A novel method of myeloablation to enhance engraftment of adult bone marrow cells in newborn mice.

This report describes the successful development of a transplantation model in which we engrafted adult murine bone marrow hematopoietic cells in congenic day-old murine pups. Newborn animals conditioned with high doses (> or = 7.0 Gy) of total-body irradiation (TBI) demonstrated severe growth retardation and untoward effects on the developing central nervous system. Newborn pups conditioned with a sublethal dose (5.0 Gy) of TBI, however, achieved normal growth and development up to 6 months posttransplantation, and donor type hematopoietic cell reconstitution exceeded 50% in these animals. A second conditioning regimen, comprising one or two doses of busulfan (15 mg/kg) administered intrapartum, resulted in significant myelosuppression in untransplanted newborn pups. This second regimen was associated, however, with engraftment and full multilineage reconstitution of the conditioned newborn recipient animals with adult bone marrow cells, and the engrafted pups grew and developed without apparent defect. A third conditioning regimen combining a single dose of busulfan with sublethal TBI also permitted engraftment and full multilineage reconstitution of the recipient animals. Thus, successful transplantation of hematopoietic cells into newborn recipient mice may be achieved without significant morbidity if a specific conditioning regimen is employed.