Effects of mouse genotype on bone wound healing and irradiation-induced delay of healing.

We tested the effects of mouse genotype (C57BL/6NHsd, NOD/SCID, SAMR1, and SAMP6) and ionizing irradiation on bone wound healing. Unicortical wounds were made in the proximal tibiae, and the time course of spontaneous healing and effects of irradiation were monitored radiographically and histologically. There was reproducible healing beginning with intramedullary osteogenesis, subsequent bone resorption by osteoclasts, gradual bridging of the cortical wound, and re-population of medullary hematopoietic cells. The most rapid wound closure was noted in SAMR1 mice, followed by SAMP6, C57BL/6NHsd, and NOD/SCID. Ionizing irradiation (20 Gy) to the leg significantly delayed bone wound healing in mice of all four genotypes. Mice with genetically-determined predisposition to early osteopenia (SAMP6) or with immune deficiency (NOD/SCID) had impairments in bone wound healing. These mouse models should be valuable for determining the effects of irradiation on bone healing and also for the design and testing of novel bone growth-enhancing drugs and mitigators of ionizing irradiation.