Abstract P041: Inhibition of MicroRNA-221 by Estradiol Contributes to its Differential Effects on Smooth Muscle Cell Growth and Endothelial Cell Capillary Formation

Abstract

MicroRNAs play a key role in vascular remodeling associated with cardiovascular disease. MiR-221 actively contributes to injury-induced neointima formation by inhibiting endothelial cell (EC) growth and promoting smooth muscle cell (SMC) growth. Since estradiol (E2) prevents neointimal thickening, we hypothesize that E2 mediates its vasoprotective actions by downregulating miR-221 expression and abrogating its effects on SMC and EC growth. RT-qPCR confirmed that both Human Umbilical Vein ECs (HUVECs) and Human Coronary Artery SMCs (HCASMCs) produce miR-221. Treatment of HCASMCs with PDGF-BB (20ng/ml) induced miR-221 levels from 100±8% to 189±9% (p<.05) and treatment with E2 (100nM) inhibited this to 126±4% (p<.05 vs PDGF). PDGF-BB stimulated DNA synthesis (BrdU incorporation), CyclinD1 expression (Western Blot) and migration (Scratch assay) in HCASMCs and these effects were mimicked by miR-221 (25nM) overexpression; and abrogated in HCASMCs transfected with miR-221 antimiR (25nM). E2 inhibited PDGF-induced HCASMC numbers by 30±4% and these effects were reversed by miR-221 (p<0.05). Inhibitory effects of E2 on PDGF-induced miR-221 production in HCASMCs were mimicked by estrogen receptor (ER) α agonist PPT, but not by ERβ and GPER agonists; and blocked by ERα antagonist MPP, suggesting these effects are ERα mediated. In contrast to SMCs, transfection of HUVECs with miR-221 mimic inhibited capillary formation and wound healing by 39±8% and 27±6%, respectively (p<.05). Neutralization of miR-221 with antimiR induced capillary formation and wound closure by 26±3 % and 51±15%, respectively (p<.05). E2 (10nM) inhibited miR-221 levels in HUVECs from 100 to 73±6% (p<.05). Moreover, transfection of HUVECs with miR-221 mimic inhibited E2-induced capillary formation (from137±9% to 85±13%; p<.05 vs E2) and wound closure (from 125±5% to 82±12%; p<.05 vs E2). Our findings provide the first evidence that E2 inhibits miR-221 production in HCASMCs and HUVECs and these effects contribute to its antimitogenic effects on HCASMCs and capillary promoting effects in HUVECs. Modulation of miR-221 by E2 represents a novel mechanism by which E2 may mediate its differential effects on SMC and EC growth, and confer vascular protection.