Fibroblasts from human postmyocardial infarction scars acquire properties of cardiomyocytes after transduction with a recombinant myocardin gene

Abstract

Myocardial scar formation impairs heart function by inducing cardiac remodeling, decreasing myocardial compliance, and compromising normal electrical conduction. Conversion of myocardial scar fibroblasts (MSFs) into (functional) cardiomyocytes may be an effective alternative treatment to limit loss of cardiac performance after myocardial injury. In this study, we investigated whether the phenotype of MSFs can be modified by gene transfer into cells with properties of cardiomyocytes. To this end, fibroblasts from postmyocardial infarction scars of human left ventricles were isolated and characterized by cell biological, immunological, and molecular biological assays. Cultured human MSFs express GATA4 and connexin 43 and display adipogenic differentiation potential. Infection of human MSFs with a lentivirus vector encoding the potent cardiogenic transcription factor myocardin renders them positive for a wide variety of cardiomyocyte-specific proteins, including sarcomeric components, transcription factors, and ion channels, and induces the expression of several smooth muscle marker genes. Forced myocardin expression also endowed human MSFs with the ability to transmit an action potential and to repair an artificially created conduction block in cardiomyocyte cultures. These finding indicate that in vivo myocardin gene transfer may potentially limit cardiomyocyte loss, myocardial fibrosis, and disturbances in electrical conduction caused by myocardial infarction.

In vivo forced expression of myocardin in ventricular myocardium transiently impairs systolic performance in early neonatal pig heart

“…4A) failed to detect differences in their transactivating capacity (van Tuyn et al, 2005(van Tuyn et al, , 2007b. The present study demonstrates that one-time direct intra-myocardial administration of naked plasmid encoding the porcine myocd-A results in the sustained expression of the delivered gene in the target regions of the piglet LVFW on day 2 post-delivery.…”

“…Of note, forced expression of similar (see Fig. 4A) human myocd-A and myocd-B isoforms in myocardial scar fibroblasts didn't reveal significant differences in their transactivating capacity, making the biological relevance of myocd-B exon 11 uncertain (Tuyn et al, 2007b). Additionally, we reasoned that since the baseline levels of myocd-A expression are low in the piglet myocardium, the consequences of forced myocd-A expression in the LVFW could be more palpable than in case of myocd-B delivery.…”

Resynchronization of Separated Rat Cardiomyocyte Fields With Genetically Modified Human Ventricular Scar Fibroblasts

“…12 Because these proteins are essential in cardiac action potential (AP) transmission and are absent or only present at low levels in native human ventricular scar fibroblasts (hVSFs), it was hypothesized that genetic modification of scar tissue cells with a recombinant MyoC gene might be a novel approach to treat conduction abnormalities. In the present study, the potential of MyoC-transduced hVSFs to resynchronize and stimulate cardiac tissue in a standardized in vitro model was investigated.…”

The Smooth Muscle Cell-restricted KCNMB1 Ion Channel Subunit Is a Direct Transcriptional Target of Serum Response Factor and Myocardin

“…One of myosin light chain kinase's substrates, the 20-kDa myosin light chain, exhibits increased phosphorylation with MYOCD overexpression coincident with SMC-like contractile activity (13). Further, the calcium transport pump, sarcoplasmic reticulum calcium-ATPase, contains a conserved CArG box (18) and is induced upon forced expression of MYOCD (19). Thus, MYOCD triggers expression of both structural and regulatory genes to enable SMC contractile force generation.…”