Endoglin expression regulates basal and TGF-beta1-induced extracellular matrix synthesis in cultured L6E9 myoblasts.
OBJECTIVE
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.


CONCLUSIONS
These results demonstrate that endoglin expression negatively regulates basal and TGF-beta1-induced CTGF and collagen expression and synthesis.
Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ciudad Universitaria, Madrid, Spain.
Juana
J
Obreo
Luisa
L
Díez-Marques
Santiago
S
Lamas
Annette
A
Düwell
Nélida
N
Eleno
Carmelo
C
Bernabéu
Atanasio
A
Pandiella
José M
JM
López-Novoa
Alicia
A
Rodríguez-Barbero
D000818:Animals; D015703:Antigens, CD; D002460:Cell Line; D024042:Collagen Type I / Q000096:biosynthesis / Q000235:genetics; D055513:Connective Tissue Growth Factor; D015536:Down-Regulation; D000071063:Endoglin; D005109:Extracellular Matrix / Q000235:genetics / Q000378:metabolism*; D005353:Fibronectins / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D017874:Immediate-Early Proteins / Q000032:analysis / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins / Q000032:analysis / Q000502:physiology; D032446:Myoblasts / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000494:pharmacology* / Q000502:physiology; D053773:Transforming Growth Factor beta1; D019010:Vascular Cell Adhesion Molecule-1 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
D015703:Antigens, CD; C526317:CCN2 protein, human; C526316:CCN2 protein, rat; D024042:Collagen Type I; C064206:ENG protein, human; D000071063:Endoglin; D005353:Fibronectins; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C508960:TGFB1 protein, human; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D019010:Vascular Cell Adhesion Molecule-1; D055513:Connective Tissue Growth Factor