Downregulated expression of microRNAs associated with cardiac hypertrophy and fibrosis in physiological pregnancy and the association with echocardiographically-evaluated myocardial function

The aim of the present study was to analyze the profiles of cardiac microRNAs (miRNAs/miRs) in healthy pregnant women and non-pregnant controls. A total of 61 healthy women >18 years of age with singleton pregnancies in the third trimester were compared with 19 non-pregnant controls. Specifically, expression of miRNAs associated with cardiac hypertrophy (miR-1, miR-17-5, miR-22, miR-34a, miR-124, miR-133a, miR-195, miR-199a-3p, miR-199b, miR-210, miR-222 and miR-1249) and miRNAs associated with cardiac hypertrophy and fibrosis (miR-15b, miR-21, miR-26a, miR-29-a, miR-29c, miR-30c, miR-101, miR-146a, miR-191, miR-208a-5p and miR-328) were analyzed and compared with echocardiographic examination results. Both groups had similar cardiac miRNA expression profiles, but differed in quantitative evaluation. Women in the third trimester of physiological pregnancy exhibited downregulation of certain profibrotic miRNAs (miR-21, miR-30c and miR-328), decreased expression of a hypertrophic and antimetabolic miRNAs (miR-146a), downregulation of an antifibrotic miRNA (miR-222), and downregulation of a hypertrophic miRNA (miR-195). In pregnant women, the indices of systolic function were associated with miR-195 expression, and an interplay between miR-17-5p and diastolic function was observed. While the profiles of cardiac miRNAs expressed in healthy pregnant women and healthy non-pregnant controls were similar, these two groups differed in terms of expression of specific miRNAs. In the third trimester of physiological pregnancy, a downregulation of miR-17-5p, miR-21, miR-30c, miR-146a, miR-195, miR-222 and miR-328 was observed. The differences in the association between echocardiographic indices with miRNAs in pregnant and non-pregnant women suggest that miRNAs regulate both the structure and function of the pregnant heart, influencing cardiac muscle thickness as well as systolic and diastolic function.