Cardiac fibroblasts counterbalance cardiomyocytes in LMNA cardiomyopathy pathogenesis

Genetic cardiomyopathies arising from mutations in the LMNA gene, encoding nuclear intermediate filaments lamin A/C, display variable age of onset, severity, and fibrosis development. This variability suggests a fundamental element in disease pathogenesis that has yet to be elucidated. Given the central role cardiac fibroblasts play in fibrosis, we explored the relevance of lamin A/C in cardiac fibroblast function, as very little is known in this regard. Using primary cardiac fibroblasts and in vivo mouse models, we show that Lmna mutations impact various aspects of cardiac fibroblast function in response to myocyte damage. We show that both lamin A/C depletion and point-mutant variant expression impair cardiac fibroblast proliferation and contraction whereas other functions such as cell migration appears to be mutation dependent. In vivo depletion of lamin A/C simultaneously in cardiomyocytes and cardiac fibroblasts significantly delayed disease progression, improved cardiac function, and prolonged survival, indicating that lamin A/C mediate an opposing balance between cardiomyocytes and cardiac fibroblasts in driving disease pathogenesis. Our results elucidate previously unexplored roles of lamin A/C in cardiac fibroblasts and suggest that interactions between cardiac fibroblasts and cardiomyocytes are important determinants of the rate of progression and the severity of LMNA cardiomyopathy.