Expression of severe acute respiratory syndrome coronavirus 2 cell entry genes, angiotensin-converting enzyme 2 and transmembrane protease serine 2, in the placenta across gestation and at the maternal-fetal interface in pregnancies complicated by preterm birth or preeclampsia

Abstract

Background: Although there is some evidence that severe acute respiratory syndrome coronavirus 2 can invade the human placenta, limited data exist on the gestational age-dependent expression profile of the severe acute respiratory syndrome coronavirus 2 cell entry mediators, angiotensin-converting enzyme 2 and transmembrane protease serine 2, at the human maternal-fetal interface. There is also no information as to whether the expression of these mediators is altered in pregnancies complicated by preeclampsia or preterm birth. This is important because the expression of decidual and placental angiotensin-converting enzyme 2 and transmembrane protease serine 2 across gestation may affect the susceptibility of pregnancies to vertical transmission of severe acute respiratory syndrome coronavirus 2.

Objective: This study aimed to investigate the expression pattern of specific severe acute respiratory syndrome coronavirus 2 cell entry genes, angiotensin-converting enzyme 2 and transmembrane protease serine 2, in the placenta across human pregnancy and in paired samples of decidua and placenta in pregnancies complicated by preterm birth or preeclampsia compared with those in term uncomplicated pregnancies.

Study design: In this study, 2 separate cohorts of patients, totaling 87 pregnancies, were included. The first cohort was composed of placentae from first- (7-9 weeks), second- (16-18 weeks), and third-trimester preterm (26-31 weeks) and third-trimester term (38-41 weeks) pregnancies (n=5/group), whereas the second independent cohort included matched decidua and placentae from pregnancies from term uncomplicated pregnancies (37-41 weeks' gestation; n=14) and pregnancies complicated by preterm birth (26-37 weeks' gestation; n=11) or preeclampsia (25-37 weeks' gestation; n=42). Samples were subjected to quantitative polymerase chain reaction and next-generation sequencing or RNA sequencing for next-generation RNA sequencing for angiotensin-converting enzyme 2 and transmembrane protease serine 2 mRNA expression quantification, respectively.

Results: In the first cohort, angiotensin-converting enzyme 2 and transmembrane protease serine 2, exhibited a gestational age-dependent expression profile, that is, angiotensin-converting enzyme 2 and transmembrane protease serine 2 mRNA was higher (P<.05) in the first-trimester placenta than in second-trimester, preterm birth, and term placentae (P<.05) and exhibited a negative correlation with gestational age (P<.05). In the second cohort, RNA sequencing demonstrated very low or undetectable expression levels of angiotensin-converting enzyme 2 in preterm birth, preeclampsia, and term decidua and in placentae from late gestation. In contrast, transmembrane protease serine 2 was expressed in both decidual and placental samples but did not change in pregnancies complicated by either preterm birth or preeclampsia.

Conclusion: The increased expression of these severe acute respiratory syndrome coronavirus 2 cell entry-associated genes in the placenta in the first trimester of pregnancy compared with those in later stages of pregnancy suggests the possibility of differential susceptibility to placental entry to severe acute respiratory syndrome coronavirus 2 across pregnancy. Even though there is some evidence of increased rates of preterm birth associated with severe acute respiratory syndrome coronavirus 2 infection, we found no increase in mRNA expression of angiotensin-converting enzyme 2 or transmembrane protease serine 2 at the maternal-fetal interface.

Keywords: angiotensin-converting enzyme 2; coronavirus disease 2019; decidua; gestation age–dependent gene expression; placenta; preeclampsia; preterm birth; severe acute respiratory syndrome coronavirus 2; term pregnancies.

Figure 1

The placental expression of ACE2 and TMPRSS2 is gestational age dependent mRNA levels of ACE2 (A) and TMPRSS2 (C) in the first- (7–9 weeks), second- (16–18 weeks), third-trimester spontaneous onset PTB (26–35 weeks) and third-trimester term (38–41 weeks) pregnancies (n=5/group). A and C, ANOVA followed by Tukey’s multiple comparisons test. B and D, Spearman correlation analysis. Data are presented as mean±SD. Different letters if P<.05. ACE2, angiotensin-converting enzyme 2; ANOVA, analysis of variance; PTB, preterm birth; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; SD, standard deviation; SDHA, succinate-ubiquinone oxidoreductase; TMPRSS2, transmembrane protease serine 2; TOP1, topoisomerase 1. Bloise et al. Angiotensin-converting enzyme 2 and transmembrane protease serine 2 in the maternal-fetal interface across pregnancy. Am J Obstet Gynecol 2021.

Figure 2

Decidual and placental ACE2 and TMPRSS2 expression in preeclampsia, preterm, and term pregnancies The values of TPM were calculated by the number of mapped raw reads, the transcript’s length and sequencing depth. The TPM normalized reads count for ACE2 and TMPRSS2 was obtained from decidual (A) and placental (B) samples in preeclampsia (n=42), preterm (n=11), and term (n=14) pregnancies. Density plots (C and D) were constructed to examine the probability of available reads numbers. Histograms were embedded in the graphs to visualize the distribution of read counts. ACE2, angiotensin-converting enzyme 2; TPM, transcripts per million; TMPRSS2, transmembrane protease serine 2. Bloise et al. Angiotensin-converting enzyme 2 and transmembrane protease serine 2 in the maternal-fetal interface across pregnancy. Am J Obstet Gynecol 2021.

Figure 3

Expression of TMPRSS2 in the human decidua and placenta The expression profile of TMPRSS2 was compared on the basis of Deseq2 normalized RNA reads. Decidua- (A) and placenta-specific (B) expressions were calculated by Kruskal-Wallis test, followed by Wilcoxon rank-sum test. P values were listed when significant differences were detected at P<.05: preeclampsia (n=42), preterm (n=11), and term (n=14), respectively. TMPRSS2, transmembrane protease serine 2. Bloise et al. Angiotensin-converting enzyme 2 and transmembrane protease serine 2 in the maternal-fetal interface across pregnancy. Am J Obstet Gynecol 2021.