LUM and Osteopenia: Ablation of LTBP-3 reduces both osteogenesis and bone resorption, and resulted in increased bone mass associated with decreased levels of TGF-β.39,40 Binding of TGF-β to small leucine-rich proteoglycans (decorin, biglycan, and lumican) restricts the TGF-β in the ECM so as to inhibit its activity.41Bgn and Dcn double deficiency results in osteopenia and a striking change in collagen fibril shape.41 ExcessiveTGF-β signaling caused by reduced binding of decorin is also found to be a common mechanism of osteogenesis imperfecta in mouse models.42