR-9   miR-9   miR-9     Wang et al.,(19) Haikalis et al.(26) e Burney et al.(29)
3     miR-106b     miR-106b miR-106b Yang et al.,(43) Azmy et al.(62) e Marí-Alexandre et al.(63)
3       miR-17 miR-17 miR-17   Wang et al.,(53) Jia et al.(61) e Azmy et al.(62)
2         miR-122   miR-122 Wang et al.(19) e Maged et al.(50)
2     miR-449b         Braza-Boïls et al.(25) e Zhao et al.(42)
2   miR-191   miR-191 miR-191     Dong et al.(35) e Suryawanshi et al.(60)
2 miR-202 miR-202 miR-202         Braza-Boïls et al.(25) e Filigheddu et al.(46)
2   miR-143     miR-143     Zheng et al.(22) e Cosar et al.(51)
2       miR-22   miR-22   Jia et al.(61) e Azmy et al.(62)
2   miR let-7g       miR let-7g   Wright et al.(31) e Azmy et al.(62)
2         miR-15b miR-15b   Wanget al.(52) e Azmy et al.(62)
2     miR-125a     miR-125a   Ramón et al.(44) e Azmy et al.(62)
2       miR-195   miR-195   Suryawanshi et al.(60) e Azmy et al.(62)
2         miR-18a miR-18a   Cosar et al.(51) e Azmy et al.(62)
2     miR-19b     miR-19b   Yanget al.(43) e Azmy et al.(62)
2 miR-146a   miR-146a         Yang et al.(21) e Yang et al.(43)
2     miR-182         Zhao et al.(42) e Filigheddu et al.(46)
2         miR-125b     Nematian et al.(49) e Cosar et al.(51)
2         miR-let-7b     Cho et al.(48) e Nematian et al.(49)

EU: endométrio eutópico de mulheres com endometriose; EN: endométrio eutópico de pacientes controle; EC: endométrio ectópico; LP: líquido peritoneal.

Dentre os 62 miRNAs identificados em amostras com possível aplicabilidade no diagnóstico pouco invasivo da endometriose, como sangue, soro e plasma, 20 também se mostraram desregulados em outros tipos de tecidos, tais EC e eutópico, e no líquido peritoneal. Destes, 35% foram identificados no mesmo tipo de tecido em mais de um estudo, incluindo miR-200b, miR-145, miR-199a, miR-424, miR-200a, miR-126 e miR-451a. Treze miRNAs mostraram-se desregulados de forma positiva ou negativa, a saber: miR-125b, miR-let-7b, miR-122, miR-451a e miR-199a no soro; miR-29c no EC em relação ao Grupo EN; e miR-145, miR-200b, miR-424, miR-200a, miR-200c, miR-449b e miR-182 no EC em relação ao EC de mulheres com endometriose (Tabela 3).

Tabela 3. Caracterização da expressão de miRNAs para regulação positiva e negativa em diferentes amostras.

miRNA n EU versus EN EC versus EN EC versus EU Plasma Soro Sangue LP
EU EN EC EN EC EU
miR-145 6 ↑ (1) ↓ (1) ↑ (1) ↓ (1) ↑ (2) ↓ (2) ↑ (1) ↑ (1) /↓ (1)    
miR-200b 5     ↑ (1) ↓ (1) ↓ (3) ↑ (3) ↓ (1)      
miR-424 5 ↓ (1) ↑ (1)     ↓ (2) ↑ (2)   ↑ (1) ↓ (1)  
miR-199a 4 ↓ (1) ↑ (1) ↓ (1) ↑ (1)     ↑ (1) ↑ (2)/↓ (1)   ↑ (1)
miR-141 4     ↑ (1) ↓ (1) ↓ (1) ↑ (1) ↓ (1) ↓ (1)    
miR-20a 4     ↑ (1) ↓ (1)     ↓ (1) ↓ (1) ↓ (1)  
miR-200a 4     ↑ (1) ↓ (1) ↓ (2) ↑ (2) ↓ (1)      
miR-29c 3 ↓ (1) ↑ (1) ↑ (2) /↓ (1) ↓ (2) / ↑(1) ↓ (1) ↑ (1)        
miR-34c 3 ↓ (1) ↑ (1) ↑ (1) ↓ (1) ↓ (1) ↑ (1)        
miR-200c 3     ↓ (1) ↑ (1) ↓ (2) ↑ (2)        
miR-21 3     ↑ (1) ↓ (1) ↓ (1) ↑ (1)     ↓ (1)  
miR-126 3 ↓ (1) ↑ (1)     ↑ (1)/↓ (1) ↓ (1)/↑ (1)     ↓ (1)  
miR-16 3         ↑ (1) ↓ (1) ↑ (1)   ↓ (1)  
miR-451a 3         ↑ (1) ↓ (1)   ↑ (2)   ↑ (1)
miR-9 3 ↓ (1) ↑ (1)     ↓ (1) ↑ (1)   ↓ (1)    
miR-106b 3         ↑ (1) ↓ (1)     ↓ (1) ↑ (1)
miR-17 3             ↓ (1) ↓ (1) ↓ (1)  
miR-122 2               ↑ (2)   ↑ (1)
miR-449b 2         ↓ (2) ↑ (2)        
miR-191 2     ↑ (1) ↓ (1)     ↑ (1) ↑ (1)    
miR-202 2 ↓ (1) ↑ (1) ↑ (1) ↓ (1) ↑ (1) ↓ (1)        
miR-143 2     ↑ (1) ↓ (1)       ↑ (1)    
miR-22 2             ↓ (1)   ↓ (1)  
miR let-7g 2     ↑ (1) ↓ (1)         ↓ (1)  
miR-15b 2               ↓ (1) ↓ (1)  
miR-125a 2         ↑ (1) ↓ (1)     ↓ (1)  
miR-195 2             ↑ (1)   ↓ (1)  
miR-18a 2               ↑ (1) ↓ (1)  
miR-19b 2         ↓ (1) ↑ (1)     ↓ (1)  
miR-146a 2 ↑ (1) ↓ (1)     ↓ (1) ↑ (1)        
miR-182 2         ↓ (2) ↑ (2)        
miR-125b 2               ↑ (2)    
miR-let-7b 2               ↓ (2)    

↑ regulação positiva; ↓ regulação negativa.

miRNA: microRNA; EU: endométrio eutópico de mulheres com endometriose; EN: endométrio eutópico de pacientes controle; EC: endométrio ectópico; PF: líquido peritoneal.

DISCUSSÃO

A endometriose pode ser uma doença debilitante e causa de má qualidade de vida.(65) Essa enfermidade tem relação com dismenorreia, dispareunia profunda, dor pélvica crônica e infertilidade,(66,67) sendo considerada um problema de saúde pública, devido ao impacto sobre a saúde física e psicológica das pacientes e ao impacto socioeconômico decorrente dos custos do diagnóstico, do tratamento e do controle clínico.(68)

Atualmente, o diagnóstico definitivo da endometriose se baseia na análise histológica da lesão, geralmente empregando-se amostras obtidas por cirurgia laparoscópica.(69) Entretanto, os métodos de imagem constituem alternativas diagnósticas não invasivas importantes para a endometriose ovariana e profunda. Tanto a abordagem cirúrgica como a não cirúrgica requerem habilidade professional considerável e disponibilidade de dados específicos, o que pode representar enorme carga econômica e de saúde em países em desenvolvimento.(4-9)

Nas últimas três décadas, pesquisadores do mundo todo tentaram identificar testes não invasivos capazes de reduzir o tempo necessário para o diagnóstico da endometriose. O CA-125 pode ser detectado no sangue ou no líquido peritoneal e é um dos biomarcadores mais bem estudados. Em alguns estudos de casos, a dosagem de CA-125 mostrou-se promissora, principalmente no diagnóstico da endometriose mais invasiva, desde que realizada no início do ciclo menstrual.(70-72)

Apesar dos resultados conflitantes referentes ao valor do CA-125 enquanto biomarcador decisivo e importante em revisões recentes, segundo Socolov et al., o CA-125 continua sendo o mais indicado para o diagnóstico e o monitoramento da endometriose.(73) Em uma revisão Cochrane mais recente, publicada em 2016, Nisenblat et al., compararam a acurácia de combinações de testes não invasivos para diagnóstico da endometriose pélvica com o diagnóstico cirúrgico, empregando como padrão de referência ensaios randomizados controlados ou estudos transversais publicados até meados de 2015. Os autores concluíram que nenhum dos biomarcadores investigados (incluindo o CA-125) pode ser devidamente avaliado por falta de evidência suficiente ou de boa qualidade, dada a heterogeneidade e o alto risco de viés nos estudos selecionados.(15)

Por mostrar-se mais elevado nos estágios avançados da endometriose, a sensibilidade do CA-125 é limitada. Além disso, a especificidade desse marcador é baixa, devido à sua regulação positiva em outras patologias ginecológicas.(74) Nesse contexto, a busca por novos biomarcadores eficazes e não invasivos, capazes de aprimorar o diagnóstico, o tratamento e o monitoramento da endometriose, permanece no topo da lista de prioridades.

Dentre os candidatos promissores, destacam-se os miRNAs circulantes, identificados pela primeira vez como marcadores sorológicos não invasivos para tumores em 2008.(75-77) A alta estabilidade dos miRNAs circulantes no plasma humano e sua resistência a diversos procedimentos de manipulação de amostras foram enfatizadas nesses estudos pioneiros.

Além disso, esses mesmos estudos estabeleceram o conceito de diagnóstico baseado em assinaturas de miRNAs livres de células específicas. Desde então, os miRNAs foram validados como marcadores diagnósticos não invasivos para diversas doenças, incluindo distúrbios oncológicos, inflamatórios, cardiovasculares, metabólicos e reprodutivos. Os miRNAs se revelaram marcadores ideais na oncologia, conforme demonstram padrões diferenciais de expressão de miRNAs circulantes em pacientes com câncer pulmonar, ovariano, colorretal, prostático e de mama, em relação a controles saudáveis.(78)

No sistema reprodutivo feminino em particular, a expressão desregulada de miRNAs foi estudada em fibroides uterinos, em diversos cânceres ginecológicos (incluindo adenocarcinomas) e em distúrbios de parto, como a pré-eclâmpsia e o parto prematuro.(79-83) Essas pequenas moléculas não codificantes associadas a diversas doenças figuram entre os candidatos úteis para o diagnóstico da endometriose.(84)

Nesta revisão, o miRNA com expressão diferencial no maior número de estudos foi o miR-145 (seis artigos). Nos 46 estudos analisados, a maioria dos miRNAs que se mostraram desregulados na endometriose foi coletada de amostras teciduais. Portanto, os fluidos corpóreos foram pouco investigados, embora possam ser úteis enquanto ferramentas diagnósticas não ou pouco invasivas. Além disso, a maioria dos estudos comparou as diferenças de expressão de miRNAs entre o endométrio eutópico e o EC de pacientes com endometriose, sendo poucos os que estabeleceram comparações com o endométrio de pacientes com endometriose, ressaltando a dificuldade dos exames baseados em biópsias endometriais.

Dentre os miRNAs desregulados em pacientes com endometriose comparados nesta revisão, 30 foram detectados no sangue, 27 no soro e 18 no plasma de mulheres com endometriose comparadas com populações controle. As diferenças de composição molecular entre o soro e o plasma são bem conhecidas.(85,86)

Ao comparar o espectro de miRNAs no soro e no sangue, Wang et al.,(19) observaram várias discrepâncias nas concentrações de RNAs determinadas pela liberação de certos miRNAs e outros RNAs durante a coagulação e sugeriram que o plasma seja utilizado como amostra de eleição para estudo de miRNAs circulantes, uma vez que os RNAs liberados durante a coagulação podem alterar o repertório real de miRNAs circulantes.

A expressão diferencial de seis miRNAs foi identificada no líquido peritoneal de pacientes com endometriose em relação a mulheres não afetadas. Portanto, alguns miRNAs presentes no líquido peritoneal podem atuar na patogênese da endometriose. Entretanto, dada a natureza desse fluido, seu emprego é limitado pela necessidade de coleta cirúrgica, ou seja, invasiva.

Um ponto digno de nota nesses estudos foram os resultados conflitantes. Eles foram relatados em estudos que investigaram a expressão dos miR-145, -424, -199a, -29c, -126, -16, -195 e -18a no mesmo tipo de amostra. As principais características desses estudos encontram-se descritas a seguir.

A regulação positiva do miR-145 foi observada no soro, em estudo com 24 pacientes com endometriose estágios III e IV e 24 pacientes controle,(51) e no plasma em um estudo com 55 pacientes com endometriose estágios I e II e 23 pacientes controle.(58) Em contrapartida, estudo com 60 casos (estágio da doença não relatado) e 25 controles relatou regulação negativa desse mesmo miRNA no soro.(19)

Um estudo com quatro pacientes com endometriose leve e três controles relatou regulação negativa do miR-424 no sangue.(62) Entretanto, esse mesmo marcador mostrou-se regulado de forma positiva no soro de 30 pacientes com endometriose mínima leve em relação a 20 indivíduos controle.(52)

A regulação positiva do miR-199a foi detectada no soro de pacientes com endometrioses em dois estudos, sendo um com 60 pacientes com endometriose estágios III e IV e 25 pacientes controle(19) e o outro com 45 pacientes com endometriose e 35 pacientes controle.(50) Entretanto, a regulação negativa do mesmo miRNA no soro foi descrita em outro estudo envolvendo 40 pacientes com endometriose e 25 pacientes controle.(54)

Um estudo com 15 casos clínicos e 11 controles revelou regulação positiva do miR-29c no EC de mulheres com endometriose em relação ao endométrio eutópico do Grupo Controle.(39) Esse achado foi reconfirmado em outro estudo envolvendo 51 mulheres com endometriose e 32 controle(25) nas fases proliferativa e secretória do ciclo menstrual. Entretanto, resultados conflitantes, sugerindo regulação negativa do miR-29c no EC de 20 mulheres com endometriose em relação ao endométrio eutópico de dez pacientes controle,(27) todas exclusivamente na fase proliferativa do ciclo, foram relatados por outro pesquisador.

A regulação positiva do miR-126 no EC comparativamente ao endométrio eutópico foi detectada em oito mulheres com endometriose estágios III e IV(45) nas fases proliferativa e secretória do ciclo menstrual. Entretanto, a regulação negativa do miR-126 foi relatada no EC comparativamente ao endométrio eutópico em 31 mulheres com endometriose estágios III e IV,(20) todas na fase secretória do ciclo menstrual.

A regulação positiva do miR-16 e do miR-195 foi observada no plasma de 33 mulheres com endometriose comparadas com 20 pacientes controles.(60) Entretanto, outro estudo identificou regulação negativa de ambos no sangue de quatro pacientes com endometriose leve comparadas com três controles.(62)

A regulação positiva do miR-18a foi observada no soro de 24 mulheres com endometriose estágios III e IV em relação a 24 pacientes controle.(51) Entretanto, a regulação negativa foi identificada no sangue de quatro pacientes com endometriose leve em relação a três controles.(62)

A discrepância nos resultados destaca a relevância de critérios como fase do ciclo menstrual, estágio da doença, tipo de amostra e tipo de procedimento, bem como a necessidade de estudos com maior número de pacientes para o desenvolvimento de testes diagnósticos para a endometriose.

O segundo objetivo deste estudo foi nortear estudos futuros destinados à identificação de um miRNA que possa constituir um biomarcador confiável e uma ferramenta para o diagnóstico preciso da endometriose. De acordo com essa revisão crítica da literatura, infelizmente não há um miRNA específico ou uma combinação de miRNAs devidamente validada para melhorar o diagnóstico da endometriose. Isso pode refletir a heterogeneidade da doença e, consequentemente, as diferenças de composição tecidual.(87) Por esse motivo, apoiamos as iniciativas da World Endometriosis Research Foundation (WERF) e do Endometriosis Phenome and Biobanking Harmonization Project (EPHect). O esforço conjunto de grupos mundiais de pesquisa para a criação de grandes bancos de dados derivados de amostras coletadas de pacientes com endometriose bem caracterizada é fundamental.

Essa é uma importante ferramenta para a identificação e a validação de biomarcadores, que pode desempenhar papel fundamental na investigação de biomarcadores em estudos futuros.(88) A inclusão de um pool global de amostras clínicas coletadas de pacientes com endometriose é fundamental para o avanço do conhecimento médico e pode ser de grande valia na implementação de terapias-alvo, melhorando a efetividade do tratamento e a qualidade de vida das pacientes que sofrem de endometriose.

Nesta revisão de literatura, não foram encontrados estudos investigando o perfil de expressão de miRNAs no fluido vaginal. Esse fluido corporal pode ser facilmente coletado durante o exame ginecológico e, apesar da alta taxa de colonização bacteriana, parece ser fonte promissora de material diagnóstico.(89,90) O valor da expressão diferencial de miRNAs no fluido vaginal enquanto teste potencial de rastreio de HPV foi avaliado, com resultados interessantes.(91-95)

Da mesma forma, nenhum dos artigos aqui revisados investigou miRNAs na saliva. Até o momento, não existem biomarcadores salivares para endometriose cientificamente comprovados. O emprego da saliva como meio de detecção de biomarcadores é adequado e desejável(96,97) e foi previamente explorado no diagnóstico da endometriose.(98,99) A ampla disponibilidade, aliada à facilidade de coleta por método não invasivo, com baixo custo e desconforto mínimo, faz da saliva um material ideal para a pesquisa de biomarcadores, que vem despertando grande interesse na esfera da saúde pública. O uso da saliva para identificação de miRNAs seria uma solução não invasiva em potencial para a eliminação dos obstáculos vigentes para o diagnóstico da endometriose.

Este estudo tem algumas limitações. Na avaliação de artigos com resultados conflitantes, não foi possível identificar os fatores responsáveis pelos diferentes desfechos. As razões por trás da heterogeneidade de miRNA também não foram encontradas.

Diversos estudos que investigaram a expressão de miRNAs em pacientes com endometriose foram discutidos nesta revisão. Em sua maioria, esses estudos foram baseados em amostras agrupadas ou pequenas. Ensaios clínicos grandes e bem planejados, destinados à validação de miRNAs associados à endometriose, fazem-se necessários para o desenvolvimento de métodos diagnósticos acurados e pouco invasivos. O impacto clínico do emprego dos miRNAs cientificamente comprovados como biomarcadores para endometriose se traduzirá em mais amplo acesso a cuidados e menor disparidade em saúde, com potencial impacto sobre a saúde global. O diagnóstico da doença em estágios mais precoces pode se traduzir em uma redução dramática dos custos de saúde, além de beneficiar os pacientes em termos de melhor saúde e qualidade de vida.

CONCLUSÃO

A expressão diferencial do miR-145 foi relatada no maior número de estudos (seis artigos). Em sua maioria, os miRNAs desregulados foram extraídos de amostras teciduais.

Nenhum miRNA específico ou combinação de miRNAs foi validado para melhorar o diagnóstico da endometriose, o que pode refletir a heterogeneidade da doença e, consequentemente, diferenças de composição tecidual. Bancos de dados grandes, que contenham dados derivados de amostras coletadas de pacientes com endometriose bem caracterizada, podem ter papel fundamental na investigação de biomarcadores em estudos futuros. O uso de amostras de saliva e fluido vaginal para a identificação de miRNAs poderia representar uma solução não invasiva em potencial para a eliminação das barreiras vigentes para diagnóstico da endometriose.

AGRADECIMENTOS

A Carlos Augusto Cardim de Oliveira, por suas orientações sobre as melhores práticas para uma boa revisão sistemática.


Articles from Einstein are provided here courtesy of Instituto de Ensino e Pesquisa Albert Einstein

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