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KrishnaPoojita Vunnava, Rohit Shetty, Subramani Murali, Murugeswari Ponnalagu, Kamesh Dhamodaran, Debashish Das; Corneal epithelial differentiation: A paradigm shift in keratoconus. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1386.
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© ARVO (1962-2015); The Authors (2016-present)
Keratoconus has always been considered as a condition characterized by stromal thinning. We have hypothesized that the corneal epithelial differentiation status differs in the cells from ectatic zone and the unaffected periphery of keratoconic eyes. In this prospective, non-randomized observational case control study we have observed the differences between the corneal epithelium over the ectatic cone and the periphery of keratoconic eyes undergoing crosslinking and have compared it with normal epithelium obtained from patients undergoing photorefractive keratectomy (PRK).
Differential corneal epithelial cells from ectatic cone and unaffected periphery of keratoconic (test) and PRK (control) eyes were collected intra-operatively. Keratoconic eyes were further classified as per the severity of keratoconus into three grades. 20 eyes were included in each group. Expression levels of genes for differentiation, apoptosis and proliferation were analyzed in the differential corneal epithelial cells of these sub-groups. Protein analysis of the corneal epithelial cells was performed with antibodies for pro-apoptotic marker (BAX), anti-apoptotic marker (BCl2), and proliferation marker (Ki67, Cyclin D1) and markers of corneal epithelial differentiation (CK3/CK12). Student t test was used to analyze the results.
Analysis of gene expression as well as immunofluorescence staining revealed a significant decrease (p≤ 0.05) in the expression of CK3/CK12 in the cells from affected cone of keratoconus. This difference was amplified with increasing grades of disease severity. A significant increase in the ratio of BAX : BCl2 and decrease in Cyclin D1 levels in the cells was detected in both ectatic cone (p≤ 0.05) and unaffected periphery (p≤ 0.05) as compared to control eyes. The variation in the increase of BAX : BCl2 expression was significantly different between the ectatic cone and periphery in keratoconus eyes. This variation was not noted in the differential epithelium collected from the controls
There is defective corneal differentiation and enhanced apoptosis of epithelial cells in the ectatic cone of keratoconus cornea with increasing disease severity. Higher rate of proliferation and lower differentiation of corneal epithelial cells is detected in non-ectatic periphery compared to ectatic cone and this has been seen to decrease with increasing grades of keratoconus.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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