Age-Related-Changes Of Cancellous And Cortical Bone Histomorphometry In Female Sprague-Dawley Rats

Double fluorescent labeled virgin female Sprague-Dawley rats were serial sacrificed between 3 and 16 months of age to characterize age-related skeletal changes. Histomorphometric analyses were performed on microradiographs and 20-mu-m undecalcified longitudinal sections of the proximal tibia and fourth lumbar vertebral body and cross sections of tibial shafts. The most consistent age-related change among all test bone sites is a decrease in skeletal cellular based metabolic activities, including reductions in both recruitment and functional activity for osteoclasts and osteoblasts. Age-related cancellous bone loss with a discontinued trabecular structure was observed in proximal tibial metaphysis. Although cancellous bone mass in the lumbar vertebral body does not change with increasing age, there was a significant increase in trabecular width. Age-related cortical bone change involves a redistribution of equal amounts of bone mass from the cortical-endosteal region to the subperiosteal region, leading to an expansion in both subperiosteal and marrow areas while cortical areas remain unchanged.