The most common method for identifying the progeny of transplanted HSCs is to use genetic differences between donor and recipient mouse strains. After sublethal irradiation these animals can be transplanted with donor 'test' cells from wild-type mice without the need for co-transplanted radioprotective cells to promote survival. In other assays, host mice are used that have defective endogenous hematopoiesis due to mutations in the c-Kit gene (e.g. In one type of assay, lethally irradiated recipient mice are coinjected with congeneic donor-derived 'test' cells along with syngeneic (host-type) 'competitor' cells to provide short term radioprotection, ensure survival, and provide a selective pressure to identify stem cells with high competitive repopulating potential. 1, 2 Various assay formats have been developed that differ in the choice of donor and host mouse strains, the method to ablate or suppress host hematopoiesis prior to donor cell transplantation, the detection methods used to identify the progeny of donor-derived stem cells, and the endpoints and criteria for 'successful' engraftment. The hematopoietic potential of mouse HSCs is assayed by injection into mice in which hematopoiesis has been suppressed by irradiation or other methods, and measuring the repopulation of the recipient BM, blood, spleen, and/or thymus with donor derived cells after a period of at least 4 months. Transplantation assays performed in mice have proven invaluable for studying murine and human stem cell biology, facilitating an improved understanding of the immunophenotype, homing ability, engraftment properties, cytokine responsiveness, and radiation sensitivity of repopulating cells. This property forms the basis of in vivo assays of HSC function. The defining property of a HSC is its ability to reconstitute hematopoiesis following transplantation. In Vivo Assays for Hematopoietic Stem and Progenitor Cells

This review provides an overview of the current status of HSPC research with a focus on (i) assays used to detect and enumerate human and mouse stem and progenitor cells, (ii) phenotypic markers and methods used for their identification and isolation, and (iii) culture systems used to amplify stem and progenitor cells or to promote their differentiation in order to produce large numbers of mature blood cells for transfusion.

HSPCs are also being investigated in cell-based therapies for non-hematopoietic disorders. Ongoing research on human hematopoietic cells is directed toward the identification, isolation, and characterization of the primitive cell types that mediate rapid and/or sustained hematological recovery after cytoreductive therapy and transplantation. The rate of platelet and neutrophil recovery after CB transplantation tends to be slower than after BM or MPB transplantation, due in part to the smaller number of stem and progenitor cells in a typical single-cord graft. Umbilical cord blood (CB) can be collected at birth and cryopreserved, and has become increasingly important as another source of HSCPs for transplantation. Autologous transplantation, using the patient’s own stem and progenitor cells, has also been found to effectively treat specific disorders, e.g., lymphomas and myelomas, and has been employed as a therapy for other malignancies when allogeneic stem cell transplantation is not possible. Transplantation of BM or mobilized PB (MPB) cells from related or HLA-matched unrelated donors (so-called allogeneic transplantation) is a potentially life-saving and curative therapy for leukemia and other diseases of the blood and immune system. Treatment with cytokines (in particular granulocyte colony-stimulating factor G-CSF), some myelosuppressive drugs used in cancer treatment, and compounds that disrupt the interaction between hematopoietic and BM stromal cells can rapidly mobilize large numbers of stem and progenitors into the circulation.

Tissue and Cell Culture Dissociation Reagentsīone marrow (BM) is the major site of hematopoiesis in humans and, under normal conditions, only small numbers of hematopoietic stem and progenitor cells (HSPCs) can be found in the peripheral blood (PB).

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Hematopoietic stem cells