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A. M. Chomyk, R. Bouhenni, J. Dunmire, S. Lin, D. P. Edward; Localization of Interphotoreceptor Retinoid-Binding Protein (IRBP) in Human Ciliary Epithelium During Development. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6311.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal expression of IRBP during embryogenesis is both spatial and temporal, coinciding with the onset of photoreceptor differentiation. In the adult eye, IRBP is also expressed in the ciliary epithelium (CE) and secreted into the aqueous humor where its function is not fully understood. The CE and retina are developmentally related as both are derived from neural ectoderm. We undertook this study to further define the spatial and temporal immunolocalization of IRBP in the developing and adult human eye, specifically the CE.
IRBP expression was studied by indirect immunofluorescence using an antibody against IRBP in human fetal eyes ages 7, 10, 11, 18, 19, 21, 22, 23 and 32 weeks (n=2 each age); as well as infant (n=2), and normal human adult (n=2) eyes. Fetal eye tissue morphology was examined by H&E staining. Immunoreactivity (IR) of IRBP was analyzed in the retina and CE. Observation of IRBP IR with respect to intensity and localization within each tissue was recorded and data were compared between each gestational age and with adult eyes.
Consistent with previous reports, observed intensity of IRBP IR in the retina remained constant in both the interphotoreceptor matrix and the photoreceptor inner and outer segments at all fetal ages studied. Localization of IRBP IR was similar for adult retina. At 7 weeks fetal age, IRBP IR localized mainly to the primitive anterior rim of the optic vesicle, the region destined to become the CE. At all later fetal ages IRBP IR was restricted to non-pigmented ciliary epithelium (NPE). The moderate to intense IR observed in NPE localized preferentially to the apical and basal cytoplasm. The intensity and distribution of IRBP IR remained consistent at all stages of fetal development beyond 7 weeks and in the well defined NPE of infant eyes. However, for adult eyes IRBP IR in the ciliary processes localized mainly to stromal tissue with moderate intensity while IR in the NPE cytoplasm was faint.
For the developing ciliary body, IRBP IR was restricted mainly to NPE and also observed in the primordial eye at the anterior rim of the optic vesicle. The intensity of IRBP IR decreased in the adult CE where IRBP localized mainly to stroma of the ciliary processes. Temporal expression of IRBP in NPE was consistent with that observed in the developing sensory retina. The strong IRBP IR in fetal eyes, temporal changes in IR, and previously reported secretion into aqueous humor suggest a possible role of IRBP in the development of the human anterior segment.
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