AB020.Inhibition of cyclic-AMP-response element binding protein and its impact on corneal wound healing in vitro and in vivo

Background:The cornea composes the outer surface of the eye and its transparency is required to allow light transmission to the retina.However,because of its position,the cornea is subjected to chemical and mechanical injuries that may lead to blindness.Our studies conducted using the human tissue-engineered cornea(hTEC)as a model provided evidence that the cyclic-AMP-response element binding protein(CREB)pathway is repressed during closure of corneal wounds.Based on these results,we hypothesized that closure of corneal wounds can be enhanced by preventing activation of CREB with the pharmacological inhibitor C646.Our goals were to proceed to the pharmacological inhibition of CREB(I)in vitro using the hTECs as a model,and then(II)in vivo using the rabbit as a model.Methods:The self-assembly approach was used to create hTECs,that were then wounded with an 8-mm diameter biopsy punch to create an epithelial defect.The tissues were then incubated with 10μM of C646(n=8).DMSO was used alone as a negative control(n=4).Closure of the wounds was monitored over a period of 5 days.Besides,the cornea of New Zealand white rabbits was debrided with an ethanol 70%solution to create an epithelial defect of 8-mm diameter.Several concentrations of C646(1,10,100μM et 1 mM)were applied as eye drops 3 times a day for up to 7 days.The wounded corneas(n=4 per concentration)were stained with fluorescein and photographed every day.Results:In vitro pharmacological inhibition of CREB with C646 considerably accelerated wound closure of all treated hTECs(4 days)compared to the control group(7 days).Moreover,the in vivo C646 treatment also accelerated wound healing of the corneas compared to the control group.The most effective concentration of C646 tested was the lowest(1μM),as it considerably enhanced the wound healing process.Conclusions:This study demonstrates that wound healing both in vitro and in vivo can be enhanced by preventing activation of CREB using a pharmacological inhibition approach.Most of all,this experiment suggests mediators from the CREB pathway as potential therapeutic targets on which we may influence to alter the wound healing dynamic of the cornea.We believe this study will lead to significant advancements in the clinical field of corneal defects.

Comparison of cytotoxicity and wound healing effect of carboxymethylcellulose and hyaluronic acid on human corneal epithelial cells

AIM: To investigate the cytotoxic effect on human corneal epithelial cells(HCECs) and the ability to faciliate corneal epithelial wound healing of carboxymethylcellulose(CMC) and hyaluronic acid(HA).METHODS: HCECs were exposed to 0.5% CMC(Refresh plus, Allergan, Irvine, California, USA) and 0.1% and 0.3%HA(Kynex , Alcon, Seoul, Korea, and Hyalein mini,Santen, Osaka, Japan) for the period of 30 min, and 4, 12,and 24 h. Methyl thiazolyl tetrazoiun(MTT)-based calorimetric assay was performed to assess the metabolic activity of cellular proliferation and lactate dehydrogenase(LDH) leakage assay to assess the cytotoxicity. apoptotic response was evaluated with flow cytometric analysis and fluorescence staining with Annexin V and propiodium iodide. Cellular morphology was evaluated by inverted phase-contrast light microscopy and electron microscopy. The wound widths were measured 24 h after confluent HCECs were scratch wounded.RESULTS: The inhibitory effect of human corneal epithelial proliferation and cytotoxicity showed the time-dependent response but no significant effect. Apoptosis developed in flow cytometry and apoptotic cells weredemonstrated in fluorescent micrograph. The damaged HCECs were detached from the bottom of the dish and showed the well-developed vacuole formations. Both CMC and HA stimulated reepithehlialization of HCECs scratched, which were more observed in CMC.CONCLUSION: CMC and HA, used in artificial tear formulation, could be utilized without any significant toxic effect on HCECs. Both significantly stimulated HCEC reepithelialization of corneal wounds.

Tranilast inhibits TGF-β-induced collagen gel contraction mediated by human corneal fibroblasts

AIM： To determine if tranilast affects human corneal fibroblast（HCFs） contraction.METHODS： HCFs cultured in a three-dimensional type I collagen gel were treated with or without transforming growth factor beta（TGF-β） or tranilast. Gel diameter was measured as an indicator for collagen contraction. Immunoblot was performed to evaluate myosin light chain（MLC） and paxillin phosphorylation. Confocal microscopy was employed to examine the focal adhesions and actin stress fiber formation. Immunoblot analysis and gelatin zymography were performed to detect tissue inhibitors of metalloproteinases and matrix metalloproteinases（MMPs） in supernatant.RESULTS： The inhibitory effect of tranilast on HCFsmediated collagen gel contraction induced by TGF-β was dose-dependent. The significant effect of tranilast was started from 100 μmol/L and maximized at 300 μmol/L. The peak effect of 300 μmol/L tranilast also relied on the duration of treatment, which showed statistical significance from day 2. TGF-β-induced paxillin and MLC phosphorylation, stress fiber formation, focal adhesions, and MMP-1, MMP-2, and MMP-3 secretion in HCFs were also inhibited by tranilast.CONCLUSION： Tranilast suppresses the HCFs-cultured collagen gel contraction induced by TGF-β. It attenuates actin stress fibers formation, focal adhesions, and the secretion of MMPs, with these actions likely contributing to the inhibitory effect on HCF contractility. By attenuating the contractility of corneal fibroblasts, tranilast treatment may inhibit corneal scarring.

MicroRNA-184 negatively regulates corneal epithelial wound healing via targeting CDC25A,CARM1,and LASP1

Background:MicroRNAs(miRNAs)play critical roles in corneal development and functional homeostasis.Our previous study identified miR-184 as one of the most highly expressed miRNAs in the corneal epithelium.Even though its expression level plummeted dramatically during corneal epithelial wound healing(CEWH),its precise role in mediating corneal epithelial renewal was unresolved.The present study aimed to reveal the function and mechanism of miR-184 in regulating CEWH.Methods:Quantitative RT-PCR analysis characterized the miR-184 expression pattern during CEWH in mice.Ectopic miR-184 injection determined its effect on this process in vivo.We evaluated the effects of miR-184 and its target genes on the proliferation,cell cycle,and migration of human corneal epithelial cells(HCECs)using MTS,flow cytometry,and wound-healing assay,respectively.Bioinformatic analysis,in conjunction with gene microarray analysis and cell-based luciferase assays,pinpointed gene targets of miR-184 contributing to CEWH.Results:MiR-184 underwent marked downregulation during mouse CEWH.Ectopic miR-184 overexpression delayed this process in mice.Furthermore,miR-184 transfection into HCECs significantly inhibited cell proliferation,cell cycle progression,and cell migration.MiR-184 directly targeted CDC25A,CARM1,and LASP1,and downregulated their expression in HCECs.CARM1 downregulation inhibited both HCEC proliferation and migration,whereas a decrease in LASP1 gene expression only inhibited migration.Conclusions:Our results demonstrate that miR-184 inhibits corneal epithelial cell proliferation and migration via targeting CDC25A,CARM1,and LASP1,suggesting it acts as a negative modulator during CEWH.Therefore,identifying strategies to suppress miR-184 expression levels has the potential to promote CEWH.

MicroRNA-184 negatively regulates corneal epithelial wound healing via targeting CDC25A,CARM1,and LASPI

Background:MicroRNAs(miRNAs)play critical roles in corneal development and functional homeostasis.Our previous study identified miR-184 as one of the most highly expressed miRNAs in the corneal epithelium.Even though its expression level plummeted dramatically during corneal epithelial wound healing(CEWH),its precise role in mediating corneal epithelial renewal was unresolved.The present study aimed to reveal the function and mechanism of miR-184 in regulating CEWH.Methods:Quantitative reverse transcriptase polymerase chain reaction(RT-PCR)analysis characterized the miR-184 expression pattern during CEWH in mice.Ectopic miR-184 injection determined its effect on this process in vivo.We evaluated the effects of miR-184 and its target genes on the proliferation,cell cycle,and migration of human corneal epithelial cells(HCECs)using MTS,flow cytometry,and wound healing assay,respectively.Bioinformatic analysis,in conjunction with gene microarray analysis and cell-based luciferase assays,pinpointed gene targets of miR-184 contributing to CEWH.Results:MiR-184 underwent marked downregulation during mouse CEWH.Ectopic miR-184 overexpression delayed this process in mice.Furthermore,miR-184 transfection into HCECs significantly inhibited cell proliferation,cell cycle progression,and cell migration.MiR-184 directly targeted CDC25A,CARMI,and LASP1,and downregulated their expression in HCECs.CARM1 downregulation inhibited both HCEC proliferation and migration,whereas a decrease in LASPI gene expression only inhibited migration.Conclusi ons:Our results dem on strate that miR-184 inhibits corneal epithelial cell proliferation and migration via targeting CDC25A,CARMI,and LASPI,suggesting it acts as a negative modulator during CEWH.Therefore,identifying strategies to suppress miR-184 expression levels has the potential to promote CEWH.

Keratinocyte growth factor-2 and autologous serum potentiate the regenerative effect of mesenchymal stem cells in cornea damage in rats

AIM:To investigate the healing process after severe corneal epithelial damage in rats treated with mesenchymal stem cells(MSCs)cultured with or without keratinocyte growth factor(KGF-2)and autologous serum(AS)on amniotic membrane(AM).Many patients are blind and devastated by severe ocular surface diseases due to limbal stem cell deficiency.Bone marrow-derived MSCs are potential sources for cellbased tissue engineering to repair or replace the corneal tissue,having the potential to differentiate to epithelial cells.METHODS:The study included 5 groups each including 10 female'Sprague Dawley'rats in addition to20 male rats used as bone marrow donors.Group I rats received AM+MSCs,Group II rats AM+MSCs cultured with KGF-2,Group III rats AM+MSCs cultured with KGF-2+AS,Group IV rats only AM and Group V rats,none.AS was derived from blood drawn from male rats and bone marrow was obtained from the femur and tibia bones of the same animals.Therapeutic effect was evaluated with clinical,histopathological and immunohistochemical assessment.MSC engraftment was demonstrated via detection of donor genotype(Y+)in the recipient tissue(X)with polymerase chain reaction.RESULTS:Corneal healing was significantly better in Groups I-III rats treated with MSC transplantation compared to Group IV and Group V rats with supportive treatment only.The best results were obtained in Group III rats with 90%transparency,70%lack of neovascularization,and 100%epithelium damage limited to less than 1/4 of cornea.CONCLUSION:We suggest that culture of MSCs with KGF-2 and AS on AM is effective in corneal repair in case of irreversible damage to limbal stem cells.