Platelet-rich plasma therapy for thin endometrium: a comprehensive review

Abstract

Background

Thin endometrium (TE) is a significant limiting factor for successful in vitro fertilization (IVF) and embryo transfer (ET), often resulting in poor pregnancy outcomes. Current therapeutic options remain limited and inconsistent in efficacy.

Objective

This review aims to comprehensively evaluate the clinical potential of platelet-rich plasma (PRP) therapy as an emerging treatment to improve endometrial thickness and fertility outcomes in patients with TE.

Methods

A systematic analysis of recent studies was conducted to summarize advancements in PRP application for TE. This includes evaluating PRP preparation techniques, treatment protocols, and reported clinical outcomes. Mechanistic insights into how PRP promotes endometrial regeneration through growth factors and angiogenesis were also explored.

Results

Evidence from current literature suggests that intrauterine infusion of PRP may enhance endometrial thickness and improve implantation and pregnancy rates in women with refractory TE. However, variations in PRP preparation methods and treatment protocols limit the comparability of results. Safety profiles appear favorable, with few reported adverse events.

Conclusion

PRP therapy holds promise as a regenerative approach for the treatment of TE. Nonetheless, the lack of standardized protocols and robust randomized controlled trials necessitates further research. Establishing consensus on preparation methods and treatment timing will be crucial for translating PRP therapy into routine clinical practice.

Introduction

In assisted reproductive technology (ART), the EMT plays a crucial role in successful embryo implantation and subsequent pregnancy outcomes [1]. Numerous studies have established a positive correlation between optimal EMT (generally considered to be ≥7–8 mm) and improved implantation rates [2, 3]. Conversely, a TE, defined as an EMT of less than 7 mm, is associated with a significantly reduced likelihood of successful pregnancy [4]. Consequently, the presence of a TE has become a prominent reason for the cancelation of in vitro fertilization (IVF) cycles and for the failure of frozen-thawed embryo transfer (FET) [5].

The etiology of TE is multifactorial, encompassing a range of physiological, pathological, and environmental factors [6–11]. Understanding these underlying causes is essential for developing effective treatment strategies. Key contributors to the development of TE include:

• Iatrogenic factors: Surgical procedures such as repeated curettage, polypectomy, and myomectomy can result in trauma to the endometrial lining, leading to scarring and impaired regenerative capacity. In addition, correction of T-shaped or septate uterus may contribute to similar complications. Many studies have documented that women who undergo recurrent uterine surgeries often present with compromised endometrial health, manifesting as reduced EMT and diminished reproductive outcomes, including an increased prevalence of Asherman’s syndrome.

• Inflammatory factors: Chronic and acute intrauterine infections can disrupt the normal physiological processes governing endometrial development and function [6]. Inflammatory processes can hinder the delicate balance of hormonal signaling necessary for optimal endometrial development.

• Endocrine factors: Endocrine dysfunction, particularly low estrogen levels, is a critical determinant of endometrial thickness. Estrogen is essential for stimulating endometrial proliferation during the menstrual cycle. Conditions such as ovarian insufficiency or the administration of anti-estrogen therapies can lead to insufficient estrogen stimulation, resulting in a TE [12].

• Other contributing factors: Several additional factors can contribute to the development of TE, including radiation therapy, congenital Müllerian anomalies, and idiopathic conditions. These factors may adversely impact the structural and functional integrity of the endometrium.

Despite the availability of various treatment options aimed at improving endometrial thickness [12–17], many patients continue to exhibit suboptimal outcomes. This underscores the need for innovative therapeutic approaches. In recent years, PRP has emerged as a potentially transformative therapy for TE. Derived from autologous blood, PRP is enriched with platelets that secrete a plethora of growth factors (e.g., PDGF, VEGF, TGF-β) known to facilitate cellular proliferation, angiogenesis, and tissue repair [18]. Preliminary studies have indicated that PRP may effectively augment endometrial thickness, enhance vascularization, and improve pregnancy rates among individuals suffering from TE [19, 20]. Recent research further suggests that PRP may benefit specific subgroups, such as non-TE recurrent implantation failure (RIF) patients undergoing frozen-thawed embryo transfer (FET). A retrospective study of 160 non-TE RIF patients found that intrauterine PRP perfusion 24–72 h before FET significantly increased clinical pregnancy, implantation, and live birth rates compared to controls, likely mediated by an elevated “C-type” endometrium rate on transfer day [21]. However, the role of PRP in heterogeneous RIF populations remains debated. Another study comparing 150 RIF and/or TE patients with controls observed that while PRP increased endometrial thickness in TE cases (from 5.85 mm to 6.65 mm, p < 0.001), it did not significantly improve clinical pregnancy or live birth rates in RIF patients, emphasizing that endometrial thickness alone may not predict PRP efficacy in certain subgroups [22]. These divergent findings highlight the need for precise patient stratification and standardized protocols to optimize PRP’s therapeutic potential.

Despite these advancements, the current body of literature on PRP therapy remains limited, with significant gaps in understanding its clinical applications and mechanisms of action. Therefore, this review seeks to provide a comprehensive examination of the existing evidence surrounding PRP therapy for TE, focusing on its biological mechanisms, clinical efficacy, and the challenges it faces in practical implementation. By analyzing the available literature, we aim to furnish valuable insights for clinicians and researchers exploring this innovative therapeutic approach.

Methodology

Literature search strategy

To comprehensively evaluate the current evidence surrounding platelet-rich plasma (PRP) therapy for TE, we conducted an extensive literature search. We employed a combination of keywords, including “platelet-rich plasma,” “thin endometrium,” “IVF-ET,” “endometrial receptivity,” “repeated implantation failure,” and “assisted reproduction.” Synonyms and variations of these terms were also incorporated to maximize search yield. The searches were performed across multiple electronic databases, including PubMed, Embase, Web of Science, and the Cochrane Library. In addition, grey literature and conference proceedings were reviewed to ensure comprehensive coverage of the topic.

Eligibility criteria

Clear inclusion and exclusion criteria were established to ensure the relevance and quality of the selected studies:

Inclusion criteria: Studies examining the effect of PRP on TE within the context of IVF-ET or other fertility treatments were included. This included randomized controlled trials (RCTs), cohort studies, case–control studies, and case reports that provided detailed methodologies and measurable outcomes. Articles reporting key outcomes such as endometrial thickness, clinical pregnancy rates, live birth rates, or vascular improvement in the endometrium were prioritized.

Exclusion criteria: Studies focusing on PRP applications unrelated to gynecology or endometrial health were excluded. Review articles were excluded unless used for background or reference purposes. In addition, articles lacking quantitative data or sufficient methodological details were not included.

Data extraction and quality assessment

To ensure accuracy and minimize bias, two independent reviewers extracted relevant data from the selected articles. Key variables included:

• Study design: types of studies (e.g., RCT, cohort).

• Sample size: the number of participants involved in each study.

• Participant demographics: information on age, fertility history, and baseline endometrial characteristics.

• Methods of PRP preparation: details regarding centrifugation steps, speeds, and temperatures.

• PRP application techniques: information on infusion methods, volume, and frequency of administration.

• Outcomes: primary and secondary outcomes, including endometrial thickness, implantation rates, clinical pregnancy rates, and live birth rates.

The quality of the included studies was assessed using appropriate tools: RCTs were evaluated using the Cochrane Risk of Bias tool, while non-randomized studies were assessed with the Newcastle–Ottawa Scale. Studies with low methodological rigor or significant bias were noted and included in the discussion to highlight potential limitations.

Analysis and integration

A narrative review was conducted for all included studies, summarizing key findings and highlighting trends or inconsistencies. Quantitative data on outcomes, such as endometrial thickness and pregnancy rates, were extracted and compared across studies where possible. Due to the heterogeneity of PRP preparation protocols and clinical application methods, meta-analyses were not performed. Subgroup analyses were conducted to explore differences based on PRP preparation methods, infusion techniques, and participant characteristics.

Preparation, mechanisms, and clinical applications of PRP in treating TE

Characterization and preparation of PRP

Platelet-rich plasma (PRP) is defined as a plasma component characterized by a significantly higher platelet concentration compared to baseline plasma levels. Normal plasma contains between 150,000 and 350,000 platelets per microliter, while PRP typically has a concentration of at least 1,000,000 platelets per microliter [18]. The primary function of platelets is facilitated by their secretory granules, which are classified into three types: α-granules, dense granules, and lysosomes.

• α-Granules: These granules are rich in a variety of growth factors essential for tissue healing and repair. Key growth factors stored in α-granules include platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), transforming growth factor-beta (TGF-β), epidermal growth factor (EGF), and insulin-like growth factor 1 (IGF-1). These growth factors are believed to stimulate cell growth, differentiation, migration, and the formation of new blood vessels. In addition, α-granules contain various interleukins and chemokines such as IL-1β, IL-8 (CXCL8), MIP-1α (CCL3), and MIP-2 (CXCL2), which also play roles in regulating angiogenesis and chemotaxis.

• Dense granules: These contain bioactive molecules, including serotonin, histamine, ADP, and ATP, which are involved in inflammatory responses and hemostasis.

• Lysosomes: These granules contain a variety of enzymes, such as cathepsins and phosphatases, responsible for protein and matrix degradation [23].

In addition to their biological functions, activated PRP provides a three-dimensional bioactive scaffold (fibrin gel) that facilitates cell migration and the formation of new extracellular matrices [24]. Due to these properties, PRP has found widespread application in various medical fields, including surgery [25], dermatology [26], orthopedics [27], and ophthalmology for tissue healing and regeneration [28]. Recently, PRP has been proposed as a promising alternative for treating infertility in patients with TE [19, 20, 29].

The preparation of PRP involves several critical steps to ensure its efficacy. A common method for PRP preparation[30] through two-step centrifugation is as follows:

1. Blood collection: Approximately 20 mL of venous blood is drawn from the patient’s upper arm into a syringe containing an anticoagulant solution.

2. First centrifugation: The blood is immediately centrifuged at 400× g for 10 min at a temperature of 21–24 °C, preventing platelet activation during the process.

3. Layer separation: The blood separates into three distinct layers: a top layer consisting of blood cells and platelets, a middle buffy coat layer, and a bottom layer containing red blood cells.

4. Transfer to new tube: The top two layers are carefully transferred into a new sterile tube.

5. Second centrifugation: The plasma is then re-centrifuged at 600× g for an additional 15 min at 21–24 °C.

6. PRP extraction: Finally, 1 to 1.5 mL of PRP is pipetted from the bottom of the tube after discarding the upper three-quarters of the plasma.

With activation by thrombin and calcium chloride, PRP is prepared for infusion, utilizing an intrauterine insemination or embryo transfer catheter. Overall, the understanding of PRP’s biological characteristics and its preparation methods is critical for its effective application in clinical settings, particularly in enhancing endometrial function for patients experiencing infertility related to TE.

Mechanisms of action of PRP

Platelet-rich plasma (PRP) exerts its therapeutic effects on TE through several key biological mechanisms, as evidenced by animal studies. The primary mechanisms include angiogenesis, cell proliferation, and modulation of inflammation.

Angiogenesis

Angiogenesis, the formation of new blood vessels, is critical for enhancing blood supply to the endometrium and improving its capacity to support embryo implantation. Key growth factors present in PRP, such as vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF), play significant roles in promoting angiogenesis. Animal studies have shown that PRP can induce significant increases in vascularization within the endometrial tissue. For instance, Marini et al., explored the effect of PRP in a bovine endometrial inflammation model in vitro. They found that PRP stimulated endothelial cell proliferation and upregulated the expression of VEGF, facilitating increased blood flow to the endometrium, which is crucial for preparing the tissue for embryo implantation [31].

Cell proliferation

PRP also promotes the proliferation of endometrial cells, which is essential for the regeneration of the endometrial lining. In a study by Jang et al., the effects of PRP on regeneration of damaged endometrium were investigated in female rats. The PRP-treated group exhibited significantly increased mitotic activity, hyperplasia of endometrial glands, and a notable reduction in endometrial fibrosis compared to the control group. The upregulation of proliferation markers such as Ki-67 and cytokeratin indicated that PRP enhances both cell proliferation and differentiation [32]. Moreover, the significant increase in the expression of HOXA10 and VEGF further supports the notion that PRP can improve implantation potential and enhance uterine vascularization, thereby increasing endometrial receptivity [32].

Modulation of inflammation

The ability of PRP to modulate inflammatory responses within the endometrium is another critical mechanism. Chronic inflammation can negatively affect endometrial health and impede embryo implantation. PRP has been shown to downregulate pro-inflammatory factors such as IL-1β and IL-8. In a murine model of Asherman syndrome (AS), Kim et al. confirmed that human PRP could inhibit fibrosis in the damaged endometrium by reducing the expression of fibrosis-related factors including Col1a1, TGFβ1, and Timp1. In addition, PRP treatment increased embryo implantation rates in AS mice, highlighting its potential to improve reproductive outcomes in patients with TE [33].

Summary of mechanisms

In summary, the mechanisms by which PRP enhances the treatment of TE involve the promotion of angiogenesis, stimulation of endometrial cell proliferation, and modulation of the inflammatory response. These combined effects contribute to an improved endometrial environment that supports successful embryo implantation and subsequent pregnancy.

Clinical applications of PRP in TE

The clinical applications of platelet-rich plasma (PRP) in managing TE have gained traction in recent years. Numerous studies have demonstrated the efficacy of PRP infusion into the uterine cavity, resulting in significant improvements in EMT and clinical pregnancy rates. To summarize the findings of the clinical trials investigating the effectiveness of PRP in treating TE, Table 1 outlines critical parameters, including study design, EMT values before and after treatment, and pregnancy outcomes across various study types. Notably, randomized controlled trials demonstrated significant improvements in both EMT and pregnancy rates. Moreover, clinical studies consistently report beneficial effects of PRP on endometrial thickness and positive pregnancy outcomes, reinforcing the potential efficacy of this treatment approach.

Table 1.

Clinical trials of PRP for TE

Author	Study design	Cut-off value of thin endometrium	Sample size		EMT of control group (mm)	EMT of PRP group (mm)	P value	P value
			Control	PRP				Chemical pregnancy	Clinical pregnancy	Ongoing pregnancy
Eftekhar et al. 2018 [20]	RCT	<7 mm	43	40	8.04 ± 0.27	8.67 ± 0.64	0.001	0.091	0.044	0.127
Nazari et al. 2019 [34]	Double-blind RCT	<7 mm	30	30	5.76 ± 0.97	7.21 ± 0.18	<0.001	0.031	0.048	/
Chang et al. 2019 [29]	NRCT	<7 mm	30	34	6.52 ± 0.31	7.65 ± 0.22	0.013	/	0.036	/
Author	Study design	Cut-off value of thin endometrium	Sample size		EMT of prior to intervention (mm)	EMT of post to intervention (mm)	P value	Chemical pregnancy Rate(%)	Clinical pregnancy Rate(%)	Live birth Rate(%)
Molina et al. 2018 [35]	Prospective cohort	*	19		/	>9 mm	/	10.5	/	26.3
Kim et al. 2019[36]	Prospective cohort	<7 mm	20		5.4 ± 0.8	6.0 ± 1.1	0.07	/	30.0	20.0
Chang et al. 2015 [19]	Cohort	<7 mm	5		5.9–6.6	≥7.0	/	20.0	80.0	/
Nazari et al. 2017 [37]	Cohort	<7 mm	10		4.0–6.0	7.1–7.5	/	50.0	25.0	/
Tandulwadkar et al. 2017 [38]	Cohort	<7 mm	68		Average 5	Average 7.22	<0.00001	29.4	38.2	/
Wang et al. 2018 [24]	Cohort	<7 mm	20		5.55 ± 0.71	7.82 ± 1.04	<0.0001	/	60.0	/
Agarwal et al. 2020 [39]	Cohort	<7 mm	32		/	/	/	41.6	8.3	20.8
Kusumi et al. 2020 [40]	Cohort	<7 mm	36		5.86 ± 0.95	7.13 ± 0.89	/	18.8	15.6	/

Clinical trial results

1. Eftekhar et al. (2018) conducted the first randomized controlled trial (RCT), enrolling 84 women with TE (EMT < 7 mm) undergoing frozen embryo transfer (FET). The study found that PRP infusion resulted in a significant increase in endometrial thickness, with the PRP group achieving an EMT of 8.67 ± 0.64 mm compared to 8.04 ± 0.27 mm in the control group. The clinical pregnancy rate was notably higher in the PRP group at 44% [20].

2. Nazari et al. (2019) performed a double-blind RCT involving 60 women with TE. The results indicated that PRP infusion on days 11–12 and 13–14 of the menstrual cycle significantly improved EMT, reaching 7.21 ± 0.18 mm compared to 5.76 ± 0.97 mm in the control group. The clinical pregnancy rate also showed a statistically significant difference, with P = 0.048 [34].

3. Chang et al. (2019) reported on a non-randomized clinical trial (NRCT) that included 30 women with TE. Following PRP infusion, the EMT improved significantly to 7.65 ± 0.22 mm from a baseline of 6.52 ± 0.31 mm, with notable clinical pregnancy outcomes [29].

4. Kim et al. (2019) administered PRP infusions to 20 women with a history of two or more failed IVF cycles and refractory TE. The average EMT growth was 0.6 mm post-PRP treatment, and the implantation rate was 12.7%, with a clinical pregnancy rate of 30% in the treatment cycle compared to previous cycles [36].

5. Tandulwadkar et al. (2017) included 68 women experiencing frozen embryo transfer cycles over a period of 8 months with a suboptimal endometrial pattern. After receiving intrauterine PRP infusion, 47 patients showed improved vascular patterns, confirming the effectiveness of PRP in enhancing vascular distribution [38].

The data presented in Table 1 clearly indicate that PRP therapy not only improves endometrial thickness but also correlates with higher clinical pregnancy rates in patients suffering from TE. These findings support the hypothesis that PRP is a viable therapeutic option for enhancing reproductive outcomes, particularly in women who have previously experienced implantation failures or suboptimal endometrial conditions.

Variability in PRP preparation methods

In response to the variability in PRP preparation methods highlighted in recent discussions, we have included detailed PRP preparation methods for each study discussed above in the narrative accompanying Table 2. The protocols used for PRP preparation and infusion vary considerably across studies, as outlined in Table 2. Differences were observed in the number of centrifugation steps, centrifugation speeds and durations, the volume of blood collected, the amount of anticoagulant used, and the final volume of PRP infused. These methodological inconsistencies not only hinder direct comparison between studies but also pose significant challenges to reproducibility and clinical translation. Furthermore, the lack of standardized preparation methods makes it difficult to determine the most effective protocol for thin endometrium. This highlights the urgent need for unified guidelines to improve consistency across research and clinical practice. Without protocol harmonization and well-designed studies, the clinical value of PRP remains uncertain.

Table 2.

Variability in PRP preparation methods across studies

Study	Number of centrifugation steps	Speed and times	Collected volume of blood (ml)	Volume of ACD-A mixed (ml)	Volume of PRP obtained (ml)	Volume of PRP infusion (ml)
Chang et al. 2015[19]	2	200 g 10 min 500 g 10 min	15	5	0.5–1	0.5–1
Nazari et al. 2017/2019[34, 37]	2	1200 rpm 12 min 3300 rpm 7 min	17.5	2.5	/	0.5
Tandulwadkar et al. 2017 [38]	2	200 g 15 min 600 g 6 min	10	/	0.5–0.8	0.5–0.8
Eftekhar et al. 2018 [20]	2	1600 g 10 min 3500 g 5 min	8.5	1.5	1.5	0.5–1
Kim et al. 2019 [36]	1	1017 g 3 min	18	2	0.7–1	0.7–1
Agarwal et al. 2020 [39]	1	3600 g 6 min *shake upside down 20 times for homogenization	8	/	/	4
Mehrafza, et al. 2019 [5]	/	/	8.5	1.5	1.5	1

ACD-A acid citrate dextrose solution A

Future directions in PRP research

Despite the promising findings regarding the efficacy of platelet-rich plasma (PRP) therapy for TE, several critical challenges and gaps in research must be addressed to optimize its clinical application. Future research directions should focus on the following key areas:

Standardization of PRP protocols

One of the primary challenges in the widespread adoption of PRP therapy is the lack of standardized protocols for its preparation and administration. Variability in the methods used for blood collection, centrifugation speeds, and activation techniques can lead to significant differences in the composition and efficacy of the PRP produced. Establishing standardized guidelines will be crucial for ensuring consistency in PRP quality and therapeutic outcomes across different clinical settings. It is recommended that future studies prioritize the development of universally accepted protocols for PRP preparation.

Variability in patient response

Individual variability in response to PRP therapy presents another significant challenge. Factors such as age, underlying reproductive health conditions, and hormonal profiles may influence the effectiveness of PRP treatment. To address this issue, future studies should focus on identifying patient characteristics that predict responses to PRP therapy. Such insights would enable clinicians to tailor treatment approaches, potentially improving outcomes for specific patient populations.

Long-term safety and efficacy

While short-term studies indicate that PRP can improve endometrial thickness and pregnancy rates, there is a paucity of data on the long-term effects of PRP therapy on reproductive outcomes and maternal health. Longitudinal studies are necessary to evaluate the safety and efficacy of PRP over extended periods, including potential impacts on subsequent pregnancies and neonatal health. This information is vital for building a robust evidence base to support the clinical use of PRP.

Exploration of combination therapies

Combining PRP with other therapeutic modalities may enhance its effectiveness in treating TE. For instance, integrating PRP with stem cell therapy or hormonal treatments could synergistically promote endometrial regeneration. Research exploring these combination therapies could lead to more effective treatment protocols for women with TE. Studies that investigate the interactions between PRP and other regenerative approaches are warranted.

Mechanistic insights

Further investigation into the precise mechanisms by which PRP exerts its effects on the endometrium is essential for improving its clinical application. Animal models and in vitro studies should be employed to elucidate the cellular and molecular pathways involved in PRP’s action, enhancing our understanding of its regenerative properties.

Addressing research gaps

Lastly, it is essential to address the existing gaps in the literature regarding PRP therapy for TE. Future research should aim to conduct larger, multi-center trials with diverse populations to validate the findings from smaller studies. This will enhance the generalizability of results and provide a clearer picture of PRP’s role in clinical practice. In addition, we suggest that future studies adopt a standardized protocol comprising several key components: first, clearly defined inclusion criteria for patients with thin endometrium (EMT < 7 mm) to ensure consistency across studies; second, a consistent PRP preparation method utilizing a two-step centrifugation technique with reported platelet concentrations to facilitate comparability of results; third, standardized timing for intrauterine infusion aligned within the proliferative phase of the menstrual cycle to optimize therapeutic effects; and finally, comprehensive outcome measures including changes in endometrial thickness, implantation rates, clinical pregnancy rates, and live birth rates. By establishing such a protocol, we believe that a reliable framework can be created for comparing results across studies and enhancing the clinical application of PRP therapy.

In conclusion, while PRP therapy holds significant promise for the treatment of TE, addressing these challenges through comprehensive research efforts will be crucial for establishing its efficacy and safety as a standard therapeutic option in reproductive medicine.

Conclusion

Platelet-rich plasma (PRP) therapy presents a novel and promising approach for the treatment of TE, a condition that significantly impacts the success rates of in vitro fertilization (IVF) and embryo transfer (ET). The current body of evidence suggests that PRP can effectively enhance endometrial thickness and improve pregnancy outcomes in women diagnosed with TE. Clinical trials have demonstrated that PRP infusion results in significant improvements in EMT and correlates with higher clinical pregnancy rates, reinforcing its role as a viable therapeutic option for patients experiencing infertility related to TE. However, despite these encouraging findings, several challenges remain in optimizing the clinical application of PRP therapy. The lack of standardized protocols for PRP preparation and administration, variability in patient responses, and the limited availability of long-term safety and efficacy data hinder its broader application. Addressing these challenges through rigorous research and the establishment of standardized guidelines will be crucial for maximizing the benefits of PRP in clinical practice. Furthermore, future research is essential to elucidate the precise mechanisms by which PRP exerts its effects on the endometrium, as well as to explore combination therapies that may enhance its effectiveness. Longitudinal studies evaluating the long-term impact of PRP therapy on reproductive health are also warranted to provide a comprehensive understanding of its safety and efficacy.

In summary, PRP therapy holds significant potential to improve reproductive outcomes for women with TE, offering hope where traditional treatment options have proven inadequate. Continued investigation and refinement of PRP therapy could solidify its role as a key therapeutic strategy in reproductive medicine.

Author contributions

Yuxin Yang contributed to the conceptualization and design of the study, conducted the literature review, and drafted the manuscript. Xiaoran Zhang assisted with data collection and analysis, and contributed to the drafting of the results and discussion sections. Yingying Zhang provided critical revisions and contributed to the final manuscript preparation. All authors read and approved the final manuscript.

Funding

No financial, professional, or personal relationships exist that could influence the findings presented.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Competing interests

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported in this study.