Urokinase-type plasminogen activator promotes corneal epithelial migration and nerve regeneration.

Urokinase-type plasminogen activator (uPA) is a serine protease that plays a central role in the pericellular fibrinolytic system, mediates the degradation of extracellular matrix proteins and activation of growth factors, and contributes to the regulation of various cellular processes including cell migration and adhesion, chemotaxis, and angiogenesis. The corneal epithelium responds rapidly to injury by initiating a wound healing process that involves cell migration, cell proliferation, and tissue remodeling. It is innervated by sensory nerve endings that play an important role in the maintenance of corneal epithelial homeostasis and in the wound healing response. We here investigated the role of uPA in corneal nerve regeneration and epithelial resurfacing after corneal injury with the use of uPA-deficient mice. Both the structure of the corneal epithelium and the pattern of corneal innervation in uPA-/- mice appeared indistinguishable from those in uPA+/+ mice. Whereas the cornea was completely resurfaced by 36-48 h after epithelial scraping in uPA+/+ mice, however, such resurfacing required at least 72 h in uPA-/- mice. Restoration of epithelial stratification was also impaired in the mutant mice. Fibrin zymography revealed that the expression of uPA increased after corneal epithelial scraping and returned to basal levels in association with completion of re-epithelialization in wild-type animals. Staining of corneal whole-mount preparations for ßIII-tubulin also revealed that the regeneration of corneal nerves after injury was markedly delayed in uPA-/- mice compared with uPA+/+ mice. Our results thus demonstrate an important role for uPA in both corneal nerve regeneration and epithelial migration after epithelial debridement, and they may provide a basis for the development of new treatments for neurotrophic keratopathy.

Urokinase-type plasminogen activator negatively regulates α-smooth muscle actin expression via Endo180 and the uPA receptor in corneal fibroblasts.

Corneal fibroblasts are embedded within an extracellular matrix composed largely of collagen type 1, proteoglycans, and other proteins in the corneal stroma, and their morphology and function are subject to continuous regulation by collagen. During wound healing and in various pathological conditions, corneal fibroblasts differentiate into myofibroblasts characterized by the expression of α-smooth muscle actin (α-SMA). Endo180, also known as urokinase-type plasminogen activator (uPA) receptor-associated protein (uPARAP), is a collagen receptor. Here we investigated whether targeting of Endo180 and the uPA receptor (uPAR) by uPA might play a role in the regulation of α-SMA expression by culturing corneal fibroblasts derived from uPA-deficient (uPA-/-) or wild-type (uPA+/+) mice in a collagen gel or on plastic. The expression of α-SMA was upregulated, the amounts of full-length Endo180 and uPAR were increased, and the levels of both transforming growth factor-ß (TGF-ß) expression and Smad3 phosphorylation were higher in uPA-/- corneal fibroblasts compared with uPA+/+ cells under the collagen gel culture condition. Antibodies to Endo180 inhibited these effects of uPA deficiency on α-SMA and TGF-ß expression, whereas a TGF-ß signaling inhibitor blocked the effects on Smad3 phosphorylation and α-SMA expression. Our results suggest that uPA deficiency might promote the interaction between collagen and Endo180 and thereby increase α-SMA expression in a manner dependent on TGF-ß signaling. Expression of α-SMA is thus negatively regulated by uPA through targeting of Endo180 and uPAR.

Corneal Perforation during Combination Chemotherapy including Cetuximab in a Patient with a History of Herpetic Keratitis.

PURPOSE: To report a case of corneal perforation, in a patient with a history of herpetic keratitis, during combination chemotherapy including cetuximab. CASE: We report the case of a 71-year-old man who was diagnosed with a hypopharyngeal carcinoma and received radiation therapy combined with cetuximab, the epidermal growth factor receptor (EGFR) inhibitor monoclonal antibody. He was referred to us because of ocular hyperemia and corneal perforation in his left eye. In spite of conservative therapy, his corneal perforation was exacerbated, with iris incarceration into the wound site and exposure to the surface of the cornea. He therefore discontinued treatment with the combination chemotherapy and underwent lamellar keratoplasty using a preserved donor cornea. After treatment with cetuximab resumed, there was no recurrence of the corneal perforation. CONCLUSION: We have presented the first case of cetuximab-related corneal perforation in a patient who had a history of recurrent herpetic keratitis. EGFR inhibitors, such as cetuximab, can induce corneal perforation in cases with a history of herpetic stromal keratitis.

Requirement for the collagen receptor Endo180 in collagen gel contraction mediated by corneal fibroblasts.

The interaction of keratocytes with extracellular matrix components plays an important role in the maintenance of corneal transparency and shape as well as in the healing of corneal wounds. In particular, the interaction of these cells with collagen and cell-mediated collagen contraction contribute to wound closure. Endo180 is a receptor for collagen that mediates its cellular internalization. We have now examined the role of Endo180 in collagen contraction mediated by corneal fibroblasts (activated keratocytes). Antibodies to Endo180 inhibited the contractile activity of mouse corneal fibroblasts embedded in a three-dimensional collagen gel and cultured in the presence of serum, with this effect being both concentration and time dependent and essentially complete at an antibody concentration of 0.2 µg/ml. Whereas corneal fibroblasts cultured in a collagen gel manifested a flattened morphology with prominent stress fibers under control conditions, they showed a spindlelike shape with few stress fibers in the presence of antibodies to Endo180. Antibodies to Endo180 had no effect on the expression of α-smooth muscle actin or the extent of collagen degradation in collagen gel cultures of corneal fibroblasts. Immunohistofluorescence analysis did not detect the expression of Endo180 in the unwounded mouse cornea. However, Endo180 expression was detected in keratocytes migrating into the wound area at 3 days after a corneal incisional injury. Together, our results suggest that Endo180 is required for the contraction of collagen matrix mediated by corneal fibroblasts and that its expression in these cells may contribute to the healing of corneal stromal wounds.

Stimulation of Phagocytic Activity in Cultured Human Corneal Fibroblasts by Plasminogen.

Purpose: Plasminogen has been detected in the corneal stroma after tissue injury and interacts with corneal fibroblasts during wound healing. We examined the effect of plasminogen on phagocytic activity of corneal fibroblasts. Methods: Cultured human corneal fibroblasts were exposed to plasminogen and then incubated with fluorescent microparticles before measurement of phagocytic activity by confocal microscopy or flow cytometry. The binding of corneal fibroblasts to immobilized plasminogen was quantitated with a real-time biomolecular interaction assay. The production of urokinase-type plasminogen activator (uPA), matrix metalloproteinases (MMPs), and IL-1ß by corneal fibroblasts was measured by fibrin zymography, by immunoblot analysis or gelatin zymography, or with an enzyme-linked immunosorbent assay, respectively. Results: Plasminogen increased phagocytic activity of corneal fibroblasts in a concentration- and time-dependent manner, with the maximal effect apparent at 30 µg/mL and 24 hours. Corneal fibroblasts bound to immobilized plasminogen in a manner dependent on time and cell number, and the stimulatory effect of plasminogen on phagocytic activity was blocked in the presence of epsilon-aminocaproic acid, an inhibitor of plasminogen binding to cell surface receptors. Plasminogen-induced phagocytic activity was not associated with changes in the production of uPA, MMPs, or IL-1ß by corneal fibroblasts. Conclusions: Plasminogen induced phagocytic activity in corneal fibroblasts in a manner dependent on its binding to the cell surface. This effect was not associated with increased production of proteases or IL-1ß. Thus, plasminogen may promote the clearance of foreign particles or damaged tissue components by corneal fibroblasts early after tissue injury.

Neurotrophic Keratopathy after Trigeminal Nerve Block for Treatment of Postherpetic Neuralgia.

PURPOSE: To report a case of persistent corneal epithelial defect that had occurred after a trigeminal nerve block. CASE PRESENTATION: A 75-year-old female had suffered from postherpetic neuralgia for 8 years. She underwent Gasserian ganglion block surgery and noticed declining visual acuity in the right eye on the following day. She presented with severe hyperemia and corneal epithelial defects in the right eye and experienced remarkable reduction of sensitivity in the right cornea. She was diagnosed with neurotrophic keratopathy. Ofloxacin eye ointment and rebamipide ophthalmic suspension ameliorated the corneal epithelial defects but superficial punctate keratopathy, corneal superficial neovascularization, and Descemet's fold persisted. Although the epithelial defects occasionally recurred, the corneal sensation and epithelial defects, Descemet's fold, and corneal superficial neovascularization all improved around 5 months after trigeminal nerve block. The HRT II Rostock Cornea Module (RCM) could not detect any corneal subbasal nerve fibers at postoperative 4 months; however, it could detect them at postoperative 6 months. CONCLUSIONS: As the nerve block effect wore off, the corneal subbasal nerve fibers slowly regenerated. As the corneal sensation improved, the corneal epithelial defects and superficial neovascularization also improved. The HRT II RCM appeared useful for observing loss and regeneration of the corneal subbasal nerve fibers.

A Case of Neurotrophic Keratopathy Associated with Nasopharyngeal Carcinoma.

PURPOSE: To report a case of neurotrophic keratopathy associated with nasopharyngeal carcinoma. CASE REPORT: A 59-year-old man who had been diagnosed with a nasopharyngeal carcinoma was referred to the authors because of visual disturbance and pain in his right eye. Slit-lamp examination revealed a corneal epithelial defect and corneal stromal edema surrounding the epithelial defect area in his right eye. Magnetic resonance imaging showed a mass in his cavernous sinus, which was identified as nasopharyngeal carcinoma (NPC). We diagnosed neurotrophic keratopathy associated with NPC and initiated treatment with preservative-free artificial tears, antibiotic eye drops, fibronectin, a therapeutic contact lens, and amniotic membrane transplantation. However, the persistent corneal epithelial defect was unresponsive to these treatments. CONCLUSION: Neurotrophic keratopathy secondary to NPC is thought to be rare. We presented a case of neurotrophic keratopathy associated with cavernous sinus metastasis of an NPC. The development of new and more effective treatments for this refractory disease is anticipated.

Spontaneous reattachment of dislocated endothelial graft after non-Descemet stripping automated endothelial keratoplasty: a case report.

BACKGROUND: Graft detachment is a complication of non-Descemet stripping automated endothelial keratoplasty (nDSAEK). We report a case of spontaneous reattachment of an extensively dislocated graft after nDSAEK. CASE PRESENTATION: A 54-year-old male underwent penetrating keratoplasty (PKP) for keratoconus in his left eye in 2001. Following graft opacity due to rejection, a second PKP was implemented in May 2014. The graft was kept in good condition after the reoperation and yet, visual acuity (VA) declined due to cataract. PEA+IOL was then performed in May 2015. Because edema appeared in the graft 6 months after the PEA+IOL, nDSAEK was carried out in May 2016. Although the donor graft well attached immediately after the nDSAEK, the graft was almost completely dislocated 3 h later except a temporal part. Air was reinjected into the anterior chamber on the following day and the detachment was resolved. Despite of the treatment, about 1/5 of the graft remained detached and the detachment deteriorated to 3/4 of the graft 9 days later. Because the patient could not decide whether to undergo another operation immediately, we decided to follow him up first and found that the partially detached graft reattached spontaneously 1 month later during the follow-up. Although the cornea had a mild edema remaining in the superior temporal area, his BCVA improved to 1.0. Three months later, the graft remained in position and the cornea kept its transparency. CONCLUSIONS: Spontaneous reattachment was observed during the follow-up in a case that had shown a comparatively extensive graft dislocation after nDSAEK.

Extracellular Collagen Promotes Interleukin-1ß-Induced Urokinase-Type Plasminogen Activator Production by Human Corneal Fibroblasts.

Purpose: Keratocytes maintain homeostasis of the corneal stroma through synthesis, secretion, and degradation of collagen fibrils of the extracellular matrix. Given that these cells are essentially embedded in a collagen matrix, keratocyte-collagen interactions may play a key role in regulation of the expression or activation of enzymes responsible for matrix degradation including urokinase-type plasminogen activator (uPA), plasmin, and matrix metalloproteinases (MMPs). We examined the effect of extracellular collagen on the production of uPA by corneal fibroblasts (activated keratocytes) stimulated with the proinflammatory cytokine interleukin-1ß (IL-1ß). Methods: Human corneal fibroblasts were cultured either on plastic or in a three-dimensional gel of type I collagen. Plasminogen activators were detected by fibrin zymography, whereas the IL-1 receptor (IL-1R) and MMPs were detected by immunoblot analysis. Collagen degradation by corneal fibroblasts was assessed by measurement of hydroxyproline in acid hydrolysates of culture supernatants. Results: Collagen and IL-1ß synergistically increased the synthesis and secretion of uPA in corneal fibroblasts. Collagen also upregulated IL-1R expression in the cells in a concentration-dependent manner. The conversion of extracellular plasminogen to plasmin, as well as the plasminogen-dependent activation of MMP-1 and MMP-3 and degradation of collagen apparent in three-dimensional cultures of corneal fibroblasts exposed to IL-1ß, were all abolished by a selective uPA inhibitor. Conclusions: Collagen and IL-1ß cooperate to upregulate uPA production by corneal fibroblasts. Furthermore, IL-1ß-induced collagen degradation by these cells appears to be strictly dependent on uPA expression and mediated by a uPA-plasmin-MMP pathway.