CCN3 (NOV) is a negative regulator of CCN2 (CTGF) and a novel endogenous inhibitor of the fibrotic pathway in an in vitro model of renal disease.
Fibrosis is a major cause of end-stage renal disease, and although initiation factors have been elucidated, uncertainty concerning the downstream pathways has hampered the development of anti-fibrotic therapies. CCN2 (CTGF) functions downstream of transforming growth factor (TGF)-beta, driving increased extracellular matrix (ECM) accumulation and fibrosis. We examined the possibility that CCN3 (NOV), another CCN family member with reported biological activities that differ from CCN2, might act as an endogenous negative regulator of ECM and fibrosis. We show that cultured rat mesangial cells express CCN3 mRNA and protein, and that TGF-beta treatment reduced CCN3 expression levels while increasing CCN2 and collagen type I activities. Conversely, either the addition of CCN3 or CCN3 overexpression produced a marked down-regulation of CCN2 followed by virtual blockade of both collagen type I transcription and its accumulation. This finding occurred in both growth-arrested and CCN3-transfected cells under normal growth conditions after TGF-beta treatment. These effects were not attributable to altered cellular proliferation as determined by cell cycle analysis, nor were they attributable to interference of Smad signaling as shown by analysis of phosphorylated Smad3 levels. In conclusion, both CCN2 and CCN3 appear to act in a yin/yang manner to regulate ECM metabolism. CCN3, acting downstream of TGF-beta to block CCN2 and the up-regulation of ECM, may therefore serve to naturally limit fibrosis in vivo and provide opportunities for novel, endogenous-based therapeutic treatments.
Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA. bruce_riser@baxter.com
Bruce L
BL
Riser
Feridoon
F
Najmabadi
Bernard
B
Perbal
Darryl R
DR
Peterson
Jo Ann
JA
Rambow
Melisa L
ML
Riser
Ernest
E
Sukowski
Herman
H
Yeger
Sarah C
SC
Riser
D000818:Animals; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology; D049109:Cell Proliferation; D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D055513:Connective Tissue Growth Factor / Q000235:genetics* / Q000378:metabolism*; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005355:Fibrosis; D005920:Glomerular Mesangium / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007124:Immunoenzyme Techniques; D066298:In Vitro Techniques; D007674:Kidney Diseases / Q000473:pathology / Q000517:prevention & control*; D008156:Luciferases; D051379:Mice; D055514:Nephroblastoma Overexpressed Protein / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology
C526316:CCN2 protein, rat; D024042:Collagen Type I; D055514:Nephroblastoma Overexpressed Protein; D012333:RNA, Messenger; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; D055513:Connective Tissue Growth Factor; D008156:Luciferases