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Cytomatrix |
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Expansion of Hematopoietic Progenitors in a novel 3-Dimensional Matrix | ||
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Kristen Biber, Bettina Ehring, Karen Ballen, Mark Popovsky,
Kathleen Pigeon, Daniel Plosky, Mark Pykett and Michael Rosenzweig. Cytomatrix, Woburn, MA, 1801, United States; New England Region, American Red Cross, Dedham, MA, 02026, United States; and Hematology/Oncology, Umass Memorial Healthcare, Worcester, MA, 01655 , United States. |
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Using a novel three-dimensional matrix, CellfoamTM, we have established a system for the maintenance and expansion of human hematopoietic progenitor cells (HPCs) from mobilized peripheral blood (mPB), bone marrow (BM) and umbilical cord blood (UCB) under serum-free, cytokine free conditions. A 2-4 fold increase in the number of CD34 + cells recovered from the CellfoamTM cultures has been observed while the number of CD34 + CD38- cells expands several logs. The in vivo reconstitution of NOD/SCID mice has demonstrated the superior performance of Cellfoam TM cultured HPCs over traditional expansion protocols. In addition to primitive progenitors necessary for sustained long-term engraftment there may be an advantage to the administration of larger numbers of cells at intermediate stages of hematopoietic development (e.g. CFU-like cells), which will contribute to the immediate blood cell recovery. In an attempt to improve the quality of transplanted HPCs, we are comparing the in vitro function and in vivo engraftment potential of HPCs from UCB, BM and/or mPB after culture in the CellfoamTM system with and without supplemental cytokines. Using cord blood-derived progenitors, we observed a remarkable enhancement in the recovery of CD34+ cells and colony-forming activity from the Cellfoam TM system when low levels of FLK2-L were present in the culture. However, addition of SCF to the culture resulted in no expansion in cell number and no enrichment of colony forming activity. Similar results were obtained using bone marrow-derived HPCs with the greatest enhancement of CD34+ CD38- cells appearing in cultures containing FLK2-L. As expected, cultures containing FLK2-L or SCF showed an increase in the number of myeloid (CD33+) progenitors and enhanced maintenance of lymphoid committed progenitors (CD3+ and CD19+) compared to cytokine-free cultures. Reconstitution studies revealed that bone marrow-derived HPCs that have been exposed to cytokines in vitro, have minimal long-term (6 weeks post injection) engraftment capability compared to those cultured under cytokine-free conditions. Preliminary evidence suggests that cytokine-exposed cells do have short-term (3 weeks post injection) engraftment potential. Therefore, the possibility exists that long-term engraftment by cytokine-free cultured HPCs can be enhanced by transplantation of cytokine-exposed HPCs that will contribute to the immune recovery of a patient following transplantation.   |
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