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-β 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-β in fibroblasts despite a 1.6-fold increase in secreted protein levels and a $1.8-fold increase in 72 kDa-progelatinase synthesis. The human fibroblasts and the osteoblast-enriched RC IV cells showed a greater TGF-β-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-β, the constitutive level of TMP transcripts in the RC I cells was >20-fold over that of the RC IV cells, but was not elevated by TGF-β. TGF-β also increased TIMP expression in fibroblasts $1.7-fold and PAI-1 levels $5-fold in RC IV cells, and >10-fold in fibroblasts.

Key Words:

• Collagenase
• Gelatinase
• Proteinases
• TIMP
• Growth Factors
• TGF-β