Mesenchymal stem cell-endothelial cell (MSC-EC) interaction promoted human MSCs to restore the integrity of human pulmonary microvascular endothelial cell (HPMEC) monolayers. We found HPMEC paracellular permeability for both MSC-EC interaction and MSC groups significantly decreased (P <0.01) (A). In addition, HPMEC paracellular permeability in the MSC-EC interaction group decreased more significantly than that of the MSC group (P <0.05) (A). Similarly, HPMEC transcellular permeability significantly decreased in two co-culture systems (P <0.01) (B), while MSC-EC interaction more significantly decreased HPMEC transcellular permeability (P <0.05) (B). (n=3, ** p < 0.01 vs. group LPS; # p < 0.05 vs. group MSC). LPS, lipopolysaccharide.