Stable and functional regulatory T cell attenuates fibrotic remodeling in heart failure

Heart failure involves myocardial fibrosis and impaired cardiac function. The transverse aortic constriction (TAC) model in mice replicates pressure overload-induced fibrosis. Immune-mediated inflammation, particularly through T lymphocytes and macrophages, plays a pivotal role in the progression of fibrosis. In vitro–induced regulatory T cells (Tregs) are limited by Foxp3 instability. To address this, stable and functional in vitro induced Tregs (S/F-iTregs) have been developed under CD28-deprived conditions, exhibiting sustained Foxp3 expression and epigenetic stability. We aimed to evaluate the therapeutic efficacy of intravenously administered S/F-iTregs in a murine TAC model of heart failure. S/F-iTregs were generated from CD4 + conventional T cells under CD28 costimulation-deficient conditions. BALB/c mice underwent TAC surgery and received S/F-iTregs intravenously. Cardiac function was assessed by echocardiography. Myocardial fibrosis was evaluated using histological staining. Bulk RNA sequencing was performed to assess transcriptomic changes in the myocardium. S/F-iTreg administration significantly improved left ventricular function and reduced myocardial fibrosis compared to those in controls. PKH26-labeled S/F-iTregs were detected within the cardiac tissue, confirming in vivo migration. RNA sequencing revealed downregulation of inflammation- and fibrosis-related pathways, including tumor necrosis factor-alpha/nuclear factor kappa-light-chain-enhancer of activated B cell, platelet-derived growth factor, transforming growth factor-beta signaling, and modulation of macrophage-related transcriptional programs. Systemic administration of S/F-iTregs attenuates cardiac fibrosis and preserves cardiac function in pressure overload–induced heart failure. These findings support S/F-iTreg–based immunomodulation as a potential approach to limit adverse fibrotic cardiac remodeling. • Stable and functional in vitro-induced regulatory T cell (S/F-iTreg) attenuates cardiac fibrosis in heart failure. • Intravenous S/F-iTreg administration is associated with preserved cardiac function and reduced fibrosis. • S/F-iTreg therapy suppressed fibrosis and inflammation programs, with downregulation of PDGF, TGF-β, and NF-κB pathways. • Systemic S/F-iTreg administration may offer an immunomodulatory approach to control fibrosis in heart failure.