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TGF-beta elicits fibronectin secretion and proliferation in cultured chick lens epithelial cells
1Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Purpose:
To determine if the cataract forming influence of TGF-beta on lens cells is due to its effects on the ECM.
Methods:
Primary cultures of chick lens annular pad cells were exposed to TGF-beta and various exogenously supplied components of the lens capsule. Proliferative response were measured through tritiated thymidine incorporation into DNA. Cell spreading accompanying increased matrix interactions and growth was monitored with phase contrast microscopy. ECM proteins were detected in culture media and as deposited matrices with Western blotting and silver staining. TGF-beta receptors were identified with Western blotting.
Results:
Chick lens cells were shown to express type I and II TGF-beta receptors. TGF-beta stimulated cell growth and ECM production particularly with regard to fibronectin. Fibronectin was secreted into the culture medium and deposited onto plastic substrates. Plating cells on ECM components found in the lens capsule further increased their growth in response to TGF-beta.
Conclusions:
These results indicate that TGF-beta may have a normal function in the lens regulating capsular protein production. The potent stimulation of lens cell growth by TGF-beta may be due to mis-regulated production of lens capsular proteins not normally found in great abundance.