In vivo cardiac reprogramming by delivery of PHF7

Cellular reprogramming of cardiac fibroblasts to cardiomyocytes following myocardial infarction (MI) is an attractive strategy to redirect the fibrotic response of the non-regenerative adult heart to a more functional myocardium. Current reprogramming strategies are inefficient or require an excess of factors in adult and human cells due to staunch epigenetic barriers. Recently, we identified the epigenetic factor PHF7 as a potent activating factor of in vitro adult fibroblast reprogramming through modification of chromatin accessibility at cardiac super-enhancers. Here, we report the ability of PHF7 to activate adult fibroblast reprogramming alongside minimal co-factors in vitro, and the efficacy of these cocktails in vivo following MI in mice. Further, delivery of PHF7 as a single factor to the mouse heart following MI induced reprogramming and improved cardiac function. Deployment of single nuclear multi-omics revealed that PHF7 induced fundamental changes in chromatin structure by enhancing accessibility at CTCF binding sites and inhibiting Jun/Fos transcription factor activity to permit reprogramming in the injured heart. Together, these data support the potential for epigenetic factors like PHF7 to achieve in vivo reprogramming in isolation when utilized in the appropriate niche. To investigate the global impact of PHF7 cocktails on reprogramming, we performed RNA sequencing using adult TTFs reprogrammed for 7 days following overexpression with retroviral constructs bearing Empty, PHF7 (P), TBX5 (T), PT, Mef2c+Tbx5 (MT), PMT, or Gata4 +MT (GMT) in biological triplicates.