Abstract 19036: Transgenic Mouse with Overexpression Hypoxamir-210: Implications on Infarct Size Attenuation and Preservation of Heart Function

Background. Hypoxamir-210 (miR-210) is a universal responder to activation of HIF-1 signaling and plays a significant role in cell survival under ischemic stress. To assess the impact of constitutive over expression of hypoxamir-210 on infarct size expansion and preservation of cardiac function, we report the development of first transgenic (TG) mouse model with miR-210 overexpression ( 210 TG). Methods and Results. miR-210 transgenic mouse was generated at the University of Cincinnati transgenic core using the C57BL/6 mouse strain. Briefly precursor miR-210 along with H1 promoter (HmiR0167-MR01 vector from Genocopiea) was amplified and cloned into pShuttle vector (Stratagene) using restriction enzymes Not1 and Sal1. Amplified vector was digested, purified and used for microinjection into the pronuclei of single cell embryos derived from superovulated C57BL/6 females. The surviving embryos were implanted into foster female mice. TG mice were identified genotyping of the tail genomic DNA by PCR. As compared to control littermates (NTG), 210 TG had significantly higher miR-210 expression in different tissues and organs including the heart and the bone marrow. Molecular studies showed altered expression of miR-210 putative traget Dffb in 210 TG animals. Age and sex-matched mouse model of permanent LAD coronary artery ligation was developed in 210 TG(n=12 animals/group) using NTGas controls. Animals were harvested on day 7 (short term) and 28 (long term) after LAD ligation. Echocardiography performed prior to euthanasia showed that cardiac function was significantly preserved in 210 TG as compared to NTG as indicated by LVEF (45.2±1.06 vs 38.9±1 p <0.001) and LVFS (18.3±1 vs 15±1), Histochemical studies showed preserved myocardial architecture and attenuated infarct size in 210 TG ( p <0.05 vs NTG). TUNEL combined with fluorescence immunostaining for cardiac troponin-1, smooth muscle actin and CD31 showed significantly reduced TUNEL positivity of cardiomyocytes, smooth muscle and endothelial cells in 210 TG heart at day 7 ( p <0.05 vs NTG hearts). Conclusions. Constitutive overexpression of hypoxamir-210 rescued global cardiac function after myocardial infarction by inhibition of cardiomyocyte apoptosis to attenuate infarct size in the heart.