In Vivo Cardiac Cellular Reprogramming Efficacy Is Enhanced by Angiogenic Preconditioning of the Infarcted Myocardium With Vascular Endothelial Growth Factor

Abstract

BackgroundIn situ cellular reprogramming offers the possibility of regenerating functional cardiomyocytes directly from scar fibroblasts, obviating the challenges of cell implantation. We hypothesized that pretreating scar with gene transfer of the angiogenic vascular endothelial growth factor (VEGF) would enhance the efficacy of this strategy.Methods and ResultsGata4, Mef2c, and Tbx5 (GMT) administration via lentiviral transduction was demonstrated to transdifferentiate rat fibroblasts into (induced) cardiomyocytes in vitro by cardiomyocyte marker studies. Fisher 344 rats underwent coronary ligation and intramyocardial administration of an adenovirus encoding all 3 major isoforms of VEGF (AdVEGF‐All6A+) or an AdNull control vector (n=12/group). Lentivirus encoding GMT or a GFP control was administered to each animal 3 weeks later, followed by histologic and echocardiographic analyses. GMT administration reduced the extent of fibrosis by half compared with GFP controls (12±2% vs 24±3%, P<0.01) and reduced the number of myofibroblasts detected in the infarct zone by 4‐fold. GMT‐treated animals also demonstrated greater density of cardiomyocyte‐specific marker beta myosin heavy chain 7+ cells compared with animals receiving GFP with or without VEGF (P<0.01). Ejection fraction was significantly improved after GMT vs GFP administration (12±3% vs −7±3%, P<0.01). Eight (73%) GFP animals but no GMT animals demonstrated decreased ejection fraction during this interval (P<0.01). Also, improvement in ejection fraction was 4‐fold greater in GMT/VEGF vs GMT/null animals (17±2% vs 4±1%, P<0.05).ConclusionsVEGF administration to infarcted myocardium enhances the efficacy of GMT‐mediated cellular reprogramming in improving myocardial function and reducing the extent of myocardial fibrosis compared with the use of GMT or VEGF alone.

Induction of diverse cardiac cell types by reprogramming fibroblasts with cardiac transcription factors

“…Interestingly, follow-up studies have revealed that many different combinations of transcription factors, including GHMT (H; Hand2), can function to reprogram fibroblasts into CM-like cells in vitro Christoforou et al, 2013;Fu et al, 2013;Nam et al, 2013;Protze et al, 2012;Song et al, 2012;Wada et al, 2013). Based on these results, several groups subsequently demonstrated direct reprogramming of activated fibroblasts toward a cardiac phenotype in vivo (Inagawa et al, 2012;Jayawardena et al, 2012;Mathison et al, 2012;Qian et al, 2012;Song et al, 2012). Taken together, these studies provide a basis for converting fibroblasts into CMs in vivo to treat a variety of cardiovascular disorders.…”

Strategies for Heart Regeneration

“…This reduction of scar in the infarcted area may be due to VEGF-mediated neovascularization or some other unknown mechanisms. 25) Jayawardena, et al reported that direct injection of lentiviruses containing four microRNAs (miR-1, miR-133, miR-208, and miR-499) into mouse infarcted hearts converted resident cardiac fibroblasts into cardiomyocyte-like cells in vivo. After injection of these microRNAs, approximately 1% of the infarcted area contained new iCMs; however, this work did not report on whether ejection fraction improved after microRNA injection.…”

Myocardial Reprogramming Medicine: The Development, Application, and Challenge of Induced Pluripotent Stem Cells

“…Interestingly, pretreatment of VEGF to infarcted myocardium was reported to enhance the efficacy of the GMT-mediated reprogramming strategy, improving myocardial function and reducing the extent of myocardial fibrosis [206]. Since the initial GMT approach was not sufficient for cardiac induction in human cardiac fibroblasts, a study screening for additional factors found that the transduction of Mesp1 and Myocd enhanced the direct reprogramming efficiency [207].…”