Long-Term Multilineage Development from Human Umbilical Cord Blood Stem Cells in a Novel SCID-HU Graft
Although human hematopoietic stem cells can be isolated based on cell surface antigen expression, their proliferative and developmental capacity must still be defined by their ability to produce multiple hematopoietic cell lineages for prolonged times in vivo. In order to derive a long-term in vivo multilineage SCID-hu graft we transplanted a human fetal bone and spleen adjacent to an HLA class I mismatched fetal thymus fragment in immunodeficient SCID mice (SCID-hu BTS). Grafts were analyzed at various times post transplant for cells expressing specific lineage markers. The bone marrow of SCID-hu BTS grafts maintained B cells and myeloid cells for at least 36 weeks post transplant. Analysis for progenitor content within grafts revealed that CD34+ cells, CFU-G/M, and CFU-GEMM were maintained in 94%(109/116), 100%(66/66) and 79%(52/66) up to 28 weeks. HSC (CD34hiThy-l+Lin-) sorted from 20 week old SCID-hu BTS grafts demonstrated potent secondary multilineage reconstituting potential when injected into HLA mismatched SCID-hu bone grafts. In addition both immature and mature T-cells, derived from progenitors within the fetal bone, were found in 87%(101/116) of grafts analyzed up to 36 weeks in vivo. Injection of irradiated SCID-hu BTS grafts with CD34+Thy-1+Lin-umbilical cord blood cells produced B-cells, myeloid cells, T-cells and CD34+ cells in individual grafts when analyzed 8 weeks post reconstitution, further demonstrating the multipotential nature of these HSC populations. This model is currently being used to define soluble factors or cells that are capable of enhancing human HSC engraftment.
KeywordsMyeloid Cell Umbilical Cord Blood SCID Mouse Post Transplant Double Positive
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