Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Serum-free cultures supplemented with IL-6, IL-3, steel factor, and erythropoietin support extensive production of erythroid cells from purified bone marrow stem cell candidates which are themselves maintained in number in such cultures. In this study, the mechanism responsible for the observed maintenance of primitive hematopoietic cells in rapidly proliferating suspension cultures was examined. The following models were considered: (1) proliferating cells represent a small minority of cells at start of culture (large quiescent pool), (2) self-renewal of primitive cells (balanced by loss through differentiation and death), and (3) asymmetrical divisions (each division of a primitive cell yielding one equally primitive daughter cell and one less primitive, i.e., committed daughter cell). To discriminate between these various models, the proliferative behavior of purified CD34+ CD71 cells was studied at a population level using the fluorescent membrane dye PKH26 and at a single cell level by studying cultures of individually sorted CD34+ CD45RAloCD71lo bone marrow stem cell candidates. The results from these experiments indicate that the majority of purified stem cell candidates do not rapidly proliferate in response to the combination of growth factors used and that limited production of CD34+ cells compensates for the loss of such cells in culture. These observations have to be taken into account in the development of clinical useful strategies for the expansion of primitive hematopoietic bone marrow cells ex vivo.
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PMID:In vitro properties of purified human stem cell candidates. 752 86

We previously described that cells with a CD34+CD71lo phenotype from adult human bone marrow are maintained at constant numbers in long-term suspension cultures supplemented with interleukin-6 (IL-6), IL-3, mast growth factor (MGF) (a c-kit ligand), and erythropoietin (Epo). In view of the large increase in cell numbers in such cultures (for example, > 10(6)-fold per cell), this was an unexpected finding. The following models for the observed maintenance of CD34+CD71lo cells in our cultures were considered: (1) survival of non-dividing cells; (2) self-renewal balanced by loss of cells; (3) asymmetrical divisions; and (4) combinations of the above. Two experimental strategies were explored to discriminate between these models. In the first, sorted CD34+CD45RAloCD71lo cells were labeled with the flourescent tracking dye PKH26, followed by analysis of PKH26 fluorescence of CD34+CD71lo and other cells present in the cultures at various times (up to 11 weeks). In the second approach, single CD34+CD45RAloCD71lo cells were directly sorted into individual wells, and growing cells were then analyzed by flow cytometry. Results from these experiments indicated a considerable variability in (1) the number of surviving input cells (ranging from 30 to 80%); (2) the proportion of cells that contributed significantly to the total cell production measured at day 20 (ranging from 1 to 5%); and (3) the number of CD34+ cells present in individual clones. Taken together, the observed maintenance of primitive CD34+ cells in our cultures apparently involves a combination of survival of CD34+CD71lo cells with a vary low turnover together with a very limited production of CD34+ cells. Clonal heterogeneity, differences in cell cycle kinetics between CD34+ and CD34- cells, and observations that the majority of bone marrow-derived CD34+CD45RAloCD71lo cells do not show a rapid proliferative response to a mixture of IL-6, IL-3, MGF, and Epo will have to be taken into account in the development of experimental strategies aimed at clinically useful expansion of primitive hematopoietic cells ex vivo.
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PMID:Maintenance of hematopoiesis in serum-free bone marrow cultures involves sequential recruitment of quiescent progenitors. 768 81