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YL Cha, SR Weon, RW Beuerman; Effect of Muscarinic Agents and the Role of Sclera Fibroblasts in Experimental Myopia . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2411.
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Purpose: In several cell types, muscarinic acetylcholine receptors, mAChRs, regulate cell growth through G-protein linked receptors. Atropine a general muscarinic antagonist which inhibits myopia both in humans and in experimental animals. The present study was undertaken to determine if muscarinic receptors are present in chick sclera fibroblasts (SF) and if atropine can modulate cell proliferation and growth factor expression. Methods: Experimental myopia in the chick was induced by attaching a plastic lens (-15D) over one eye. The action of atropine was tested both in vivo by daily injections into the conjunctiva (1% atropine sulfate, 50µl) and in cultures of chick fibroblasts (SF) from the fibrous sclera (0.1-100 µM atrpine). Presence of mAChRs were investigated by immunohistochemistry and immunoblotting. Effect of muscarinic agents on SF proliferation were measured by BrdU incorporation. The changes in growth factors (FGF-2, TGF-ß) and matrix metalloproteinases in response to atropine were measured by ELISA. Results: In the chick model of myopia, atropine injection reduced myopia by inhibiting axial elongation and normalised the thickness of fibrous sclera. Muscarinic receptor proteins, m1-m4, were detected in sclera fibroblasts. Atropine and pirenzepine inhibited proliferation of SF while carbachol increased cell proliferation (p<0.05, ANOVA). Experimental myopia decreases FGF-2 in chick sclera. Atropine treatment in vivo and in vitro increased the levels of FGF-2 (p<0.01, t-test, p<0.05, ANOVA respectively). MMP-2 was found to be expressed by SF and its steady state level and activity were increased by atropine (p<0.05, ANOVA). Conclusions: In the present study, evidence has been presented that the mAChR subtypes are present in the sclera and they are able to mediate sclera growth and remodelling. Supported in part by a NMRC grant.
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