CXCR4 and acute respiratory distress syndrome: Future studies should clarify: (1) whether CXCL12/CXCR4 signaling directly regulates endothelial glycocalyx maintenance and junctional protein stability; (2) how endothelial-derived CXCL12 shapes communication with circulating and resident immune cells to propagate or resolve injury; and (3) whether this axis promotes maladaptive angiogenesis or vascular regeneration during ALI recovery.