Decreased bone mass and bone elasticity in mice lacking the transforming growth factor-β1 gene

Transforming growth factor-β1 (TGF-β1) knockout (TGF-β1−/−) mice were used to investigate the role of TGF-β1 in postnatal bone development. Volumetric bone mineral density (BMD) and mineral content (BMC) in these mice and in their normal (TGF-β1+/+) and heterozygous (TGF-β1+/−) littermates were analyzed by quantitative computed tomography (pQCT). Analysis of the proximal tibial metaphysis showed a significant decrease in the BMC of the TGF-β1−/− mice compared to TGF-β1+/+ or TGF-β1+/− mice; however, no significant difference was observed in BMD between the groups of mice. pQCT analysis of the tibial midshaft diaphysis showed no difference in the BMD or BMC of cortical bone between the groups. Histomorphometry revealed no significant difference in trabecular connectivity or in trabecular bone volume, number, or thickness. However, the width of the tibial growth plate and the longitudinal growth rate were significantly decreased in the TGF-β1−/− mice, resulting in shorter tibia. Acoustic velocity measurements showed significant differences between the groups of mice with an apparent dosage effect of TGF-β1 expression on the anisotropic properties of the bone. These data show that longitudinal growth and total mineral content are affected in mice lacking TGF-β1, as well as the elastic properties of the bone, consistent with an important role for TGF-β1 in bone modeling and bone quality.