Ex vivo culture rescues hematopoietic stem cells with long-term repopulating capacity following harvest from lethally irradiated mice.

OBJECTIVE: High-dose ionizing radiation can cause lethal myeloablation in exposed individuals. We examined whether ex vivo culture could rescue hematopoietic stem cells with repopulating capacity following harvest from lethally irradiated animals.
METHODS: We exposed B6.SJL mice to 1050 cGy, harvested their irradiated bone marrow (BM), and examined whether ex vivo culture of the irradiated BM mononuclear cells (MNC) with porcine microvascular endothelial cells (PMVEC) or cytokines alone could rescue hematopoietic cells with in vitro colony-forming activity, in vivo radioprotective capacity, and long-term repopulating potential.
RESULTS: PMVEC coculture supported the recovery of fourfold and 80-fold greater numbers of total cells and colony-forming cells (CFC) compared to cyokines alone following 1050 cGy irradiation. All control mice irradiated with 1050 cGy died by day 30, as did mice transplanted with 1050 cGy-irradiated BM MNC. In contrast, transplantation of 1050 cGy-irradiated/PMVEC-cultured BM was fully radioprotective in 12 of 16 recipient mice (75%) exposed to 1050 cGy. Six of the 12 CD45.2+ mice (50%) transplanted with 1050 cGy-irradiated/PMVEC-cultured cells showed long-term (>6 months) multilineage repopulation derived from irradiated donor CD45.1+ cells. Surprisingly, transplantation of identical doses of 1050 cGy-irradiated/cytokine-cultured BM was also radioprotective in 50% of irradiated recipient mice and 50% of these mice demonstrated donor-derived repopulation.
CONCLUSIONS: Fully functional BM stem and progenitor cells can be rescued following harvest from lethally irradiated animals via ex vivo culture with PMVEC or cytokines alone. This method can serve as a model for the rapid ex vivo rescue and transplantation of autologous BM progenitors in the treatment of victims of radiation injury.