Histological assessment of cortical bone changes in diabetic rats.

Background: Diabetes mellitus weakens bone strength due to deterioration of bone quality; however, the histological mechanisms are still unknown. We hypothesized that histological assessment of cortical bone would enable us to determine the cause of the bone strength reduction associated with diabetes mellitus. Our aim was to evaluate the histomorphometric changes of cortical bone associated with deterioration of intrinsic bone properties and bone quality in diabetes mellitus.

Methods: We compared the outcomes of mechanical tests, bone mineral density measured using micro-computed tomography, and histological assessments, by applying Villanueva's bone stain, to the tibial bones of 40-week-old diabetic and control male rats.

Results: With respect to mechanical testing, the maximum load and energy absorption were significantly lower in the diabetic than in the control group, although fracture displacement and stiffness were not significantly different between the two groups. Bone mineral density was significantly higher in the diabetic group than in the control group. Bone histomorphometry revealed that the diabetic rats had fewer osteocytes, greater cortical porosity, and increased mineralization in cortical bone compared with the control group.

Conclusions: Increased mineralization of the cortical bone with greater cortical porosity leads to a weakening of bone strength in diabetes mellitus.