| Objective: The pathological mechanism of myopia is verycomplicated.There are no scientific and reliable methods toprevent and treat myopia up to now. Experimental myopia is animportant way to study myopia. In order to explain the role ofvarious retina-originated messengers related to the occurrence ofmyopia in experimental myopia ,this research used alens-induced method to obtain the experimental guinea pigmyopia model, then observed the expressional changes ofMMP-2,TIMP-2,TGF-β2 in the retina, choroid and sclera,observed the pathological and ultrastructure of sclera and retina,studied the biomechanical properties of sclera of the model.Some conclusions were valuable for revealing the pathologicalmechanism of myopia and treating it.Methods: 39 two-week-old guinea pigs were divided intothree groups randomly.In each group, the guinea pigs werelens-induced monocularly, A spherical lenses of -10.0D wereweared to unilateral eyes, another eye in each animal wasuntreated as control. Before the experiment, the refraction andthe length of optic axis of guinea pigs eyeball were measured. At10th,30th,50th day, the lens were removed respectively, thesedata were measured again.Immunohistochemistry was used todetect the expression of MMP-2,TIMP-2 and TGF-β2.Thesection of eyeballs were observed by light and electronicmicroscope. The sclera specimens were obstained and put to thetest on the Instron-5544 biomechanical machine. These data wasstatistically analysed by SPSS 11.0 system.Results:1 At 10th,30th,50th day in comparision to the control eyes,the lens-weared eyes became myopia on average 5.48±2.012D,7.04±1.31D and 8.96±0.94D and elongated on average0.52±0.22mm,0.87±0.47mm and 2.03±0.83mm respectively.There were statistic significance among them (p<0.01).2 Histopathological changes were observed: In 30th and50th day group, the thickness of lens-induced eye's posteriorsclera were 0.32±0.03mm and 0.34±0.03mm while those of thecontrol eye were 0.37±0.02mm and 0.36±0.03mm respectively.There were statistic significance among them(p<0.05). Theseproved that the sclera of experimental guinea pig myopia modelwas significantly thinner than that of the control eye.However, in10th day group,there was no remarkable difference(P>0.05).Under light microscopy, vacuolar degeneration of collage fiber inposterior sclera appeared, collagen fibers arranged disorderly.There was dilatation of rough endoplasmic reticulams (RER)inthe fibroblasts under electronic microscope. The rod and conecells of retina were in disorder. The normal RPE cells stretchedout bruch-like. In the lens-induced eyes, the membrane disc wasnot intact and the bruch-like became shorter and disorder, someof them partly dissolved and disappeared, all these changesbecame more and more obviously with time going on. There wasno histopathological change in choroids under light microscopy.3 The immunohistochemistry showed that the expression ofMMP-2 located in cytoplasm,TGF-β2 in cytoplasm and nuclearmembrane ,and TIMP-2 in cytoplasm and cell nucleusrespectively. Rod and cone cells expressed MMP-2 obviously.TGF-β2 expression was present on each layer of retina. TIMP-2was displayed mainly in outer nuclear layer. The expressions ofMMP-2 and TGF-β2 in model eyes were higher than control eyes.There were significant diference of the expression of MMP-2 andTGF-β2 between model eyes and control eyes(P<0.05). But nostatistic significance for TIMP-2 (P>0.05). Expression ofMMP-2,TIMP-2,TGF-β2 were not detected in sclera.4 The correlation between MMP-2 and TGF-β2 was positivesignificantly (r=0.6573,p<0.05). But no correlation betweenTIMP-2 and TGF-β2 ( r=0.2176,p>0.05).5 Biomechanical research for sclera:For the elastic modulus,the lens-induced eye's posterior sclera was 1.43±0.32MPa, whilethe control eye's was 1.74±0.32 MPa in 50th day group. Therewas statistic significance between them(p<0.05). These revealedthe elastic modulus of myopic eye was lower than that of controleye.The creep rate of the lens-induced eye was 17.70±6.98%,while the control eye was 8.62±2.13% .The creep rate of myopiaeye's sclera was higher than that of normal eye. There was...
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