Abstract
Purpose: :
To investigate the expression and function of Thrombospondin–1 (TSP–1) in human keratocytes in vitro. A main reason for impaired vision after corneal ulcers or refractive surgery is a scarring response of keratocytes, causing an opacity of the corneal stroma. One factor that is triggering this process is transforming growth factor–ß (TGF–ß). TGF–ß is a secreted protein that has to be activated to exert its function. A potent in vivo activator for TGF–ß is the matricellular protein TSP–1. The activation of TGF–ß by TSP–1 is inhibited by a specific peptide (LSKL).
Methods: :
TSP–1 expression was assessed by immunohistochemistry of human corneal ulcers in vivo. Also TSP–1 expression was quantified by Western and Northern blot analyses of cultured human keratocytes following incubation with TGF–ß1 and –ß2. In addition, BrdU cell proliferation assays were performed after incubation with latent TGF–ß1 and the TSP–1 inhibiting LSKL–peptide.
Results: :
Strong immunolabeling for TSP–1 was observed in the inflammatory zone adjacent to the human corneal ulcers. After incubation with activated TGF–ß1 and –ß2 a marked increase of TSP–1 expression was detected in cultured human keratocytes. Addition of latent TGF–ß1 markedly increased cell proliferation in human keratocytes. Incubation with latent TGF–ß1 and the TSP–1 inhibiting LSKL–peptide significantly reduced cell proliferation of human keratocytes compared to controls that were only treated with latent TGF–ß1.
Conclusions: :
Incubation of human keratocytes with TGF–ß promotes cell proliferation and induces TSP–1 expression. Proliferation of human keratocytes was reduced by adding the TSP–1 inhibiting LSKL–peptide. Therefore, the LSKL–peptide could be a helpful tool to reduce the scarring response caused by corneal ulcers or refractive surgery.
Keywords: cornea: stroma and keratocytes