IκB kinase β regulates epithelium migration during corneal wound healing

MicroRNAs Expression in Response to rhNGF in Epithelial Corneal Cells: Focus on Neurotrophin Signaling Pathway

PURPOSE

Nerve growth factor efficacy was demonstrated for corneal lesions treatment, and recombinant human NGF (rhNGF) was approved for neurotrophic keratitis therapy. However, NGF-induced molecular responses in cornea are still largely unknown. We analyzed microRNAs expression in human epithelial corneal cells after time-dependent rhNGF treatment.

METHODS

Nearly 700 microRNAs were analyzed by qRT-PCR. MicroRNAs showing significant expression differences were examined by DIANA-miRpath v.3.0 to identify target genes and pathways. Immunoblots were performed to preliminarily assess the strength of the in silico results.

RESULTS

Twenty-one microRNAs (miR-26a-1-3p, miR-30d-3p, miR-27b-5p, miR-146a-5p, miR-362-5p, mir-550a-5p, mir-34a-3p, mir-1227-3p, mir-27a-5p, mir-222-5p, mir-151a-5p, miR-449a, let7c-5p, miR-337-5p, mir-29b-3p, miR-200b-3p, miR-141-3p, miR-671-3p, miR-324-5p, mir-411-3p, and mir-425-3p) were significantly regulated in response to rhNGF. In silico analysis evidenced interesting target genes and pathways, including that of neurotrophin, when analyzed in depth. Almost 80 unique target genes (e.g., PI3K, AKT, MAPK, KRAS, BRAF, RhoA, Cdc42, Rac1, Bax, Bcl2, FasL) were identified as being among those most involved in neurotrophin signaling and in controlling cell proliferation, growth, and apoptosis. AKT and RhoA immunoblots demonstrated congruence with microRNA expression, providing preliminary validation of in silico data.

CONCLUSIONS

MicroRNA levels in response to rhNGF were for the first time analyzed in corneal cells. Novel insights about microRNAs, target genes, pathways modulation, and possible biological responses were provided. Importantly, given the putative role of microRNAs as biomarkers or therapeutic targets, our results make available data which might be potentially exploitable for clinical applications.

Gene Expression Profile of Vascular Endothelial Growth Factors (VEGFs) and Platelet-derived Growth Factors (PDGFs) in the Normal Cornea

BACKGROUND/AIM

Angiogenic growth factors expression is not known in the normal cornea. The aim was to study corneal gene expression profile of VEGF and PDGF pathways influencing the avascular state of cornea.

MATERIALS AND METHODS

cDNA synthesis was performed from mRNA extracted from five fresh pig corneas followed by cDNA synthesis and analysis of VEGF and PDGF pathways by TaqMan Array gene expression profile.

RESULTS

Normal pig cornea lacks VEGFR2 and VEGFR3 gene expression. MK2 and AKT1 genes were significantly overexpressed (p=0.000684, p=0.050995, respectively). Six PDGF pathway genes were overexpressed: TIAM1 (p=0.047), PIK3CA (p=0.00005), IKBKG (p=0.000006), PAK4 (p=0.034), RAC1 (p=0.000006 and PTGS2, p=0.00375). PDGF A was up-regulated, but not with a statistical significance (p=0.79911), while PDGFRα was down-regulated and PDGFRβ was not expressed.

CONCLUSION

Normal cornea avascularity is given by growth factor receptors down-regulation. Rapid corneal neovascularisation is induced by activation of the main angiogenic growth factors that induce angiogenic cascade and vessel recruitment.

The role of Gelam honey in accelerating reepithelialization of ex vivo corneal abrasion model

This study aimed to investigate the role of Gelam honey (GH) in accelerating reepithelialization of corneal abrasion. Corneal epithelial cells (CEC) isolated from New Zealand white rabbit corneas, were cultured and circular-shaped wounds were created onto them, representing the corneal abrasion model. These wounds were treated with basal (BM) and cornea media (CM) supplemented with GH. The percentage of wound closure was measured on day 0, 3, and 5. Expressions of cytokeratin 3 (CK3), cluster of differentiation 44 (CD 44), and connexin 43 (Cx43) were analyzed via qRT-PCR and immunocytochemistry. The results showed CEC cultured in GH-enriched media reepithelialized faster compared to control. Corneal abrasion treated with CM supplemented with GH closed completely on day 5. CK3, CD44, and Cx43 expressions correspond to the stages of reepithelialization. In conclusion, GH promotes the healing of the ex vivo corneal abrasion model. Further explorations of its potential as adjuvant therapy in treating corneal injuries are needed. PRACTICAL APPLICATIONS: Honey has been reported to have many medicinal properties including antibacterial, anti-inflammatory, and the ability to promote skin wound healing. However, the effects of honey on corneal wound healing have not been fully elucidated. In the present study, we aimed to determine the effects of Gelam honey (GH), well-known local honey obtained from the beehive of Gelam trees (Melaleuca spp.), on the ex vivo corneal abrasion model via cell migration study and analysis of genes and proteins during corneal epithelial wound healing. GH has proven to have accelerated effects on the corneal epithelial cell migration during the closure of the ex vivo corneal abrasion wound model. The expressions of the genes and proteins of the corneal epithelial wound healing markers were in accordance with the stages of healing. Therefore, GH has the potential to be developed as adjuvant therapy in the form of GH-based eye drop in treating corneal injuries.

The Role of SKQ1 (Visomitin) in Inflammation and Wound Healing of the Ocular Surface

Introduction

SkQ1 (Visomitin) is a novel mitochondrial-targeted antioxidant that holds promise in the treatment of inflammation associated with ocular surface diseases such as dry eye disease (DED) and corneal wounds. However, the specific role of SkQ1 in ocular surface epithelial tissue has yet to be explicated. The goal of this study is to identify roles of SkQ1 in conjunctival inflammation and corneal wound healing.

Methods

To determine the role of SkQ1 in inflammation, human conjunctival epithelial (HCjE) cell cultures were sensitized with pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) followed by treatments with SkQ1. The production of inflammatory biomarker prostaglandin E2 (PGE2) and cell viability were quantitatively evaluated. To determine the role of SkQ1 in wound healing, human corneal limbus epithelial (HCLE) cell cultures were streaked to create wounds. The wound closure times, ability to support single HCLE cell proliferation and changes of cell migration in the presence of SB203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK), were further compared.

Results

The HCjE and HCLE cultures showed no apparent cytotoxicity to SkQ1 in concentrations up to 250 nM (HCjE) or 2500 nM (HCLE). The HCLE cultures showed no toxicity to SkQ1 at all the SkQ1 concentrations tested. SkQ1 significantly suppressed PGE2 production of HCjE at concentrations < 300 nM (24 h) and 50 nM (48 h), apparently being SkQ1 dose and treatment time dependent. The wound closure rates were increased by 4% in 4 h and by 9% after 8–12 h in the presence of 50 nM SkQ1. Furthermore, as little as 25 nM of SkQ1 significantly stimulated HCLE single-cell proliferation. Lastly, the SkQ1-stimulated wound healing was completely abolished by SB203580.

Conclusion

Results of the current study demonstrate that SkQ1 exhibits an anti-inflammatory role and can be safely applied to ocular surface epithelium up to a concentration of 300 nM (181 ng/ml) for 24 h. SkQ1 also significantly enhances corneal epithelial wound healing, likely through enhancement of cell proliferation and migration. The data provide solid support for SkQ1 as a promising new therapeutic strategy for treatment of conjunctival inflammation as well as corneal wounds.

Funding

This study was sponsored by Mitotech SA Pharmaceuticals.

Electronic supplementary material

The online version of this article (10.1007/s40123-018-0158-2) contains supplementary material, which is available to authorized users.

The role of corneal stroma: A potential nutritional source for the cornea

Corneal stroma plays a pivotal role in normal visual function. Anatomically, it is located between the outer epithelium and the inner endothelium and is the thickest layer of the cornea. Keratocytes in the stroma produce a variety of cellular products, including growth factors/cytokines, extracellular matrix (ECM) components, and kinases. These products support normal corneal development and homeostasis.

Low concentrations of neutrophil extracellular traps induce proliferation in human keratinocytes via NF-kB activation

INTRODUCTION

Granulocytes play a pivotal role in innate immune response, as pathogen invasion activates neutrophils, a subclass of granulocytes, inducing the production of neutrophil extracellular traps (NETs). In this study, it has been evaluated how NETs could affect human keratinocytes (HaCaT cells) behaviour.

MATERIALS AND METHODS

HaCaT cells were treated with increasing NETs concentrations (0.01-200ng/ml) and the effect on cell proliferation was evaluated by MTT assay. Inhibition studies were performed by pre-treating cells with dexamethasone, chloropromazine or amiloride. NF-kB pathway activation was evaluated by western blot.

RESULTS

HaCaT cells stimulation with increasing concentrations of NETs (0.01-50ng/ml) for 48h resulted in a modulation of cell proliferation with a maximum increase corresponding to 0.5-1ng/ml stimulation. NETs low concentrations not only increased cell proliferation, but were also able to induce a faster wound closure in an in vitro scratch assay. NETs scaffold, composed by histone proteins and DNA, is recognized by Toll Like Receptor 9 (TLR 9) that, in turn, activates the NF-kB pathway. In fact, NETs induced proliferation was inhibited by chloropromazine (1nM), that blocks chlatrin vesicles formation, and by amiloride (50nM) that inhibits macropinocytosis. Moreover, dexamethasone, an inhibitor of NF-kB, was able to abolish the NETs effect.

DISCUSSION

This study thus demonstrates that low NETs concentrations undergo internalization finally resulting in a quick NF-kB pathway activation and HaCaT cells proliferation increase, suggesting a close relationship between first immune response and wound healing onset.

Effects of mannose-binding lectin on pulmonary gene expression and innate immune inflammatory response to ozone

Ozone is a common, potent oxidant pollutant in industrialized nations. Ozone exposure causes airway hyperreactivity, lung hyperpermeability, inflammation, and cell damage in humans and laboratory animals, and exposure to ozone has been associated with exacerbation of asthma, altered lung function, and mortality. The mechanisms of ozone-induced lung injury and differential susceptibility are not fully understood. Ozone-induced lung inflammation is mediated, in part, by the innate immune system. We hypothesized that mannose-binding lectin (MBL), an innate immunity serum protein, contributes to the proinflammatory events caused by ozone-mediated activation of the innate immune system. Wild-type (Mbl(+/+)) and MBL-deficient (Mbl(-/-)) mice were exposed to ozone (0.3 ppm) for up to 72 h, and bronchoalveolar lavage fluid was examined for inflammatory markers. Mean numbers of eosinophils and neutrophils and levels of the neutrophil attractants C-X-C motif chemokines 2 [Cxcl2 (major intrinsic protein 2)] and 5 [Cxcl5 (limb expression, LIX)] in the bronchoalveolar lavage fluid were significantly lower in Mbl(-/-) than Mbl(+/+) mice exposed to ozone. Using genome-wide mRNA microarray analyses, we identified significant differences in transcript response profiles and networks at baseline [e.g., nuclear factor erythroid-related factor 2 (NRF2)-mediated oxidative stress response] and after exposure (e.g., humoral immune response) between Mbl(+/+) and Mbl(-/-) mice. The microarray data were further analyzed to discover several informative differential response patterns and subsequent gene sets, including the antimicrobial response and the inflammatory response. We also used the lists of gene transcripts to search the LINCS L1000CDS(2) data sets to identify agents that are predicted to perturb ozone-induced changes in gene transcripts and inflammation. These novel findings demonstrate that targeted deletion of Mbl caused differential levels of inflammation-related gene sets at baseline and after exposure to ozone and significantly reduced pulmonary inflammation, thus indicating an important innate immunomodulatory role of the gene in this model.

Effects of Topically Applied Vitamin D during Corneal Wound Healing

Vitamin D is an important regulator of immune function and largely acts to dampen chronic inflammatory events in a variety of tissues. There is also accumulating evidence that vitamin D acts to enhance initial inflammation, beneficial during both infection and wound healing, and then promotes resolution and prevention of chronic, damaging inflammation. The current study examines the effect of topical vitamin D in a mouse of model of corneal epithelial wound healing, where acute inflammation is necessary for efficient wound closure. At 12 and 18 hours post-wounding, vitamin D treatment significantly delayed wound closure by ~17% and increased infiltration of neutrophils into the central cornea. Basal epithelial cell division, corneal nerve density, and levels of VEGF, TGFβ, IL-1β, and TNFα were unchanged. However, vitamin D increased the production of the anti-microbial peptide CRAMP 12 hours after wounding. These data suggest a possible role for vitamin D in modulating corneal wound healing and have important implications for therapeutic use of vitamin D at the ocular surface.

Corneal Wound Healing Requires IKB kinase β Signaling in Keratocytes

IkB kinase β (IKKβ) is a key signaling kinase for inflammatory responses, but it also plays diverse cell type-specific roles that are not yet fully understood. Here we investigated the role of IKKβ in the cornea using Ikkβ^ΔCS mice in which the Ikkβ gene was specifically deleted in the corneal stromal keratocytes. The Ikkβ^ΔCS corneas had normal morphology, transparency and thickness; however, they did not heal well from mild alkali burn injury. In contrast to the Ikkβ^F/F corneas that restored transparency in 2 weeks after injury, over 50% of the Ikkβ^ΔCS corneas failed to fully recover. They instead developed recurrent haze with increased stromal thickness, severe inflammation and apoptosis. This pathogenesis correlated with sustained myofibroblast transformation with increased α smooth muscle actin (α-SMA) expression, higher levels of senescence β-Gal activity and scar tissue formation at the late stage of wound healing. In addition, the Ikkβ^ΔCS corneas displayed elevated expression of hemo-oxygenase-1 (HO-1), a marker of oxidative stress, and activation of stress signaling pathways with increased JNK, c-Jun and SMAD2/3 phosphorylation. These data suggest that IKKβ in keratocytes is required to repress oxidative stress and attenuate fibrogenesis and senescence in corneal wound healing.

The effects of acacia honey on in vitro corneal abrasion wound healing model

Background

Acacia honey (AH) has been proven to improve skin wound healing, but its therapeutic effects on corneal epithelium has not been elucidated to date. This study aimed to investigate the effects of AH on cultured corneal epithelial cells (CEC) on in vitro corneal abrasion wound healing model. Six New Zealand white rabbits’ CEC were isolated and cultured until passage 1. Circular wound area was created onto a confluent monolayer CEC using a corneal trephine which mimicked corneal abrasion and treated with 0.025% AH supplemented in basal medium (BM) and complete cornea medium (CCM). Wound healing was measured as the percentage of wound closure by the migration of CEC on day 0, day 3 and day 6, post wound creation. The morphological changes of CEC were assessed via phase contrast microscopy. Gene and protein expressions of cytokeratin (CK3), fibronectin and cluster of differentiation 44 (CD44) in AH treated groups and control groups were determined by real-time PCR and immunocytochemistry, respectively.

Results

Cultured CEC exhibited similar morphology of polygonal shaped cells in all culture media. CEC cultured in AH-supplemented media showed higher percentage of wound closure compared to the controls. Gene expression of CK3 increased in AH-supplemented groups throughout the study. Fibronectin expression was increased at the initial stage while CD44 expression was increased at day 3, post wound creation. The protein expression of CEC cultured in all media was in accordance to their respective gene expressions.

Conclusion

Supplementation of AH in BM and CCM media accelerates CEC wound closure of the in vitro corneal abrasion model by increasing the expression of genes and proteins associated with CEC wound healing.

IKK phosphorylates RelB to modulate its promoter specificity and promote fibroblast migration downstream of TNF receptors

TNFα is a potent cytokine that plays a critical role in numerous cellular processes, particularly immune and inflammatory responses, programmed cell death, angiogenesis, and cell migration. Thus, understanding the molecular mechanisms that mediate TNFα-induced cellular responses is a crucial issue. It is generally accepted that global DNA binding activity of the NF-κB avian reticuloendotheliosis viral (v-rel) oncogene related B (RelB) subunit is not induced upon TNFα treatment in fibroblasts, despite its TNFα-induced nuclear accumulation. Here, we demonstrate that RelB plays a critical role in promoting fibroblast migration upon prolonged TNFα treatment. We identified the two kinases IκB kinase α (IKKα) and IκB kinase β (IKKβ) as RelB interacting partners whose activation by TNFα promotes RelB phosphorylation at serine 472. Once phosphorylated on serine 472, nuclear RelB dissociates from its interaction with the inhibitory protein IκBα and binds to the promoter of critical migration-associated genes, such as the matrix metallopeptidase 3 (MMP3). Further, we show that RelB serine 472 phosphorylation status controls MMP3 expression and promigration activity downstream of TNF receptors. Our findings provide new insights into the regulation of RelB activity and reveal a novel link between selective NF-κB target gene expression and cellular response in response to TNFα.

Postnatal Notch1 activation induces T‑cell malignancy in conditional and inducible mouse models

The Notch1 signaling pathway is essential for hematopoietic development. However, the effects of postnatal activation of Notch1 signaling on hematopoietic system is not yet fully understood. We previously generated ZEG‑IC‑Notch1 transgenic mice that have a floxed β‑geo/stop signal between a CMV promoter and intracellular domain of Notch1 (IC‑Notch1). Constitutively active IC‑Notch1 is silent until the introduction of Cre recombinase. In this study, endothelial/hematopoietic specific expression of IC‑Notch1 in double transgenic ZEG‑IC‑Notch1/Tie2‑Cre embryos induced embryonic lethality at E9.5 with defects in vascular system but not in hematopoietic system. Inducible IC‑Notch1 expression in adult mice was achieved by using tetracycline regulated Cre system. The ZEG‑IC‑Notch1/Tie2‑tTA/tet‑O‑Cre triple transgenic mice survived embryonic development when maintained on tetracycline. Post‑natal withdrawal of tetracycline induced expression of IC‑Notch1 transgene in hematopoietic cells of adult mice. The triple transgenic mice displayed extensive T‑cell infiltration in multiple organs and T‑cell malignancy of lymph nodes. In addition, the protein levels of p53 and alternative reading frame (ARF) were decreased in lymphoma‑like neoplasms from the triple transgenic mice while their mRNA expression remained unchanged, suggesting that IC‑Notch1 might repress ARF‑p53 pathway by a post‑transcriptional mechanism. This study demonstrated that activation of constitutive Notch1 signaling after embryonic development alters adult hematopoiesis and induces T‑cell malignancy.

Differentially expressed wound healing-related microRNAs in the human diabetic cornea

MicroRNAs are powerful gene expression regulators, but their corneal repertoire and potential changes in corneal diseases remain unknown. Our purpose was to identify miRNAs altered in the human diabetic cornea by microarray analysis, and to examine their effects on wound healing in cultured telomerase-immortalized human corneal epithelial cells (HCEC) in vitro. Total RNA was extracted from age-matched human autopsy normal (n=6) and diabetic (n=6) central corneas, Flash Tag end-labeled, and hybridized to Affymetrix® GeneChip® miRNA Arrays. Select miRNAs associated with diabetic cornea were validated by quantitative RT-PCR (Q-PCR) and by in situ hybridization (ISH) in independent samples. HCEC were transfected with human pre-miR™miRNA precursors (h-miR) or their inhibitors (antagomirs) using Lipofectamine 2000. Confluent transfected cultures were scratch-wounded with P200 pipette tip. Wound closure was monitored by digital photography. Expression of signaling proteins was detected by immunostaining and Western blot. Using microarrays, 29 miRNAs were identified as differentially expressed in diabetic samples. Two miRNA candidates showing the highest fold increased in expression in the diabetic cornea were confirmed by Q-PCR and further characterized. HCEC transfection with h-miR-146a or h-miR-424 significantly retarded wound closure, but their respective antagomirs significantly enhanced wound healing vs. controls. Cells treated with h-miR-146a or h-miR-424 had decreased p-p38 and p-EGFR staining, but these increased over control levels close to the wound edge upon antagomir treatment. In conclusion, several miRNAs with increased expression in human diabetic central corneas were found. Two such miRNAs inhibited cultured corneal epithelial cell wound healing. Dysregulation of miRNA expression in human diabetic cornea may be an important mediator of abnormal wound healing.

Oncoprotein E7 from beta human papillomavirus 38 induces formation of an inhibitory complex for a subset of p53-regulated promoters

Our previous studies on cutaneous beta human papillomavirus 38 (HPV38) E6 and E7 oncoproteins highlighted a novel activity of IκB kinase beta (IKKβ) in the nucleus of human keratinocytes, where it phosphorylates and stabilizes ΔNp73α, an antagonist of p53/p73 functions. Here, we further characterize the role of the IKKβ nuclear form. We show that IKKβ nuclear translocation and ΔNp73α accumulation are mediated mainly by HPV38 E7 oncoprotein. Chromatin immunoprecipitation (ChIP)/Re-ChIP experiments showed that ΔNp73α and IKKβ are part, together with two epigenetic enzymes DNA methyltransferase 1 (DNMT1) and the enhancer of zeste homolog 2 (EZH2), of a transcriptional regulatory complex that inhibits the expression of some p53-regulated genes, such as PIG3. Recruitment to the PIG3 promoter of EZH2 and DNMT1 resulted in trimethylation of histone 3 on lysine 27 and in DNA methylation, respectively, both events associated with gene expression silencing. Decreases in the intracellular levels of HPV38 E7 or ΔNp73α strongly affected the recruitment of the inhibitory transcriptional complex to the PIG3 promoter, with consequent restoration of p53-regulated gene expression. Finally, the ΔNp73α/IKKβ/DNMT1/EZH2 complex appears to bind a subset of p53-regulated promoters. In fact, the complex is efficiently recruited to several promoters of genes encoding proteins involved in DNA repair and apoptosis, whereas it does not influence the expression of the prosurvival factor Survivin. In summary, our data show that HPV38 via E7 protein promotes the formation of a multiprotein complex that negatively regulates the expression of several p53-regulated genes.

The SULFs, extracellular sulfatases for heparan sulfate, promote the migration of corneal epithelial cells during wound repair

Corneal epithelial wound repair involves the migration of epithelial cells to cover the defect followed by the proliferation of the cells to restore thickness. Heparan sulfate proteoglycans (HSPGs) are ubiquitous extracellular molecules that bind to a plethora of growth factors, cytokines, and morphogens and thereby regulate their signaling functions. Ligand binding by HS chains depends on the pattern of four sulfation modifications, one of which is 6-O-sulfation of glucosamine (6OS). SULF1 and SULF2 are highly homologous, extracellular endosulfatases, which post-synthetically edit the sulfation status of HS by removing 6OS from intact chains. The SULFs thereby modulate multiple signaling pathways including the augmentation of Wnt/ß-catenin signaling. We found that wounding of mouse corneal epithelium stimulated SULF1 expression in superficial epithelial cells proximal to the wound edge. Sulf1^−/−, but not Sulf2^−/−, mice, exhibited a marked delay in healing. Furthermore, corneal epithelial cells derived from Sulf1^−/− mice exhibited a reduced rate of migration in repair of a scratched monolayer compared to wild-type cells. In contrast, human primary corneal epithelial cells expressed SULF2, as did a human corneal epithelial cell line (THCE). Knockdown of SULF2 in THCE cells also slowed migration, which was restored by overexpression of either mouse SULF2 or human SULF1. The interchangeability of the two SULFs establishes their capacity for functional redundancy. Knockdown of SULF2 decreased Wnt/ß-catenin signaling in THCE cells. Extracellular antagonists of Wnt signaling reduced migration of THCE cells. However in SULF2- knockdown cells, these antagonists exerted no further effects on migration, consistent with the SULF functioning as an upstream regulator of Wnt signaling. Further understanding of the mechanistic action of the SULFs in promoting corneal repair may lead to new therapeutic approaches for the treatment of corneal injuries.

Epidermal growth factor (EGF)-induced corneal epithelial wound healing through nuclear factor κB subtype-regulated CCCTC binding factor (CTCF) activation

Epidermal growth factor (EGF) plays an important role in corneal epithelial migration and proliferation to improve the wound healing process. This study aimed to understand the role of NFκB in EGF-induced corneal epithelial wound healing through regulation of CTCF activity, which plays important roles in cell motility and migration to promote wound healing. The effect of NFκB p50 on corneal epithelial wound healing was investigated by comparing the eyes of wild-type and p50 knockout mice. We found that there was a significant retardation in corneal epithelial wound healing in the corneas of p50 knockout mice. Wound closure rates were measured in human corneal epithelial cells transfected with an NFκB activation-sensitive CTCF expression construct to demonstrate the effect of human CTCF expression under the control of EGF-induced NFκB activation on wound healing. EGF stimulation activated NFκB, which directly triggered the expression of the exogenous human CTCF in transfected cells and, subsequently, promoted human corneal epithelial cell motility, migration, and wound healing. Overexpression of CTCF in corneal epithelial cells and mouse corneas significantly enhanced the wound healing process. Furthermore, the effect of overexpressing NFκB p50 in corneal epithelial cells on the promotion of wound healing was abolished by knockdown of CTCF with CTCF-specific shRNA. Thus, a direct regulatory relationship between EGF-induced NFκB p50 and CTCF activation affecting corneal epithelial wound healing has been established, indicating that CTCF is, indeed, a NFκB p50-targeted and effective gene product in the core transcriptional network downstream from the growth factor-induced NFκB signaling pathway.

Accelerated In Vitro Degradation of Optically Clear Low β-Sheet Silk Films by Enzyme-Mediated Pretreatment

PURPOSE

To design patterned, transparent silk films with fast degradation rates for the purpose of tissue engineering corneal stroma.

METHODS

β-sheet (crystalline) content of silk films was decreased significantly by using a short water annealing time. Additionally, a protocol combining short water annealing time with enzymatic pretreatment of silk films with protease XIV was developed.

RESULTS

Low β-sheet content (17%-18%) and enzymatic pretreatment provided film stability in aqueous environments and accelerated degradation of the silk films in the presence of human corneal fibroblasts in vitro. The results demonstrate a direct relationship between reduced β-sheet content and enzymatic pretreatment, and overall degradation rate of the protein films.

CONCLUSIONS

The novel protocol developed here provides new approaches to modulate the regeneration rate of silk biomaterials for corneal tissue regeneration needs.

TRANSLATIONAL RELEVANCE

Patterned silk protein films possess desirable characteristics for corneal tissue engineering, including optical transparency, biocompatibility, cell alignment, and tunable mechanical properties, but current fabrication protocols do not provide adequate degradation rates to match the regeneration properties of the human cornea. This novel processing protocol makes silk films more suitable for the construction of human corneal stroma tissue and a promising way to tune silk film degradation properties to match corneal tissue regeneration.

Interactions between NF-κB and SP3 connect inflammatory signaling with reduced FGF-10 expression

Inflammation inhibits normal lung morphogenesis in preterm infants. Soluble inflammatory mediators present in the lungs of patients developing bronchopulmonary dysplasia disrupt expression of multiple genes critical for development. However, the mechanisms linking innate immune signaling and developmental programs are not clear. NF-κB activation inhibits expression of the critical morphogen FGF-10. Here, we show that interactions between the RELA subunit of NF-κB and SP3 suppress SP1-mediated FGF-10 expression. SP3 co-expression reduced SP1-mediated Fgf-10 promoter activity, suggesting antagonistic interactions between SP1 and SP3. Chromatin immunoprecipitation of LPS-treated primary mouse fetal lung mesenchymal cells detected increased interactions between SP3, RELA, and the Fgf-10 promoter. Expression of a constitutively active IκB kinase β mutant not only decreased Fgf-10 promoter activity but also increased RELA-SP3 nuclear interactions. Expression of a dominant-negative IκB, which blocks NF-κB nuclear translocation, prevented inhibition of FGF-10 by SP3. The inhibitory functions of SP3 required sequences located in the N-terminal region of the protein. These data suggested that inhibition of FGF-10 by inflammatory signaling involves the NF-κB-dependent interactions between RELA, SP3, and the Fgf-10 promoter. NF-κB activation may therefore lead to reduced gene expression by recruiting inhibitory factors to specific gene promoters following exposure to inflammatory stimuli.

Corneal wound healing is compromised by immunoproteasome deficiency

Recent studies have revealed roles for immunoproteasome in regulating cell processes essential for maintaining homeostasis and in responding to stress and injury. The current study investigates how the absence of immunoproteasome affects the corneal epithelium under normal and stressed conditions by comparing corneas from wildtype (WT) mice and those deficient in two immunoproteasome catalytic subunits (lmp7(-/-)/mecl-1(-/-), L7M1). Immunoproteasome expression was confirmed in WT epithelial cells and in cells of the immune system that were present in the cornea. More apoptotic cells were found in both corneal explant cultures and uninjured corneas of L7M1 compared to WT mice. Following mechanical debridement, L7M1 corneas displayed delayed wound healing, including delayed re-epithelialization and re-establishment of the epithelial barrier, as well as altered inflammatory cytokine production compared to WT mice. These results suggest that immunoproteasome plays an important role in corneal homeostasis and wound healing.

Nuclear Factor-κB: central regulator in ocular surface inflammation and diseases

The nuclear factor-κB (NF-κB) is a key transcription factor pathway that is responsible for many key biological processes, such as inflammation, apoptosis, stress response, corneal wound healing, angiogenesis, and lymphangiogenesis. Numerous recent studies have investigated NF-κB in the context of ocular surface disorders, including chemical injury, ultraviolet radiation-induced injury, microbial infections, allergic eye diseases, dry eye, pterygium, and corneal graft rejection. The purpose this article is to summarize key findings with regard to the pathways regulating NF-κB and processes governed by the NF-κB pathway. In the innate defense system, NF-κB is involved in signaling from the toll-like receptors 2, 3, 4, 5 and 7, which are expressed in conjunctival, limbal, and corneal epithelial cells. These determine the ocular responses to infections, such as those caused by Pseudomonas aeruginosa, Staphylococcus aureus, adenovirus, and herpes simplex-1 virus. Natural angiogenic inhibitors enhance NF-κB, and this may occur through the mitogen-activated protein kinases and peroxisome proliferator-activated receptor γ. In alkali injury, inhibition of NF-κB can reduce corneal angiogenesis, suggesting a possible therapeutic strategy. The evaluation of NF-κB inhibitors in diseases is also discussed, including emodin, besifloxacin, BOL-303242-X (mapracorat), thymosin-β4, epigallocatechin gallate, Perilla frutescens leaf extract and IKKβ-targeting short interfering RNA.

Temporal smad7 transgene induction in mouse epidermis accelerates skin wound healing

The expression of Smad7, a tumor growth factor-β (TGFβ) antagonist, is increased during cutaneous wound healing. To assess this significance, we temporally induced Smad7 transgene expression in wounded skin in gene-switch-Smad7 transgenic (Smad7 tg) mice. Smad7 induction in epidermal keratinocytes caused an increase in keratinocyte proliferation with reduced Smad2 activation, indicating that Smad7 abrogated TGFβ-mediated growth inhibition. Additionally, wounded skin from Smad7 tg mice exhibited accelerated re-epithelialization, with increased activation of extracellular signal-regulated kinase (Erk), and an in vitro migration assay revealed that Erk activation contributed to Smad7-mediated keratinocyte migration. Notably, epidermis-specific Smad7 transgene expression also has a profound effect on the wound stroma, resulting in reduced inflammation, angiogenesis, and production of type I collagen. Reduced Smad2 activation was observed in wounded stroma from Smad7 transgenic (Smad7 tg) mice, possibly owing to fewer infiltrated TGFβ-producing leukocytes compared to those in wounds from control mice. Because Smad7 is not secreted, these effects could reflect functional changes in Smad7 tg keratinocytes. Supporting this notion, the activation of NF-κB, a nonsecreted protein complex that transcriptionally activates inflammatory cytokines, was reduced in wounded epidermis from Smad7 tg mice compared to that in wounded wild-type epidermis. In sum, epidermal Smad7 overexpression accelerated wound healing through its direct effects on keratinocyte proliferation and migration, and through indirect effects on wound stroma.