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Hanjae Lee, Esther Yang, Dong Hyun Jo, Young Suk Yu, Jeong Hun Kim; Norrin Expression In The Endothelial Cell In Developing Retina. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2551.
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To investigate the Norrin expression during retinal angiogenesis and trace the primary source of Norrin to find out whether a specific cell group is involved in the process, and if so, how these cells might be implicated with the activation of the classical wnt pathway.
Using the developing retina of postnatal 4, 8, 12, 16 and 28 mouse (C57BL/6), we first examined the expression of Norrin through immunohistochemistry. Then, to confirm the primary source of Norrin, immunofluorescence was performed for Norrin and Collagen Type IV (EC marker).
We confirm, for the first time, that Norrin protein is expressed from the endothelial cells (ECs) of the retinal blood vessels. Through immunohistochemistry, it was observed that Norrin expression coincided with the vascularization of the developing retina. In the early stage of the development, during which retinal angiogenesis mainly occurs in the ganglion cell layer (GCL), the Norrin expression was also limited to the GCL. In the later stage, as more ocular capillaries formed in the deeper layer of the retina, more Norrin was expressed in the deeper layer as well. From this pattern and shape of Norrin expression in the developing retina, ECs were hypothesized to be the primary source of Norrin. This was confirmed through double immunofluorescence of Norrin and Collagen Type IV.
Since Norrin is crucial in the normal development and maintenance of ocular capillaries, our finding suggests the Norrin’s involvement in the self generative and protective mechanism of the ECs, which themselves seem to secret Norrin and activate the wnt pathway.
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