Introduction: Fetal growth restriction (FGR) is associated to immediate and long-term endothelial dysfunction that would result from an altered eNOS expression mediated by epigenetic mechanisms. Evidence show that DNA methylation and histone modifications participate in this process, however, no studies have determined the role of hypoxia inducible microRNAs (e.g. miR-21) in eNOS programming, as well as its effects on genes involved in the NO-dependent vasodilator pathway. Here we propose that miR-21 is programmed by FGR and contributes to the hypoxia regulation of NO-related genes in the umbilical artery endothelium.
Method: Levels of miR-21, as well as, eNOS, DDAH1, Nrf2 and ARG2 mRNA were determined in primary cultures of human umbilical artery endothelial cells (HUAEC) from FGR and control pregnancies, and control HUAEC exposed to hypoxia (1% O2, 0 - 48 h) by qPCR. Intrauterine miR-21 programming was determined by studying the DNA methylation pattern of MIR21 promoter region by pyrosequencing. Control HUAEC were transfected with a miR-21 mimic to determine the effects on eNOS and DDAH1 transcript levels and half-life.
Results: FGR-HUAEC showed higher levels of eNOS, but decrease levels of DDAH1, Nrf2 and miR-21. Decreased levels of miR-21 were associated with increased levels of DNA methylation in MIR21 promoter in FGR-HUAEC. Control HUAEC exposed to hypoxia showed a transient increase in eNOS, DDAH1 with a parallel decrease in miR-21. Overexpression of miR-21 led to a decrease in eNOS and DDAH1 levels and half-life, and block their induction by hypoxia.
Conclusions: These results suggest that FGR programs a hypoxia-related miRNA that contributes to the regulation of NO pathway; the negative regulation of pro-NO enzymes by miR21 suggests that the decreased miR-21 levels might represent a compensatory mechanism in response to the altered vascular function in the FGR. The specific interaction of eNOS transcript with miR21 are under study.
Funding Fondecyt1181341