Induction of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs correlates with outcome of acute experimental pseudomonal keratitis

This study aimed to investigate expressions and sources of matrix metalloproteinases (MMP)-2 and MMP-9, and of tissue inhibitors of MMP (TIMP)-1 and TIMP-2 in experimental Pseudomonas aeruginosa keratitis in rabbits. Pseudomonal keratitis was induced in New Zealand white rabbits, and macroscopic and microscopic examinations were performed at appropriate time points (3, 9, 12, 18, 24, 72 h). Expressions and sources of MMP-2, 9, and TIMP-1, 2 were determined using immunohistochemistry, gelatin zymography, ELISA, and RT-PCR. A typical corneal ulcer with a ring abscess was observed 12-72 h post-infection (p.i.) with P. aeruginosa. In microscopic examinations, massive inflammatory cell (mostly polymorphonuclear leukocytes, PMNs) infiltration and liquefactive necrosis were characteristic features. MMP-2 was constitutively expressed in keratocytes, and its expression was not apparently enhanced after pseudomonal infection as evidenced by zymography, immunostaining, and RT-PCR. However, MMP-9 and its activated form were induced, and were significantly enhanced 12-24 h p.i. MMP-9 appeared to derive from PMNs rather than from resident corneal cells. TIMP-1 was expressed in PMNs, macrophages, and keratocytes, and its expression was enhanced 72 h p.i. Although TIMP-2 was constitutively expressed as seen by immunostaining and RT-PCR, its concentration was below detection limits during the experiments. We demonstrated that MMP-9 was one of the important factors for corneal tissue destruction, because it was induced and significantly expressed in keratocytes and inflammatory cells after pseudomonal infection. Although TIMP-1 was expressed in later stages of infection, enhancement and activation of MMP-9 were much faster and stronger than those of TIMP-1, thereby facilitating tissue destruction leading to corneal ulceration.     

Stimulatory effect of pseudomonal elastase on collagen degradation by cultured keratocytes

PURPOSE. The pathobiology of corneal ulceration induced by Pseudomonas aeruginosa was investigated by characterization of the pseudomonal pathogenic factors responsible for degradation of the collagen matrix. METHODS. Three-dimensional gels of type I collagen containing (or not) rabbit keratocytes were incubated in the presence of either culture supernatant of P. aeruginosa strain PAO1 or pseudomonal pathogenic factors (elastase, lipopolysaccharide, or exotoxin A), and the extent of collagen degradation was assessed after 24 hours by measurement of released hydroxyproline. Activation of matrix metalloproteinases (MMPs) produced by keratocytes was also examined by gelatin zymography and immunoblot analysis. RESULTS. In the absence of keratocytes, the PAO1-conditioned medium increased the extent of collagen degradation. The conditioned medium also promoted keratocyte-mediated collagen degradation. Of the pseudomonal pathogenic factors examined, only elastase degraded collagen directly as well as stimulated keratocyte-mediated collagen degradation. Culture supernatant of elastase-deficient P. aeruginosa (lasR or lasB) mutants had no effect on collagen degradation in the absence or presence of keratocytes. Elastase also induced the conversion of the inactive precursors of MMP-1, -2, -3, and -9 produced by keratocytes to the active forms of the enzymes. CONCLUSIONS. These results suggest that pseudomonal elastase both degrades type I collagen directly and promotes collagen degradation mediated by keratocytes, the latter effect being likely attributable, at least in part, to the activation of proMMPS:     

Regulation of MMP-9 activity in human tear fluid and corneal epithelial culture supernatant

PURPOSE: To evaluate human corneal epithelial culture supernatant and tear fluid for the presence of activators and inhibitors of matrix metalloproteinase (MMP)-9, MMP-3, and tissue inhibitor of metalloproteinase (TIMP)-1, respectively, and to evaluate the effect of MMP-3 on the activation of MMP-9 in these specimens. METHODS: Unstimulated tear fluid was collected from patients with ocular rosacea and normal control subjects. Levels of MMP-9, MMP-3, and TIMP-1 were determined by enzyme-linked immunosorbent assay (ELISA) and/or immunoblot analysis. Supernatants from primary human corneal epithelial cultures and human tear fluid were incubated with MMP-3. Cultured epithelial cells and their supernatants were also treated with doxycycline before MMP-3 was added. Gelatin zymography was used to identify activated 82-kDa MMP-9. MMP-9 activity was assessed with a commercial MMP-9 activity assay system. RESULTS: MMP-9 and TIMP-1 were detected at significantly higher concentrations in rosacea-affected than in normal tear fluids. MMP-3 was detected exclusively in the tear fluid of patients with ocular rosacea who had corneal epithelial disease. Treatment of the supernatant and tear fluid with MMP-3 resulted in two bands with molecular weights of 92 kDa and 82 kDa, representing pro-MMP-9 and activated MMP-9, respectively. Doxycycline added to the conditioned media did not affect activation of MMP-9 by MMP-3. However, 24-hour treatment of corneal epithelial cultures with doxycycline resulted in a lower concentration and activity of MMP-9 in their supernatants. CONCLUSIONS: MMP-9 and TIMP-1 are produced by the human corneal epithelium and are present in tear fluid. MMP-3 alone is sufficient to activate MMP-9 on the ocular surface. Doxycycline does not directly inhibit this activation by MMP-3, but it decreases MMP-9 activity when added to corneal epithelial cultures.     

Pseudomonas keratitis and folliculitis from whirlpool exposure

A local outbreak of pseudomonal folliculitis from whirlpool exposure occurred in 12 persons. A corneal ulcer developed in one patient within 48 hours of using the whirlpool. Treatment with fortified gentamicin resolved the corneal infiltrate and vision returned to normal. A second patient, who had not showered immediately after leaving the whirlpool, was left with areas of skin hyperpigmentation and scarring despite treatment with ultraviolet rays and tetracycline. Although the skin rash may be self-limited, the potential for visual loss from pseudomonal keratitis emphasizes the need for proper disinfection of swimming and whirlpool water.     

Expression of matrix metalloproteinase-2 (MMP-2) and vascular endothelial growth factor (VEGF) in inflammation-associated corneal neovascularization

Matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) are all implicated in the development of neovascularization. To investigate the possible role of these factors in corneal neovascularization we have analysed the expression of MMP-2, MMP-9 and VEGF in a rat model of inflammation-associated corneal neovascularization. In this model, corneal neovascularization was induced in Long-Evans rats by krypton laser photocoagulation whereafter eyes were enucleated at 1, 4, 7, 10 and 20 days. Slit-lamp biomicroscopy and histologic analysis revealed a gradual development of corneal neovascularization that peaked 7-10 days after treatment when newly formed vessels could be seen throughout the corneal surface reaching deep into the stroma. Antisense and sense riboprobes were generated using DNA complementary to MMP-2, MMP-9 and VEGF, and mRNA expression was analysed using in situ hybridization. The expression of MMP-2 and MMP-9 in untreated corneas was low or absent whereas VEGF was weakly expressed in the corneal epithelium. MMP-2 expression was increased during corneal neovascularization and was mainly localized to the cells infiltrating areas of new vessel formation. Many of these cells appeared to be inflammatory cells. VEGF expression had a similar overall distribution to MMP-2 during neovascularization with the exception that its expression in the corneal epithelium remained and even increased slightly. MMP-9 was prominently expressed at the border of regenerating corneal epithelium in areas with epithelial wounding but was not detected in the vascularized stroma. Together, the results of the present study support a role for MMP-2 and VEGF in inflammation-associated corneal neovascularization whereas MMP-9 instead appears to be involved in corneal epithelial wound-healing.     

羊膜移植对大鼠角膜碱烧伤后基质金属蛋白酶的影响

目的探讨羊膜移植对大鼠角膜中度碱烧伤后角膜上皮细胞和基质成纤维细胞中基质金属蛋白酶(matrix metalloproteinase，MMP)变化的影响。方法将12只SD大鼠随机分成2组，每组6只，分别作为碱烧伤后1d组和14d组。在2组中，所有大鼠角膜建立中度碱烧伤模型，左眼行羊膜移植，右眼作为对照。应用免疫组化法，分别观察碱烧伤后1d和14d实验组与对照组中MMP-9和MMP-2表达的变化。结果碱烧伤后1d，实验组与对照组中，角膜上皮细胞内的MMP-9和MMP-2的表达与正常角膜上皮细胞内的MMP-9和MMP-2的表达相比明显升高，但两组间的表达差异无显著性；而2组成纤维细胞内的MMP-9和MMP-2的表达与正常成纤维细胞内的MMP-9和MMP-2的表达相比明显升高，两组间的表达差异无显著性。碱烧伤后14d，2组中角膜上皮细胞内的MMP-9和MMP-2的表达与碱烧伤后1d情况相似，两组间的表达差异无显著性；2组成纤维细胞内的MMP-9和MMP-2的表达与碱烧伤后1d组相比明显升高，并且实验组中的MMP-9和MMP-2的表达与对照组相比也有明显升高。结论碱烧伤后大鼠角膜上皮细胞和基质成纤维细胞中的MMP-9和MMP-2的表达都有升高。羊膜移植能增强MMP-9和MMP-2在成纤维细胞中的表达，提示羊膜在加快角膜碱烧伤后的重塑中起一定作用。     

热烧伤后的人角膜组织中基质金属蛋白酶-2、-9表达的研究

目的:研究热烧伤后人角膜组织中的基质金属蛋白酶-2、-9(MMP-2、MMP-9)的表达与分布,探讨其含量的变化与角膜病变的相关性。方法:收集铁水烫伤后行角膜移植患者病变角膜19例,正常角膜组织10例。应用免疫组化染色方法检测MMP-2、MMP-9在角膜各层次中的分布与表达,应用图像分析系统进行半定量分析。结果:MMP-2、MMP-9在正常角膜组织中均未见阳性表达,平均灰度值分别为117.8188±3.7967,119.1902±0.9679。热烧伤后角膜组织中,MMP-2的阳性表达主要分布于角膜基质层,平均灰度值为94.4197±5.8327;MMP-9的阳性表达主要分布于角膜上皮层和基底膜附近,平均灰度值为115.0188±0.7149。将正常角膜组织中和病变角膜组织中两种酶的平均灰度值分别进行统计学分析,P值均<0.05。随着病程的发展,在病变角膜组织中MMP-2的阳性表达先呈现逐渐增高趋势14d后逐渐下降,角膜基质层溶解达高峰时阳性表达的量最高;MMP-9在患病初期角膜基底膜病变明显时表达较高,后期逐渐下降。结论:MMP-2、MMP-9对热烧伤后的人角膜组织病变的发展起重要的作用。MMP-2主要参与角膜基质层的损害,MMP-9主要参与角膜上皮层和基底膜的损害。     

Late corneal perforation after photorefractive keratectomy associated with topical diclofenac: involvement of matrix metalloproteinases

OBJECTIVE: To report a case of a 50-year-old man who was initially seen with a corneal perforation in his right eye 2 months after a photorefractive keratectomy (PRK) procedure and to discuss the roles of topical diclofenac and matrix metalloproteinases (MMPs). DESIGN: Case report with tissue analysis. MAIN OUTCOME MEASURES: Ocular examination, diagnostic workup, surgical treatment, and histologic, immunofluorescent, zymography, and real time-polymerase chain reaction studies on corneal button. RESULTS: Slit-lamp examination of the right eye revealed a 4-mm diameter area of central corneal thinning with a 2-mm diameter perforation at its center. Predisposing factors included prolonged postoperative topical diclofenac therapy for more than 2 months and a 10-year history of well-controlled diabetes mellitus. An extensive diagnostic workup ruled out a systemic autoimmune disease. A penetrating keratoplasty was performed. Results of immunohistochemical studies of the corneal button showed stromal accumulation of temporary type III and IV collagens, MMP-3, and MMP-9 in the anterior wounded stroma and MMP-9 in the basal corneal epithelial cells of the leading edge. Differential activity and expression of MMP-2 and MMP-9 were found between the central and peripheral corneal buttons. CONCLUSIONS: Prolonged use of diclofenac and diabetes mellitus might be responsible for the corneal perforation after PRK in our patient. MMP-9 and MMP-3 might be involved in delayed wound closure and corneal melting.     

Expression of matrix metalloproteinases 2 and 9 in experimental corneal injury and fungal keratitis

PURPOSE: Levels of matrix metalloproteinases (MMPs) can be modulated during corneal infection, but little is known about MMP profiles during fungal keratitis. The purpose of this study was to determine the effect of corneal trauma and immunosuppressive treatment on the expression kinetics of MMP-2 and MMP-9 during experimental keratomycosis. METHODS: Corneas of immunocompetent and cyclophosphamide-treated adult BALB/c mice were topically inoculated with 1 x 10 culturable units of Fusarium solani or mock-inoculated with or without superficial corneal scarification. Eyes were scored daily for disease severity and processed for zymography after 1.5 hours, 6 hours, 1 day, 4 days, or 8 days. Gelatinase activity was densitometrically quantitated and normalized to MMP-2 and MMP-9 controls. RESULTS: MMP-9 levels in nontraumatized eyes transiently increased at 6 hours after fungal exposure, but this increase was inhibited by cyclophosphamide treatment. Corneal injury significantly induced early MMP-9 expression that returned to baseline levels within 4 days. Cyclophosphamide pretreatment reduced and delayed MMP-9 after scarification. Fusarium exposure dampened the MMP-9 response to corneal trauma in immunocompetent and cyclophosphamide-treated animals. Ocular levels of MMP-2 were not affected by scarification, fungal exposure, or immunosuppressive treatment. CONCLUSIONS: Ocular MMP-9 levels, but not MMP-2 levels, increased soon after corneal injury. A similar, although muted, MMP-9 response occurs during early filamentous fungal keratitis, with a kinetic profile similar to corneal disease progression. The early stage of ulcerative keratitis may involve selective regulation of corneal matrix metalloproteinases, suggesting an initial opportunity for therapeutic intervention.     

Expression of matrix metalloproteinases 2 and 9 and tissue inhibitors of metalloproteinase 1 and 2 in inflammation-induced corneal neovascularization.

PURPOSE: Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) have been linked to the angiogenic process in general. In order to understand the potential roles of MMP-2, MMP-9 and TIMPs in the corneal neovascularization process, we examined the expression and activities of MMP-2, MMP-9 and TIMPs during the course of cauterization-induced corneal neovascularization in a rat model. METHODS: Neovascularization of rat corneas was induced by silver nitrate cauterization. The expression of MMP-2, MMP-9, TIMP-1 and TIMP-2 was examined by immunohistochemistry and RT-PCR. The protein activities of MMPs and TIMPs were compared in pre- and postcauterization corneas by gelatin zymography and reverse zymography, respectively. RESULTS: MMP-2, TIMP-1 and TIMP-2 immunoreactivities were expressed in normal corneas, predominantly in the corneal epithelium. After injury, immunoreactivities of both MMPs and TIMPs were increased, notably in the healing corneal epithelium, infiltrating inflammatory cells, stromal fibroblasts and ingrowing vascular endothelial cells. The increase in gross MMP-2 enzymatic activity paralleled the maximal vascular ingrowth on day 4, while the gross MMP-9 enzymatic activity rose immediately on day 1, then decreased steadily, which paralleled the magnitude of inflammatory cell infiltration. The immunoreactivity of MMPs/TIMPs decreased significantly 2 weeks after cauterization. On day 35, MMP-2, TIMP-1 and TIMP-2 staining was seen only in corneal epithelium and vascular endothelial cells. Both the RT-PCR and reverse zymography results revealed a more constant expression of TIMP-2, while the TIMP-1 expression appeared to be more inducible. CONCLUSION: MMPs as well as TIMPs were upregulated in cauterization-induced corneal neovascularization, suggesting that both may participate in extracellular matrix remodeling in the corneal wound healing, inflammation and neovascularization processes.     

Corneal burns and matrix metalloproteinases (MMP-2 and -9): the effects of human amniotic membrane transplantation

PURPOSE: Human amniotic membranes have recently been used in ophthalmology to restore deleted ocular surface after burns. Matrix metalloproteinases-2 and -9 have been implicated in the development of neovascularization. In this study, MMP-2 and MMP-9 expression was analyzed by in situ zymography on rabbit corneal chemical burns with and without human amniotic membrane graft. Method: Corneal neovascularization was induced in 10 Fauve de Bourgogne rabbits by means of a heptanol chemical burn on controlled deep keratotomy using a Chiron ALK-E corneal shaper. Half of rabbits received acute amniotic membrane transplantation 30mn after chemical burn; the remaining five rabbits received medical treatment. In situ zymography is a recent nondestructive technique which preserved the fine morphological details of the cornea and showed the active enzyme location in different corneal layers. The MMP-2 and -9 substrate was gelatin, which was detected by fluorescent microscopy. RESULTS: There was an overexpression of MMP-2 and -9 in corneal burns versus control corneas. Expression of MMP-2 and -9 was low in corneal burn without amniotic membrane graft. Following amniotic membrane transplantation, MMP-2 and -9 were strongly expressed and clinical neovascularization and inflammation decreased. Active enzymes were located in epithelium layers in the uncovered group. In the covered group, the active enzymes were located in the anterior and posterior stromal layers. CONCLUSION: The results support a role for MMP-2 and MMP-9 in corneal burn neovascularization. Amniotic membrane transplantation can play a protective role by up-regulation of their biological expression.     

Activation of corneal fibroblast-derived matrix metalloproteinase-2 by tryptase

PURPOSE: The presence of the active form of matrix metalloproteinase (MMP)-2 and an increased concentration of tryptase are characteristics of tear fluid of individuals with vernal keratoconjunctivitis. Although tryptase does not mediate the activation of purified MMP-2, we have now examined whether it might activate MMP-2 in the presence of cultured human corneal fibroblasts. METHODS: Corneal fibroblasts were cultured in the absence or presence of tryptase, and the activation status of MMP-2 was determined by gelatin zymography. RESULTS: MMP-2 released from corneal fibroblasts was activated by exogenous tryptase. This effect was not mediated by protease-activated receptor 2 or the plasmin-plasminogen system, and it was not apparent on incubation of tryptase with medium conditioned by corneal fibroblasts. It was inhibited by tissue inhibitor of metalloproteinase (TIMP)-2 but not by TIMP-1. CONCLUSIONS: Tryptase activates MMP-2 released from corneal fibroblasts. This action requires the presence of the cells themselves and might be responsible for the presence of activated MMP-2 in tear fluid of individuals with vernal keratoconjunctivitis.     

Amnionmembrantransplantation bessert experimentelle herpetische Keratitis

PURPOSE: Transplantation of human amniotic membrane (AMT) accelerates the healing of experimental ulcerative herpetic keratitis. Here the expression and activity of matrix metalloproteinase (MMP)-9 was studied. METHODS: BALB/c mice were corneally infected with HSV-1. Whereas the infected corneas of mice in group 1 were covered with AM, tarsorrhaphies were performed in others (group 2). After 2 days, the appearance of corneal ulcers and stromal inflammation was judged clinically, and the corneal PMN infiltration was studied histologically. The expression of MMP-9 in the corneas was localized by immunohistochemistry and analyzed by Western-blot technique. The MMP-9 activity in the corneas was determined by zymography. RESULTS: On day 14, the ulcerating corneas had a dense PMN infiltration, the ulcers and the majority of PMNs were highly positive for MMP-9, and the active forms of MMP-9 were detected. Gelatinolytic activity was found in these corneas by zymography. Compared with the mice of group 2, ulceration, stromal inflammation and neovascularization markedly improved clinically and histologically within 2 days in mice of group 1. This was associated with a reduced expression of MMP-9 in corneal tissue and in PMNs. The gelatinolytic activity of MMP-9 was reduced after AMT. CONCLUSIONS: These observations suggest that improvement of herpetic corneal ulcers and reduced corneal neovascularization after AMT may result from a reduced expression and activity of MMP-9.     

The role ofPseudomonas aeruginosa elastase in corneal ring abscess formation in pseudomonal keratitis

In order to identify the causative factors of ring abscess, which is the characteristic feature of pseudomonal keratitis, pseudomonal endotoxin, exotoxin A, and elastase were each separately injected into guinea pig cornea. There was no formation of ring abscess. Injection of livingPseudomonas aeruginosa strains IFO3455 and Takamatsu which produce all three molecules, clearly induced ring abscess. In contrast, when heat-killed bacteria strain IFO3455 or living bacteria of the non-elastase-producing strain PA103 were injected, ring abscess was not induced. Furthermore, when living bacteria strain IFO3455 were injected with anti-elastase antibody or a protease inhibitor, ovomacroglobulin, ring abscess formation was significantly inhibited. Histological examination demonstrated that the ring abscess was a dense accumulation and aggregation of polymorphonuclear leukocytes (PMN) with debris of cells and lamellae in the deep stroma at the corneal margins, suggesting prevention of PMN migration to the central lesion. The presence of anti-elastase antibody or a specific elastase inhibitor facilitated PMN migration towards living bacteria strain IFO3455 in an in vitro model. These results indicate that pseudomonal elastase is a necessary but not sufficient factor in the formation of ring abscess in pseudomonal keratitis.     

The control of matrix metalloproteinase-2 expression in normal and keratoconic corneal keratocyte cultures

PURPOSE: Early phase keratoconic corneas and their cultured keratocytes abnormally produce the Mr 62,000 form of the matrix metalloproteinase-2 (MMP-2). It is known that platelet derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) are involved in the regulation of MMP activity and tissue inhibitor of metalloproteinase (TIMP) production in non-ocular tissues. The purpose of this enquiry was to determine whether these growth factors also play a role in the activity and/or production of corneal MMP-2 and TIMP, and whether their activity could account for the existence of the Mr 62,000 form of MMP-2 in keratoconic corneas. METHODS: Confluent cultures of normal and early-phase keratoconic corneal keratocytes were established and incubated in serum-free media in the presence or absence of PDGF and TGF-beta. The proteins secreted by these cells over periods of 7 days were harvested for analysis. The total protein produced was determined spectrophotometrically. MMP-2 was visualised by SDS-gelatin polyacrylamide gel electrophoresis and assayed using radiolabelled type IV collagen as substrate. The enzyme inhibitors, TIMP-1 and TIMP-2, were quantified by dot blot immunoassay. RESULTS: The addition of PDGF or TGF-beta to the culture medium of keratoconic corneal keratocytes had no significant effect on overall protein production, MMP-2 activity or on the amounts of TIMP- 1 and TIMP-2 secreted. These observations also applied to normal corneal keratocytes, with the exception that PDGF induced expression of the Mr 62,000 species of MMP-2. CONCLUSIONS: PDGF may be involved in the production of the Mr 62,000 species of MMP-2 that is abnormally produced by early-phase keratoconic corneal keratocytes.     

基质金属蛋白酶-9在人正常角膜及真菌性角膜溃疡中的基因表达

目的:研究基质金属蛋白酶-9(matrix metalloproteinase-9,MMP-9)在人正常角膜及真菌性角膜溃疡中的基因表达,探讨MMP-9在真菌性角膜溃疡形成中的作用。方法:搜集24份真菌性角膜溃疡标本(溃疡组)及12份人正常角膜组织标本(对照组),其中12份真菌性角膜溃疡组织和6份正常的角膜组织分别抽提组织总的RNA,以Primer5.0软件设计MMP-9的特异引物,并对标本RNA进行RT-PCR扩增,以MMP-9目的电泳条带与β-actin内参照条带灰度值比值代表相对表达量。分12份角膜溃疡组织和6份正常的角膜组织进行免疫组化检测MMP-9表达,通过免疫组化染色的灰度值进行统计学分析。结果:MMP-9在真菌性角膜溃疡中的表达明显高于正常角膜,且主要位于角膜上皮层、基底膜以及基质层。结论:真菌性角膜溃疡组织中MMP-9的基因表达明显上调。MMP-9在真菌性角膜溃疡的发生、发展及角膜穿孔中起着重要作用。加强MMP-9在真菌性角膜溃疡中的作用机制的研究,有望对真菌性角膜溃疡的治疗提供新的途径。