Dissociation between stem cell phenotype and NOD/SCID repopulating activity in human peripheral blood CD34+ cells after ex vivo expansion

CD166 regulates human and murine hematopoietic stem cells and the hematopoietic niche

“…Most importantly, differences in the settings WT→WT vs KO→KO were consistent whether grafts contained low-density BM cells (data not shown), lineage depleted BM cells, or LSK cells ( Figure 5C). A smaller percentage of BM-homed KO cells from the central region were in G0/G1 compared with WT cells (Figure 5D), but these differences were not significant, which suggests that increased cell cycle kinetics 27,28 are most likely not responsible for the gradual decline in the engraftment of these cells. Interestingly, expression of CXCR4 on KO HSPC cells was not altered (Figure 5E), suggesting that CD166 is not involved in directed homing of HSPC to the BM.…”

Ex vivo expansion of umbilical cord blood stem cells for transplantation: growing knowledge from the hematopoietic niche

“…Early data suggested that spleen repopulating cells (SRC) were CD34 þ CD38À in contrast to CFC and LTC-IC which were also found in the CD34 þ CD38 þ fraction. 13,40,41 Although CD34 expression has been the most commonly selected surface marker for ex vivo expansion, 15,42 CD34 is often expressed on more differentiated cells and large animal models suggest that CD34 þ cells are not the cells primarily involved in marrow reconstitution, 43,44 and following ex vivo culture, dissociation between CD34 þ CD38À cell expansion and SCID-repopulating capacity has been observed. 45 Preliminary data suggests that as UCB units are made up of progenitor cells that possess both a CD34 þ and a CD34À phenotype, 46,47 isolating a more primitive marker CD133 þ may identify cells that are less mature than those that express CD34.…”

Indian hedgehog gene transfer augments hematopoietic support of human stromal cells including NOD/SCID–ß2m–/– repopulating cells.

“…4 For this reason, many approaches to ex vivo expansion of HSCs have been attempted, and valuable information has been gathered regarding methods to retain stem cell functions during ex vivo culture. [5][6][7] Until recently, interactions between stromal and hematopoietic cells were viewed as essential to the maintenance of stem cell properties, such as the ability to reconstitute the hematopoietic system in vivo after transplantation or in vitro in long-term cultures. 8,9 Several studies have shed light on the molecular mechanisms involved in stromal HSC support ability.…”