Heterogeneity of Latent Transforming Growth Factor-β Isolated from Bone Matrix Proteins

Transforming growth factor-β (TGFβ) is a family of 25-kDa peptides that appear to be important regulators of cell proliferation, differentiation, and differentiated function in many tissues. TGFβ is present in platelets and serum and is released by cultured cells as several distinct large mol wt complexes of TGFβ with other proteins. These complexes are biologically inactive and are generically called latent TGFβ (LTGFβ). Large quantities of TGFβ are present in bone matrix. This study was undertaken to determine whether the TGFβ in bone matrix was present as a free 25-kDa peptide or a large mol wt L-TGFβ complex. TGFβ activity was determined by inhibition of [3H]methylthymidine incorporation in mink lung epithelial cells. The specificity of inhibition was determined by treating fractions with a polyclonal rabbit antiporcine TGFβ-blocking antibody before assay. Latency was examined by assaying untreated and acid-treated fractions for TGFβ activity. Acid treatment of EDTA extracts of the bovine bone matrix ...