Studies On Hematopoietic Reconstitution By Cotransplantation Of Human Mesenchymal Stem Cells And Hematopoietic Stem Cells

Objectives and background In addition to hematopoietic stem cells(HSCs)from which all formed elements of the blood originate, the bone marrow contains a second type of stem cells capable of giving rise to multiple mesenchymal cell lineages. These cells, recently termed mesenchymal stem cells (MSCs), are adherent cells capable of multilineage differentiation and self-renewal. They are able to differentiate into multiple mesodermal tissue types, including osteoblasts, adipocytes, chondrocytes, myocytes, neural elements, and stromal fibroblasts under defined in vitro or in vivo conditions. Existing technology permitting ex vivo expansion of human MSCs without apparent loss of phenotype or function. A number of cytokines are secreted by MSCs, such as hematopoietic growth factors, nonhematopoietic factors and chemokines, which modulate the bone marrow microenviroment, and facilitate the proliferation and differentiation of hematopoietic cell and MSCs. The latter do not constitutively express major histocompatibility class Ⅱ antigens or T-cell costimulatory B7. Furthermore, human MSCs are not substantially immunogenic and may actually inhibit both primary and secondary mixed lymphocyte reaction (MLR), which has a great capacity of immunomodulatory. Animal models demonstrating the potential for MSCs to enhance engraftment of allogeneic HSCs have provided a rationale for clinical trials in the allogeneic setting. In addition, since MSCs process immunosuppressive properties in vivo, there is the potential that MSCs could ameliorate or perhaps even prevent graft versus host disease (GVHD) reactions. The capacity of MSCs to repair or replace stromal matrix damaged by genetic mutation or intensive chemotherapy, may improve either the overall rate of engraftment or pace of hematopoietic recovery following HSCs transplantation. MSCs can conveniently come from several resources, and ethics is seldomly involved in its manufacture, so, it likely represent one of the most promosing stem cell sources for tissue replacement therapy. Although numerous studies has provided evidence that cotransplantation of human ex vivo-expanded MSCs together with HSC hasten hematopoietic recovery following a bone marrow (BM) transplantation in animal models and in humans, the clinical application of MSCs is still in preliminary stage. To date, some questions are still under study, such as how many MSCs are most suitable for stem cell transplantation (SCT)? And when is the transplantation opportunity? Once engraftment, do MSCs remain its multilineage differentiation potential? Above all, the 7PDF 文件使用 "pdfFactory" 试用版本创建 www.fineprint.com.cn第二军医大学博士研究生学位论文 英文摘要 possibility of isolating MSCs and manipulating their growth under defined ex vivo culture conditions are essential prerequisites for clinical applications using culture-expanded MSCs as a supplement for SCT. In this project, we have delved into the isolation and ex vivo expansion of human BM MSCs. The biology characteristics of expanded MSCs were studied. And its manufacture process was according to Good Manufacture Practise. With MSCs as feeder layer, it was demonstrated that MSCs could maintain long-term culture-initiating cells (LTC-IC) of umbilical cord blood (UCB) CD34+ cells. The role of ex vivo expanded MSCs on engraftment of UCB CD34+ cells in NOD/SCID xenotransplantation model was evaluated. And the ratio and time for cotransplantation were also studied. Our study can lay a sound foundation for the MSCs usage in clinical settings. Part One Isolation, characterization and ex vivo expansion of human BM MSCs in a large-scale Methods BM cells were obtained from iliac crest aspirates from 5 healthy donors (age 14...