Transforming growth factor beta (TGF-beta) levels in the conditioned mediaof human bone cells: Relationship to donor age, bone volume, and concentration of TGF-beta in human bone matrix in vivo

Transforming growth factor-beta (TGF-beta) is thought to play an important role in human bone remodeling. In the present study, we examined constituti ve differences in TGF-beta levels in primary bone cell cultures from the il iac crest of 112 women, aged 28-79 years. TGF-beta 1 was the major TGF-beta isoform in the conditioned media, as determined by neutralizing TGF-beta a ctivity with specific antibodies against TGF-beta 1-3 in the mink lung cell bioassay, and by enzyme-linked immunoassay (ELISA), TGF-beta 1 levels in t he conditioned media did not change with donor age, There was a lack of ass ociation between TGF-beta levels in vitro and the concentration of matrix-a ssociated TGF-beta in vivo. TGF-beta 1 levels failed to be associated with the local trabecular bone volume in the complete study population (r = +0.1 5, p = 0.16, n = 89). A significant association between TGF-beta 1 levels a nd bone volume was present in premenopausal women (r = +0.39, p = 0.02, n = 33), but was largely accounted for by the two samples with the highest TGF -beta concentrations. In conclusion, our data suggest that TGF-beta 1 is th e major TGF-beta isoform produced by human bone cells in vitro, and that th e constitutive secretion of TGF-beta by bone cells does not change with age . Whether constitutive differences in TGF-beta secretion may be a determina nt of human bone mass remains to be clarified in further studies. (Bone 24: 565-569; 1999) (C) 1999 by Elsevier Science Inc. All rights reserved.