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TGF-beta isoforms in renal fibrogenesis.
Ling Yu1, Wayne A Border, Yufeng Huang
1Fibrosis Research Laboratory, Division of Nephrology, University of Utah School of Medicine, Salt Lake City, Utah, USA.
Kidney International
|August 13, 2003
Summary
All three transforming growth factor-beta (TGF-beta) isoforms promote kidney fibrosis by increasing matrix production and reducing degradation. Blocking all isoforms may offer the best therapeutic strategy for renal fibrosis.
Area of Science:
- Nephrology
- Cell Biology
- Biochemistry
Background:
- Transforming growth factor-beta1 (TGF-beta1) is the primary known mediator of fibrosis.
- The roles of TGF-beta2 and TGF-beta3 in fibrosis are less understood.
- Targeted therapies for fibrosis require precise knowledge of TGF-beta isoform actions.
Purpose of the Study:
- To compare the effects of individual TGF-beta isoforms (TGF-beta1, TGF-beta2, TGF-beta3) on extracellular matrix (ECM) production and degradation in renal cells.
- To investigate the interplay between TGF-beta isoforms in regulating ECM homeostasis.
- To assess the potential of isoform-specific blockade for treating renal fibrosis.
Main Methods:
- Cultured rat mesangial cells, renal fibroblasts, and tubular epithelial cells were treated with varying concentrations of TGF-beta isoforms, alone or in combination.
- Cell viability was assessed using MTT assays.
- Fibronectin, TGF-beta isoform concentrations, collagen, and proteoglycan production were quantified using ELISA and radiolabel incorporation.
- Gene expression and matrix degradation were analyzed via Northern blot and radiolabeled matrix release, respectively.
Main Results:
- All three TGF-beta isoforms demonstrated similar fibrogenic effects, increasing matrix synthesis and reducing degradation in renal cells.
- Combinations of TGF-beta isoforms exhibited additive effects on matrix production.
- TGF-beta2 and TGF-beta3 significantly stimulated endogenous TGF-beta1 production, with 80% of TGF-beta3's fibrogenic activity mediated by TGF-beta1.
- A pan-specific TGF-beta antibody was most effective in blocking plasminogen activator inhibitor type 1 (PAI-1) synthesis under oxidative stress.
Conclusions:
- All TGF-beta isoforms contribute to renal fibrogenesis.
- The fibrogenic actions of TGF-beta2 and TGF-beta3 are, in part, mediated through TGF-beta1.
- Combined blockade of all TGF-beta isoforms may represent a superior therapeutic approach for mitigating renal fibrosis.