Abstract

Hematopoietic stem cells (HSCs) are commonly used in transplantation therapy to rescue the hematopoietic and immune systems following systemic chemotherapy or irradiation. However, some patients receive inadequate numbers of HSCs and this often results in delayed reconstitution of hematopoiesis and immune function and associated toxicities. We previously demonstrated that a stabilized derivative of prostaglandin (PG) E2 increases vertebrate HSCs both in vivo and in vitro. 16,16-dimethyl PGE2 (dmPGE2) significantly increased HSCs during zebrafish embryogenesis and in the adult marrow following injury. Incubation of murine embryonic stem cells with dmPGE2 during embryoid body differentiation resulted in a dose-dependent increase in hematopoietic colonies, demonstrating that the function of PGE2 in HSC regulation is conserved in mammals. Finally, ex vivo treatment of murine bone marrow with dmPGE2 resulted in a 2-fold increase in engrafting cells in a limiting dilution competitive repopulation assay. No negative effects on serial transplantability of HSCs were observed in these animal models. To investigate the therapeutic potential of PGE2 for the amplification of blood stem cells, we exposed human cord blood (hCB) cells to dmPGE2 in vitro and measured the effects on stem and progenitor populations both in vitro and in vivo. Red cell depleted umbilical cord blood specimens, cryopreserved for clinical use, were thawed and divided for parallel processing. Ex vivo treatment of hCB cells for 1 hour with dmPGE2 in dextran/albumin had no negative impact on absolute cell count or the viability and relative distribution of both CD45 and CD34 positive cells compared to vehicle treated control hCB cells. Significantly, hCB treated with dmPGE2 produced enhanced numbers of GM and GEMM colonies in methylcellose CFU-C assays compared to controls. Human CB cells treated ex vivo with dmPGE2 for 1 hour and transplanted at a dose of 20 million live CD45+ cells per recipient were capable of repopulating NOD/SCID mice after sublethal irradiation. In comparative studies at 6 weeks post transplantation, human CD34+ and CD45+ cells could be detected in the marrow (>2%) of dmPGE2 treated (4/8) and control treated (1/6) recipients. Long-term and competitive transplantation experiments to assess the effect of dmPGE2 treatment on functional HSCs are currently in progress. Our data suggests that treatment of human cord blood products with dmPGE2 will be both safe and effective in achieving expansion of hematopoietic stem cells for transplantation in the clinical setting. TE North and W Goessling contributed equally to this work.

Author notes

Disclosure: No relevant conflicts of interest to declare.