| Hematopoietic stem cell transplantation (HSCT) is a hematologic field where great progresses have been achieved in recent thirty years. It has been extensively developed and resulted in satisfactory curative effects as operative methods for curing hematologic malignancy and solid carcinomas as well as some inherited diseases. But patients' hematopoietic recovery is frequently delayed and causes serious infections and hemorrhage, results in transplantation failure or death in the ultimate. Autologous stem cell transplantation is the most extensively developed kind of various stem cell transplantations in the clinical setting. The recovery of peripheral blood including neutrophils and platelets need more time after autologous bone marrow transplantation than allogeneic stem cell transplantation and autologous peripheral blood stem cell transplantation, especially for platelets recovery.In the plerosis procedure after bone marrow injury, or in every stage of hematopoietic reconstitution after hematopoietic stem cell transplantation, stromal components usually recover prior to hematopoietic reconstitution.The conditioning regimens including high-dose chemotherapy and radiation exposure before transplantation severely damage structure and function of hematopoietic microenvironment, and hematopoietic regeneration is inevitably tempered. So regeneration and reconstitution of hematopoietic microenvironment is a formost precondition for hematopoietic recovery.The normal hematopoiesis in vivo depends on a complicated andintegrated microenvironment system and cell component is the key of this system. Mesenchymal stem cell(MSC) in adult marrow is the most important cell component in microenvironment as precursors of stromal cell lines, and MSC is the source for renewing stromal cells as well as producing a series of hematopoietic growth factors to facilitate the homing, location, proliferation and differentiation. MSCs play a very important role in hematopoietic regulation and hematopoietic reconstitution mechanism. Date from preclinical transplantation studies suggested that MSCs are transplantable cells without toxicity associated with infusion and can be engrafted in a permanent state. Preclinical and early clinical safety studies are paving the way for further applications of mesenchymal stem cells in field of transplantation with respect to hematopoietic support, graft facilitation and immunoregulation. MSCs' ex vivo expansion and cotransplantation will be efficient supplement and consummation to conventional stem cell transplantion mode.It is worth researching and discussing further. Our studies aim at hematopoietic support of human marrow-derived MSCs in vitro and in vivo with a view to provide experimental and clinical evidence for further applications in clinic.Efficient culture-expansion ex vivo is essential and obligatory in order to utilize bone marrow-derived MSCs. In the first part of our studies, an uniform population of human bone marrow-derived MSCs were obtained by means of gradient centrifugation with a Percoll (density 1. 073g/ml) and early adhesion separation. The growth curve, adhesion rate and split exponent were investigated.The isolated cultured MSCs developed into colonies and exhibited a fibroblast-like morphology. And MSCs exhibited a uniform population after passaging. The double time of subcultured MSCs was 30 hours. The split exponent was up to 30%o. More than 90% of subcultured MSCs were adhesive in 12 hours after replating, indicating the high proliferative potential. MSCs can achieve asignificant culture-expansion in a low-serum medium. Representative monoclonal antibodies were used for flow cytometry(FCM) analysis. Culture-expanded MSCs were universally positive for CD166, CD105, CD29 and CD13, and negative for CD34, CD45 and HLA-DR. The purity of MSCs exceeded 99%.Special formula of media complements were used to demonstrate the subcultured MSCs' capabilities of multipotential differentiation. MSCs can differentiate into cells of osteogenic, adipogenic, chondrogenic and neu...
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