β2-Microglobulin as a potential factor for the expansion of mesenchymal stem cells

Multipotent mesenchymal stem cells (MSCs) hold great promise in regenerative medicine, but one of the biggest challenges facing for their application is the ex vivo expansion to obtain enough undifferentiated cells. Fetal bovine serum (FBS), which can elicit possible contaminations of prion, virus, zoonosis or immunological reaction against xenogenic serum antigens, still remains essential to the culture formulations. There is an urgent need to identify potential factors for the undifferentiated expansion of MSCs to reduce the use of FBS or eventually replace it. A previously recognized housekeeping gene, beta2-microglobulin (beta2M), is demonstrated to act as a novel growth factor to stimulate the undifferentiated ex vivo expansion and preserve the pluripotency of adult MSCs from various sources. The use of beta2M might have promising implications for future clinical application of MSCs.