Diminished transforming growth factor beta2 production leads to increased expression of a profibrotic procollagen alpha2 type I messenger RNA variant in embryonic fibroblasts of UCD-200 chickens, a model for systemic sclerosis.
OBJECTIVE
A procollagen alpha2(I) 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 proalpha2(I) 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 beta1 (TGFbeta1) and TGFbeta2 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 proalpha2(I) mRNA variant. TGFbeta1 stimulated the proliferation of UCD-200-CEF, but not NWL-CEF. The 115 bp:180 bp ratio was increased by TGFbeta1 in both NWL-CEF and UCD-CEF. TGFbeta2 and TGFbeta3 reduced the expression of the profibrotic proalpha2(I) mRNA in UCD-200-CEF to the same levels observed in healthy control NWL-CEF. In culture supernatants, NWL-CEF produced 4.1 times more TGFbeta2 than that produced by UCD-CEF. Inhibition of endogenous TGFbeta2 in NWL-CEF resulted in the same 115 bp:180 bp ratio as seen in untreated UCD-CEF.


CONCLUSIONS
TGFbeta2 reduces the expression of a profibrotic proalpha2(I) mRNA variant in UCD-200-CEF. The constitutive overproduction of this proalpha2(I) mRNA variant and the diminished synthesis of TGFbeta2 in untreated UCD-200-CEF suggest that TGFbeta2 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 TGFbeta2 in human systemic sclerosis.
Prelog
Martina
M
Innsbruck Medical University, Innsbruck, Austria.
Scheidegger
Paul
P
Peter
Silvia
S
Gershwin
M Eric
ME
Wick
Georg
G
Sgonc
Roswitha
R
D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D024042:Collagen Type I / Q000096:biosynthesis*; D005347:Fibroblasts; D023421:Models, Animal; D012333:RNA, Messenger / Q000096:biosynthesis; D012595:Scleroderma, Systemic / Q000276:immunology*; D016212:Transforming Growth Factor beta / Q000096:biosynthesis*; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2
D024042:Collagen Type I; D012333:RNA, Messenger; C508960:TGFB1 protein, human; C509041:TGFB2 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2