Hepatocyte growth factor (HGF) secreted by mesenchymal stem cell-endothelial cell (MSC-EC) interaction induces proliferation in human pulmonary microvascular endothelial cells (HPMECs). To explicit effect of HGF secreted by MSCs on HPMEC proliferation, cell proliferation was analysed by bromodeoxyuridine (BrdU) incorporation assay. The results indicated that MSCs induce proliferation in HPMECs injured by lipopolysaccharide (LPS). Interestingly, the proliferation ratio in the MSC-EC interaction group was higher than that of the MSC group (P <0.05). However, the MSC-EC interaction effect was significantly blocked by anti-HGF antibody (P <0.01), which explains why there are more HPMECs in the MSC-EC group. The result suggested that HGF secreted by MSC-EC interaction induces proliferation in HPMECs (n = 3, *P <0.01 versus control group, #
P <0.01 versus LPS group; &
P <0.05 versus MSC group, $
P <0.01 versus MSC-EC interaction).