A Histomorphometric Study of Effects and Mechanism of Localized Cobalt-60 Irradiation on Bone

Abstract

The purpose of this study were to investigate the effects and mechanism of localized cobalt-60 irradiation (IR) on bone using static and dynamic bone histomorphometric analysis and the mechanisms of irradiation-induced bone loss. Sixty four 3-month old male ICR mice were randomly assigned into control and irradiated (IR) groups. Eight rats of each group were aacrified at 1, 7, 14 or 28 days after 12 Gy of localized cobalt-60 irradiation on right femur and tibia. The parameters of bone formation and bone resorption, and the mechanism of IR on bone tissue were evaluated using static and dynamic bone histomorphometry. Seven days after localized cobalt-60 irradiation, there were significant increases in osteoclastic number and activity, and decreases in OB/mm^2. A significant decrease in OC/mm^2 occurred 14 days after irradiation. No significant difference wre found in percent hard tissue, percent bone, trabecular thickness, mineral apposition rate and bone formation rate between the cobalt-60 irradiated and control group 1 day after irradiation. However, they became significantly less on day 7 and began to resume on the day 28 after irradiation. Therefore, cobalt-60 irradiation could significantly increase osteoclastic bone resorption. In addition, it significantly decrease osteoblast differentiation and induce dramatic bone loss. In conclusion, cobalt-60 could result in osteopenia.