| Objective:As the most common complication after cataract surgery,posterior capsular opacification is still the main reason of visual acuity decreased again. Researches report that the incidence of posterior capsular opacification after extracapsular cataract extraction surgery in adults is 50%, in children is almost 100%[1,2].Faced such a high incidence of posterior capsular opacification, how to prevent it has become a hot research. Recently, trials found low molecular weight heparin can inhibit lens epithelial cells cultivated in vitro[3]. However, the mechanism is not clear, we need more animal experiments to test the theory.The New Zealand white rabbits were randomized to different groups, and then were given two ways to intervene:anterior chamber perfusion of low molecular weight heparin during phacoemulsification surgery and eye injection of low molecular weight heparin after phacoemulsification surgery. After that, we observed the level of posterior capsule opacification, the morphological changes of lens epithelial cells, the expression of proliferating cell nuclear antigen(PCNA)in the lens epithelial cells with by immunohistochemical SP method,test the changes of the concentration of platelet-derived growth factor (PDGF), epidermal growth factor(EGF) in aqueous humor. By doing these, we could found the difference between the ways of using low molecular weight heparin, to provide the theoretic foundation and experimental evidence for new means of prevention and therapy on posterior capsular opacification on mechanisms.Methods:Thirty New Zealand white rabbits were equally divided between male and female, weight 1.5～2kg, no eye diseases, eye lens transparency, given ciprofloxacin eye drops 3 days before surgery. Randomly divided into 3 groups:A group, surgery group 10 (Right eye phacoemulsification, no low molecular weight heparin sodium)B group, surgery + eyedropping group 10 (Right eye phacoemulsification, then dropping eyes by 12.5g/L low molecular weight heparin sodium)C group, surgery + perfusion group 10 (Right eye phacoemulsification, anterior chamber perfuse low molecular weight heparin sodium injection 5000IU)Dropping eyes with tobramycin and dexamethasone, during two week after surgery, 6 times a day, all rabbits were measured before and after 1, 3 days of intraocular pressure. Evaluate the posterior capsular opacification according to Odrich method, observe cornea and photograph the anterior segment, and test the concentration of PDGF and EGF with 0.2ml aqueous after 3, 14, 28, 60 days respectively. Execute the rabbits after 60 days, take the right eyes and observe morphological changes of the cell under the light microscope, detect the expression of PCNA in the lens epithelial cells with by immunohistochemical SP method. The data was given by ( X±S), and the statistical analysis was described by SPSS13.0 software.Results:1 Observation of anterior segment changes and photo of them with slit lamp microscope1.1 Cornea edema:Corneas are slightly edema after 1 day, occurred at the seams in the surgery group and surgery + perfusion group. Corneas become clear and edema disappear after 3 days.1.2 The grade of the posterior capsule opacificationRating according to Odrich method: zero grade: no posterior capsule opacification; first grade: posterior capsule opacification, changes of lens epithelial cells can be seen entirely; second grade: posterior capsule opacification, fundus can be seen partly; three grade: posterior capsule opacification, fundus can't be seen completely. In the course of the experiment, by the statistical test, posterior capsule opacification in surgery group and surgery + eyedropping group have no significant difference after 60 day(P>0.05), posterior capsule opacification in surgery + perfusion group have significant different from in surgery group and surgery + eyedropping group after 60 day(P<0.05).2 Intraocular pressure changesAll rabbits were measured and after 1, 3 days of intraocular pressure in before is 25.30±2.10mmHg,after 1 days is 34.43±2.68mmHg,after 3 days is 27.07±1.48mmHg. By the statistical test, intraocular pressure have significant difference in after 1 day and before, after 3 days(P<0.05). Intraocular pressure have no significant difference in before and after 3 days(P>0.05).3 Morphology changesUnder the light microscope, three groups of rabbits find lens epithelial cells, the surgery group and the surgery + eyedropping group have significantly increase in the number of cells, morphology general normally, the surgery group appear proliferation of lens fibers. Surgery + perfusion group only coverage single epithelial cell.4 Immunohistochemical staining of PCNAPCNA in the three groups have positive staining, but the IOD of the surgery + perfusion group is lower than the surgery group and the surgery + eyedropping group (P<0.05), the IOD of the surgery group and the surgery + eyedropping group have a significant difference(P<0.05). The decrease of IOD shows that the proliferation ability of lens epithelial cell is decline.5 Measure the PDGF and EGF levels in aqueousPDGF and EGF levels in aqueous in three groups have significant difference after 3 day(P<0.05). EGF levels in aqueous in the surgery group after 14 day are significantly higher than in the surgery + perfusion group and the surgery + eyedropping group (P<0.05), EGF levels in aqueous in the surgery + eyedropping group after 14 day have no significant difference in the surgery + perfusion group(P>0.05). PDGF levels in aqueous in this three groups after 14 day have no significant difference(P>0.05). PDGF and EGF levels in aqueous in this three groups after 28 and 60 day have no significant difference(P>0.05).Conclusion:1 Perfuse Low molecular weight heparin inhibits the expression of PCNA and posterior capsular opacification after cataract surgery significantly.2 Perfuse low molecular weight heparin early inhibits the expression of PDGF in aqueous humor significantly.3 Perfuse low molecular weight heparin early inhibits the expression of EGF in aqueous humor significantly.4 Perfuse Low molecular weight heparin during surgery can directly effect on the lens epithelial cells, and also conducive to absorb, the way may be better than the other way.
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