Abstract 3949: High Glucose Impairs Electrophysiological Function of Human Cardiac Progenitor Cells: Roles of microRNAs
Development of diabetic cardiomyopathy is associated with significant morbidity and mortality, and characterized by electrical remodeling and apoptosis. microRNAs are novel biomarkers, modulators and therapeutic targets for heart disease. The microRNA expression and the link between microRNA, apoptosis and potassium (K+) current have not been investigated in cardiac progenitor cells (CPCs). Western blot showed that CPCs isolated from a health human heart expressed the embryonic stem cell marker Oct 4. They were also positive in expression of CD90, CD29 and CD105 as assessed by flow cytometry. They expressed the mRNAs for c-kit and Sca-1. Exposure to high glucose (25 mM) dose-dependently increased both miR-1 (2.8 ± 0.3 fold increase vs control, p<0.05) and miR-133 expression (2.6 ± 0.5 fold increase vs control, p<0.05) at 16 h determined by the mirVana qRT-PCR miRNA detection assay. Glucose (0 – 25 mM) did not alter mitochondrial membrane potential (early-stage of apoptosis) assessed by Rh123, did not decrease cell numbers (0 – 48 h) as determined by Cell Viability Assay, and did not induce apoptosis (0 – 48 h) assessed by Death ELISA. Whereas glucose did not alter growth factor (IGF-1 and VEGFR2) gene expression, glucose dose-dependently decreased potassium channel gene expression including HERG, KCNE1 and KCNQ1. Using prediction algorithms, HERG, KCNE1 and KCNQ1 genes were identified as the targets of both miR-1 and miR-133. Using whole-cell patch clamp recording, we found that glucose (25 mM) decreased slow delayed rectifier K+ current (Iks) (84% ± 6% reduction compared to control) encoding by KCNQ1 and KCNE1 gene, whereas we did not detect rapid delayed rectifier K+ current (Ikr) encoding by HERG gene. Consistent with the effects of high glucose on specific K+ current, KCNE1 was expressed in CPCs shown by immunofluorescence. Thus, high glucose exposure increases expression of miR-1 and miR-133, and decreases K+ current in human myoblasts, indicating that down-regulation of miR-1 and miR-133 and up-regulation of K+ current may be a useful strategy to prevent diabetic cardiomyopathy.
This research has received full or partial funding support from the American Heart Association, AHA South Central Affiliate (Arkansas, New Mexico, Oklahoma & Texas).