Abstract Body: Background: Myocardial infarction (MI), which affects about 3 million people globally each year, permanently damages the heart and reduces cardiac function. Recent studies have indicated that activating YAP in cardiomyocytes (CMs) promotes cardiac regeneration and mitigates pathological remodeling in mouse and pig MI models. However, the risk of oncogenicity makes sustained high YAP expression or activity untenable as a translational therapy, necessitating precise regulation of YAP for clinical application. This study explores a novel, inducible YAP activation system to precisely regulate YAP expression and assess its therapeutic potential in cardiac repair.
Methods: We developed an adeno-associated virus 9 (AAV9)-based therapy, termed CM-YAP^on, which triggers YAP activation in CMs upon exposure to a small molecule LMI070. To evaluated system specificity and leaky expression, we conducted single-nucleus RNA sequencing (snRNA-seq) and Western blot (WB). We tested CM-YAP^on function in vivo by two experimental conditions: (1) transient YAP activation in CMs following MI; (2) transient YAP activation in CMs two weeks before MI. Magnetic resonance imaging (MRI) and echocardiography (Echo) were used to assess cardiac function. BaseScope detecting virus RNA determined viral infection efficiency. Cardiac injury was evaluated by Sirius Red staining (fibrosis assessment), TUNEL staining (apoptosis detection), and area-at-risk (AAR) staining.
Results: snRNA-seq in CM-YAP^on mice confirmed YAP activation and minimal off-target expression in CMs in the absence of LMI070. WB analysis demonstrated that a single LMI070 injection induced a transient expression of active YAP (YAP5SA), which was degraded within a week. YAP activation post-MI improved cardiac function when viral infection efficiency ranged between 30% and 50%. Notably, administering a single LMI070 injection two weeks prior to MI provided sustained cardioprotection by reprogramming the cardiac microenvironment, reducing apoptosis and improving cardiac function. However, this protective effect diminished by four weeks after transient YAP activation, indicating a time-limited benefit.
Conclusions: The novel gene therapy CM-YAP^on provides a transient, tunable approach to YAP activation in CMs, demonstrating both therapeutic and prophylactic potential in MI-induced cardiac injury.