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Andre Torricelli, Vivek Singh, Vandana Agrawal, Steven Wilson; Abnormal epithelial basement membrane ultrastructure in corneas with haze after PRK in rabbits. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5226.
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To assess the ultrastructure of the cornea epithelial basement membrane (EBM) using transmission electron microscopy (TEM) in corneas with haze after -9D PRK and corneas without haze after -4.5D PRK compared to control corneas in rabbits.
Two groups of six rabbits each were included in this study. The first group had -4.5 diopter (D) PRK and the second group had -9.0 D PRK. Photorefractive keratectomy (PRK) was performed with epithelial scrape using a VISX Star S4 IR laser. Contralateral eyes of each animal were used as unwound controls. Rabbits were sacrificed at 4 weeks after surgery. Immunohistochemical analysis was performed to detect the myofibroblast marker alpha-smooth muscle actin (SMA). TEM was performed to analyze the ultrastructure of the epithelial basement membrane in PRK and control corneas.
At 4 weeks after PRK, high numbers of alpha-SMA+ myofibroblasts were observed in the subepithelial stroma of rabbit eyes that had -9.0 D PRK whereas few myofibroblasts were noted in the subepithelial stroma of eyes that had -4.5 D PRK. At one month after -9D PRK, the epithelial basement membrane was irregular and discontinuous and lacking in typical morphology in all four corneas in the group (Figure) compared to the epithelial basement membrane in the four corneas in the -4.5D PRK group or 4 corneas in the control group.
Transmission electron microscopy at 4 weeks after haze generating -9D PRK in rabbits reveals structural defects in the regenerated epithelial basement membrane that are not observed in corneas that had -4.5D or control corneas. These structural defects likely correlate with decreased basement membrane function that increases penetration of epithelium-derived growth factors such as TGF beta, which both drive development of stromal myofibroblasts from precursor cells and maintain myofibroblast viability. The epithelial basement membrane is a critical regulator of myofibroblast development and persistence.
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