c-kit dysfunction impairs myocardial healing after infarction

Background - We hypothesized that c-kit receptor function in the bone marrow is important for facilitating healing, leading to efficient cardiac repair after myocardial infarction (MI). Methods and Results - We used Kit(W)/Kit(W-v) c-kit mutant mice and their wild-type littermates to assess the importance of c-kit function in cardiac remodeling after coronary ligation. We found that mutant mice developed 1.6-fold greater ventricular dilation (P = 0.008) attributable to a 1.3-fold greater infarct expansion by day 14 after MI (P = 0.01). The number of proliferating smooth muscle alpha-actin expressing cells was 1.8-fold lower in mutant mice at day 3 (P < 0.01), resulting in a 1.6 to 1.8-fold reduction in total regional nonvascular smooth muscle alpha-actin expressing cells by both microscopy and flow cytometry (P < 0.001 for both). This decrease was accompanied by a 1.4-fold reduction in the number of CD31 expressing blood vessels (P < 0.05). Prior transplantation of wild-type bone marrow cells into mutant mice rescued the efficient establishment of vessel-rich repair tissue by inducing a 1.5-fold increase in nonvascular smooth muscle alpha-actin expressing cells and CD31 expressing blood vessels (P < 0.05 for both). The increased recruitment of cells into the infarct region in the chimeric mice was associated with reduced infarct expansion (P < 0.03) compared to wild-type levels. Conclusions - Bone marrow c-kit function critically impacts the myofibroblast repair response in infarcted hearts. Interventions that increase the infiltration of c-kit(+) cells to the infarcted heart may potentiate this endogenous repair response, prevent infarct expansion, and improve the recovery of cardiac function after MI.