Radiation effects and radioprotection in MC3T3-E1 mouse calvarial osteoblastic cells.

Abstract

Little is known about the mechanisms and treatment of radiation-induced inhibition of craniofacial bone growth. In an earlier study, the radioprotector amifostine (WR-2721) administered to rabbits before irradiation radioprotected cultured orbitozygomatic complex periosteal osteoblast-like cells. This study assessed the effects of amifostine and its active metabolite on the radiation survival, function, and phenotype of mouse calvarial osteoblast-like cells in a cell culture model. MC3T3-E1 newborn mouse calvarial osteoblast-like cells underwent gamma-radiation (0 to 10 Gy) in the presence or absence of either WR-2721 or WR-1065, its active metabolite (10 to 10 M). The effects of radiation with and without drugs were assessed using endpoints of colony-forming ability, cell viability, alkaline phosphatase activity, and expression of osteoblastic phenotype genes (alkaline phosphatase, collagen type I, osteocalcin, and osteopontin). All experiments were replicated at least in triplicate. Irradiation resulted in a dose-dependent inhibition of clonogenic cell survival. Pretreatment with WR-1065, but not WR-2721, resulted in a significant improvement of osteoblast-like cell survival. Specifically, maximum radioprotection was observed with 10 M WR-1065 at a clinically relevant 2-Gy dose of irradiation. No significant radioprotection was observed at the lower (5 x 10 M) concentration of WR-1065. Furthermore, radiation seemed to suppress the expression of osteoblastic phenotype-related genes in a dose-dependent manner. This study reveals improved survival after irradiation in osteoblast-like cells treated with WR-1065 in vitro and corroborates previous findings from animal models. Further studies using this agent and similar drugs are important for devising strategies to prevent radiation-induced inhibition of craniofacial bone growth.