A comprehensive investigation of skeletal dynamics in the aging rat

The authors hypothesize that the age-related decline in bone formation will be reflected in an altered pattern of gene expression for proteins found in the extracellular matrix (ECM) of bone. Further, this decline in bone formation and altered ECM composition contribute to a decreased mechanical competence. Previous studies have investigated age-related changes in bone mechanics and bone metabolism independently. Further, these studies have used different strains of rats with varied growth rates and life spans making interpretation difficult. The present study is the first comprehensive investigation of the effect of aging on bone at the molecular, cellular and whole organ levels. The results showed that the decline in bone formation and material properties was associated with a corresponding decrease in the steady-state levels of type I collagen, osteopontin and osteocalcin mRNA. The abundance and orientation of collagen fibers contribute to the material properties of bone, as may the abundance of osteopontin and osteocalcin. Therefore, the authors´ results suggest a decrease in ECM production and composition may contribute to age-related changes in bone material properties