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Jiucheng He, Azucena H. Kakazu, Tiffany C. Russ, Haydee E. Bazan; Differential Expression Of Neuropeptide Y (npy) And Its Receptor Y2 In Corneal Cells. Invest. Ophthalmol. Vis. Sci. 2011;52(14):286.
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NPY is abundantly distributed in neural tissues of the central and peripheral nervous systems and exerts a multiplicity of biological activities. In the cornea, a limited amount of sympathetic NPY positive nerves have been reported in the corneosclera limbus. Recent studies have shown that NPY is also expressed in non-neuronal tissues and cells including adrenal medulla, endocrine pancreas, liver, heart, spleen, adipocytes andendothelial cells of blood vessels. This study was undertaken to examine the expression of neuropeptide Y and its receptors in human and rabbit corneas as well as in isolated corneal cells.
Fresh human and rabbit corneas were fixed and double-stained with a goat anti-NPY polyclonal antibody and a mouse anti-βIII-tubulin monoclonal antibody. Whole mount views of images were taken by a fluorescence microscope equipped with a digital camera. After whole mount examination, the same corneas were embedded in OCT, serial 20-µm cryostat sections were cut, and images were taken. To further study the expression of NPY and its receptors in the corneal cells, in vitro cultures of primary rabbit corneal epithelial cells (RCEC), keratocytes and myofibroblasts, and of a human corneal epithelial cell (HCEC) line were stained with anti-NPY and anti-NPY receptors (Y1, Y2 and Y4). To exclude non-specific staining, human umbilical vein endothelial cells were used as positive control. For negative control, the primary antibody was replaced with normal serum.
Whole mount view of images showed that NPY was strongly stained in the corneal superficial epithelia. The positive staining appeared as fine granules in the cell plasma membrane. Staining was uneven. Cross-sections revealed that NPY-positive staining was found in the epithelia but not in the stroma. No NPY-positive nerves were found in the central cornea as shown by double-staining with βIII-tubulin, but a few positively stained nerves were detected in the stroma near the limbus in the human cornea. In vitro experiments confirmed that NPY was strongly stained in RCEC as well as in HCEC. NPY-positive staining was also found in corneal myofibroblasts, but not in keratocytes. Corneal epithelial cells and myofibroblasts also expressed NPY receptor 2 (Y2), but not Y1 or Y4.
Corneal epithelial cells constitutively expressed NPY and its Y2 receptor, suggesting that this neuropeptide may, by autocrine or paracrine stimulation, play a role in maintaining a healthy ocular surface. The expression of NPY in differentiated myofibroblasts suggests a possible role in wound healing.
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