Short Pulse of a Small Peptide Agonist of Stromal Cell-Derived Factor - 1 (SDF-1) Enhances the Engraftment of Expanded Human Cord Blood Hematopoietic Progenitor Cells in NOD/SCID Mice.

SDF-1 is the ligand to the chemokine receptor CXCR-4. A small synthetic peptide agonist of SDF-1 (CTCE-0214) has been shown to expand human cord blood hematopoietic stem and progenitor cells. In this study, we investigated whether a brief exposure of expanded cord blood hematopoietic cells to CTCE-0214 can improve engraftment of the cells into NOD/SCID mice. Published in vivo studies demonstrated that the administration of CTCE-0214 to transplanted NOD/SCID mice mobilized human colony forming cells (CFC) and enhanced human thrombopoiesis (Exp Hematol 32, 300, 2004). Our earlier study showed that CTCE-0214 added to single factors of thrombopoietin (TPO), stem cell factor (SCF), or Flt-3 ligand (F3L) synergistically increased the survival of enriched cord blood CD34+ cells (Blood 102, 960a, 2003). In this study, we further investigated the effects of CTCE-0214 on the ex vivo expansion of CD34+ cells to multi-lineage progenitors and the homing and engraftment capacity of expanded human progenitor cells after a short in vitro exposure to the peptide prior to infusion into NOD/SCID mice. Enriched CD34+ cells (MACS) derived from cord blood were cultured for 8 days in serum-free medium QBSF-60 containing TPO (50 ng/ml), SCF (50 ng/nl) and F3L (80 ng/ml) (TSF), with or without CTCE-0214 (0.01 ng/ml) (TSF+CTCE-0214) added at day 4. Progenitor cells expanded for 8 days in the absence of CTCE-0214 were pulsed with the peptide (100 ng/ml) for 4 hours (TSFpCTCE-0214). Results are summarized in Table. CTCE-0214 significantly (N=30, p≤0.05, paired t-test) increased the fold expansion of total nucleated cells (TNC), CD34+ cells, CD34+CD38- cells, CFU-GM, CFU-E, and CFU-MK (total CFC). Expanded progenitor cells (with and without CTCE-0214) were then infused into irradiated NOD/SCID mice. After 6 weeks, enhanced engraftments of human CD45+ cells (p≤0.05, N=21) were demonstrated in the bone marrow (BM) of mice that received cells cultured in TSF+CTCE-0214. Interestingly, a short pulse of cells expanded in TSF to CTCE-0214 for 4 hours also significantly increased the NOD/SCID engraftment (N=18), although no major changes to the in vitro read-out parameters were observed. The mechanism could be associated with the increased homing capacity of progenitor cells after pulsing with CTCE-0214. In conclusion, our results showed that CTCE-0214 enhances the proliferation of early progenitor cells in culture and exposure to the peptide can enhance the engraftment potential of expanded cells in NOD/SCID mice. The SDF-1 peptide agonist could be developed for application to hematopoietic stem cell transplantation and ex vivo expansion.

NOD/SCID Engraftment of Expanded Cord Blood Stem Cells