Mesenchymal Stem Cell-Laden In Situ-Forming Hydrogel for Preventing Corneal Stromal Opacity.

PURPOSE: The aims of this study were to construct a mesenchymal stem cell (MSC)-laden in situ-forming hydrogel and study its effects on preventing corneal stromal opacity. METHODS: The native gellan gum was modified by high temperature and pressure, and the rabbit bone marrow MSCs were encapsulated before adding Ca 2+ to initiate cross-linking. The effects of the hydrogel on 3D culture and gene expression of the rabbit bone marrow MSCs were observed in vitro. Then, the MSC-hydrogel was used to repair corneal stromal injury in New Zealand white rabbits within 28 days postoperation. RESULTS: The short-chain gellan gum solution has a very low viscosity (<0.1 Pa·s) that is ideal for encapsulating cells. Moreover, mRNA expressions of 3D-cultured MSCs coding for corneal stromal components (decorin, lumican, and keratocan) were upregulated (by 127.8, 165.5, and 25.4 times, respectively) ( P < 0.05) on day 21 in vitro and were verified by Western blotting results. For the in vivo study, the corneal densitometry of the experimental group was (20.73 ± 1.85) grayscale units which was lower than the other groups ( P < 0.05). The MSC-hydrogel downregulated mRNA expression coding for fibrosis markers (α-smooth muscle actin, vimentin, collagen type 5-α1, and collagen type 1-α1) in the rabbit corneal stroma. Furthermore, some of the 5-ethynyl-2'-deoxyuridine (EdU)-labeled MSCs integrated into the upper corneal stroma and expressed keratocyte-specific antigens on day 28 postoperation. CONCLUSIONS: The short-chain gellan gum allows MSCs to slowly release to the corneal stromal defect and prevent corneal stromal opacity. Some of the implanted MSCs can integrate into the corneal stroma and differentiate into keratocytes.

Current Status of Familial LCAT Deficiency in Japan.

Lecithin cholesterol acyltransferase (LCAT) is a lipid-modification enzyme that catalyzes the transfer of the acyl chain from the second position of lecithin to the hydroxyl group of cholesterol (FC) on plasma lipoproteins to form cholesteryl acylester and lysolecithin. Familial LCAT deficiency is an intractable autosomal recessive disorder caused by inherited dysfunction of the LCAT enzyme. The disease appears in two different phenotypes depending on the position of the gene mutation: familial LCAT deficiency (FLD, OMIM 245900) that lacks esterification activity on both HDL and ApoB-containing lipoproteins, and fish-eye disease (FED, OMIM 136120) that lacks activity only on HDL. Impaired metabolism of cholesterol and phospholipids due to LCAT dysfunction results in abnormal concentrations, composition and morphology of plasma lipoproteins and further causes ectopic lipid accumulation and/or abnormal lipid composition in certain tissues/cells, and serious dysfunction and complications in certain organs. Marked reduction of plasma HDL-cholesterol (HDL-C) and corneal opacity are common clinical manifestations of FLD and FED. FLD is also accompanied by anemia, proteinuria and progressive renal failure that eventually requires hemodialysis. Replacement therapy with the LCAT enzyme should prevent progression of serious complications, particularly renal dysfunction and corneal opacity. A clinical research project aiming at gene/cell therapy is currently underway.

Plasma rich in growth factors versus Mitomycin C in photorefractive keratectomy.

ABSTRACT: To evaluate the efficacy and safety of plasma rich in growth factors (PRGF) in photorefractive keratectomy (PRK) versus Mitomycin C (MMC).This is a comparative, longitudinal and retrospective case-control study (MMC vs PRGF), in patients with a spherical correction from -0.25 to -8.00 D and cylinder correction from -0.25 to -3.00. The uncorrected distance visual acuity (UDVA), refractive efficacy and safety indices, and changes in endothelial cell density were evaluated. The predictability was assessed with the postoperative manifest spherical equivalent.Forty-four patients (72 eyes) were treated with MMC and twenty-five patients (45 eyes) with PRGF. The final UDVA (LogMar) in MMC was 0.029 ±â€Š0.065 and in PRGF it was 0.028 ±â€Š0.048 (p = 0.383). The efficacy index for MMC was 0.98 ±â€Š0.10 and 1.10 ±â€Š0.46 for patients treated with PRGF (p = 0.062). The safety index for MMC was 1.03 ±â€Š0.11 and 1.12 ±â€Š0.46 (p = 0.158) for PRGF group. The change percentage of endothelial cell density was 0.9 ±â€Š11.6 for MMC and 4.3 ±â€Š13.1 for PRGF (p = 0.593). The predictability for MMC was 92.1% and for the PRGF was 91.9% (p = 0.976). Hyperemia, eye pain and superficial keratitis were observed in 11.1% of the MMC group; no adverse events were observed with the PRGF.The use of PRGF in PRK surgery is as effective as MMC. The PRGF shows a better safety profile than MMC for its intraoperative use in PRK.

Mitomycin C for the prevention of corneal haze in photorefractive keratectomy: a meta-analysis and trial sequential analysis.

PURPOSE: To evaluate the anti-haze effect and visual outcome after intraoperative mitomycin C (MMC) use during photorefractive keratectomy (PRK) in myopia or myopic astigmatism patients. METHODS: We searched in PubMed, EMBASE, Cochrane Library and Google Scholar comprehensively to obtain studies comparing the clinical effects after PRK with and without MMC published until February 2020. Meta-analysis of primary outcome (corneal haze rate) and secondary outcomes [predictability, efficacy, safety and corneal endothelial cell density (ECD)] were conducted. We used trial sequential analysis (TSA) in an effort to collect firm evidence supporting our conclusion. RESULTS: Of the included 11 randomized controlled trials, five cohort and one case-control studies, 3536 eyes (2232 and 1304 in the MMC and control groups, respectively) were enrolled for meta-analysis. The TSA disclosed strong evidence of decline in corneal haze rate in the MMC group compared with that of the control group. In the subgroup analysis of duration, MMC seemed to reduce corneal haze rate in early-onset and late-onset haze. Predictability of refraction and visual acuity were greater in the MMC groups, not significantly though. The proportion of patients losing at least two lines of best corrected visual acuity postoperatively in the MMC groups was lower than that in the control groups. The corneal postoperative ECD showed no significant difference between the MMC and control groups. CONCLUSION: Our meta-analysis revealed that MMC is an important anti-haze agent in PRK for reducing both early- and late-onset haze and can also help improving predictability of refraction and subjective postoperative visual acuity.

Corneal blindness in Plato's cave: the acting forces to prevent and revert corneal opacity. Part I: epidemiology and new physiopathological concepts.

The burden of corneal blindness and visual deficiency can be felt worldwide. Its association with several endemic diseases such as childhood blindness, trauma, infectious keratitis (including variants caused by herpes, hanseniasis, and fungi), vitamin A deficiency, diabetes mellitus, and other dry eye syndromes reflects its poorly understood underlying mechanisms and suggests that the actual frequency of the disease is underestimated. The low effectiveness of preventive and therapeutic strategies against corneal scarring or deformity predicts a high frequency of patients with corneal blindness in the future. Corneal blindness is associated with environmental factors and socioeconomic limitations that restrain health assistance and maintain a modest efficiency of the current therapeutic strategies for resolving corneal diseases in large-scale programs. We present here a critical review of the concepts associated with corneal blindness that need to be considered when planning strategies to prevent and treat corneal blindness worldwide (to be able to leave Plato's cave, where corneal blindness is encaged.

Biological effects of mitomycin C on late corneal haze stromal fibrosis following PRK.

This review details the current understanding of the mechanism of action and corneal effects of mitomycin C (MMC) for prophylactic prevention of stromal fibrosis after photorefractive keratectomy (PRK), and includes discussion of available information on dosage and exposure time recommended for MMC during PRK. MMC is an alkylating agent, with DNA-crosslinking activity, that inhibits DNA replication and cellular proliferation. It acts as a pro-drug and requires reduction in the tissue to be converted to an active agent capable of DNA alkylation. Although MMC augments the early keratocyte apoptosis wave in the anterior corneal stroma, its most important effect responsible for inhibition of fibrosis in surface ablation procedures such as PRK is via the inhibition of mitosis of myofibroblast precursor cells during the first few weeks after PRK. MMC use is especially useful when treating eyes with higher levels of myopia (≥approximately 6 D), which have shown higher risk of developing fibrosis (also clinically termed late haze). Studies have supported the use of MMC at a concentration of 0.02%, rather than lower doses (such as 0.01% or 0.002%), for optimal reduction of fibrosis after PRK. Exposure times for 0.02% MMC longer than 40 s may be beneficial for moderate to high myopia (≥6D), but shorter exposures times appear to be equally effective for lower levels of myopia. Although MMC treatment may also be beneficial in preventing fibrosis after PRK treatments for hyperopia and astigmatism, more studies are needed. Thus, despite the clinical use of MMC after PRK for nearly twenty years-with limited evidence of harmful effects in the cornea-many decades of experience will be needed to exclude late long-term effects that could be noted after MMC treatment.

Loss of Osteopontin Expression Reduces HSV-1-Induced Corneal Opacity.

Purpose: Corneal opacity and neovascularization (NV) are often described as outcomes of severe herpes simplex virus type 1 (HSV-1) infection. The current study investigated the role of colony-stimulating factor 1 receptor (CSF1R)+ cells and soluble factors in the progression of HSV-1-induced corneal NV and opacity. Methods: MaFIA mice were infected with 500 plaque-forming units of HSV-1 in the cornea following scarification. From day 10 to day 13 post-infection (pi), mice were treated with 40 µg/day of AP20187 (macrophage ablation) or vehicle intraperitoneally. For osteopontin (OPN) neutralization experiments, C57BL/6 mice were infected as above and treated with 2 µg of goat anti-mouse OPN or isotypic control IgG subconjunctivally every 2 days from day 4 to day 12 pi. Mice were euthanized on day 14 pi, and tissue was processed for immunohistochemistry to quantify NV and opacity by confocal microscopy and absorbance or detection of pro- and anti-angiogenic and inflammatory factors and cells by suspension array analysis and flow cytometry, respectively. Results: In the absence of CSF1R+ cells, HSV-1-induced blood and lymphatic vessel growth was muted. These results correlated with a loss in fibroblast growth factor type 2 (FGF-2) and an increase in OPN expression in the infected cornea. However, a reduction in OPN expression in mice did not alter corneal NV but significantly reduced opacity. Conclusions: Our data suggest that CSF1R+ cell depletion results in a significant reduction in HSV-1-induced corneal NV that correlates with the loss of FGF-2 expression. A reduction in OPN expression was aligned with a significant drop in opacity associated with reduced corneal collagen disruption.

CCR6-Positive γδ T Cells Provide Protection Against Intracorneal HSV-1 Infection.

Purpose: γδ T cells offer an important early immune defense against many different pathogens, both bacterial and viral. Herein, we examined the capacity of γδ T cell subsets to provide protection in the cornea against herpes simplex virus-1 (HSV-1). Methods: C57Bl/6 (wild-type [WT]), γδ T-cell deficient (TCRδ-/-) and CCR6-deficient (CCR6-/-) mice were infected intracorneally with HSV-1. At multiple time points following infection, corneas were excised, and cells were immunostained for surface markers, intracellular cytokines, and analyzed using flow cytometry. WT and CCR6-/- γδ T cells were adoptively transferred into TCRδ-/- mice and corneal scores and survival were measured. Results: Intracorneal infection of mice lacking γδ T cells exhibited increased corneal opacity scores, elevated viral titers, and higher mortality compared with WT mice. Both CCR6+ and CCR6neg γδ T cell subsets were observed in corneas after virus infection. CCR6+ γδ T cells produced IL-17A and were predominantly CD44+CD62L+, consistent with natural IL-17+ γδ T cells. In contrast IL-17A production by CCR6neg γδ T cells was infrequent, and this subset was largely single positive for CD62L or CD44. The CCR6+ subset appeared to provide protection against HSV-1 as follows: (1) CCR6-/- mice had more severe corneal opacity compared with WT mice; and (2) adoptive transfer of γδ T cells from WT mice restored protection in TCRδ-/- mice whereas transfer of γδ T cells from CCR6-/- mice did not. Conclusions: γδ T cells in the cornea can be divided into CCR6+ and CCR6neg subsets with the former conferring protection early after intracorneal HSV-1 infection.

Clinical Study of Mitomycin C in Reducing Haze Formation After Ultraviolet A/Riboflavin Crosslinking for Keratoconus.

OBJECTIVES: To evaluate the safety and efficacy of mitomycin C (MMC) in haze formation after ultraviolet A/riboflavin corneal crosslinking (CXL) for progressive keratoconus. METHODS: A total of 60 keratoconic eyes of 48 patients were enrolled in this prospective comparative study after obtaining informed consent. In the CXL group, standard corneal CXL was performed, whereas in the CXL+MMC group, 0.02% MMC was used for 30 s soon after CXL. Comprehensive ophthalmologic examinations were performed on all patients before surgery and at 1, 3, 6, and 12 months after surgery. RESULTS: The epithelium recovered within 3 to 4 days after CXL, and the healing time was comparable in the two groups. There was no significant endothelial cell density loss after CXL in both groups. Eyes in both groups showed improvement of uncorrected distance visual acuity (Snellen) and best-corrected visual acuity (Snellen; P<0.05), and there was a decrease in K-max, cylinder degree, and central corneal thickness (CCT) (P<0.05). There was no significant statistical difference between the groups regarding postoperative K-max reduction, refraction, and CCT (P>0.05). Corneal haze scores were significantly higher in the CXL group at 1 and 3 months after CXL (P=0.012 and P=0.028, respectively), but were similar to the MMC group at 6 and 12 months after surgery (P=0.329 and P=0.543, respectively). CONCLUSIONS: Prophylactic intraoperative use of 0.02% MMC can significantly reduce CXL-associated haze formation, especially in the early postoperative period, and no signs of weakening CXL efficacy were observed.

Chitosan and thiolated chitosan: Novel therapeutic approach for preventing corneal haze after chemical injuries.

Corneal haze, commonly caused by deep physical and chemical injuries, can greatly impair vision. Growth factors facilitate fibroblast proliferation and differentiation, which leads to haze intensity. In this study, the potential effect of chitosan (CS) and thiolated-chitosan (TCS) nanoparticles and solutions on inhibition of fibroblast proliferation, fibroblast to myofibroblast differentiation, neovascularization, extracellular matrix (ECM) deposition, and pro-fibrotic cytokine expression was examined. Transforming growth factor beta-1 (TGFß1) was induced by interleukin-6 (IL6) in human corneal fibroblasts and expression levels of TGFß1, Platelet-derived growth factor (PDGF), α-smooth muscle actins (α-SMA), collagen type I (Col I), fibronectin (Fn) and vascular endothelial growth factor (VEGF) were quantified using qRT-PCR. To assess wound-healing capacity, TCS-treated mice were examined for α-SMA positive cells, collagen deposition, inflammatory cells and neovascularization through pathological immunohistochemistry. The results revealed that CS and TCS could down-regulate the expression levels of TGFß1 and PDGF comparable to that of TGFß1 knockdown experiment. However, down-regulation of TGFß1 was not regulated through miR29b induction. Neovascularization along with α-SMA and ECM deposition were significantly diminished. According to these findings, CS and TCS can be considered as potential anti-fibrotic and anti-angiogenic therapeutics. Furthermore, TCS, thiolated derivative of CS, will increase mucoadhesion of the polymer at the corneal surface which makes the polymer efficient and non-toxic therapeutic approach for corneal injuries.

Efficacy and Safety Comparison Between Suberoylanilide Hydroxamic Acid and Mitomycin C in Reducing the Risk of Corneal Haze After PRK Treatment In Vivo.

PURPOSE: This study compared the efficacy and safety of suberoylanilide hydroxamic acid (SAHA) and mitomycin C (MMC) up to 4 months in the prevention of corneal haze induced by photorefractive keratectomy (PRK) in rabbits in vivo. METHODS: Corneal haze in rabbits was produced with -9.00 diopter PRK. A single application of SAHA (25 µM) or MMC (0.02%) was applied topically immediately after PRK. Effects of the two drugs were analyzed by slit-lamp microscope, specular microscope, TUNEL assay, and immunofluorescence. RESULTS: Single topical adjunct use of SAHA (25 µM) or MMC (0.02%) after PRK attenuated more than 95% corneal haze and myofibroblast formation (P < .001). SAHA did not reduce keratocyte density, cause keratocyte apoptosis, or increase immune cell infiltration compared to MMC (P < .01 or .001). Furthermore, SAHA dosing did not compromise corneal endothelial phenotype, density, or function in rabbit eyes, whereas MMC application did (P < .01 or .001). CONCLUSIONS: SAHA and MMC significantly decreased corneal haze after PRK in rabbits in vivo. SAHA exhibited significantly reduced short- and long-term damage to the corneal endothelium compared to MMC in rabbits. SAHA is an effective and potentially safer alternative to MMC for the prevention of corneal haze after PRK. Clinical trials are warranted. [J Refract Surg. 2017;33(12):834-839.].

Exposure Stress Induces Reversible Corneal Graft Opacity in Recipients With Herpes Simplex Virus-1 Infections.

Purpose: Most of the inflammation in murine herpes simplex virus type 1 (HSV-1)-induced stromal keratitis (HSK) is due to exposure stress resulting from loss of corneal nerves and blink reflex. Corneal grafts often fail when placed on corneal beds with a history of HSK. We asked if corneal exposure contributes to the severe pathology of corneal grafts on HSV-1-infected corneal beds. Methods: Herpes simplex virus type 1-infected corneas were tested for blink reflex. Opacity and vascularization were monitored in allogeneic and syngeneic corneal grafts that were transplanted to corneal beds with no blink reflex or to those that retained blink reflex in at least one quadrant following infection. Results: Retention of any level of blink reflex significantly reduced inflammation in HSV-1-infected corneas. Corneal allografts placed on HSV-1-infected beds lacking corneal blink reflex developed opacity faster and more frequently than those placed on infected beds that partially or completely retained blink reflex. Corneal grafts placed on infected corneal beds with no blink reflex rapidly became opaque to a level that would be considered rejection. However, protecting these grafts from exposure by tarsorrhaphy prevented or reversed the opacity in both syngeneic and allogenic grafts. Conclusions: Exposure due to HSV-1-engendered hypoesthesia causes rapid, severe, persistent, but reversible opacification of both allogeneic and syngeneic corneal grafts. This opacity should not be interpreted as immunologic rejection. Exposure stress may contribute to the high rate of corneal graft pathology in patients with recurrent HSK.

Aplicação da mitomicina C na cirurgia refrativa / Mitomycin C application in refractive surgery

RESUMO A mitomicina C teve seu uso profilático e terapêutico estabelecido, ao longo dos anos, para diminuir o haze depois da ablação superficial. A mitomicina C é segura e eficaz como uma terapia adjuvante aplicada após um procedimento primário de ceratectomia fotorrefrativa ou após um retratamento com ceratectomia fotorrefrativa após o laser in situ keratomileusis LASIK. A mitomicina age modulando a cicatrização após a cirurgia. Constitui-se num potente inibidor de mitose, bloqueia a ativação e a profliferação dos fibroblastos e a diferenciação dos miofibroblastos. Embora existam muitos estudos apontando a segurança da mitomicina nas doses ultilizadas, ainda persistem dúvidas quanto à segurança, a longo prazo, do uso da mitomicina. Quando as córneas são examinadas com microscópios confocal, após depleção inicial dos ceratócitos, a densidade celular parece retornar ao normal seis a 12 meses após o uso de mitomicina C . A maioria dos estudos clínicos não encontrou diferença significativa entre a densidade endotelial celular préoperatória e pós-operatória quando a mitomicina C 0.02% foi aplicada durante a cirurgia com um tempo de exposição de 2 minutos ou menos. Em aproximadamente 14 anos, a mitomicina C mostrou-se eficaz na prevenção e tratamento do haze corneano.

ABSTRACT Over the years, mitomycin C has been used by refractive surgeons to prophylactically decrease haze after surface ablation procedures and therapeutically in the treatment of preexisting haze. Development of mitomycin C treatments has had a significant role in the revival of surface ablation techniques. We reviewed the literature regarding mechanism of action of mitomycin C, its role in modulating wound healing after refractive surgery, and its safety and efficacy as adjuvant therapy applied after primary photorefractive keratectomy surgery or after photorefractive keratectomy re-treatment after laser in situ keratomileusis and other corneal surgeries and disorders. The drug is a potent mitotic inhibitor that effectively blocks keratocyte activation, proliferation, and myofibroblast differentiation. Many studies have suggested that mitomycin C is safe and effective in doses used by anterior surface surgeons, although there continue to be concerns regarding long-term safety. After initial depletion of anterior keratocytes, keratocyte density seems to return to normal 6 to12 months after the use of mitomycin C when corneas are examined with the confocal microscope. Most clinical studies found no difference between preoperative and postoperative corneal endothelial cell densities when mitomycin C 0.02% was applied during refractive surgery,with exposure time of 2 minutes or less. After approximately 14 years of use, mitomycin C has been found to be effective when used for prevention and treatment of corneal haze.

Inhibition of Rho-Associated Kinase Prevents Pathological Wound Healing and Neovascularization After Corneal Trauma.

PURPOSE: To investigate the effect of AMA0526, a specific inhibitor of rho-associated protein kinase (ROCK), on corneal neovascularization (NV) and scarring in different in vitro and in vivo experimental models. METHODS: The effect of AMA0526 on cell viability, proliferation, and migration of human umbilical vein endothelial cells was determined. Its in vivo topical effect on NV was investigated in the corneal micropocket mouse model (bevacizumab as a control). The vessel length, clock hours, and NV area were measured on photographs. The effect of AMA0526 on pathological wound healing was investigated in the alkali burn mouse model (dexamethasone as a control). Corneas were scored for corneal opacity (CO) and NV after burn injury. Immunohistochemistry was performed to study inflammation, blood vessel density, and collagen III deposition after 7 days. RESULTS: ROCK inhibition significantly inhibited vascular endothelial cell proliferation and migration in vitro in a dose-dependent manner. In the micropocket model, NV was significantly reduced by AMA0526 (37% reduction, P < 0.05) comparable to bevacizumab. CO and NV were reduced after AMA0526, compared with the vehicle (P < 0.05 at all time points from day 3) after chemical burn. AMA0526 resulted in decreased inflammatory cell infiltration (26% reduction, P < 0.01), angiogenesis (47% reduction, P < 0.01), and collagen III deposition (27% reduction, P = 0.009) in the alkali burn model. AMA0526 administration showed results similar to those of dexamethasone with an additional antifibrotic effect. CONCLUSIONS: The ROCK inhibitor, AMA0526, efficiently inhibited angiogenesis in vitro, reduced CO and NV, and controlled the complete process of wound healing in vivo. These results warrant further investigation of the therapeutic potential of AMA0526 for corneal NV and scarring.

Transient downregulation of microRNA-206 protects alkali burn injury in mouse cornea by regulating connexin 43.

PURPOSE: Chemical burn in cornea may cause permanent visual problem or complete blindness. In the present study, we investigated the role of microRNA 206 (miR-206) in relieving chemical burn in mouse cornea. METHOD: An alkali burn model was established in C57BL/6 mice to induce chemical corneal injury. Within 72 hours, the transient inflammatory responses in alkali-treated corneas were measured by opacity and corneal neovascularization (CNV) levels, and the gene expression profile of miR-206 was measured by quantitative real-time PCR (qPCR). Inhibitory oligonucleotides of miR-206, miR-206-I, were intrastromally injected into alkali-burned corneas. The possible protective effects of down-regulating miR-206 were assessed by both in vivo measurements of inflammatory responses and in vitro histochemical examinations of corneal epithelium sections. The possible binding of miR-206 on its molecular target, connexin43 (Cx43), was assessed by luciferase reporter (LR) and western blot (WB) assays. Cx43 was silenced by siRNA to examine its effect on regulating miR-206 modulation in alkali-burned cornea. RESULTS: Opacity and CNV levels, along with gene expression of miR-206, were all transiently elevated within 72 hours of alkali-burned mouse cornea. Intrastromal injection of miR-206-I into alkali-burned cornea down-regulated miR-206 and ameliorated inflammatory responses both in vivo and in vitro. LR and WB assays confirmed that Cx43 was directly targeted by miR-206 in mouse cornea. Genetic silencing of Cx43 reversed the protective effect of miR-206 down-regulation in alkali-burned cornea. CONCLUSION: miR-206, associated with Cx43, is a novel molecular modulator in alkali burn in mouse cornea.

Corneal Regeneration After Photorefractive Keratectomy: A Review.

Photorefractive keratectomy (PRK) remodels corneal stroma to compensate refractive errors. The removal of epithelium and the ablation of stroma provoke the disruption of corneal nerves and a release of several peptides from tears, epithelium, stroma and nerves. A myriad of cytokines, growth factors, and matrix metalloproteases participate in the process of corneal wound healing. Their balance will determine if reepithelization and stromal remodeling are appropriate. The final aim is to achieve corneal transparency for restoring corneal function, and a proper visual quality. Therefore, wound-healing response is critical for a successful refractive surgery. Our goal is to provide an overview into how corneal wounding develops following PRK. We will also review the influence of intraoperative application of mitomycin C, bandage contact lenses, anti-inflammatory and other drugs in preventing corneal haze and post-PRK pain.

TSG-6 protects corneal endothelium from transcorneal cryoinjury in rabbits.

PURPOSE: To investigate the effect of an anti-inflammatory protein, TNF-α stimulated gene/protein (TSG)-6 and an antiapoptotic protein, stanniocalcin (STC)-1 on corneal endothelium in rabbits with transcorneal cryoinjury. METHODS: Transcorneal freezing (-80°C) was applied to rabbit corneas for 30 seconds. Immediately post injury, either TSG-6 (10 µg/100 µL), STC-1 (10 µg/100 µL), or the same volume of balanced salt solution (BSS) was injected into the anterior chamber. Each eye was examined for corneal opacity, corneal thickness, endothelial cell density, and endothelial hexagonality every 2 to 6 hours for 48 hours post injury. The concentrations of myeloperoxidase (MPO) and IL-1ß were measured in the aqueous humor every 6 hours. At 48 hours post injury, each cornea was assayed for TNF-α, IL-1ß, IL-6, and MPO, and histologically evaluated with alizarin red-trypan blue staining, hematoxylin-eosin staining, and immunostaining for neutrophils. RESULTS: Tumor necrosis factor-α stimulated gene/protein-6 significantly decreased the development of corneal opacity and edema after cryoinjury compared with STC-1 or BSS. The corneal endothelial cell density and hexagonality were markedly preserved by TSG-6. The mRNA levels of TNF-α, IL-1ß, and IL-6 in the cornea and the protein levels of MPO and IL-1ß in the aqueous humor and cornea were significantly lower in TSG-6-treated eyes than BSS-treated controls. Similarly, the expression of fibroblast growth factor-2 was reduced by TSG-6 treatment. Histologic evaluation demonstrated that neutrophil infiltration of the cornea was decreased in TSG-6-treated eyes. CONCLUSIONS: Tumor necrosis factor-α stimulated gene/protein-6 protected corneal endothelial cells from transcorneal cryoinjury through suppression of inflammation.