Cardiac fibroblasts-specific USP7 drives post-infarction cardiac fibrosis by deubiquitinating Krüppel-like factor 7 to promote myofibroblast activation.

Although cardiac fibroblast-to-myofibroblast transition (FMT) can critically exacerbate collagen deposition and adverse remodeling after myocardial infarction (MI), the underlying regulatory mechanisms remains unclear. While ubiquitin-specific protease 7 (USP7), a deubiquitinating enzyme, has been implicated in cardiomyocyte ischemia injury, its role in myofibroblast transition following MI is unknown. Here, we identify cardiac fibroblasts-specific USP7 as a key mediator of FMT and fibrosis. USP7 expression was upregulated in infarcted murine hearts and isolated cardiac fibroblasts, and the upregulated expression was correlated with human fibrotic myocardium. Silencing of USP7 expression suppressed transforming growth factor (TGF)-β1-induced FMT and reduced the expression of α-SMA. In comparison with the findings in USP7flox/flox mice, specific knockout of USP7 in cardiac fibroblasts and in myofibroblasts greatly attenuated fibrotic remodeling and ventricular dysfunction post-MI. Mechanistically, USP7 directly bound to Krüppel-like factor 7 (KLF7) through the N-terminal tumor necrosis factor receptor-associated factor (TRAF)-like domain, causing deubiquitination of KLF7. Cysteine at position 223 (C223) of USP7 induced K48 deubiquitination to promote KLF7 nuclear accumulation, thereby facilitating transcription of GATA3 by directly binding to the GATA3 promoter to induce the expression of pro-fibrosis genes. Adeno-associated virus 9 (AAV9)-mediated USP7 overexpression worsened systolic dysfunction and adverse remodeling. The protective effects of USP7 knockout were abolished by KLF7 overexpression. Our results indicate that USP7 contributes to FMT, thereby aggravating adverse remodeling and cardiac dysfunction by deubiquitinating KLF7 post-MI. Our findings characterize the USP7-KLF7-GATA3 axis as a novel regulator of FMT and propose fibroblast USP7 as a therapeutic target for post-MI remodeling.