CXCR4 and acute respiratory distress syndrome: BM-MSCs inhibit the apoptosis of alveolar epithelial cells in mice with ALI through the CXCL12/CXCR4 signaling axis.233 MSC-CM alleviates neutrophil apoptosis in the context of endotoxin-induced ALI by inhibiting the NF-κB pathway.234 BM-MSCs overexpressing HO-1 could improve the survival rate and attenuate lung impairment in ALI rats by inhibiting apoptosis and enhancing the paracrine effects of MSCs.235