Effects of Ionizing Radiation on In Vitro Differentiation of Osteoblasts Derived from Rat Bone Marrow Stroma

Abstract

Radiotherapy influences bone formation at the surfaces of endosseous implants used for maxillofacial prosthetic rehabilitation in patients with oral tumors. This study indicates that higher doses of radiation interfere with differentiation and delay the mineralization of bone matrix in vitro. AbstractPurpose: Radiotherapy influences bone formation at the surfaces of endosseous implants used for maxillofacial prosthetic rehabilitation in patients with oral tumors. We hypothesize that ionizing irradiation affects the differentiation and cellular physiology of osteoblasts, and thereby impairs matrix formation and mineralization during bone wound healing. The aim of this study was to investigate how the dosage of ionizing radiation affects differentiation of osteoblasts in vitro.Methods: Osteoblasts were isolated from the bone marrow of Wistar rats. They were exposed to 0, 40, 400, or 4000 mGy of gamma-radiation (using cobalt-60) and cultured for 5, 7, 10, or 14 days. Assays were performed for cell adhesion and alkaline phosphatase activity. Electron probe microanalysis was used to monitor bone matrix mineralization. The reverse transcription-polymerase chain reaction was used to determine mRNA expression for alkaline phosphatase, bone sialoprotein, collagen I, osteocalcin, heat shock protein 47, and β-actin. Results: Irradiation of less than 400 mGy induced no significant changes in cell adhesion, alkaline phosphatase activity, or osteoblastic gene expression, compared to controls. Electron probe microanalysis indicated that P and Ca signals were more evident throughout the culture period at doses of up to 400 mGy than at 4000 mGy. Bone matrix mineralization was reduced at 4000 mGy. Conclusion:These results suggest that the phenotypic and molecular changes induced in osteoblasts by higher doses of ionizing radiation interfere with differentiation and delay the mineralization of bone matrix.