The Effect Of BMPs On In Vitro Expansion Characteristics And Physiological Functions Of HSCs

In vitro expansion of hematopoietic stem cells (HSCs) is the main solution of the limited amount of HSCs in clinical transplantation. Due to the differences between in vitro culture conditions and in vivo microenvironment, the amount of expanded HSCs is still unable to satisfy the clinical requirements, and the physiological functions of the cells may be lost after expansion. The research on the regulatory factors that modulates the development of HSCs in hematopoietic niche provides important evidences for optimizing the in vitro culture conditions. Bone morphogenetic proteins (BMPs) present in bone marrow niche play an important role in regulating hematopoiesis. In here, CD34+cells freshly isolated from umbilical cord blood were cultured with serum-free medium containing the cytokine combination of SCF+TPO+FL. Different concentrations and subtypes of BMPs were studied for the effects on in vitro expansion of hematopoietic stem/progenitor cells (HSPCs), and nonobese diabetic/severe combined immune-deficient (NOD/SCID) mice were applied to investigate the effects of BMPs on the physiological functions of expanded cells. The results were as follow:(1) Proliferations of total cells and HSPCs were not affected by the addition of5-50ng/ml BMP2to serum-free medium. Colony forming efficiency of CD34+cells and the composition of various lineage cells also remained unaffected by the addition of BMP2.(2) Increases of total cells and HSPCs were yielded respectively by the additions of25ng/ml BMP4and5ng/ml BMP7to serum-free medium.(3) The cells cultured with serum-free medium contain-ing5ng/ml BMP7showed better engraftment capability and multilineage reconstitution ability after injection into NOD/SCID mice through tail vein, while the cells cultured with5ng/ml BMP2showed same engraftment capability and multilineage reconstitution ability as the cells cultured without BMPs. The above results were helpful for optimizing in vitro culture conditions and achieving the effective expansion of cord blood HSCs, so that the clinical application of in vitro expanded HSCs could be further facilitated.