Diminished transforming growth factor β2 production leads to increased expression of a profibrotic procollagen α2 type I messenger RNA variant in embryonic fibroblasts of UCD-200 chickens, a model for systemic sclerosis

Objective. A procollagen alpha 2(l) messenger RNA (mRNA) variant, with a 115-bp band and an expected band of 180 bp, was found to be increased during early, acute scleroderma-like disease in UCD-200 chickens. The present study investigated the influence of cytokines on the expression of these 2 pro2 alpha(l) mRNA variants. Methods. Embryonic fibroblasts of UCD-200 chickens (UCD-200-CEF) and normal white leghorns (NWL-CEF) were grown in 3-dimensional collagen gels. Procollagen mRNA expression was analyzed by RNase protection assay, and proliferation was determined by 3 H-thymidine incorporation. Transforming growth factor beta 1 (TGF beta 1) and TGF beta 2 were measured in culture supernatants by enzyme-linked immunosorbent assay. Results. Compared with NWL-CEF, UCD-200-CEF expressed 7.2 times more of the smaller profibrotic pro alpha 2(l) mRNA variant. TGF beta 1 stimulated the proliferation of UCD-200-CEF, but not NWL-CEF. The 115 bp:180 bp ratio was increased by TGF beta 1 in both NWL-CEF and UCD-CEF. TGF beta 2 and TGF beta 3 reduced the expression of the profibrotic pro alpha 2(l) mRNA in UCD-200-CEF to the same levels observed in healthy control NWL-CEF. In culture supernatants, NWL-CEF pro-duced 4.1 times more TGF beta 2 than that produced by UCD-CEF. Inhibition of endogenous TGF beta 2 in NWL-CEF resulted in the same 115 bp:180 bp ratio as seen in untreated UCD-CEF. Conclusion. TGF beta 2 reduces the expression of a profibrotic pro alpha 2(l) mRNA variant in UCD-200-CEF. The constitutive overproduction of this pro alpha 2(I) mRNA variant and the diminished synthesis of TGF beta 2 in untreated UCD-200-CEF suggest that TGF beta 2 can act as an antifibrotic cytokine and might be a key player during fibrosis onset. These results shed light on the contradictory observations regarding the role of TGF beta 2 in human systemic sclerosis.