Similar repopulating capacity of mitotically active and resting umbilical cord blood CD34+ cells in NOD/SCID mice

Abstract

It was hypothesized that during mammalian development, the extensive need for hematopoietic cells requires equal contribution to blood cell production from both quiescent and cycling hematopoietic stem cells (HSCs) while maintaining the stem cell pool. To investigate this hypothesis, the engraftment potential of umbilical cord blood (UCB) CD34+ cells residing in either G0(G0CD34+ cells) or G1(G1CD34+ cells) phases of the cell cycle was assessed in nonobese diabetic/severe combined immune-deficient (NOD/SCID) mice. Whereas the level of chimerism in mice transplanted with UCB G0CD34+ cells was 69.9% ± 24.0%, mice receiving equal numbers of G1CD34+ cells harbored 46.7% ± 21.3% human cells 8 weeks posttransplantation. Both groups of cells sustained multilineage differentiation and the production of CD34+cells in recipient animals. The relationship between the number of transplanted G0CD34+ or G1CD34+ cells and the level of chimerism was analyzed by a general linear models procedure. Although the initial level of chimerism following transplantation of G0CD34+ cells was higher than that sustained by G1CD34+ cells, the increment in the degree of chimerism obtained with each additional 103 cells of either phenotype was identical, suggesting that the reconstitution potential of these 2 types of cells was similar. Of interest is that human cells recovered from primary recipients of both G0CD34+ and G1CD34+cells engrafted in secondary NOD/SCID recipients, albeit at a substantially lower level, confirming the primitive nature of UCB CD34+ cells residing in G1.

Very Low O2 Concentration (0.1%) Favors G0 Return of Dividing CD34+ Cells

“…Indeed, some studies concluded that bone marrow mononuclear cells and mobilized CD34 ϩ blood cells in G 0 have a better engraftment potential than cells in other phases of the cell cycle [30,40,41]. By contrast, other studies showed no differences in engraftment capacity of CB and fetal cells, whatever their cell cycle phase [42,43], and unimpaired SRC activity of HSCs cycling actively ex vivo [44 -46]. Thus, our results could reflect the maintenance of engraftment capacity of actively proliferating SRCs at 20% of O 2 (in line with [43][44][45][46]), the loss of homing/engraftment capacity of SRCs after re-entering in G 0 at 0.1% O 2 , or the expression of genes independent of cell cycle status and involved in bone marrow homing of SRCs.…”

Early‐acting cytokine‐driven ex vivo expansion of mobilized peripheral blood CD34+ cells generates post‐mitotic offspring with preserved engraftment ability in non‐obese diabetic/severe combined immunodeficient mice

“…In contrast, our results in PBSC and those by Glimm & Eaves (1999) in CB and fetal liver demonstrate that the long‐term repopulating ability of primitive stem cells is not only confined to the cytokine‐non‐responsive compartment, and, moreover, this ability is not necessarily lost after mitotic activation with early‐acting growth factors. In addition, recently it has been proven that CB CD34 + cells residing in either G 0 or G 1 have similar reconstitution potential in NOD/SCID mice (Wilpshaar et al , 2000). Although our methodology can not determine the number of divisions that a group of cells has undergone, the high resolution of PKH26 dye ensured that all the cells transplanted into NOD/SCID mice were post‐mitotic, and therefore that some kind of self‐renewal occurred in our cultures with early‐acting cytokines.…”

Rapid mobilization of murine and human hematopoietic stem and progenitor cells with AMD3100, a CXCR4 antagonist

“…The human SRC assay was performed in sublethally irradiated (300 cGy) NOD-SCID mice as described previously (48), using limiting dilution analysis (49).…”