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M. A. Watsky, V. Pintea, Z. Yin; Vitamin D Enhances Corneal Epithelium Barrier Function. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1945.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if Vitamin D3 (25(OH)D) and/or its active metabolite, 1α,25-dihydroxyvitamin D (1,25-(OH)2D), can enhance corneal epithelial barrier function. We also determined if corneas contain mRNA for Vitamin D receptors (VDR) and 1α-hydroxylase, the enzyme required to convert 25(OH)D to 1,25-(OH)2D.
RT-PCR was utilized to examine mouse cornea VDR and 1α-hydroxylase mRNA. Corneas from 8 mice were pooled, and total RNA was extracted. Primers were designed based on published sequences (NCBI #’s D31969 and AF 235021, respectively). The VDR primer spans introns 8-9 and 9-10, while the 1α-hydroxylase primer spans introns 6-7, 7-8, and 8-9. Barrier function experiments were performed by measuring inulin permeability (IP) and/or transepithelial resistance (TER) in control, 25(OH)D, and 1,25-(OH)2D treated human and rabbit corneal epithelial monolayers cultured on permeable inserts. Ca++ was removed then reintroduced to the culture medium while IP and/or TER readings were taken. After the last measurements were taken, cells were fixed on the permeable membranes for immunostaining with ZO-1 and occludin antibodies. Confocal microscopy was used to view immunostained cells.
Mouse corneas were positive for both VDR and 1α-hydroxylase mRNA. In Ca++ reversal experiments, epithelial cells showed significantly increased TER and decreased IP when cultured in the presence of 25(OH)D and 1,25-(OH)2D. Immunostaining for both ZO-1 and occludin were stronger and more uniform in cells cultured in 25(OH)D and 1,25-(OH)2D compared to controls, which showed disrupted staining patterns.
Corneas contain mRNA for VDR and 1α-hydroxylase. Vit D3 and its active metabolite 1,25-(OH)2D, both enhance corneal epithelial barrier function. Enhanced barried function with 25(OH)D likely means active 1α-hydroxylase activity in these cells.
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