Characteristics of human umbilical cord mesenchymal stem cells during ex vivo expansion

Human umbilical cord mesenchymal stem cells (hUCMSCs) have potential clinical applications in different types of diseases. In order to acquire enough cells, hUCMSCs have to be expanded ex vivo. However, it remains to be elucidated whether the characteristics of hUCMSCs are altered during ex vivo expansion. In the present study, the quality of hUCMSCs, which is important for successful therapeutic use, was systematically examined during hUCMSC expansion ex vivo. Morphologically, hUCMSCs exhibited no visible changes during culture. In addition, hUCMSCs retained their proliferative ability between passages 0-5. At the molecular level, the cells continued expressing the specific positive surface markers, CD29, CD73 and CD90, and did not express the negative surface markers, CD14, CD34 or CD45, during culture ex vivo. Furthermore, the hUCMSCs exhibited low immunogenicity, which was maintained when cultured for five passages. However, the immunological properties of hUCMSCs were altered at passage 10, at which the percentage of hUCMSCs expressing human leukocyte antigen-I was significantly increased. Collectively, these results suggested that hUCMSCs used for cell-based therapies require obtaining from cells, which have been expanded for fewer than five passages.