TGF-β alters collagen XII and XIV mRNA levels in cultured equine tenocytes

The effects of TGF-beta1, beta2 and beta3 (TGF-beta) on levels of mRNA corresponding to the a chains of type XII and type XIV collagens in equine tenocyte cultures were assessed using the ribonuclease protection assay (RPA). The level of alpha1(XII) mRNA in untreated monolayer cultures was approximately 50- to 100-fold greater than alpha1(XIV) mRNA level. Addition of TGF-beta resulted in an increase in the amount of alpha1(XII) present and a decrease of alpha1(XIV) mRNA in a dose-dependent manner. Specifically, the level of alpha1(XII) mRNA was doubled, but alpha1(XIV) was decreased to 30% of control by the addition of 2 ng/ ml of TGF-beta1 to the cultures. These effects were completely abrogated by neutralizing antibody specific for TGF-beta. In addition, electron microscopy demonstrated that bundled collagen fibers were formed in the intercellular spaces of multilayered tenocytes which had been cultured for 2 weeks in the presence of exogenous TGF-beta1 together with ascorbic acid phosphate. These results suggest that type XII and/or type XIV collagens modulate the structure of ECM formed by tenocytes in culture. (C) 2002 Elsevier Science B.V. and International Society of Matrix Biology. All rights reserved.