Induction of Cardiomyocyte-Like Cells in Infarct Hearts by Gene Transfer of Gata4, Mef2c, and Tbx5

Abstract

Rationale: After myocardial infarction (MI), massive cell death in the myocardium initiates fibrosis and scar formation, leading to heart failure. We recently found that a combination of 3 cardiac transcription factors, Gata4, Mef2c, and Tbx5 (GMT), reprograms fibroblasts directly into functional cardiomyocytes in vitro. Objective: To investigate whether viral gene transfer of GMT into infarcted hearts induces cardiomyocyte generation. Methods and Results: Coronary artery ligation was used to generate MI in the mouse. In vitro transduction of GMT retrovirus converted cardiac fibroblasts from the infarct region into cardiomyocyte-like cells with cardiac-specific gene expression and sarcomeric structures. Injection of the green fluorescent protein (GFP) retrovirus into mouse hearts, immediately after MI, infected only proliferating noncardiomyocytes, mainly fibroblasts, in the infarct region. The GFP expression diminished after 2 weeks in immunocompetent mice but remained stable for 3 months in immunosuppressed mice, in which cardiac induction did not occur. In contrast, injection of GMT retrovirus into α-myosin heavy chain (αMHC)-GFP transgenic mouse hearts induced the expression of αMHC-GFP, a marker of cardiomyocytes, in 3% of virus-infected cells after 1 week. A pooled GMT injection into the immunosuppressed mouse hearts induced cardiac marker expression in retrovirus-infected cells within 2 weeks, although few cells showed striated muscle structures. To transduce GMT efficiently in vivo, we generated a polycistronic retrovirus expressing GMT separated by 2A “self-cleaving” peptides (3F2A). The 3F2A-induced cardiomyocyte-like cells in fibrotic tissue expressed sarcomeric α-actinin and cardiac troponin T and had clear cross striations. Quantitative RT-PCR also demonstrated that FACS-sorted 3F2A-transduced cells expressed cardiac-specific genes. Conclusions: GMT gene transfer induced cardiomyocyte-like cells in infarcted hearts.

Nuclear Calcium/Calmodulin-dependent Protein Kinase II Signaling Enhances Cardiac Progenitor Cell Survival and Cardiac Lineage Commitment

“…Additionally, transfection of non-myocytes with Mef2c and GATA4 enhances expression of mature cardiac genes (41). We observed a marked increase in nuclear Mef2c in CPCe␦B, which supports the up-regulation of mature cardiac and smooth muscle markers ␣-sarcomeric actinin, cTNT and ␣-SMA observed in Fig.…”

Steroid Receptor Coactivator-2 Is a Dual Regulator of Cardiac Transcription Factor Function

“…These modifications likely affect which factors the DNA-bound transcription factor interacts with, including the exchange of corepressors to coactivators as well as differential chromatin modifiers, but specifically which role these modifications play in regulating their interactions with SRC-2 remains to be determined. Furthermore, with the recent evidence that overexpression of GATA-4, MEF2, and Tbx5 can drive differentiation of fibroblasts to cardiomyocytes (38,39), it is tempting to consider that introduction of SRC-2 or modula- tion of its activity could be beneficial in the efficacy of these factors in driving this differentiation program.…”

BAF60 A, B, and Cs of muscle determination and renewal

“…Instead, a complex transcriptional network consisting of GATA4, HAND2, MEF2C, MESP1, NKX2.5, and TBX5 directs cardiac muscle formation (Olson 2006). Despite this complex network, several recent reports show that a minimal set of transcription factors are capable of directing the formation of cardiomyogenic progenitors from dermal fibroblasts using MesP1 and Ets2 (Islas et al 2012) and even immature cardiomyocytes from either embryonic mesoderm using Gata4, Tbx5, and BAF60c (Takeuchi and Bruneau 2009); fibroblasts with Gata4, Mef2c, and Tbx5 (Ieda et al 2010;Inagawa et al 2012;Qian et al 2012); or the same with Hand2 (Song et al 2012). The latter two instances reprogrammed cells directly in vivo following myocardial infarction and successfully added new cardiomyocytes to the myocardial wall, improved cardiac function, and reduced adverse remodeling, suggesting that this approach might be adapted therapeutically, although the efficiency of the approach has been questioned (Chen et al 2012).…”