Abstract
Purpose :
Ciliary processes are covered by a bilayer of specialized ciliary epithelium, the nonpigmented epithelium (NPE) and pigmented epithelium (PE). The outer pigmented ciliary epithelium is continuous with the retinal pigment epithelium (RPE), which expresses the nonvisual opsins, RGR and peropsin. In this study, we explore potential light-absorbing capability of ciliary epithelium and cells in the ciliary marginal zone (CMZ) by investigation of RGR opsin expression in NPE, PE, and CMZ.
Methods :
Postmortem human eyes were fixed in 10% formalin, and the tissues were embedded in paraffin. Antigen retrieval was performed, and sections were incubated with a polyclonal antipeptide antibody (DE15) that is directed against a peptide sequence partly conserved in RGR across different species. Immunohistochemical staining was detected with horseradish peroxidase-conjugated secondary antibody and DAB substrate. Immunofluorescent labeling was detected with FITC-conjugated secondary antibody and analyzed by multi-photon confocal microscopy.
Results :
Immunostaining of human retinas showed labeling of RGR in the PE, but not NPE. DAB labeling was detected throughout the PE cytoplasm. The lamina propria was negative, except for some concentrated staining within the loose connective tissue. Immunofluorescent labeling of RGR was located specifically in the PE layer. Confocal microscopy indicated that RGR was present in the cytoplasm evident as punctate speckles. Pigmented cells in the CMZ, as well as a few internal nonpigmented cells, also were positive for immunofluorescent labeling. The NPE of the ciliary body was negative, and immunofluorescent staining was absent in control slides that were incubated in parallel without primary antibody.
Conclusions :
The results demonstrate that the PE of the ciliary body and CMZ contain a nonvisual opsin and therefore, these epithelial cells may have a novel response to light or retinoids. Furthermore, the study of opsins in the anterior most pigmented epithelia may reveal additional regulation of functions of the ciliary epithelium.
This is a 2020 ARVO Annual Meeting abstract.