Gene Therapy Targeting <i>Pkp2</i> Deficiency Attenuates Cardiac Fibrosis: Insights From Single‐Cell Transcriptomics in <i>Pkp2</i> ‐Knockout Rats

Heart failure (HF), characterized by maladaptive cardiac fibrosis and progressive functional deterioration, remains a therapeutic challenge. In this study, we established a cardiac organoid HF model derived from human-induced pluripotent stem cells (hiPSCs) and observed a significant downregulation of the desmosomal protein plakophilin-2 (PKP2) in this model. Reduced PKP2 expression was detected in both HF rat and mouse. Subsequent in vivo studies on <i>Pkp2-</i>knockout (<i>Pkp2</i>-KO) rats demonstrated that adeno-associated virus serotype 9 (AAV9)-mediated restoration of PKP2 not only restored cardiac PKP2 expression but also attenuated the progression of fibrosis. Administration of AAV9-PKP2 could also inhibit myocardial fibrosis and slow down disease progression in HF mouse. Single-cell RNA sequencing analysis in rats revealed enriched pathological profibrotic cardiac fibroblasts (CFs) in PKP2-deficient myocardium. Mechanistically, AAV9-PKP2 administration induced the phenotypic conversion of activated CFs into quiescent antifibrotic states. Integrated bioinformatics identified that protein tyrosine phosphatase receptor type C (<i>Ptprc</i>) was a pivotal regulator orchestrating this cellular reprogramming. Our findings thus unveil PKP2 as a master regulator of fibroblast activation and propose AAV9-PKP2 gene therapy as a promising novel therapeutic strategy targeting pathological fibrosis in HF.