Proteoglycans in the eye.
OBJECTIVE
Various proteoglycans are expressed in ocular tissues. We investigated and reviewed the distribution and the potential roles of proteoglycans in cornea, trabecular meshwork, and retinal tissues.


METHODS
Immunohistochemical studies were performed in rat ocular tissues. The concentration of transforming growth factor (TGF)-beta2, which regulates the expression of proteoglycans in aqueous humor from human glaucomatous eyes, was evaluated by enzyme-linked immunosorbent assay (ELISA). In retinal tissues, we examined the localization of 2 soluble nervous tissue-specific chondroitin sulfate proteoglycans, neurocan and phosphacan, by immunohistochemical analysis, then investigated the effect on the neurite outgrowth of cultivated retinal ganglion cells.


RESULTS
The expression of chondroitin sulfate in stroma was upregulated at early postnatal stages and reduced during development in rat eyes. In trabecular meshwork tissues, immunohistochemical studies showed the intense expression of decorin. Moreover, elevated levels of TGF-beta2 in the aqueous humor from glaucomatous patients were observed. In retinal tissues, neurocan and phosphacan were expressed mainly in nerve fiber-rich layers during rat postnatal stages. In vitro, the neurite extension from retinal ganglion cells was inhibited by neurocan and phosphacan.


CONCLUSIONS
Soluble extracellular proteoglycans in corneal and trabecular meshwork tissues contribute to the stromal transparency in the corneal tissues and the resistance of the aqueous humor outflow in trabecular meshwork tissues. In retinal tissues, chondroitin sulfate and heparan sulfate proteoglycans are not only secreted into the extracellular space of retinal tissues but also expressed in the membrane of the retinal cells, contributing to the neural network formation and the maintenance of the interphotoreceptor matrix.
Tanihara
Hidenobu
H
tanihara@pearl.ocn.ne.jp
Inatani
Masaru
M
Koga
Takahisa
T
Yano
Tsuyoshi
T
Kimura
Akira
A
D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D003315:Cornea / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005901:Glaucoma / Q000378:metabolism; D007124:Immunoenzyme Techniques; D011509:Proteoglycans / Q000378:metabolism*; D051381:Rats; D012160:Retina / Q000378:metabolism*; D014129:Trabecular Meshwork / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism
D011509:Proteoglycans; D016212:Transforming Growth Factor beta