Transforming Growth Factor-β Regulation of Collagenase, 72Kda-Progelatinase, Timp and Pai-1 Expression in Rat Bone Cell Populations and Human Fibroblasts

Abstract

Quiescent cultures of normal fetal rat calvarial bone cell populations (RC I and RC IV) and human fibroblasts were incubated with 1.0 ng/ml TGF-beta and the conditioned culture media were processed individually to separate collagenase and 72 kDa-progelatinase from TIMP, the tissue inhibitor of matrix metalloendoproteinases, using mini-columns of heparin- and gelatin-Sepharose. Collagenase synthesis was decreased progressively by TGF-beta in fibroblasts despite a 1.6-fold increase in secreted protein levels and a approximately 1.8-fold increase in 72 kDa-progelatinase synthesis. The human fibroblasts and the osteoblast-enriched RC IV cells showed a greater TGF-beta-induced stimulation in 72 kDa-progelatinase levels over controls compared with the RC I cells. In contrast to RC IV cells, in which TIMP mRNA levels were increased 2.9-fold by TGF-beta, the constitutive level of TIMP transcripts in the RC I cells was greater than 20-fold over that of the RC IV cells, but was not elevated by TGF-beta. TGF-beta also increased TIMP expression in fibroblasts approximately 1.7-fold and PAI-1 levels approximately 5-fold in RC IV cells, and greater than 10-fold in fibroblasts.