| Allogeneic hematopoietic stem cell transplantation (HSCT) has been used to treat thousands of patients with leukemia, lymphoma, inborn immunodeficiency, metabolic disease, autoimmune illness, and other life-threatening hematogical diseases. Umbilical cord blood (UCB) is an alternative source of hematopoietic stem cells to bone marrow (BM) and mobilized peripheral blood (MPB). Although UCB has many theoretical advantages, such as higher proliferation and self-renewal potential, the relatively low number of stem cells contained in a single unit is the major limitation in the use of cord blood for allogeneic HSCT. An optimized ex vivo expansion of UCB HSPC would be an urgent resolution way for the widespread clinical application of UCB.The transplanted HSPCs possess the proliferation and self-renewal potential, and the ability to home to the BM microenvironment, which are two critical issues for the hematopoietic reconstitution and long-term engraftment after HSCT. There are many ex vivo expansion protocols have been extensively evaluated, in which the expanded HSPCs would sustain their proliferation and self-renewal potential. However, the homing-related characteristics and function were rarely evaluated in previous reports.Our previous study demonstrated that short-term culture system, consists of defined QBSF-60 serum-free medium with a simple early-acting cytokine combination of SCF, FL and TPO, could substantially support simultaneous expansion of various UCB HSPC populations. Sufficient CD34~+ cells for transplantation in adults would be obtained from most UCB collections after 10-14 days culture in the system. And more important is that the expanded CD34~+ cells sustained the in vitro characteristics of initial unmanipulated CD34~+ UCB cells. AC 133 is a novel HSPC antigen, and more and more data indicate that AC133~+ cells may be more primitive than CD34~+ cells. Concerning about this, the objectives of part I were to evaluate the expansion efficiency of AC133~+ cells in...
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