Objective
The administration of a variety of reprogramming factor cocktails has now been shown to reprogram cardiac fibroblasts into induced cardiomyocyte-like cells (iCMs). Reductions in ventricular fibrosis observed after reprogramming factor administration, however, seem to far exceed the extent of iCM generation in vivo. We therefore investigated whether reprogramming factor administration might primarily play a role in activating anti-fibrotic molecular pathways.
Methods
Adult rat cardiac fibroblasts (RCFs) were infected with lentivirus encoding the transcription factors Gata4, Mef2c or Tbx5, all three vectors (GMT) or a GFP control vector. Gene and protein expression assays were performed to identify relevant anti-fibrotic targets of these factors. The anti-fibrotic effects of these factors were then investigated in a rat coronary ligation model.
Results
GMT administration to RCFs in vitro significantly downregulated expression of Snail, and the pro-fibrotic factors, CTGF, Collagen1a1, and Fibronectin. Of these factors, Gata4 was shown to be the one responsible for the downregulation of the pro-fibrotic factors, and Snail (mRNA expression fold change relative to GFP for Snail, Gata4: 0.5 ± 0.3, Mef2c: 1.3 ± 1.0, Tbx5: 0.9 ± 0.5, GMT: 0.6 ± 0.2, p<0.05). ChIP qPCR identified Gata4 binding sites in the Snail promoter. In a rat coronary ligation model, only Gata4 administration alone also improved post– infarct ventricular function and also reduced the extent of post-infarct fibrosis.
Conclusions
Gata4 administration reduces post–infarct ventricular fibrosis and improves ventricular function in a rat coronary ligation model, potentially as a result of Gata4 mediated downregulation of the pro-fibrotic mediator Snail.