Abstract 11165: Activation of IGF-1/PI3/GSK-3ß Signaling Prevents High Glucose-induced Transition of Human Cardiac Progenitor Cells Into Fibroblasts
Background: Cardiac progenitor cells (CPC) can repair the myocardium injured by infarction. However, CPC may not function well under the diabetic condition. Exposure to high levels of glucose (HG) may induce cardiomyopathy and fibrosis in patients with diabetes. Signaling transduction via transforming growth factor-β (TGF-β) and its responding transcription factor, Snail, (TGF-β/Snail) is involved in fibrosis. Insulin-like growth factor (IGF-1) decreases TGF-β expression. Thus, it is important to investigate whether IGF-1 activation of the PI3 kinase/glycogen synthase kinase 3β (GSK-3β) signaling pathway prevents HG-induced transition of CPC to fibroblasts.
Methods and Results: Human CPC were isolated and cultured from normal human heart tissue. They were exposed to different concentrations of glucose. Compared to CPCs incubated in normal glucose (NG) (5 mM), CPC incubated in HG (25 mM) showed increased TGF-β mRNA levels (3.1 ± 0.5 fold, p<0.05, n=4) and Snail (2.9 ± 0.4 fold, p<0.05, n=4) in a dose- and time-dependent manner. HG exposure also decreased cardiac transcription factors (GATA4 and Nkx2.5) mRNA expression as assessed by qRT-PCR assay. Mannitol (25 mM, osmotic control) had no such effect. ELISA showed that HG increased TGF-β protein expression in CPCs. IGF-1 (30 ng/ml) prevented HG-induced effects on TGF-β/snail, GATA4 and Nkx2.5. IGF-1’s effects were attenuated by PI3 kinase inhibitor (LY294002, 30 μM), but not by MAP kinase inhibitor (PD98059, 0-30 μM). IGF-1 treatment also increased GSK-3β and GSK-3β’s downstream β-catenin. Furthermore, the regulatory effects of IGF-1 on HG-induced the transition of CPCs to fibroblast were attenuated by silencing IGF-1R with small interference RNA (siRNA-IGF-1R). The impact of IGF-1 on CPC transition to fibroblasts was reduced by silencing β-catenin gene expression with siRNA-β-catenin. Cells treated with non-targeting scrambled siRNA showed no changes.
Conclusion: Activated signal transduction via the IGF-1/PI3/GSK-3β/β-catenin pathway may prevent HG-induced transition from CPCs to fibroblasts, and therefore reduce fibrosis. The data provide a new paradigm in which IGF-1 signaling prevent HG-exposure associated myocardial fibrosis during the development of diabetic cardiomyopathy.
- © 2013 by American Heart Association, Inc.