Bone marrow transplantation enhances trafficking of host-derived myelomonocytic cells that rescue intestinal mucosa after whole body radiation

[[abstract]]BACKGROUND: Bone marrow (BM)-derived cells were demonstrated within intestines after radiation damage and were reported to be responsible for intestine repair. However, there was a discrepancy between intestine epithelial clonogenic regeneration, and mouse survival after BM transplantation (BMT) and radiation. The contribution of BM to acute intestine repair after radiation needed further investigation. METHODS: Mouse survival, intestine microcolony assay, immunohistochemical studies of both intestine and BM were evaluated in mice after whole body irradiation (WBI) and BMT. Immunoblotting, flowcytometry, and double immunostaining were used to evaluate the amount and the character of stroma cells within intestines of recipient mice after receiving gender-mismatched BMT or BMT from green fluorescence donors. RESULTS: Stromal cell proliferation within the lamina propria correlated with the beneficial effect of BMT to intestine recovery and day-8 survival of mice. Few donor-derived cells were found before the completion of intestine repair. The number of host but not donor-derived myelomonocytic and stromal cells increased dramatically within one week after radiation and BMT. Depletion of myelomonocytic cells of recipient mice abolished the mitigating effect of BMT. CONCLUSIONS: Besides rescuing injured BM from aplasia, BMT triggers trafficking of host CD11b(+) myelomonocytic cells from the host marrow to the radiation-injured intestinal mucosa, enhancing the proliferation of intestinal stroma cells, leading secondarily to epithelial regeneration