Abstract: Objective To explore the role of apelin-13 in regulating stem cell differentiation into vascular net. Methods Mesenchymal stem cells were isolated from human umbilical Wharton’ s jelly using tissue adherence method．Their immunophenotypes were detected by flow cytometry . Passage 3 of WJ-MSCs (Wharton’ s jelly-mesenchymal stem cells)were inoculated in 4 flasks, denoted as A1, A2, A3, A4 group. Twenty μL of apelin-13 at concentrations of 0, 1×10－6, 10 ×10－6 and 100 ×10－6 mol/L were added to A1, A2, A3 and A4 respectively each day. After being induced for 7 days, cell morphology and viability were observed under inverted microscope. Von Willebrand factor (vWF) was examined by immunofluorescence and CD31 was identified by flow cytometry. Upon incubating with three dimensional culture medium of hydrogel,those cultured A1, A2, A3 and A4 were renumbered as S1, S2, S3, S4. Again, twenty μL of apelin-13 at concentrations of 0,1×10－6, 10 ×10－6and 100 ×10－6 mol/L were used to treat S1, S2, S3 and S4 respectively. After 7 days, cell morphology, viability and vas -like networks were observed with inverted microscope. Results Our study showed that WJ-MSCs can be induced by apelin 13 to differentiate into endothelial cells lineage indicated by positive of vWF staining. Moreover, CD31 expression increases significantly upon apelin-13 addition in a dosage dependent manner. The endothelial cells line formed vas like networks when cultured with three-dimensional medium containing hydrogel. Conclusion This study demonstrated that apelin-13 could promote human umbilical cord-MSCs to differentiate into endothelium lineage then to form vascular networks.

Key words: mesenchymal stem cells, apelin-13, angiogenesis, 3-dimensional culture, umbilical cord