The Role Of MMP-2 In Scleral Collagen Metabolism Of Myopia Induced By Long Wavelength Light Irradiation

Myopia is a common form of ocular pathlolgy in which the visual image is focused anterior to the retina resulting in an increase in the anterior-posterior(axial)dimension of the eye and is associated with extracellular matrix remodeling caused by the increased activity of MMP-2 in the sclera.A normal visually guided emmetropization mechanism fine tunes the growth of the juvenile eye to match the eye's axial length to its optical power.Because the fact that long wavelength light is focuced behind the retina,as an abnormal visual experience, long wavelength light irridation may affect the normal process of emmetropization and cause myopia.The purpose of this study is to investigate the effect of long wavelength light to refractive status and the role of MMP-2 in scleral collagen metabolism of myopia induced by long wavelength light irradiation. This study included three parts: 1) Construction of an animal model of myopia by raising Guinea pigs in long wavelength light irridation,optical and structural parameters were measured to prove it.The results showed that long wavelength light exposure group was more myopic than the control group, which were raised under white light and natural raise condition(P<0.001), and the axial length elongation especially the vitreous chamber depth elongation of treated group were statistically longer than that of control groups(P<0.001) and the gained myopia diopter was significantly correlated with the vitreous chamber depth elongation in treated group(r=0.803,P=0.002).2)To investigate the mechanism of this phenomenon, we chosed the sclera as target tissue and detected the effects of long wavelength light on the collagen metabolism of sclera,The results showed that the collagen density and the expression of collagenⅠat the posterior sclera of the long wavelength light irradiated eyes were significantly lower than that of control eyes and normal eyes (P<0.001).3) To investigate the role of MMP-2 in scleral collagen metabolism of myopia induced by long wavelength light irradiation,the activity and the expression of MMP-2,TIMP-2,TGF-β and also the MMP-2 expression under using of synthetic specific MMP-2 inhibitor were detected. The results showed that the activity of MMP-2 and the expression of MMP-2 and TGF-β at the posterior sclera of the long wavelength light exposure eyes were significantly higher than that of control group,while the expression of TIMP-2 was lower than that of control group,synthetic specific MMP-2 inhibitor reduced the myopia induced by long wavelength light exposure through inhibiting the activity of MMP-2 in a dose-dependent manner.So, we have a conclusion that as an abnormal visual experience, long wavelength light irridation can effect the normal process of emmetropization and cause myopia, one of its mechanism may be break the balance between the synthesis and decompose of collagen metabolism of sclera,increased MMP-2 activity plays an important role in the development of myopia induced by long wavelength light irridation. This study settled a background for the clarification of the pathogeny of myopia and indicated a new possible method of myopic therapy.