HGF and idiopathic pulmonary fibrosis: Sub-optimal HGF concentrations impair repair and possibly further compensatory increase in PDGF and bFGF concentration may lead to bFGF mediated proliferation and ECM secretion by synthetic, non-migratory IPF fibroblasts and the recruitment and activation of heterogenous fibroblast populations form other areas of the lung forming an activated myofibroblast pool at the injury site.