| Myopia is common ocular disease. It can be divided into refractive myopia and high myopia. The high myopia is also named pathologic myopia, which have high prevalence rate and severe complications. It is one of the common causes of blindness. The posterior sclera reinforcement (PSR) operation is an effective way that can treat pathological myopia, which is designed to strengthen the weakened and thinned sclera by using reinforcement materials, thus to prevent the axial elongation of the eyeball and the deterioration of optical function.There are different views on the efficacy of PSR. It is necessary to study the therapeutic mechanism of PSR further and completely. In this paper, New Zealand white rabbits were treated to build experimental high myopia eye model and the experimental myopia eyes were treated by PSR, then obtain the scleral tissue and scleral fibroblasts. Our aim is to explore the therapeutic mechanism of PSR by the studies of the protein expression of scleral tissue and scleral fibroblasts, the proliferation activity and the viscoelasticity of scleral fibroblasts after PSR, and the response to mechanical stimulation of scleral fibroblasts. It will provide the valuable theoretical evidence and powerful guidance for clinical therapy.The main content and conclusions are following:1. Three-week-old New Zealand white rabbits were monocularly treated by eyelid suturation randomly to build experimental high myopia eye model, the eyes that not operated on were the normal control. After 60 days, the diopter and eye axis measurement were used to show the success of experimental high myopia eye model. The diopter decreased by 1.80±0.72D and the axes extended by 0.45±0.29mm after the eyes were treated by eyelid saturation, there was significant difference when compared with respective normal eyes (P<0.05). It was showed that the experimental high myopia eye model was successful.2. The experimental myopia eyes were treated by PSR. After 3 and 6 months, the posterior pole tissue of sclera (normal sclera and sclera after PSR) were obtained for detecting the expressions of MMP-2, TIMP-2, TGF-β1 and bFGF in sclera tissue by immunohistochemical detection. The immunohistochemistry results:the expression of MMP-2 was less in sclera after PSR than in normal sclera; the expression of TIMP-2, TGF-(31 and bFGF were more in sclera after PSR than in normal sclera.3. After 3 and 6 months, obtain the scleral fibroblasts of normal sclera, sclera after operation and fusion region of sclera and reinforcing band after operation by tissue pieces culture method; the cells were identified with immunocytochemical method. Identification results: Vemintin (+), Desmin (-), keratin (-), S-100 (-). The results showed that the obtaining cells were scleral fibroblasts.The proliferation activity of scleral fibroblasts was measured with ATP based bioluminescence method; the MMP-2, TIMP-2, TGF-β1 and bFGF expression of every group scleral fibroblasts were examined by immunocytochemistry and ELISA; the micropipette aspiration technique was used to investigate the viscoelasticity of scleral fibroblasts. The research results:(1). The proliferation activity of the scleral fibroblasts after PSR operation were significantly higher when compared with normal sclera (p<0.05); the scleral fibroblasts proliferation activity of fusion region after operation was higher than sclera after operation (p<0.05).(2). There was no difference of the scleral fibroblasts MMP-2 expression between the normal sclera and the sclera after operation (P>0.05), the MMP-2 expression of fusion region scleral fibroblasts was significantly lower than the scleral fibroblasts of sclera after operation (P<0.05); the TIMP-2,TGF-β1 expression of sclera and fusion region after operation scleral fibroblasts were significantly higher than the scleral fibroblasts of normal sclera (P<0.05); the bFGF expression of the scleral fibroblasts after PSR operation were significantly higher than normal sclera (p<0.05); the scleral fibroblasts bFGF expression of fusion region after operation was higher than sclera after operation (p<0.05).(3). The cellular viscoelasticity (Eo,E∞andμ) of the fusion region after operation scleral fibroblasts was significantly lower than the sclera after operation and the normal sclera (P<0.05), there was no significant difference between the sclera after operation and the normal sclera (P>0.05).These showed that:After the PSR operation, the MMP-2 expression of scleral fibroblasts was reduced, the TIMP-2,TGF-β1 and bFGF expression were increased, the results were consistent with the study of immunohistochemistry; The PSR operation did not change the viscoelasticity of scleral fibroblasts, the new scleral fibroblasts of fusion region after operation had lower viscoelasticity.4. Scleral fibroblasts isolated from normal sclera, sclera after operation and fusion region after operation (after 6 months) were subjected to cyclic stretch regimen of 3% and 6% elongation at 0.1 Hz respectively. The proliferation activity, the expression of MMP-2, TIMP-2, TGF-β1 and bFGF, the cellular viscoelasticity were assayed after stretch at 48h respectively. The results:(1). The scleral fibroblasts proliferation activity of normal sclera, sclera after operation were significantly increased after cyclic stretch (p<0.05), there was significant difference in the proliferation activity between 3% group and 6% group (p<0.05); after cyclic stretch, there was no difference in the proliferation activity of fusion region after operation (P>0.05).(2). After cyclic stretch, the MMP-2 expression was significantly reduced and the TIMP-2 expression was significantly increased of the scleral fibroblasts of the normal sclera and the sclera after operation (p<0.05), the scleral fibroblasts MMP-2 and TIMP-2 expression was no changed of the fusion region after operation (P>0.05); the TGF-β1 expression was significantly increased of the three groups scleral fibroblasts (p<0.05); The scleral fibroblasts bFGF expression of the normal sclera and the sclera after operation were significantly increased (p<0.05) and there was no difference in the scleral fibroblasts bFGF expression of the fusion region after operation (P>0.05).(3) Following 48h stretch, the cellular viscoelastic parameters were significantly decreased when compared with respective static groups (P<0.05) in normal sclera and the sclera after operation; for the fusion region after operation, the scleral fibroblasts viscoelasticity of stretch group were significantly higher than static control group (P<0.05). There was no difference between 3% and 6% stretch group in each group (P>0.05); the viscoelastic behaviors of all the scleral fibroblasts become more identical. These were showed that:the mechanical stimulation could regulate the proliferation activity, the MMP-2, TIMP-2, TGF-β1 and bFGF expression and the viscoelasticity of scleral fibroblasts after PSR. This could promote the fusion of the sclera and reinforcing band, the sclera remodeling and hyperplasia, enhance the biomechanical property of sclera, and thus control the development of high myopia. |
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