Keratocytes promote corneal neovascularization through VEGFr3 induced by PPARα-inhibition

As the peroxisome proliferator - activated receptor alpha (PPARα) agonist, fenofibrate has been widely used to be a good lipid-regulating drug in the clinical application. In this study, we investigated the mechanism by which keratocytes inhibit the corneal neovascularization (CNV) through PPARα - activation. To do this, the CNV model was established by alkali burn, followed by being divided into three groups including control, fenofibrate and vehicle group. The expression of VEGFr3, MMP13 and PPARα in corneas of normal mouse and alkali-burned mouse was determined via quantitative RT- PCR (qRT-PCR) and Western blot analysis (WB). The CNV area was observed under a slit lamp microscope. The location of PPARα expression in the corneas was determined via immunohistochemistry. In cultured primary keratocytes, the effect of fenofibrate on PPARα, VEGFr3 and MMP13 expression was determined by qRT-PCR and WB. Besides, PPARα knockout (PPARα-/-) mouse CNV and keratocytes model were established to further confirm the effect of PPARα on VEGFr3 and MMP13 expression. We found that PPARα was expressed in epithelium, stroma and endothelium of the normal cornea, however, with relatively low level in the corneal stroma. Meanwhile, its expression was decreased markedly in the cornea during the stage of CNV formation. After treatment of fenofibrate, PPARα expression was promoted and the expression of VEGFr3 and MMP13 was inhibited in both CNV mice model and primary keratocytes, and CNV areas were decreased in CNV mice model. However, the results in PPARα-/- CNV and keratocytes model were opposite. Our results suggest that keratocytes could promote the expression of VEGFr3 and MMP13, and CNV formation through PPARα downregulation.