The Experimental Study Of After Cataract Inhibition By All=trans Retinoic Acid

ObjectiveOne of the most important complications in the modern cataract extraction and intraocular lens implantation is PCO - Posterior Capsular Opacification, that is also called after cataract. The incidence rate of PCO after 3 years varies from 30% to 50% and even up to 100% among children.The main therapy to PCO at present include Nd; YAG laser capsulotomy and surgerical capsulotomy, both have not so perfect outcomes duo to the complications such as vitreous membrane rupture, intraocular pressure increase, IOL dislocation, cystoid macular edema and retinal detachment. What is more, the theraputic damage of the posterior capsule has deviated from the originally surgical intend of saving the whole capsular membrane. Others should also be taken into account are the heavily mental and economical burdens loaded by these ways. All these call for the prevention of PCO during or after the surgical operation.The studies of preventing PCO now concentrate in two aspects; cleaning lens epithelial cells thoroughly and inhibiting the proliferation of the remained lens epithelial cells ( LECs). Such inhibition is further explored in non - pharmaceutical and pharmaceutical ways. The outcome of the former method is unsatisfactory nor is the cleaning cells during operation. The key point is the inhibition of the LECs proliferation at present. Scientists have tested many drugs but only heparin has succeded on clinical practice by making a smear on the posterior surface of IOL, which also increases the tendency of anterior chamber hemor-rhage due to its anticoagulation function. Daunomycin and harritonine are the most expectable candidates but also showed too many complications in the animal experiment study. Generally speaking, there is no widely accepted drug as a first choice in preventing PCO.Retinoic Acid is a natural derivative of vitamin A within the body and it mainly affects the bony growth and epithelial metabolism. It also maintains the normal structure of skin, cornea, the epithelia of upper respiratory tract and the urogenital tract. It is a powerful compound in cancer treatment and it has been fully proven in leukemia recovery. It is expected in dealing with various prolifer-ative diseases due to its effect on tumor cell growth and differentiation as well as the epithelial and interstitial cells. In these years, studies on the relationship between retinoic acid and cell proliferation and differentiation stayed on the level of molecular and cell culture in vitro, and its branch reaches into a wide area.The researches of retinoic acid in ophthalmological field are concentrated in the prevention of vitreous proliferative disease at present; Doyle observed the effect of retinoic acid on cultured retinal pigmented epithelial ( RPE) proliferation and suggested that retinoic acid could inhibit RPE proliferation. Others dissolved retinoic acid into silicone oil or its chloride compound and observed its effect on the PVR model. The results were the same and retinoic acid had no side effect on retina. In preventing the after cataract, Chan injected retinoic acid and others drugs like colchicines, actinomycin, aminopterina into primate anterior chamber after cataract extraction and found that retinoic acid was effective in preventing after cataract with slight toxicity to both eye tissue and optic nerve. In recent years, many researchers have revealed that all - trans retinoic acid (ATRA) can inhibit the proliferation, migration and attachment of rabbit lens epithelial cells. Others modified ATRA onto the implanted IOL and found the concentration of ATRA in anterior chamber could maintain al an effective level. Iann injected ATRA into capsular bag while hydrodissection and after phacoemulsification and found it could inhibit PCO. So, it is possible for retinoic acid to be an ideal drug in preventing PCO.In this research, ATRA of various concentrations are dissolved into BSS irrigation fluid and used during rabbit eye modern cataract extraction while thecontrol group used blank BSS irrigation fluid. After operation, PCO formation of every group is observed to evaluate the inhibition effect by ATRA at a certain time. At mean time, the changes of the other tissues within the rabbit eyeball are also observed to find out the safe effective dosage of ATRA. The Western blot method is employed to find out the expression of P27NNF - kBxBc1 -2 gene in lens epithelial cells on the capsular bag at the same time of different concentration and of the same concentration at different time. The PCNA is also detected as a marker of cell proliferation and then prove ATRA inhibition function by the former three factors through some up - regulating mechanisms.Up to now, the researches about retinoic acid inhibition stay at the stage of live animal and cultured cells observation, there is no report on the molecular level study.Material and methods1. animal grouping: 84 selected healthy rabbits, body weight from 2. 0 to 2.6kg, all have normal external eye state and normal fundus on examine. Both eyes are performed in surgery and account for statistics. Grouping based on scheduled design by random way. The light and electron microscope specimen of the experiment one and two are sampled from the same rabbits. The sample choosing and preparing are performed each time after the statistically biological observations of every group are ended.2. surgery method: ATRA is dissolved in anhydrous alcohol and then added into BSS irrigating fluid before operation in non transparent black pack. Same a-mount of anhydrous alcohol is added into BSS irrigating fluid as blank control. Modern extracapsular cataract extraction is employed to all cases by author a-lone.3. PCO formation of each group is evaluated at certain time, and so do the conjunctiva, cornea, anterior chamber reaction, iris, ciliary body and fundus examination. All results are recorded and used in statistically calculation. Each time after observation, randomly chosen rabbits of each group are put to death to get specimen periodically and used to light microscope, electronic microscopeand western blot examine.Results1. The megascopic PCO can be distinguished about 1 week after surgery on control group rabbits, and the distinct PCO is observed one month later. PCO of various degrees can be found in different concentration ATRA and control group at one month after operation, see Table 1Table 1 PCO grade of every group one month after operationPCO gradecontrol2|xg/ml5|xg/ml1C)|xg/ml20(xg/ml005910121375532312013103010F( among 5groups)34.862(P<0.01)F(2jjLg/mland lOfjLg/ml)3.908(P= 0.048 P<0.05)F(5|xg/mland 20(xg/ml)1.215(P= 0.27 P>0.05)2. From 2|xg/ml to 20uJg/ml, ATRA applied in BSS irrigating fluid has no side effect to bulbar conjunctiva, iris, ciliary body and retina. But notable cornea edema and decrease of corneal endothelial count are found in 20jxg/ml ATRA group. Although marked intraocular pressure decrease exists before and after operation in every group, there is no difference between the control and experimental group at every same period.3. The expression of PCNA^P27 NNF - KB and Bel - 2 checked by Western blot method: the PCNA expression decreases with ATRA concentration elevates; P27 expression increases with ATRA concentration elevates; NF - kB and Bel -2 expression decreases with ATRA concentration elevates.After processed with 10(xg/ml ATRA, PCNA expression has inconspicuous change within 7days, but it increases at 14 and 30 days check. The same chan-...