CCL2 and acute respiratory distress syndrome: Recent studies have demonstrated that the genetically engineered stem cells with overexpression of CXCR4 [53], angiotensin-converting enzyme 2 [54], IL-33 antagonist soluble IL-1 receptor-like-1 [55], keratinocyte growth factor, angiopoietin 1 [56] and dominant-negative inhibitor of CCL2 [57] could greatly facilitate treatment of ALI in rodents.