Abstract
Background:
Normal development of the human placenta, referred to as villous tree maturation, entails formation of vasculo-syncytial membranes. These structures develop by the approximation of syncytiotrophoblasts with villous capillary endothelium and constitute the most efficient sites of gaseous exchange in the placenta. Defective maturation of villous tree can lead to deficient vasculo-syncytial membranes, implicated in high incidence of hypoxic complications. Hypoxia, in turn, can stimulate production of erythropoietin whereby an increased fetal plasma or amniotic fluid concentrations of this hormone reflects fetal hypoxemia. The current study was undertaken to determine whether delayed villous maturation is associated with changes in amniotic fluid erythropoietin concentrations.
Methods:
Placental histologic examination was performed using hematoxylin and eosin. Subsequent to histologic assessment of delayed villous maturation, the diagnosis was confirmed with CD15 immunohistochemistry. The controls (n=61) were pregnancies without villous maturation abnormalities and cases (n=5) were pregnancies with delayed villous maturation. Amniotic fluid erythropoietin concentrations were measured using a specific immunoassay.
Results:
Concentrations of erythropoietin in amniotic fluid 1) of controls were less than the limit of detection and 2) of cases with delayed villous maturation were significantly higher than controls (p-value = 0.048).
Conclusion:
Delayed villous maturation is associated with higher concentrations of amniotic fluid erythropoietin.
Keywords: CD-15, human placental maturation disorders, disorders of villous maturation, vasculo-syncytial membranes, erythropoietin, amniotic fluid
Introduction
Vasculo-syncytial membranes are unique structures of the human placenta [1], which include the apposition of the trophoblasts (synctio- and cyto-) with the fetal chorionic villous endothelium (Figure 1). These structures are essential for the normal oxygen and nutrient exchange between the maternal and fetal circulations. The formation of the vasculo-syncytial membranes is part of the normal development of the human placenta and is specifically referred to as villous tree maturation. Defective villous tree maturation can lead to deficient vasculo-syncytial membranes that, in turn, have been implicated in nutritional disorders such as fetal growth restriction, respiratory failure of the placenta or fetal hypoxia. We previously reported that 20.7% of placentas of structurally normal cases of fetal death have delayed villous maturation, a condition in which there is insufficient development of the terminal villi, reduced vascularization of the chorionic villi and deficiency of vasculo-syncytial membranes [2].
Figure 1. Term placentas: normal histology (A–C) and delayed villous maturation (D–F).
Normal term placenta: (A) Normal chorionic plate with subchorionic villi that are mature and appropriate for gestational age. (B) Terminal villi with vasculosyncytial membranes (arrows); (C) Chorionic villous capillary endothelium negative for CD-15 staining. Delayed villous maturation in term placenta. (D) Chorionic villi exhibiting monotonous immature villous population recapitulating the histology of early pregnancy with substantially more villous stroma, more centralized vessels, and fewer and less well-formed vasculosyncytial membranes than that of normal pregnancy for gestational age; (E and F) CD-15-positive immature endothelium considered as a diagnostic marker of persisting villousimmaturity and chronic placental dysfunction. (E) 100× and (F) 200× magnification; brown stain CD-15 positive villous endothelium.
Chronic fetal hypoxemia can stimulate production and secretion of erythropoietin [3]. Since erythropoietin does not cross the placenta and is not stored, increased fetal plasma or amniotic fluid concentrations of this hormone is considered to reflect chronic fetal hypoxemia. The current study was designed to determine whether delayed villous maturation is associated with changes in amniotic fluid erythropoietin concentrations.
Subjects and Methods
This was a retrospective observational study of singleton pregnant women without pre-eclampsia, gestational hypertension, abruption or gestational diabetes who a) underwent an elective cesarean section at 37–42 weeks of gestation; b) had amniotic fluid retrieved at the time of cesarean delivery; c) had a live-birth newborn; d) had a placental histologic examination at Hutzel Women’s Hospital, Detroit, MI, USA; and e) provided written informed consent and agreed for such information to be used for research purposes. Controls (n=61) were pregnancies without villous maturation abnormalities and cases (n=5) were pregnancies with delayed villous maturation. The collection of data was approved by the Human Investigation Committee of Wayne State University.
Placental histologic examination was performed using hematoxylin and eosin and CD15 immunohistochemistry by a perinatal pathologist (SJ) blinded to clinical information, except gestational age at delivery. Histologic assessment of delayed villous maturation was made by the presence of a monotonous immature villous population (at least 10 such villi), constituting up to at least one-third of the sampled villi, with a) substantially more villous stroma; b) more centralized vessels; c) fewer and less well-formed vasculo-syncytial membranes than that of normal pregnancy for gestational age; d) recapitulation of the histology of early pregnancy; [4] and e) CD 15 positivity [5]. Accelerated villous maturation cannot be ascertained in placentas delivered at term [4].
Amniotic fluid erythropoietin concentrations were measured using a commercially available specific immunoassay (American Laboratory Products Company [ALPCO], Salem, NH, USA). The sensitivity of the assay was 1.8 mIU/ml, and coefficients of variation for intra- and inter-assays were 6.1% and 9.2%, respectively. For statistical analysis, a result that was below the limit of detection was replaced by 99% of the minimum observed value.
Results
1) Concentrations of erythropoietin in amniotic fluid was measurable only in 41% (25/61) of controls (25th percentile and 50th percentile of amniotic fluid erythropoietin were less than the limit of detection; 75th percentile of amniotic fluid erythropoietin = 4.2 mIU/ml). 2) Patients who had delayed villous maturation (n=5) had a significantly higher concentration of amniotic fluid erythropoietin than those in the control group (n=61) (Wilcoxon rank sum test p-value = 0.048) (Figure 2).
Figure 2. Concentrations of erythropoietin in the amniotic fluid.
The dashed line indicates 99% of the minimum observed value of the erythropoietin in the amniotic fluid (1.3 mIU/mL). The median concentration of erythropoietin in controls was below the level of detection. Concentrations of erythropoietin in the amniotic fluid was measurable in 80% (4/5) of cases (25th percentile = 3.0 mIU/mL; 50th percentile = 3.5 mIU/mL; 75th percentile = 11.9 mIU/mL). Cases had a significantly higher concentration of amniotic fluid erythropoietin than those in the control group (P = 0.048).
Conclusion
This study is the first to demonstrate that delayed villous maturation is associated with higher concentrations of amniotic fluid erythropoietin than the absence of these lesions. This observation suggests that the structural abnormalities in the vasculo-syncytial membranes may lead to impaired exchange and fetal hypoxemia in a fraction of the cases.
Acknowledgments
Research funding: This research was supported, in part, by the Perinatology Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, U.S. Department of Health and Human Services (NICHD/NIH/DHHS); and, in part, with Federal funds from NICHD/NIH/DHHS under Contract No. HHSN275201300006C.
List of Abbreviations:
- ALPCO
American Laboratory Products Company
Footnotes
Employment or leadership: Dr. Romero has contributed to this work as part of his official duties as an employee of the United States Federal Government.
Honorarium: None declared.
Competing interests: The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.
References
- 1.Benirschke KKP, Baergen RN. Pathology of the Human Placenta, 5th Edition New York: Springer-Verlag New York; 2006. XX, 1050 p. [Google Scholar]
- 2.Pacora P, Romero R, Jaiman S, Erez O, Bhatti G, Panaitescu B, et al. Mechanisms of death in structurally normal stillbirths. J Perinat Med. 2019;47:222–40. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Teramo KA, Widness JA. Increased fetal plasma and amniotic fluid erythropoietin concentrations: markers of intrauterine hypoxia. Neonatology. 2009;95:105–16. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Khong TY, Mooney EE, Ariel I, Balmus NC, Boyd TK, Brundler MA, et al. Sampling and Definitions of Placental Lesions: Amsterdam Placental Workshop Group Consensus Statement. Arch Pathol Lab Med. 2016;140:698–713. [DOI] [PubMed] [Google Scholar]
- 5.Seidmann L, Suhan T, Kamyshanskiy Y, Nevmerzhitskaya A, Gerein V, Kirkpatrick CJ. CD15 - a new marker of pathological villous immaturity of the term placenta. Placenta. 2014;35:925–31. [DOI] [PubMed] [Google Scholar]