Stem cell factor improves SCID-repopulating activity of human umbilical cord blood-derived hematopoietic stem/progenitor cells in xenotransplanted NOD/SCID mouse model

Abstract

Summary:Poor in vivo homing capacity of hematopoietic stem/ progenitor cells (HS/PCs) from umbilical cord blood (UCB) can be reversed by short-term ex vivo manipulation with recombinant human stem cell factor (rHuSCF). This study was designed to evaluate the effect of ex vivo manipulation of UCB-derived HS/PCs with rHuSCF on human cell engraftment rates in xenotransplanted NOD/ SCID mouse model. The human cell engraftment rates in xenotransplanted primary and secondary NOD/SCID mice were characterized using four-color flow cytometric analysis and progenitor assay. Grafts of rHuSCF-treated UCB CD34 þ cells resulted in significantly higher levels of human cell engraftment than that of nontreated ones in both xenotransplanted primary and secondary NOD/ SCID recipients. Fresh UCB CD34 þ cells did not express either of the matrix metalloproteinase (MMP) family members MMP-2 or MMP-9. rHuSCF-treated UCB CD34 þ cells expressed significant levels of MMP-2 and MMP-9. Pretreatment of UCB CD34 þ cells with the specific MMP inhibitor completely blocked human cell engraftment in xenotransplanted NOD/SCID recipients. Our results indicate that ex vivo manipulation of human HS/PCs with rHuSCF might provide an optimal approach to develop more effective stem cell-based therapies in situations where engraftment is delayed due to limiting HS/PCs number, for example, UCB transplantation.

Protein kinase B (PKB/c-akt) regulates homing of hematopoietic progenitors through modulation of their adhesive and migratory properties

“…Although inhibition of PKB activity significantly reduced integrin expression (Figure 3), the levels were comparable with those on CD34 ϩ cells analyzed immediately after isolation (Figure 4C-D). Although it has been shown that ex vivo culture of UCB-derived hematopoietic progenitors with SCF results in enhanced engraftment levels compared with untreated progenitors, [31][32][33] our results suggest that abrogation of culture induced up-regulation of integrin expression by inhibition of PKB activity could further enhance the homing capacity.…”

How do stem cells find their way home?

“…Similarly, incubation with SCF induces expression of MMP-2/9 and moreover, increased homing and repopulation of NOD/SCID mice. 69,105 Preliminary results document that the cell-surface proteolytic enzyme membrane type 1 matrix metalloproteinase (MT1-MMP) is expressed by human CD34 ϩ progenitors, is activated by SDF-1 and G-CSF, and is needed for SDF-1-induced migration in vitro and for in vivo homing and mobilization. 106,107 Interestingly, proteolytic enzymes also negatively regulate cell migration.…”

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

“…SCF has been shown to improve homing capacity of UCB cells in preclinical models. 53 FL leads to short-term expansion 54,55 and helps regulate 56 the expression of very late antigen (VLA)-4 and VLA-5, adhesion molecules which play a part in proliferation and differentiation either directly or through the modulation of cytokineinduced signals. 57,58 In a study to evaluate cytokine combinations that lead to expansion without change in repopulating potential, Levac et al 59 cultured CD34 þ CD38ÀLinÀ cord blood cells in serum-free media with SCF and FL and found that TPO may be able to replace IL-3, IL-6 and G-CSF without changing the number of SRC.…”