A prospective study of matrix metalloproteinases in proliferative vitreoretinopathy.

PURPOSE: The migration, proliferation, differentiation, and adhesion of cells and other cellular functions are influenced by the surrounding extracellular matrix, in normal and wound-healing conditions. The matrix metalloproteinases (MMPs) are a family of enzymes that degrade and remodel the extracellular matrix and, thus, play a central role in the wound-healing process. Proliferative vitreoretinopathy (PVR), a wound-healing process in the retina, is a major cause of the failure of retinal detachment surgery. The role of MMPs in the pathobiology of PVR is unknown. We have investigated the presence of MMPs in the vitreous of patients with retinal detachment and the predictive value of MMPs for the future development of PVR. METHODS: A prospective study was conducted on 140 consecutive patients with a rhegmatogenous retinal detachment in whom vitrectomy was considered necessary because of a giant retinal tear and the presence of preoperative PVR, among other reasons. Vitreous samples were obtained and analyzed by zymography for the presence of MMPs. The patients were then followed up for the development of postoperative PVR (mild and severe). RESULTS: Two species of MMPs were detected in the vitreous: MMP-2 and MMP-9. MMP-2 was detected in all of the vitreous samples obtained, whereas MMP-9 was found in only 64 (47%) of 136 samples. The levels of MMPs detected were not significantly associated with the presence of preoperative PVR (P > 0.05), but they were significantly associated (P < 0.05) with the development of postoperative PVR (mild and severe). CONCLUSIONS: The results from this prospective study suggest that MMPs may be an important predictor and may also play a role in the development of postoperative PVR.

Expression of vitreous cytokines in proliferative vitreoretinopathy: a prospective study.

PURPOSE: Proliferative vitreoretinopathy (PVR) is a major cause of failure of retinal detachment surgery. It is believed to be a wound-healing process in the retina. Many of the cellular functions are influenced by cytokines and growth factors such as interleukins (ILs). The present study was conducted to investigate the presence of transforming growth factor-beta 2 (TGF-beta2), basic fibroblast growth factor (bFGF), IL-1beta, IL-6, and protein in the vitreous of patients with retinal detachment and to determine the value of these mediators in predicting the future development of PVR. METHODS: A prospective study was conducted in 140 consecutive patients with rhegmatogenous retinal detachment in whom vitrectomy was considered necessary. Vitreous samples were analyzed for the presence of TGF-beta2, bFGF, IL-1beta, IL-6, and protein. Patients were then followed up for 3 months for the development of postoperative PVR. RESULTS: The mean levels of TGF-beta2, bFGF, IL-1beta, and protein in the vitreous were significantly higher (P < 0.05) in patients with preoperative PVR compared with those without. The mean levels of TGF-beta2, bFGF, IL-6, and protein in the vitreous were significantly higher (P < 0.05) in patients who had postoperative PVR compared with those who did not. Multivariate logistic regression analysis showed IL-6 and protein to be significant (P < 0.05), independent, predictive risk factors for the development of PVR. CONCLUSIONS: The various cytokines may play a role in the pathobiology of PVR. High vitreous levels of IL-6 and protein were identified as significant risk factors for PVR. A model was developed to predict the probability of development of postoperative PVR in these patients, and it may be used to indicate intravitreal pharmacologic treatment for those at risk.

A new way to use the Ishihara test.

The Ishihara plates are widely used as a test for colour vision. Originally designed for the purpose of detecting congenital red-green colour blindness, the test also has some value in demonstrating acquired colour vision defects. There are, however, several disadvantages in the present arrangement of the plates. A modification of the test, involving the rearrangement of the order of the plates, is presented which, together with a new recording chart, simplifies both the administration and the interpretation of the test.

Effects of single, short-term exposures of human retinal pigment epithelial cells to thiotepa or 5-fluorouracil: implications for the treatment of proliferative vitreoretinopathy.

AIM: To investigate the effects of single, short-term (5 or 30 minutes) exposures to thiotepa or 5-fluorouracil (5-FU) on collagen lattice contraction and retinal pigment epithelial (RPE) cell proliferation. METHODS: For collagen contraction studies, RPE cells seeded into free floating type I collagen lattices were exposed to single 5 or 30 minute treatments with thiotepa (0.06-4 mg/ml), or 5-FU (0.25-25 mg/ml), or phosphate buffered saline alone as a control. For proliferation studies, RPE cell monolayers were similarly exposed to these agents. The degree of contraction, effects on cell number, and viability were determined up to 14 days after treatment. RESULTS: Contraction of collagen lattices containing RPE cells and proliferation of RPE cells were significantly inhibited (p < 0.05) by thiotepa and 5-FU at concentrations above 0.06 mg/ml and 0.25 mg/ml respectively (for both 5 and 30 minute treatments), compared with controls. Cell death did not occur except for exposure of the RPE cells in collagen lattices to the highest concentration of thiotepa (4 mg/ml). CONCLUSION: It was concluded that single 5 or 30 minute exposures to thiotepa or 5-FU significantly inhibited collagen contraction and the proliferation of RPE cells. These findings suggest that short, single, non-toxic exposures to thiotepa or 5-FU which can be reproduced clinically may be useful in the modulation of proliferative vitreoretinopathy.

Risk factors for proliferative vitreoretinopathy after primary vitrectomy: a prospective study.

AIM: To assess clinical variables and vitreous protein as risk factors for the development of postoperative proliferative vitreoretinopathy (PVR). METHODS: A prospective study was conducted on 140 patients with a rhegmatogenous retinal detachment in whom a primary vitrectomy was performed. 12 clinical variables were recorded and vitreous samples obtained for measurement of protein concentration. Univariate and multivariate logistic regression analysis was used to determine the risk factors for PVR. RESULTS: Complete data were available for 136 of 140 patients. 40 of the 136 patients (29.4%) developed postoperative PVR. Univariate regression revealed that significant (p<0.05) risk factors included aphakia, presence of preoperative PVR, size of detachment, the use of silicone oil, and high vitreous protein level. Multivariate regression analysis revealed only aphakia (odds ratio 2.72), the presence of preoperative PVR (odds ratio 3.01), and high vitreous protein concentration (odds ratio 1.11) to be significant (p<0.05) independent, predictive risk factors for the development of PVR. CONCLUSIONS: This study has shown that the significant risk factors for PVR are preoperative PVR, aphakia, and high vitreous protein levels. Two models (clinical factors only and clinical factors and vitreous protein) were constructed to predict the probability of developing postoperative PVR and may be used to identify those at risk for possible intravitreal pharmacological treatment.

Silicone oil concentrates fibrogenic growth factors in the retro-oil fluid.

AIM: To determine whether silicone oil concentrates protein and growth factors in the retro-oil fluid. METHODS: A laboratory analysis of intraocular fluid and vitreous specimens obtained from patients undergoing removal of silicone oil, revision vitrectomy, or primary vitrectomy for macular hole, proliferative vitreoretinopathy (PVR), or retinal detachment. Patients were prospectively recruited from routine vitreoretinal operating lists. Vitreous cavity fluid and vitreous samples were analysed for the presence of transforming growth factor beta (TGF-beta2), basic fibroblast growth factor (bFGF), interleukin 6 (IL-6), and total protein using either commercially available enzyme linked immunosorbent assays (ELISA) or protein assay kits. RESULTS: The median levels of bFGF, IL-6, and protein in the retro-oil fluid were raised (p<0.05) compared to all the other vitreous and vitreous cavity fluid samples. bFGF, IL-6, and protein levels were raised in PVR vitreous compared to non-PVR vitreous. TGF-beta2 levels were not significantly raised in retro-oil fluid or in PVR vitreous. CONCLUSIONS: The concentration of fibrogenic (bFGF) and inflammatory (IL-6) growth factors and protein is raised in retro-silicone oil fluid. This may contribute to the process of retro-oil perisilicone proliferation and subsequent fibrocellular membrane formation.

A new colour vision test for clinical use.

Several tests are available for assessing colour vision but they can be expensive, complicated or too time consuming to perform. We have produced a new plate test based on pseudoisochromatic principles. The test, using an error score, examines both the red-green and blue-yellow axes, with four levels of difficulty for each axis. Results from a pilot study show that error scores from congenital red-green blind subjects are significantly higher than those of age-matched controls (p < 0.01) only when using the red-green plates and not the blue-yellow plates. In optic neuritis patients, error scores using both the red-green and blue-yellow plates were significantly higher than those of controls throughout the 6 month follow-up. The test, including scoring, takes 6 minutes to complete. These preliminary results suggest that the new test is effective for screening congenital red-green blindness and monitoring colour vision defects in acquired diseases such as optic neuritis.

Matrix metalloproteinases: a role in the contraction of vitreo-retinal scar tissue.

The most common cause of failure of retinal reattachment surgery is formation of fibrocellular contractile membranes on both surfaces of the neuroretina. This intraocular fibrosis, known as proliferative vitreoretinopathy, results in a blinding tractional retinal detachment because of the contractile nature of the membrane. Contractility is a cell-mediated event that is thought to be dependent on locomotion and adhesion to the extracellular matrix. Interactions between cells and the extracellular matrix can be influenced by matrix metalloproteinases (MMPs) and we investigated the role of MMPs in two in vitro models (two- and three-dimensional) of human retinal pigment epithelial (RPE) cell-mediated contraction. MMP activity was detected using enzyme-linked immunosorbent assays and zymography techniques that revealed MMP-1, -2, -3, and -9 positivity during the collagen matrix contraction assays. RPE-populated collagen matrix contraction (three-dimensional) was inhibited using a cocktail of anti-MMP antibodies and with Galardin (a broad-spectrum MMP inhibitor). Galardin inhibition was dose-dependent, reversible, and dependent on cell number. MMP inhibitors had no effect on contraction when RPEs were seeded on two-dimensional collagen matrices or on cellular adhesion to collagen type I. Our results suggest that MMP activity may be required for three-dimensional but not two-dimensional RPE-collagen matrix contraction.

Adjuvant 5-fluorouracil and heparin prevents proliferative vitreoretinopathy : Results from a randomized, double-blind, controlled clinical trial.

PURPOSE: To assess the safety and efficacy of adjuvant combination therapy using 5-fluorouracil (5-FU) and low molecular weight heparin (LMWH) for prevention of proliferative vitreoretinopathy (PVR) after vitrectomy and retinal reattachment surgery. DESIGN: Prospective randomized, double-masked, placebo controlled trial. PARTICIPANTS: One hundred seventy-four high-risk patients were randomized to receive either 5-FU and LMWH therapy or placebo. Patients were selected from all patients undergoing primary vitrectomy for rhegmatogenous retinal detachment. METHOD: Results of standard surgery with 5-FU and LMWH therapy or placebo were compared at the 6-month follow-up. MAIN OUTCOME MEASURES: Development of postoperative PVR, retinal reattachment at 6 months after surgery, single operation reattachment rate, number of reoperations, and best-corrected visual acuity. RESULTS: There were 87 patients in the 5-FU and LMWH therapy group and 87 in the placebo group. The incidence of postoperative PVR was significantly lower (P = 0.02) in the 5-FU and LMWH therapy compared with the placebo group. In 26.4% (23/87) of the placebo group and in 12.6% (11/87) of the 5-FU and LMWH group, postoperative PVR developed. In the 5-FU and LMWH group, the number of patients undergoing more than one operation was 19.5% (17/87) and the number of reoperations resulting from PVR was 52.9% (9/17). In the placebo group, the number of patients undergoing more than one operation was 25.3% (22/87) and the number of reoperations resulting from PVR was 72.7% (16/22). The difference in visual acuity was not statistically different in the two treatment groups, although those patients in whom postoperative PVR developed tended to have poorer vision (P < 0.0001). There were no differences in complication rates between the two groups. CONCLUSIONS: There is a significant reduction in the incidence of postoperative PVR in patients receiving the 5-FU and LMWH therapy and in the reoperation rate resulting from PVR. This trial shows that incidence of PVR can be reduced with inexpensive and simple pharmacologic treatment with 5-FU and LMWH and should be used routinely in the treatment of patients at risk of developing PVR.

How to predict proliferative vitreoretinopathy: a prospective study.

PURPOSE: To determine prospectively the accuracy of a predictive risk formula for the development of postoperative proliferative vitreoretinopathy (PVR) when applied in a clinical setting. DESIGN: Prospective noncomparative interventional case series. PARTICIPANTS: Two hundred nineteen subjects undergoing primary vitrectomy for rhegmatogenous retinal detachment were studied. METHOD: By use of a formula-based discriminant rule, subjects were classified as either high or low risk for the development of PVR. All subjects were followed prospectively. OUTCOME MEASURES: Development of postoperative PVR as defined by the updated the Retina Society Classification. RESULTS: Complete data were available on 212 of 219 subjects. There were 130 subjects identified as low risk and 82 subjects as high risk; 9.2% of the low-risk (12 of 130) compared with 28% (23 of 82) of the high-risk subjects had postoperative PVR develop. This difference was statistically significant (P < 0.001). CONCLUSIONS: Our study has shown that using a clinical model it is possible to identify subjects at greater risk of PVR developing after primary vitrectomy.