Background/aims: TGF-beta1 plays a major role in extracellular matrix (ECM) accumulation in tissue fibrosis. Connective tissue growth factor appears to play a critical role in this effect. Endoglin is a component of the transforming growth factor b (TGF-beta) receptor complex. Endoglin is upregulated by TGF-beta1, but its functional role in ECM regulation is unknown. Using rat myoblasts as a model system, we have assessed the role of endoglin on regulating CTGF expression and ECM synthesis and accumulation in the presence or absence of TGF-beta1.
Methods: L6E9 myoblast cell line was transfected with human endoglin, and collagen, fibronectin and CTGF production was assessed by Western blot and by proline incorporation to collagen proteins.
Results: Northern blot analysis revealed that parental rat myoblasts L6E9 do not express endogenous endoglin. Upon endoglin transfection, endoglin-expressing cells displayed a decreased CTGF expression and decreased collagen and fibronectin accumulation respect to mock transfectants. Northern blot analysis also revealed a decreased alpha2 (I) procollagen mRNA expression in endoglin transfectants. TGF-beta1 treatment induced an increase in CTGF expression and collagen synthesis and accumulation in L6E9 myoblasts. This effect was significantly lower in endoglin-transfected than in mock-transfected cells.
Conclusion: These results demonstrate that endoglin expression negatively regulates basal and TGF-beta1-induced CTGF and collagen expression and synthesis.
Copyright 2004 S. Karger AG, Basel