To analyze the cell surface antigen expression, 5×105 fresh cells from third passage were harvested by trypsin-EDTA. Cells were centrifuged at 100 g for 1 min, resuspended in stain buffer (PBS, 2% FBS) and then incubated on ice for 10 minutes. Trypsin was neutralized by centrifuge and isolated cells were washed twice with PBS and finally resuspended in stain buffer. Cells were incubated in dark environment for 30 minutes. After incubation, the cells were labeled with anti-human monoclonal antibodies (MAbs) conjugated to fluorochromes. These antibodies were as follow: anti-CD90-fluorescein isothiocyanate (FITC), CD73-phycoerythrin (PE), CD11b-FITC, CD34-FITC, CD44-FITC, CD45-PE, CD105-PE. The frequencies of all immunolabeled cells were analyzed by FACS Canto II flow cytometer, in which approximately 500,000 events were assessed and data were analyzed using FlowJo software (version 10.0).