Cellular localization of placenta-specific human endogenous retrovirus (HERV) transcripts and their possible implication in pregnancy-induced hypertension.
We previously investigated tissue specificity and temporal changes in expression of five human endogenous retroviruses (HERVs), including syncytin/ERVWE1 and syncytin 2. In the current study, we examined the cellular localization and quantified the transcripts of five HERVs, syncytin, syncytin 2, HERV-H7/F(XA34), HERV-Fb1, and HERV-HML6-c14, in order to elucidate their physiological and etiological roles in the placenta and in pregnancy-induced hypertension (PIH), respectively. In situ hybridization revealed trophoblast-specific transcription of all five HERVs. Consistent with a previous immunohistochemical analysis, syncytin 2 transcripts were detected only in cytotrophoblasts. All the HERVs except HERV-HML6-c14 (HML6-c14) were predominantly localized in the cytoplasm of syncytiotrophoblasts and/or cytotrophoblasts. Quantitative analysis showed that transcriptional levels of these four HERVs were lower in placentas obtained from pregnant women with PIH (n=22) than in those from normotensive pregnant women (n=87) and that the differences were statistically significant (p=0.001, 0.01, <0.001, and 0.04 for syncytin, syncytin 2, HERV-H7/F(XA34), and HERV-Fb1, respectively). In contrast to the other HERVs, HML6-c14 transcripts localized to the nucleus and the average transcriptional level of HML6-c14 was higher in PIH placentas than in control placentas from normotensive pregnant women, although the differences did not reach significance (p=0.19). These results suggest that placenta-specific HERVs may have some function in the human placenta and that their reduced expression in PIH placentas is not merely a secondary effect derived from the pathology of PIH placentas.
D000328:Adult; D016022:Case-Control Studies; D020077:Endogenous Retroviruses / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005865:Gestational Age; D006801:Humans; D046110:Hypertension, Pregnancy-Induced / Q000209:etiology* / Q000235:genetics / Q000378:metabolism; D007231:Infant, Newborn; D008297:Male; D009928:Organ Specificity; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism*; D047929:Term Birth / Q000378:metabolism; D014018:Tissue Distribution
D012333:RNA, Messenger