Effects of a Single Dose of X-Ray Irradiation on MMP-9 Expression and Morphology of the Cerebellum Cortex of Adult Rats.

Although radiation is a strategy widely used to inhibit cancer progression, which includes those of the neck and head, there are still few experimental reports on radiation effects in the cerebellum, particularly on the morphology of its cortex layers and on the Matrix metalloproteinases' (MMPs') expression, which, recently, seems to be involved in the progression of some mental disorders. Therefore, in the present study, we evaluated the morphology of the cerebellum close to the expression of MMP-9 from 4 up to 60 days after a 15-Gy X-ray single dose of X-ray irradiation had been applied to the heads of healthy adult male rats. The cerebellum of the control and irradiated groups was submitted for an analysis of cell Purkinje count, nuclear perimeter, and chromatin density using morphometric estimatives obtained from the Feulgen histochemistry reaction. In addition, immunolocalization and estimative for MMP-9 expression were determined in the cerebellar cortex on days 4, 9, 14, 25, and 60 after the irradiation procedure. Results demonstrated that irradiation produced a significant reduction in the total number of Purkinje cells and a reduction in their nuclear perimeter, along with an increase in chromatin condensation and visible nuclear fragmentation, which was also detected in the granular layer. MMP-9 expression was significantly increased on 4, 9, and 14 days, being detected around the Purkinje cells and in parallel fibres at the molecular layer. We conclude that the effects of a single dose of 15-Gy X-ray irradiation in the cerebellum were an increase in MMP-9 expression in the first 2 weeks after irradiation, especially surrounding the Purkinje cells and in the molecular layers, with morphological changes in the Purkinje cell and granular cell layers, suggesting a continuous cell loss throughout the days evaluated after irradiation.