Research progress of secreted protein acidic and rich in cysteine in glaucoma filtering bleb scarring / 上海交通大学学报（医学版）

Filtering bleb scarring is the main cause of glaucoma filtration surgery failure. Subconjunctival injection of antimetabolites, such as mitomycin and 5-fluorouracil, is widely used clinically to reduce the incidence of scarring, which improves the success rate of the surgery. However, accompanied side effects such as cytotoxicity should not be ignored. Secreted protein acidic and rich in cysteine (SPARC) as a matricellular protein is widely distributed in the eyes, which plays an important role in the process of wound repairing and tissue remodeling. The expression of SPARC is significantly elevated in the mouse model of subconjunctival scarring. Researches suggest that SPARC participates in and regulate the formation of bleb scarring through multiple pathways, therefore it may become a specific new target in the anti-scarring therapy.

Mechanisms of scar formation and research progress in anti-fibrosis therapy after glaucoma filtration surgery / 国际眼科杂志(Guoji Yanke Zazhi)

@#Filtering channels carring and subsequent obstruction are the main cause of operation failure after glaucoma filtration surgery. During the process of scarring, human Tenon fibroblasts are transformed into myofibroblasts and secrete a large amount of extracellular matrixproteins. The derangement of the collagen fiber is also observed. A large number of studies have been carried out by domestic and foreign researchers on the treatment of postoperative filtering channel scarring. In this review we summarize the mechanisms of scar formation after glaucoma filtration surgery and corresponding research progress in recent years.

Exploration and application of polyhydroxyalkanoates and polylactic acid membranes during glaucoma filtering surgery and interlaminar transplantation in rabbits / 中国比较医学杂志

Objective To evaluate the effect of two polymer membranes, polyhydroxyalkanoates(PHA)and polylactic acid(PLA)during glaucoma filtration surgery(GFS),and to evaluate the morphology of membranous PHA after interlamellar implantation. Methods Twenty-eight New Zealand white rabbits were chosen and twenty-four of them were randomly divided into 6 groups(n=4):the PHA-low group,PHA-high group,PLA-low group,PLA-high group,positive control group(MMC group)and blank control group. The rabbits in each group received GFS. The corresponding polymer membranes were implanted under the scleral flap,while the MMC group was treated with 0.2 mg/mL mitomycin C(MMC) for 3 minutes,and the blank control group was treated without extra drugs. The intraocular pressure(IOP)was examined at 0 d,1 d, 3 d, 7 d, 14 d, 28 d and 84 d after GFS. The corneal layers of four rabbits were implanted with PHA membranes and the corneal morphological changes were observed after 84 d. Results The IOP of the PHA-low and PLA-high groups was lower than that of the blank control group at 84 d after GFS(P < 0.05),and was similar with that of the MMC group(P> 0.05). Morphological studies showed that there were no collagenous fibers filling in the duct, and the collagenous fibers around the membranes were generally arranged in parallel. There were no obvious changes in the peripheral collagen structure after implantation of PHA membranes between the corneal layers. Conclusions Application of PHA and PLA membranes during GFS in rabbits may maintain the level of IOP,and the effect is similar with MMC. The mechanism may be achieved through the mechanical blocking of fibrous tissue.

Role of Ex-Press Glaucoma Shunt Implant in Glaucoma Filtering Surgery.

Glaucoma filtration surgery is a challenge for any glaucoma surgeon, because of its variable results and numerous complications. The Ex-PRESS glaucoma shunt, when used along with trabeculectomy gives a controlled drainage of aqueous and hence most of the complications due to over filtration like hypotony, choroidal detachment could be avoided. Tissue erosion and migration of device were initially noted, but later became rare due to modifications in techniques, like use under a sclera flap. The Ex-PRESS glaucoma shunt implant is a promising device in glaucoma filtration surgery, if used judiciously.

Inhibitory Effect of alpha-Tocopherol on Fibroblast Proliferation in Glaucoma Filtration Surgery with Rabbits

Generally, the postoperative failure of glaucoma filtrationsurgery(GFS) is caused by scarring of filtering site. Mitomycin C(MMC) has been commonly used for preventing the scarring of filtering site. Though the antifibroblastic effect of this drug is approved clinically, its cytotoxic side effect cannot be overlooked,. alpha-tocopherol is known to inhibit proliferation of fibroblast without cytotoxic complications. In this study, we used alpha-tocopherol in GFS of rabbits and investigated the maintenance of bleb formation, complications and inhibition of fibroblast proliferation compared with MMC. Thirty six rabbits were divided into 6 groups Negative control groups were the balanced salt solution soaked group and the 19% ethanol soaked group and positive control group was soaked with 0.2mg/ml MMC during GFS. As experimental groups, group I, II, III were soaked with 100micrometer, 1mM and 10mM alpha-tocopherol. The results were as follows: For the maintenance of bleb formation, at postoperative 2 weeks, all extinguished in negative control groups and each experimental groups from I to III showed 16.7%, 33.3%, 50%, with highest rate of 66.7% in MMC soaked group, but at 2 months, group III and MMC soaked group showed 33.3% equally. Various complications were present in MMC soaked group but rare in alpha-tocopherol soaked groups. On histologic examinations, proliferation of fibroblast and infiltration of lymphocyte in group II, III and MMC soaked group except group I were much less than those of negative control groups and the degree of inhibition was proportional to concentration of tocopherol. There was no statistic difference(P>0.05) in area of reticulin fibers between group III and MMC soaked group and antifibroblastic effects were also similar between these two groups. These result suggest when directlyconcentration(1mM<) as much as MMC. Moreover, it is expected to be used more safely during GFS withous serious cytotoxic complications. However, application method, dosageand possible long term complications.

The Effect of Transforming Growth Factor-beta and Mannose-6-Phosphate on the Proliferation of Subconjunctival Fibroblast of Rabbit

The main cause of failure in glaucoma filtering surgery is obstruction of aqueous outflow due to subconjunctival fibrosis. Transforming growth factor-beta(TGF-beta) is known to be a growth factor for subconjunctival fibroblast. Recently, mannose-6-phosphate(M-6-P) is reported to be an inhibitor of TGF-beta activity. In this study, we evaluated the effects of TGF-betas and M-6-P on the proliferation of cultured subconjunctival fibroblast of white rabbit in vitro. Cell proliferation was determined by 3H-thymidine DNA incorporation method. TGF-beta1, 2, 3 all promoted proliferation of subconjunctival fibroblast in a concentration dependent fashion and the effect of TGF-beta1 was most prominent among 3 types. Low concentration (0.01mM) of M-6-P paradoxically increased cell proliferation, but with the concentration of 1.0mM, the inhibitory effects were varied in the range of 45% to 7%.

The Effect of 5-Fluorouracil or Mitomycin-C in Glaucoma Filtration Surgery on the Rabbit Cornea and Sclera

The authors investigated the toxicity of two antimetabolites. 5-fluorouracil(5-FU) and mitomycin-C(MMC) on the rabbit cornea and sclera following glaucoma filtration surgery(GFS). Forty rabbits were divided into four groups; the first control group(I) was the balanced salt solution soaked group(BSS) during GFS, the second(II) was the 5-FU subconjunctival injected group(5-FU SC) after GFS, the third(III) was the 5-FU soaked group(5-FU) during GFS, and the fourth(IV) was the MMC soaked group(MMC) during GFS. At the fifth day after GFS, scanning electron microscopic findings showed that corneal epithelial cells were most seriously damaged in 5-FU SC group, slightly damaged in 5-FU group, and no change in MMC and BSS group. At six months after GFS, transmission electron microscopic observation on sclera revealed the most profound degenerative changes in 5-FU group, and followed by an order of MMC, 5-FU SC, and BSS group. These results suggest that the dosage and application method of antimetabolites should be selected with great caution to prevent ocular toxicity.

Efficacy of 5-Fluorouracil and Mitomycin-C on Glaucoma Filtration Surgery in Rabbits

Antimetabolites, 5-fluorouracil(5-FU) and mitomycin-C(MMC), are used to promote the success rate of the glaucoma filtration surgery(GFS). The authors observed and compared the duration of bleb formation and complications by slit-lamp biomicroscopy, and the inhibition of fibroblast proliferation and of fibrosis by light microscopy following GFS in 4 group rabbits. One hundred and twenty rabbits comprised in this study were divided into four groups; the first control group(I) was the balanced salt solution soaked group(BSS) during GFS, the second(II) was the 5-FU subconjunctival injected group(5-FU SC) after GFS, the third(III) was the 5-FU soaked group(5-FU) during GFS, and the fourth(IV) was the MMC soaked group(MMC) during GFS. For the maintenance of bleb formation, MMC, 5-FU SC, 5-FU and BSS group showed 0%, 26.7%, 16.7%, 100% at the 1 month after GFS, and 0%, 0%, 0%, 73.3% at the 2 months after GFS, respectively, which suggested that MMC group lasted longest. The inhibition of fibrosis and fibroblast proliferation became higher in the order of MMC, 5-FU, 5-FU SC, BSS group at 2 weeks after the surgery. At 3 months after GFS, there was no conspicuous statistic difference(P>0.05) between 5-FU SC and 5-FU group, but some differences(P<0.001) in the rest groups. From these results, we concluded that antimetabolites such as 5-FU and MMC could be used effectively in cases of poor prognosis of GFS. However, the dosage and application method of antimetabolites should be considered very carefully and further research will be necessary to find out the optimal dosage with minimum toxicity.

The Tissue Changes of Filtering Site Following Glaucoma Filtration Surgery with Various Mitomycin C Concentrations

The most common cause of the postoperative failure of glaucoma filtration surgery(GFS) is scarring secondary to fibroblast proliferation and fibrosis at the interface of the episclera and conjunctive. To inhibit this process, mitomycin C(MMC) has been studied experimentally, both in vivo and in vitro. In evaluating the toxicity of MMC, we observed the inhibition of fibroblast proliferation and of fibrosis by light microscope, and the ultrastructual changes of the sclera by transmission electron microscope following the soaking of MMC during GFS in rabbit eyes. The sixty rabbits which comprised this study were divided into four groups; the first control group(I) was soaked with the BSS during GFS, the second(II), the third(III), and the fourth(IV) group were soaked with the 0.2 mg/ml, 0.5 mg/ml, and 0.5 mg/ml MMC soaked groups, respectively, during GFS as experimental groups. On histologic examination, the degree of proliferation of fibroblasts with fibrosis and infiltration of lymphocytes in MMC soaked groups was less than those of BSS soaked group at 2 weeks and 2 months after GFS. At six months after GFS, there was ultrastructural evidence of degenerative changes of scleral fibroblasts such as clumping of nuclear chromatin, wrinkling of nuclear membrane, and cystic dilatation of rough endoplasmic reticulum in MMC soaked groups. Higher concentration of MMC caused more degenerative changes in cellular structures. These results surggested that the scar formation after GFS could be significantly suppressed by a single application of MMC during surgery, and MMC could be0 used effectively in cases of poor prognosis of GFS. Further experiments need to be conducted to determine the optimal concentration, exposure time, and application method of MMC.

The Safety of Mitomycin-C in Glaucoma Filtration Surgery in Rabbits

To investigate the safety of subconjunctivally injected mitomycin-C(MMC) as an adjunctive therapy following the glaucoma filtration surgery(GFS), various amounts of MMC have been given to rabbit eyes after the surgery. To the control group, balanced salt solution(BSS) was injected subconjunctivally and 0.05mg MMC dissolved in BSS was given to the I experimental group I, 0.1mg to the group II, and 0.2mg to the group III. When the concentration of MMC in aqueous humor and cornea were measured at 30 min after the administration of MMC by high performance liquid chromatography, while no MMC was detected in aqueous humor, 1.2 +/- 0.5 micro gram of MMC/g of corneal tissue was detected for group III and 0.3 +/- 0.1 micro gram/g was found in group II. No MMC could be detected in corneal tissues of group I. The scanning electron microscopy which was done on the third day after surgery, revealed the most serious destructive changes of corneal endothelium in group III, while slight changes in group II, and no alteration in group I and control group. Based on these observations, subconjunctival injection of low dose(0.05mg) of MMC may be safe as an adjunctive method to enhance the success rate of GFS.