Expression of Fibroblast Activation Proteins in Corneal Stromal Neovascularization

Purpose: To observe changes of the factors in corneal stroma during corneal neovascularization and to investigate the mechanism of corneal neovascularization. Methods: Forty-eight Wister rats were used, including eight in the control group. Corneal neovascularization was induced by alkali burns in 40 rats. Frozen sections, which were cut across the corneal center, were prepared on days 1, 3, and 7 post-burn, respectively. Transforming growth factor- 1 (TGF- 1) was examined by immunohistochemistry, and fibroblast activation protein (FAP) and a-smooth muscle actin (a-SMA) were detected by double-labeling fluorescent immunohistochemistry. Blood vessel endothelium was identified for PECAM-1 (CD31). Expressions of FAP in the cornea with or without neovascularization were monitored with reverse transcription-polymerase chain reaction on days 3 and 7. Results: In the alkali-burned eyes, TGF-ss1 first expressed in the corneal stroma, and some stromal cells expressed a-SMA and FAP. The FAP+ keratocytes were found around the CD31+ endothelium of angiogenesis. FAP was expressed in the corneas with neovascularization, but not in those without neovascularization. Conclusion: Factors in corneal stroma may change when corneal neovascularization occurs. The stromal keratocytes can express FAP+ cells surrounding the endothelium of angiogenesis.