Immunoconfocal localization of gelatinase B expressed by migrating intrastromal epithelial cells after deep annular excimer keratectomy

The Glaucoma Italian Pediatric Study (GIPSy): The Long-term Effect of Topical Latanoprost on Central Corneal Thickness

PRECIS

Central corneal thickness (CCT) may increase over time in children affected by primary congenital glaucoma and treated with latanoprost for at least 30 months.

PURPOSE

The purpose of this study was to investigate CCT modification over time in a population of primary pediatric glaucoma (PPG) patients prescribed a monotherapy of latanoprost.

MATERIALS AND METHODS

The present paper reports the results of a post hoc analysis on patients enrolled in the Glaucoma Italian Pediatric Study (GIPSy). Children affected by PPG, with a postsurgical intraocular pressure between 22 and 26 mm Hg and treated with latanoprost monotherapy for at least 30 months were eligible for the analysis. CCT variation from baseline was investigated over the follow-up using univariable and multivariable longitudinal linear mixed models. The impact of age, sex, and intraocular pressure on CCT variation were evaluated taking into account the interaction of each variable with time.

RESULTS

Twenty-seven eyes (20 patients) were included in the analysis. Mean duration of latanoprost treatment was 36.6 months (SD 2.5) and mean CCT at baseline was 551 μm (SD 37.7). A significant increase of CCT over time was revealed by multivariable analysis, taking into account the impact of age at baseline and its interaction with time (P=0.03). The interaction between age and time was significant (P=0.04), indicating that older age at baseline was associated with lower increase of CCT over time. No variation of CCT was found in univariable analysis (P=0.28).

CONCLUSION

In this population of PPG patients treated with latanoprost for at least 30 months, CCT significantly increased over time, when the impact of age and its interaction with time were considered.

Mediators of ocular angiogenesis

Angiogenesis is the formation of new blood vessels from pre-existing vasculature. Pathologic angiogenesis in the eye can lead to severe visual impairment. In our review, we discuss the roles of both pro-angiogenic and anti-angiogenic molecular players in corneal angiogenesis, proliferative diabetic retinopathy, exudative macular degeneration and retinopathy of prematurity, highlighting novel targets that have emerged over the past decade.

The effect of prostaglandin analogs and prostamide on central corneal thickness

OBJECTIVE

The aim of this study was to verify the influence of prostaglandin analogs and prostamide on central corneal thickness (CCT).

METHODS

A prospective analysis was done of CCT in glautomatous patients submitted to monotherapy with prostaglandin analogs (latanoprost 0.005% or travoprost 0.004%) or prostamide (bimatoprost 0.03%) during an 8-week period. A control group of patients without any ocular medication was also evaluated. CCT measurements were performed with a commercially available ultrasound pachymeter. A total of 73 patients were included in this study. Mean age was 68.5 +/- 9.2 (range, 48-85) years old.

RESULTS

A statistically significant reduction in CCT was observed in all groups, except the control group (n = 21): Bimatoprost 0.03% group (n = 21): 544.41 +/- 35.4 vs. 540.35 +/- 35.9 microm (P = 0.039); travoprost 0.004% group (n = 17): 538.47 +/- 32.0 vs. 532.25 +/- 30.4 microm (P = 0.009); latanoprost 0.005% group (n = 14): 548.57 +/- 32.4 vs. 543.88 +/- 35.6 microm (P = 0.036).

CONCLUSION

Topical therapy with prostaglandin analogs and bimatoprost is associated with CCT reduction over a period of at least 8 weeks.

TIMP-1 role in protection against Pseudomonas aeruginosa-induced corneal destruction

To establish the role of TIMP-1 in protection against Pseudomonas aeruginosa-induced corneal destruction, corneas of adult 8-week-old (resistant) and aged 12-month-old (susceptible) mice were infected with the bacterium. Corneas were analyzed for TIMP-1 protein by immunocytochemistry and Western blotting. Basement membrane (BM) integrity was assessed by immunostaining for type IV collagen. Additionally, resistant 8-week-old mice were treated systemically with neutralizing TIMP-1 polyclonal antibody (pAb) or pre-immune normal rabbit serum (NRS). Ocular and BM integrity as well as MMP-9 expression were examined in these mice. A greater amount of TIMP-1 protein was observed in the cornea of 8-week-old mice. In the cornea, the strongest staining was found in the superficial epithelium, but positive staining also was seen in the basal epithelium and stroma. When type IV collagen was analyzed in the BM of both age groups of mice, a distinct staining pattern was observed in only the young adult mice. Treatment of 8-week-old resistant mice with neutralizing TIMP-1 pAb vs NRS increased the amount of MMP-9 in the cornea of TIMP-1 pAb-treated mice and affected the ability of these mice to deposit BM components. These studies suggest that adequate expression of TIMP-1 protects against BM and stromal degradation via multiple processes.

Anti-angiogenic role of angiostatin during corneal wound healing

The purpose of this study is to determine whether angiostatin is involved in maintaining corneal avascularity after wounding. We generated polyclonal rabbit anti-mouse angiostatin antibodies directed against each of the five kringle domains, (K1-5) and anti-mouse plasmin B chain antibodies. Mouse corneas were immunostained with anti-K1 angiostatin antibody after excimer laser keratectomy. Corneal epithelial cell lysate was harvested and angiostatin was isolated using lysine sepharose. Purified plasminogen was incubated with lysate of mouse corneal epithelial cells from wild type mice in the presence or absence of MMP inhibitors. Angiostatin activity was determined using calf pulmonary artery endothelial (CPAE) cell proliferation assay with and without angiostatin immunoprecipitation; and corneal neovascularization was assayed by intrastromal injection of anti-plasminogen, anti-K1-3 or anti-B chain antibodies after corneal wounding. Using the anti-mouse angiostatin antibodies that we generated, we confirmed that angiostatin-like molecules were expressed in the corneal epithelium and in cultured corneal epithelial cells. Western blotting after incubation of scraped corneal epithelial cell lysate with purified plasminogen showed reduction of the plasminogen bands at 6, 12, and 24 hr, respectively. Complete cleavage of plasminogen occurred by 48 hr. Functional assays in which corneal epithelial cell extracts were incubated with CPAE cells resulted in inhibition of vascular endothelial cell proliferation. Depletion experiments using anti-angiostatin (K1) antibodies resulted in a 25 +/- 1.2% increase in vascular endothelial cell proliferation as compared to 12 +/- 1.8% using the protein A control (p < 0.05). Corneal neovascularization was observed after excimer laser keratectomy when anti-angiostatin antibodies were injected into the cornea (65 +/- 13%) which was significantly higher than when plasmin B chain antibodies were injected (10 +/- 2.6%; p < 0.05). Plasminogen and angiostatin are produced in the cornea. They may play a role in preventing vascularization and may contribute to the maintenance of corneal avascularity after excimer laser keratectomy.

Characteristic clinical findings and visual outcomes

PURPOSE

To describe a potentially serious complication of laser in situ keratomileusis (LASIK) that can masquerade as a persistent epithelial defect.

SETTING

Refractive surgery centers in academic institutions.

METHODS

Charts of 4 eyes in which epithelial-defect-masquerade syndrome was diagnosed were reviewed to determine the time to diagnosis and the presence of associated features that may have contributed to the delay in diagnosis. Clinical findings and outcomes of medical and surgical intervention were recorded.

RESULTS

All eyes developed an epithelial defect involving the edge of the flap during surgery. The diagnosis of epithelial ingrowth was delayed because of the presence of stromal edema (n = 4), diffuse lamellar keratitis (n = 3), and contraction of the flap leading to gutter widening (n = 4). Epithelial ingrowth was diagnosed 5, 7, 15, and 60 days after LASIK. All eyes satisfied the following criteria: convexity of the peripheral epithelium at the edge of the flap associated with light reflections at the end of the flap, fluorescein pooling in the gutter, stromal edema, reduced best spectacle-corrected visual acuity (<20/60 in 3 eyes), and partial healing of the epithelial defect limited to the flap hinge. One eye developed stromal scarring and ulceration that required fortified antibiotics. Surgical repair included epithelial scraping after the flap was lifted and ironing followed by placement of a contact lens after surgery. The epithelial defect healed 5, 7, 21, and 24 days after surgery. The final uncorrected visual acuity ranged from 20/15 to 20/100.

CONCLUSIONS

Epithelial ingrowth following LASIK-associated epithelial defects may masquerade as stromal edema associated with a persistent epithelial defect. A high index of suspicion for epithelial ingrowth is essential to avoid a delayed diagnosis, which can result in irreversible visual loss due to stromal melting and infectious keratitis.

Temporal and spatial expression of matrix metalloproteinases during wound healing of human corneal tissue

Our understanding of MMP expression during corneal repair has previously relied upon animal models, isolated human biopsy specimens and cell culture studies. The aim of this study was to determine the temporal and spatial expression of matrix metalloproteinases following wounding of cultured human corneal tissue. Human corneas were cultured and cut into six pieces. The epithelium was removed with a corneal brush. The tissue was then re-cultured and tissue pieces were fixed up to 7 days post-wounding. Matrix metalloproteinases were detected by in situ hybridisation and immunohistochemistry. Intracellular laminin-5, a marker of migratory epithelial cells, was located immunohistologically. In the time scale studied tissue series from nine corneas achieved coverage of the stroma with epithelial cells and partial repair of damaged basement membrane, demonstrated by the Periodic acid-Schiff reaction and haematoxylin and eosin counter-staining. By day 3, migrating epithelial cells and stromal cells beneath the wounded area expressed collagenase-1 (MMP-1). Stromelysin-1 (MMP-3) was expressed only by fibroblast-like stromal cells. Stromelysin-2 (MMP-10) was detected in migrating epithelial cells and remained when the stroma was surrounded by a monolayer of epithelial cells. By day 7, development of multi-layered epithelium around the tissue coincided with cessation of MMP expression in both epithelial and stromal cells, except for MMP-9, which remained in epithelial basal cells. Tissue inhibitor of matrix metalloproteinase-1 was mainly associated with stromal cells and was reduced upon formation of a multi-layered epithelium. This study demonstrates matrix metalloproteinase expression in epithelial and fibroblast-like cells following wounding of human corneal tissue in culture where the cells remain in contact with their natural matrices.

Matrix metalloproteinases in disease and repair processes in the anterior segment

The pathogenesis of many anterior segment disorders and ocular complications following surgery are secondary to the wound healing response. The extent of clinical damage observed is closely related to the amount of scarring and tissue contraction. Matrix metalloproteinases (MMPs) are a family of enzymes that play a vital role in all stages of the wound healing process. They degrade all extracellular matrix components and also have the ability to synthesize collagen and extracellular matrix members, and are therefore important in the remodeling of a wound. Overexpression of MMPs results in excessive extracellular matrix degradation, leading to tissue destruction and loss of organ function. In the case of the anterior segment, this may mean the loss of visual function. This review focuses on the role MMPs have in the development of various anterior segment disorders. The importance of MMPs in the wound healing response and its potential modulation to manipulate the scarring response is being recognized, and current developments will be described.

Corneal neovascularization

Corneal neovascularization (NV) is a sight-threatening condition usually associated with inflammatory or infectious disorders of the ocular surface. It has been shown in the field of cancer angiogenesis research that a balance exists between angiogenic factors (such as fibroblast growth factor and vascular endothelial growth factor) and anti-angiogenic molecules (such as angiostatin, endostatin, or pigment epithelium derived factor) in the cornea. Several inflammatory, infectious, degenerative, and traumatic disorders are associated with corneal NV, in which the balance is tilted towards angiogenesis. The pathogenesis of corneal NV may be influenced by matrix metalloproteinases and other proteolytic enzymes. New medical and surgical treatments, including angiostatic steroids, nonsteroidal inflammatory agents, argon laser photocoagulation, and photodynamic therapy have been effective in animal models to inhibit corneal NV and transiently restore corneal "angiogenic privilege."

Induction of matrix metalloproteinases 2 and 9 following stress to the lens

Matrix metalloproteinase 2 and 9 (MMP-2 and 9, also known as gelatinase A and B) have been implicated in a number of eye diseases, but their possible involvement in lens pathology is yet to be determined. In the present study, we therefore investigated a possible role of matrix metalloproteinases in cataract and posterior capsule opacification. Whole porcine lenses were removed from the eye and cultured in either Eagles Minimum Essential Medium (EMEM) or EMEM supplemented with 1 m M hydrogen peroxide. The medium was sampled and changed every 2 days. On some occasions a sham cataract operation was performed on cultured lenses. The resulting capsular bag was secured to a Petri dish and cultured in EMEM. Culture media from all preparations were analysed for MMP-2 and 9 activity by gelatin zymography. Media samples from lenses which maintained clarity over the 6 day culture period did not display any detectable gelatinolytic activity. However, media from cataractous lenses demonstrated a gelatinolytic band, which had similar molecular weights to the pro-form of MMP-2. In addition to this band, bands with a similar molecular weight to pro-MMP-9 and its dimeric form were also detected in samples obtained from capsular bag preparations within 24 hr. The data presented indicate that normal lenses have undetectable gelatinase activity. However, there is an associated expression of gelatinases with pathological states of the lens, and therefore gelatinase expression could play an important role in cataractogenesis and posterior capsule opacification.

Identification of matrix metalloproteinases and their tissue inhibitors type 1 and 2 in human masseter muscle

Changes in masticatory muscle structure and function are either developmental, as seen in anomalies of facial form, or adaptive, as seen during procedures such as orthognathic surgery and functional-appliance orthodontic therapy. Remodelling of muscle extracellular matrix is pivotal in these processes. This turnover is mediated via members of the family of enzymes known as matrix metalloproteinases (MMP) and inhibited by the tissue inhibitors of metalloproteinases (TIMP). The aim here was to investigate the in vivo pattern of expression and distribution of MMPs and TIMPs in masseter muscle of humans with both normal and abnormal facial forms. Masseter muscle biopsies were taken from 10 patients, four with long-face syndrome and six normal controls as confirmed by cephalometry. Immunohistochemical techniques were used to show the pattern and distribution of MMPs and TIMP proteins in the muscle. Zymography of tissue extracts was used to determine the presence of MMP activity. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to detect the presence of MMP and TIMP-2 mRNA. MMP-1 was expressed around the individual muscle fibres, especially in those fibre surfaces in contact with the interstices of the connective tissue and around blood vessels. MMP-9 staining was less intense and was expressed in the interstices of the connective tissue and around blood vessels. Zymography of protein extracts confirmed that MMP-9 activity was present. MMP-2 and MMP-3 were not expressed in the samples, although MMP-2 mRNA could be detected by RT-PCR and its activity could be detected by zymography. Intense TIMP-1 staining was present around each muscle fibre, in the interstices of the connective tissue and surrounding blood vessels; TIMP-2 mRNA could be detected in all samples. These staining patterns were seen in all biopsies examined and were irrespective of the facial form of the donor. These findings provide evidence that the mechanisms required for matrix remodelling are present in the human masseter muscle.