Notably, these hypofibrotic fibroblasts (1) are isolated from ACF hearts that have elevated levels of the profibrotic factors TGF-β relative to control hearts, (2) secrete more TGF-β in culture than CF from control hearts, and (3) fail to exhibit the increased collagen type-1 secretion in culture in response to exogenous TGF-β seen in control CF [14]. The gene discussed is TGFB1; the disease is cystic fibrosis.