T cell-derived IFNγ instructs ECM crosslinking by cardiac fibroblasts through LOXL3 in experimental cardiometabolic HFpEF.

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is a major clinical challenge characterized by diastolic dysfunction. Left ventricular stiffening and inflammation are hallmarks of HFpEF, yet the contribution of extracellular matrix (ECM) stiffness and the immune-stromal mechanisms driving ECM stiffening in cardiometabolic HFpEF remain poorly understood. METHODS: We used the murine "2-hit model" of cardiometabolic HFpEF, in which the combination of high fat diet and hypertension induced by L-NAME causes diastolic dysfunction. We evaluated diastolic function by echocardiography and ECM mechanics by uniaxial tensile testing of decellularized cardiac tissue. Functional in vivo studies included genetic depletion of T cells, interferon-γ (IFNγ) knockout mice, and pharmacological lysyl oxidase inhibition. We combined co-cultures of CD4(+) T cells and cardiac fibroblasts (CFB) with mechanical testing of cardiac ECM and molecular biology to elucidate cellular and molecular mechanisms. RESULTS: Left ventricular ECM stiffness strongly correlated with impaired diastolic function in experimental cardiometabolic HFpEF. Cardiac CD4(+) T cell infiltration was required for ECM stiffening and upregulation of lysyl oxidase enzymes in CFB. CD4(+) T cell-derived IFNγ was both necessary and sufficient to induce LOXL3 in CFB, which increased ECM stiffness in vitro. Mechanistically, IFNγ signaling activated hypoxia-inducible factor-1α (HIF1α) in CFB, driving LOXL3 expression and subsequent collagen crosslinking. Genetic or pharmacologic disruption of this IFNγ-HIF1α-LOXL3 axis in vivo attenuated adverse ECM remodeling and improved diastolic function. CONCLUSIONS: CD4(+) T cells promote pathological ECM stiffening in cardiometabolic HFpEF through IFNγ-mediated, LOXL3-dependent ECM crosslinking by CFB. Targeting this immune-stromal pathway may offer a novel therapeutic strategy for HFpEF.