Efeitos da radiação ionizante no osso imaturo: influência na rede de osteócitos, padrão de colágeno e microarquitetura

Abstract

Ionizing radiation causes changes in bone repair process. The aim of the present study was to evaluate the effects of ionizing radiation on immature bone of an injured area. Twenty rabbits underwent surgery for the creation of bone defects in their left tibias. After 2 weeks, they were randomly divided in two groups (n = 10): NoIr (control group); Ir (irradiated group). Ir animals were irradiated (single dose 30 Gy) in the operated tibias. Four weeks after the surgical procedure the animals were euthanized. Three-dimensional microarchitecture was analyzed by X-ray microtomography (micro CT). Results showed that the trabecular thickness of the Ir was smaller than NoIr (p = 0.028), but no difference was found for bone volume fraction. Osteocyte network, bone area quantification and collagen pattern were histomorphometrically analyzed. Analysis of osteocyte network showed that lacunae filled by osteocytes were more numerous (p <0.0001) in NoIr (2.61 ± 0.64) than Ir (1.97 ± 0.53) and empty lacunae were more present (p <0.003) in Ir group (0.14 ± 0.10) compared to NoIr (0.09 ± 0.10). Mean size of osteocyte lacunae revealed higher values (P <0.01) for Ir (15.41 ± 4.41) than NoIr group (12.72 ± 3.73). Analysis of the bone area quantification showed no statistically significant difference between groups. Analysis of Picrosirius Red revealed a higher amount (p <0.05) of mature collagen in NoIr group (28.96 ± 5.31) than Ir group (23.42 ± 4.47). Quantification of immature collagen showed no statistical difference between the groups. Results evidenced a delay in repair process of irradiated bone, 14 days after radiotherapy.