HGF and acute respiratory distress syndrome: HGF is a growth factor which can be secreted by numerous other cell types, such as alveolar macrophages, hepatocytes, melanocytes, and keratinocytes, and a prosurvival mediator that regulates vascular barrier integrity maintenance and appears at raised concentrations in the lung under pathological conditions such as ALI, sepsis, ventilator-induced lung injury, and lung inflammation.