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Inhibition of normal rat kidney cell growth by transforming growth factor-beta is mediated by collagen
1Roche Institute of Molecular Biology, Roche Research Center, Nutley, New Jersey 07110.
Abstract:
We have investigated the mechanism of inhibition of the serum-free monolayer growth of normal rat kidney (NRK) cells by transforming growth factor-beta (TGF-beta). NRK cells grown on fibronectin-coated dishes exhibited a biphasic response to TGF-beta. Monolayer growth was slightly stimulated by subpicomolar concentrations, while picomolar concentrations of TGF-beta inhibited NRK cell growth in the presence or absence of epidermal growth factor. NRK cells exhibited a similar biphasic growth response to exogenous type I collagen. TGF-beta induced a 3-5-fold increase in the deposition of type I collagen-like proteins into the extracellular matrix of NRK cells during serum-free growth. Type I collagen-like proteins were identified by their sensitivity to degradation by purified bacterial collagenase and by Western blot analysis. The TGF-beta dose-response curves for induction of extracellular matrix-localized collagen and inhibition of NRK cell growth were similar. Finally, the inclusion of a purified bacterial collagenase, which did not degrade TGF-beta or TGF-beta receptors, or alter control NRK growth, prevented exogenous collagen or TGF-beta from inhibiting the serum-free growth of NRK cells. Our results demonstrate that an increase in collagen secretion plays an important role in the inhibition of the growth of NRK cells by TGF-beta.
Insights
Transforming growth factor-beta (TGF-beta) inhibits normal rat kidney (NRK) cell growth by increasing collagen deposition. Bacterial collagenase treatment prevented this TGF-beta-induced growth inhibition, highlighting collagen
Area of Science:
- Cell Biology
- Biochemistry
- Extracellular Matrix Research
Background:
- Transforming growth factor-beta (TGF-beta) is a key regulator of cell growth and extracellular matrix production.
- The precise mechanisms by which TGF-beta influences normal rat kidney (NRK) cell proliferation remain under investigation.
- Extracellular matrix components, such as collagen, can modulate cell behavior and growth responses.
Purpose of the Study:
- To elucidate the mechanism by which TGF-beta inhibits the serum-free monolayer growth of NRK cells.
- To investigate the role of collagen deposition in TGF-beta-mediated growth inhibition.
- To determine if modulating collagen levels affects TGF-beta's impact on NRK cell growth.
Main Methods:
- NRK cells were cultured under serum-free conditions on fibronectin-coated dishes.
- Cells were treated with varying concentrations of TGF-beta and exogenous type I collagen.
- Collagen deposition was assessed via bacterial collagenase degradation and Western blot analysis; growth inhibition was quantified.
- The effect of bacterial collagenase on TGF-beta- and collagen-induced growth inhibition was evaluated.
Main Results:
- TGF-beta exhibited a biphasic effect on NRK cell growth, with inhibition observed at picomolar concentrations.
- TGF-beta treatment led to a 3-5 fold increase in type I collagen-like protein deposition in the extracellular matrix.
- A strong correlation was observed between TGF-beta-induced collagen deposition and growth inhibition.
- Inclusion of bacterial collagenase abolished the inhibitory effects of both TGF-beta and exogenous collagen on NRK cell growth.
Conclusions:
- Increased collagen secretion is a significant mechanism underlying TGF-beta's inhibition of NRK cell growth.
- Modulating extracellular matrix collagen levels can counteract TGF-beta-induced growth inhibition.
- These findings provide critical insights into the interplay between growth factors and the extracellular matrix in regulating cell proliferation.