HGF and acute respiratory distress syndrome: Also, engrafted MSCs into the lung epithelium of acute respiratory distress syndrome have secreted paracrine factors, such as KGF (keratinocyte growth factor), VEGF (vascular endothelial growth factor), and HGF (hepatocyte growth factor), to promote the protective effects of pulmonary vascular permeability and the proliferation of epithelial cell [29].