The wound healing effects of vitamin A eye drops after a corneal alkali burn in rats

Abstract

We investigated the wound healing effect of retinyl palmitate eyedrops following a corneal alkali burn in rats. A total of 160 Sprague-Dawley male rats were divided into two groups and central corneas were injured by contacting eyes with filter paper saturated with 0.01 m NaOH for 45 seconds. Vitamin A group was treated with retinyl palmitate and antibiotic (Cravit(®) : 0.5% levofloxacin) eye drops four times daily for 3 days and the control group with vehicle and antibiotic eye drops. Corneal wound healing by fluorescein staining and impression cytologic analysis were conducted at 0, 24, 48 and 72 hr after injury. Vascular endothelial growth factor A (VEGF-A), thrombospondin 2, matrix metalloproteinase 9 (MMP 9) and transforming growth factor-β (TGF-β) were measured in corneas by ELISA, immunofluorescent staining and real-time PCR. Corneal wound healing was better in the vitamin A group than in the control group. Early sprouting of new vessel was observed in the control group at 72 hr, but not in the vitamin A group. Corneal thrombospondin 2 proteins in ELISA were higher in the vitamin A group, but VEGF-A, MMP 9 and TGF-β proteins were higher in the control group (p < 0.05). Similarly, thrombospondin 2 immunofluorescent staining was stronger, whereas VEGF-A, MMP 9 and TGF-β staining were weaker in the vitamin A group (p < 0.05). In addition, thrombospondin 2 mRNA levels were higher, whereas VEGF-A, MMP 9 and TGF-β mRNA levels were lower in the vitamin A group (p < 0.05). Retinyl palmitate eye drops can inhibit VEGF-A and activate thrombospondin 2 and improve conjunctival impression cytologic findings. Furthermore, retinyl palmitate eye drops were found to promote corneal healing after an alkali burn in rats.