More hepatocyte growth factor (HGF) was secreted under mesenchymal stem cell-endothelial cell (MSC-EC) interactions. We adopted two different co-culture conditions through transwell insert including MSC-EC interactions (A) and MSCs (B). Then we measured the concentration of HGF in the culture medium by using an enzyme-linked immunosorbent assay (ELISA) kit. The results indicated that the concentration of HGF in direct co-culture and indirect co-culture media was significantly higher than that of the lipopolysaccharide (LPS) group. Interestingly, HGF levels in direct co-culture medium were much higher than that of indirect co-culture medium (C) (n = 3, **P <0.01 versus LPS group; ##
P <0.01 versus indirect co-culture group). We further tested HGF concentration by ELISA quantification in conditioned medium from six different formats. The results showed that the concentration of HGF in the MSC group was significantly higher than that of the EC group. HGF levels had no significant difference between the upper and lower of the MSC-EC indirect co-culture group, which were higher compared with the MSC group and the sum of the human pulmonary microvascular endothelial cell (HPMEC) and MSC alone group (D) (P <0.05 and P <0.01). However, HGF levels in the MSC-EC interaction group were highest in all six groups (D) (P <0.01) (n = 3, *P <0.01 versus EC group, #
P <0.01 versus MSC group; &
P <0.05, &&
P <0.01 versus MSC + EC group, $
P <0.01 versus upper of MSC-EC indirect group or lower of MSC-EC indirect group). CM, conditioned media; hMSC, human mesenchymal stem cell.