**5. Conclusion and perspective**

MSCs provide huge opportunities in translational medicine for treatment of a range of diseases or medical conditions. MSCs are multipotent stem cells and such cells can be isolated from various tissues including bone marrow, a major source of human MSCs. Given that a large number of MSCs are required for the clinical application, *in vitro* expansion of MSCs is critical. However, MSCs at higher passage could lead to the culture-associated alterations, such as cellular morphology, immunological surface markers, proliferation, differentiation, and cell genetics. Due to *in vitro* long-term culture associated spontaneous transformation of MSCs, the safety of MSC therapy remains the major concerns. Human MSCs from various tissues present the varies biological properties. At present, consensus is lacking regarding materials and culture protocols, culture conditions, supplement of growth factors, freezing and thawing (e.g. media), and functional assays. Therefore, standardizing the procedures for preparation of MSCs would be needed for pre-clinical studies and clinical application of MSCs.
