T-Cell-Derived IFNγ Instructs ECM Crosslinking by Cardiac Fibroblasts Through LOXL3 in Experimental Cardiometabolic...

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 ECM (extracellular matrix) stiffness and the immune-stromal mechanisms driving ECM stiffening in cardiometabolic HFpEF remain poorly understood.

We used the murine 2-hit model of cardiometabolic HFpEF, in which the combination of high-fat diet and hypertension induced by L-nitro-arginine-methyl ester 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, IFNγ (interferon-γ) knockout mice, and pharmacological lysyl oxidase inhibition. We combined cocultures of CD4⁺ T cells and cardiac fibroblasts with mechanical testing of cardiac ECM and molecular biology to elucidate cellular and molecular mechanisms.

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 cardiac fibroblast. We discovered that CD4⁺ T-cell-derived IFNγ was required to induce LOXL3 in cardiac fibroblast, which increased ECM stiffness in vitro. Mechanistically, we demonstrate that a signaling axis involving IFNγ, PI3K (phosphoinositide 3-kinase), AKT, and HIF1α (hypoxia-inducible factor-1α) drives LOXL3 expression and subsequent collagen crosslinking. Genetic or pharmacological disruption of this IFNγ-HIF1α-LOXL3 axis attenuated adverse ECM remodeling and improved diastolic function.

CD4⁺ T cells promote pathological ECM stiffening in cardiometabolic HFpEF through IFNγ-mediated, cardiac fibroblast LOXL3-dependent ECM crosslinking. Targeting this immune-stromal pathway may offer a novel therapeutic strategy for HFpEF.