PURPOSE. This study aimed to investigate the role of nicotinamide phosphoribosyltransferase (NAMPT) deficiency in the pathogenesis of Fuchs endothelial corneal dystrophy (FECD) and to explore potential therapeutic strategies. METHODS. NAMPT expression was examined in three GEO datasets (GSE74123, GSE142538, GSE171830) and multiple FECD samples. A UVA-induced late-onset FECD mouse model with NAMPT knockdown was established via intracameral injection of AAVshNAMPT. Corneal thickness, endothelial morphology, and endothelial-mesenchymal transition (EnMT) status were evaluated. In vitro, a chronic oxidative injury model with NAMPT downregulation was generated using small interfering RNA. RNA sequencing, ATP synthesis, lysosomal acidification, autophagic flux, and V-ATPase subunit expression were assessed to elucidate NAMPT function. Rescue experiments were conducted using NAD+ supplementation in vitro and nicotinamide riboside (NR, an NAD+ precursor) in vivo. RESULTS. A significant negative correlation was observed between ATP/energy metabolism and EnMT/extracellular matrix (ECM) remodeling in FECD specimens. NAMPT was consistently downregulated across multiple FECD datasets and the UVA mouse model. NAMPT knockdown induced significant corneal edema, endothelial cell loss, guttae formation, excessive EnMT and thickened Descemet's membrane in mice. In vitro, NAMPT inhibition altered the expression of energy metabolism-related enzymes, activated ECM remodeling pathways, reduced ATP production, blocked autophagic flux, impaired lysosomal acidification, and reduced V-ATPase expression. Importantly, these functional and molecular defects were ameliorated by supplementation with NAD+ in vitro and NR in vivo. CONCLUSIONS. These results indicate that NAMPT preserves corneal endothelial cell density and suppresses EnMT by sustaining energy metabolism, autophagic flux, and lysosomal acidification. Thus, NAMPT may emerge as a novel therapeutic target for delaying FECD progression.

Purpose:We aimed to investigate whether hydrogen sulfide (H2S)-preconditioned mesenchymal stem cells (MSCs) could enhance the anti-ferroptotic effects in a murine model of corneal alkali burn. Methods:MSCs were treated with various concentrations of GYY4137 (an H2S donor) and Western blot was used to detect the expression of IL-10 and cleaved-caspase-3. Slit-lamp photography and hematoxylin and eosin (H&E) staining were used to observe corneal structure after receiving a single subconjunctival injection of H2S-MSCs. Quantitative PCR (QPCR) or Western blot were used to detect the expression of pro-inflammatory cytokines, ferroptosis-regulatory molecules (SLC7A11, GPX4, 4-HNE, and FTH1) and AMPK/Nrf2/HO-1 pathway on day 7 after corneal injury. A co-culture model of human corneal epithelial cells (HCECs) and MSCs was used to investigate the anti-ferroptotic effects of MSCs. Results:Under the stimulation of 1 µmol/L GYY4137 for 48 hours, MSCs showed enhanced expression of IL-10. Furthermore, H2S pretreatment suppressed hydrogen peroxide (H2O2)- or serum deprivation-induced MSC apoptosis in vitro. On days 7 and 14 post-treatment, corneal opacity was ameliorated and corneal structure was more regular in the H2S-MSC group. H2S-MSC effectively attenuated ferroptosis in the cornea and HCECs by upregulating the expression of SLC7A11 and GPX4, while suppressing the level of 4-HNE and FTH1. Meanwhile, H2S-MSC activated AMPK/Nrf2/HO-1 pathway in vitro and in vivo. Knockdown of IL-10 via siRNA attenuated the inhibitory effects of H2S-MSC on erastin-induced ferroptosis in HCECs. Conclusions:H2S preconditioning augmented the anti-inflammatory and anti-ferroptotic effects of MSCs via activation of the AMPK/Nrf2/HO-1 pathway in an IL-10-dependent way, offering a novel strategy for corneal alkali burn treatment.

Purpose:Fuchs endothelial corneal dystrophy (FECD) is the most common corneal endothelial dystrophy and guttae are crucial in causing progressive loss of corneal endothelium. This study aimed to find a way to inhibit the formation of guttae in FECD. Methods and Results:Mitochondria fatty acid β-oxidation (FAO) and tricarboxylic acid (TCA) cycle processes were negatively enriched in the FECD group according to gene set enrichment analysis in GSE171830. In vivo UV-A-induced late-onset FECD mouse model were established. After irradiation, aged proliferator-activated receptor alpha (PPARα-/-) mice manifested greater corneal opacity, cornea edema, and varied corneal endothelial cell morphology compared with wild-type mice. The total metabolites in cornea of aged PPARα-/- mice and wild-type mice were detected by mass spectrometry. Metabolites of the FAO pathway were decreased in corneas of PPARα-/- mice, coincident with enzymes of FAO decreased in GSE171830. The score for FAO energy metabolism was negatively related to that of the TGF-β pathway according to gene set variation analysis. The express of alpha smooth muscle actin (αSMA) and Col1a were increased in aged PPARα-/- mice and small interfering PPARα B4G12 cell lines. After irradiation, activation or overexpression of PPARα demonstrated reduced corneal endothelial damage and reversal of Descemet membrane thickening, along with downregulation of fibrosis-related genes such as αSMA and collagen type I alpha 1 (Col1a). In vitro experiments revealed that fenofibrate could reverse fibrosis and damage of cell-to-cell connections induced by TGF-β. Additionally, fenofibrate was found to alleviate mitochondrial damage in B4G12 and increase oxygen consumption rates after TGF-β treatment. Conclusions:Overall, we suggested that the overexpression or activation of PPARα can inhibit FAO energy dysfunction of corneal endothelium and the abnormal extracellular matrix formation in Descemet's membrane, which is the primary pathology of FECD. Thus, PPARα may be a potential target for attenuating the progression of FECD.

The transcription factor forkhead box protein (FOX)-O3 is a core regulator of cellular homeostasis, stress response, and longevity. The cellular localization of FOXO3 is closely related to its function. Herein, the role of FOXO3 in cataract formation was explored. FOXO3 showed nuclear translocation in lens epithelial cells (LECs) arranged in a single layer on lens capsule tissues from both human cataract and N-methyl-N-nitrosourea (MNU)-induced rat cataract, also in MNU-injured human (H)-LEC lines. FOXO3 knockdown inhibited the MNU-induced increase in expression of genes related to cell cycle arrest (GADD45A and CCNG2) and apoptosis (BAK and TP53). H2 is highly effective in reducing oxidative impairments in nuclear DNA and mitochondria. When H2 was applied to MNU-injured HLECs, FOXO3 underwent cleavage by MAPK1 and translocated into mitochondria, thereby increasing the transcription of oxidative phosphorylation-related genes (MTCO1, MTCO2, MTND1, and MTND6) in HLECs. Furthermore, H2 mediated the translocation of FOXO3 from the nucleus to the mitochondria within the LECs of cataract capsule tissues of rats exposed to MNU. This intervention ameliorated MNU-induced cataracts in the rat model. In conclusion, there was a correlation between the localization of FOXO3 and its function in cataract formation. It was also determined that H2 protects HLECs from injury by leading FOXO3 mitochondrial translocation via MAPK1 activation. Mitochondrial FOXO3 can increase mtDNA transcription and stabilize mitochondrial function in HLECs.

Corneal alkali burns cause extensive damage not only to the cornea but also to the intraocular tissues. As an anti-inflammatory therapy, subconjunctival administration of mesenchymal stem cells (MSCs) for corneal protection after corneal alkali burn has been explored. Little evidence demonstrates the potential of subconjunctival MSCs delivery in protecting the post-burn intraocular tissues. This study aimed to evaluate the therapeutic efficacy of subconjunctival injection of human placental (hP)-MSCs in protecting against ocular destruction after the burn. hP-MSCs were subconjunctivally administered to C57/BL mice after corneal alkali burn. Western blot of iNOS and CD206 was performed to determine the M1 and M2 macrophage infiltration in the cornea. Infiltration of inflammatory cells in the anterior uvea and retina was analyzed by flow cytometry. The TUNEL assay or Western blot of Bax and Bcl2 was used to evaluate the anti-apoptotic effects of MSCs. MSCs could effectively facilitate cornea repair by suppressing inflammatory cytokines IL-1β, MCP-1, and MMP9, and polarizing CD206 positive M2 macrophages. Anterior uveal and retinal inflammatory cytokines expression and inflammatory cell infiltration were inhibited in the MSC-treated group. Reduced TUNEL positive staining and Bax/Bcl2 ratio indicated the anti-apoptosis of MSCs. MSC-conditioned medium promoted human corneal epithelial cell proliferation and regulated LPS-stimulated inflammation in RAW 264.7 macrophages, confirming the trophic and immunoregulatory effects of MSCs. Our findings demonstrate that subconjunctival administration of MSCs exerted anti-inflammatory and anti-apoptotic effects in the cornea, anterior uvea, and retina after corneal alkali burn. This strategy may provide a new direction for preventing post-event complications after corneal alkali burn.

Alterations in histone modification have been linked to cancer development and progression. Celastrol, a Chinese herbal compound, shows potent anti-tumor effects through multiple signaling pathways. However, the involvement of histone modifications in this process has not yet been illustrated. In this study, barcode sequencing of a eukaryotic genome-wide deletion library revealed that histone modifications, especially histone acetylation associated with the NuA4 histone acetyltransferase complex, were involved in the anti-proliferation actions of celastrol. The essential roles of histone modification were verified by celastrol sensitivity tests in cells lacking specific genes, such as genes encoding the subunits of the NuA4 and Swr1 complex. The combination of celastrol and histone deacetylase inhibitors (HDACi), rather than the combination of celastrol and histone acetyltransferase inhibitors, synergistically suppressed cancer cell proliferation. In addition to upregulating H4K16 acetylation (H4K16ac), celastrol regulates H3K4 tri-methylation and H3S10 phosphorylation. Celastrol treatment significantly enhanced the suppressive effects of HDACi on lung cancer cell allografts in mice, with significant H4K16ac upregulation, indicating that a combination of celastrol and HDACi is a potential novel therapeutic approach for patients with lung cancer.

Transglutaminase 2 (TG2) is the most abundant crosslinking enzyme in murine and human cornea, while retinoids are well-known inducers of TG2 expression. This study aims to determine if the retinoic acid supplementation can increase corneal stiffness by crosslinking through upregulating the corneal TG2 expression. The right eyes of C57BL/6 mice were treated with 2 x 10-2M retinol palmitate (VApal) eyedrops or control eyedrops and hold for 30 min, once a day for 28 consecutive days. The WB and qPCR results showed increased expression of TG2 in murine cornea with the prolongation of VApal eyedrop application. After 28 days of VApal eyedrop treatment, the increased TG2 were found catalytically active and distributed in corneal epithelium and stroma as detected by 5-(biotinamido) pentylamine (5-BP) incorporation method and immunofluorescence staining. The transmission electron microscope image revealed that VApal treated cornea manifested with increased collagen density in anterior and middle layer of stroma. The higher elastic module was found among VApal treated cornea by nano-indentation test. In cultured corneal epithelial cells and keratocytes, all-trans retinoid acid (ATRA) treatment increased the content of TG2 in cell lysis and in culture medium. These results indicate that retinoic acid induce the reinforcement of the cornea by TG2 mediated crosslinking via increasing the TG2 expression in corneal epithelium and keratocyte. As TG2 was found to be less in the cornea of keratoconus patients in several RNA-sequencing studies, retinoic acid could serve as a non-invasive prevention method for keratoconus progression.

Purpose: To understand the relationship between ciliogenesis and autophagy in the corneal epithelium. Methods: siRNAs for EphA2 or PLD1 were used to inhibit protein expression in vitro. Morpholino-anti-EphA2 was used to knockdown EphA2 in Xenopus skin. An EphA2 knockout mouse was used to conduct loss of function studies. Autophagic vacuoles were visualized by contrast light microscopy. Autophagy flux, was measured by LC3 turnover and p62 protein levels. Immunostaining and confocal microscopy were conducted to visualize cilia in cultured cells and in vivo. Results: Loss of EphA2 (i) increased corneal epithelial thickness by elevating proliferative potential in wing cells, (ii) reduced the number of ciliated cells, (iii) increased large hollow vacuoles, that could be rescued by BafA1; (iv) inhibited autophagy flux and (v) increased GFP-LC3 puncta in the mouse corneal epithelium. This indicated a role for EphA2 in stratified epithelial assembly via regulation of proliferation as well as a positive role in both ciliogenesis and end-stage autophagy. Inhibition of PLD1, an EphA2 interacting protein that is a critical regulator of end-stage autophagy, reversed the accumulation of vacuoles, and the reduction in the number of ciliated cells due to EphA2 depletion, suggesting EphA2 regulation of both end-stage autophagy and ciliogenesis via PLD1. PLD1 mediated rescue of ciliogenesis by EphA2 depletion was blocked by BafA1, placing autophagy between EphA2 signaling and regulation of ciliogenesis. Conclusion: Our findings demonstrate a novel role for EphA2 in regulating both autophagy and ciliogenesis, processes that are essential for proper corneal epithelial homeostasis.

Purpose: Previous work by our group has demonstrated the value of N-methyl-N-nitrosourea (MNU)-induced corneal endothelial decompensation in animal models. The aim of this study was to investigate the effect of molecular hydrogen (H2) on MNU-induced corneal endothelial cell (CEC) injury and the underlying mechanism. Methods: MNU-induced animal models of CEC injury were washed with hydrogen-rich saline (HRS) for 14 days. Immunofluorescence staining, immunohistochemical staining, and corneal endothelial assessment were applied to determine architectural and cellular changes on the corneal endothelium following HRS treatment. MNU-induced cell models of CEC injury were co-cultured with H2. The effect of H2 was examined using morphological and functional assays. Results: It was shown that MNU could inhibit the proliferation and specific physiological functions of CECs by increasing apoptosis and decreasing the expression of ZO-1 and Na+/K+-ATPase, whereas H2 improved the proliferation and physiological function of CECs by anti-apoptosis. Cell experiments further confirmed that H2 could reverse MNU damage to CECs by decreasing oxidative stress injury, interfering with the NF-κB/NLRP3 pathway and the FOXO3a/p53/p21 pathway. Conclusions: This study suggests that topical application of H2 could protect CECs against corneal damage factors through anti-apoptotic effect, reduce the incidence and severity of corneal endothelial decompensation, and maintain corneal transparency.

microRNAs regulate numerous biological processes, making them potential therapeutic agents. Problems with delivery and stability of these molecules have limited their usefulness as treatments. We demonstrate that synthetic high-density lipoprotein nanoparticles (HDL NPs) topically applied to the intact ocular surface are taken up by epithelial and stromal cells. microRNAs complexed to HDL NPs (miR-HDL NPs) are similarly taken up by cells and tissues and retain biological activity. Topical treatment of diabetic mice with either HDL NPs or miR-HDL NPs significantly improved corneal re-epithelialization following wounding compared with controls. Mouse corneas with alkali burn-induced inflammation, topically treated with HDL NPs, displayed clinical, morphological and immunological improvement. These results should yield a novel HDL NP-based eye drop for patients with compromised wound healing ability (diabetics) and/or corneal inflammatory diseases (e.g. dry eye).

Autophagy is a multistage catabolic process that mediates stress responses. However, the role of autophagy in epidermal proliferation, particularly under conditions when the epidermis becomes "activated" (hyperproliferative), remains unclear. We have shown that inhibition of Beclin 1, a key activator in the initiation phase of autophagy, attenuates imiquimod (IMQ)-induced epidermal hyperplasia in adult mice as well as naturally occurring hyperproliferation in neonatal mouse epidermis. Inhibition of Beclin 1 did not change the levels of several key inflammatory molecules or the numbers of immune cells in lesional skins. This indicates that autophagy does not affect inflammatory regulators in IMQ-treated mouse skin. Bioinformatic analysis combined with gene expression quantitative assays, revealed that a deficiency in autophagy decreases the expression of PDZ Binding Kinase (PBK), a regulator of the cell cycle, in mouse epidermis and human epidermal keratinocytes (HEKs). Interestingly, the decrease in PBK results in inhibition of proliferation in HEKs and such reduced proliferation can be rescued by activation of p38, the downstream signaling of PBK. Collectively, autophagy plays a positive role in epidermal proliferation, which is in part via regulating PBK expression.

The anterior surface of the eye functions as a barrier to the external environment and protects the delicate underlying tissues from injury. Central to this protection are the corneal, limbal and conjunctival epithelia. The corneal epithelium is a self-renewing stratified squamous epithelium that protects the underlying delicate structures of the eye, supports a tear film and maintains transparency so that light can be transmitted to the interior of the eye (Basu et al., 2014; Cotsarelis et al., 1989; Funderburgh et al., 2016; Lehrer et al., 1998; Pajoohesh-Ganji and Stepp, 2005; Parfitt et al., 2015; Peng et al., 2012b; Stepp and Zieske, 2005). In this review, dedicated to James Funderburgh and his contributions to visual science, in particular the limbal niche, corneal stroma and corneal stromal stem cells, we will focus on recent data on the identification of novel regulators in corneal epithelial cell biology, their roles in stem cell homeostasis, wound healing, limbal/corneal boundary maintenance and the utility of single cell RNA sequencing (scRNA-seq) in vision biology studies.

Whereas much is known about the genes regulated by ΔNp63α in keratinocytes, how ΔNp63α is regulated is less clear. During studies with the hydroxylase, factor inhibiting hypoxia-inducible factor 1 (FIH-1), we observed increases in epidermal ΔNp63α expression along with proliferative capacity in a conditional FIH-1 transgenic mouse. Conversely, loss of FIH-1 in vivo and in vitro attenuated ΔNp63α expression. To elucidate the FIH-1/p63 relationship, BioID proteomics assays identified FIH-1 binding partners that had the potential to regulate p63 expression. FIH-1 interacts with two previously unknown partners, Plectin1 and signal transducer and activator of transcription 1 (STAT1) leading to the regulation of ΔNp63α expression. Two known interactors of FIH-1, apoptosis-stimulating of P53 protein 2 (ASPP2) and histone deacetylase 1 (HDAC1), were also identified. Knockdown of ASPP2 upregulated ΔNp63α and reversed the decrease in ΔNp63α by FIH-1 depletion. Additionally, FIH-1 regulates growth arrest and DNA damage-45 alpha (GADD45α), a negative regulator of ΔNp63α by interacting with HDAC1. GADD45α knockdown rescued reduction in ΔNp63α by FIH-1 depletion. Collectively, our data reveal that FIH-1 positively regulates ΔNp63α in keratinocytes via variety of signaling partners: (a) Plectin1/STAT1, (b) ASPP2, and (c) HDAC1/GADD45α signaling pathways.

A distinct boundary exists between the progenitor cells in the basal limbal epithelium and the more differentiated corneal epithelial basal cells. We have shown that reciprocal expression patterns of EphA2 and Ephrin-A1 are likely to contribute to normal limbal-corneal epithelial compartmentalization as well as play a role in response to injury. How this signaling axis is regulated remains unclear. We have demonstrated that microRNAs (miRNAs) play critical roles in corneal epithelial wound healing and several miRNAs (e.g. miR-210) have been predicted to target ephrins. Previous expression profiling experiments demonstrated that miR-210 is prominently expressed in corneal epithelial cells. RNA-seq data acquired from miR-210-depleted HCECs showed up-regulation of genes involved in cellular migration. In addition, miR-210 is decreased after corneal injury while EphA2 is increased. Moreover, antago-210-treated HCECs markedly enhanced wound closure in a scratch wound assay. Antago-210 treatment resulted in increased EphA2 protein levels as well as pS897-EphA2, the pro-migratory form of EphA2. As expected, Ephrin-A1 levels were reduced, while levels of a well-known target of miR-210, Ephrin-A3, were increased by antago-210 treatment. The increase in migration with antago-210 could be inhibited by Ephrin-A1 overexpression, Ephrin-A1-Fc treatment or siRNA depletion of EphA2. However, depletion of Ephrin-A3 did not have effects on the antago-210-induced increase in migration. In addition, Ephrin-A1 overexpression and siEphA2 dampened EGFR signaling, which is increased by antago-210. Our data clearly demonstrate a link between miR-210 and EphA2/Ephrin-A1 signaling that regulates, in part, corneal epithelial migration. This interaction might potentially control the limbal-corneal epithelial boundary.

Angiotensin converting enzyme 2 (ACE2) plays an important role in inflammation, which is attributable at least, in part, to the conversion of the pro‐inflammatory angiotensin (Ang) II peptide into angiotensin 1‐7 (Ang 1‐7), a peptide which opposes the actions of AngII. ACE2 and AngII are present in many tissues but information on the cornea is lacking. We observed that mice deficient in the Ace2 gene (Ace2−/−), developed a cloudy cornea phenotype as they aged. Haze occupied the central cornea, accompanied by corneal edema and neovascularization. In severe cases with marked chronic inflammation, a cell‐fate switch from a transparent corneal epithelium to a keratinized, stratified squamous, psoriasiform‐like epidermis was observed. The stroma contained a large number of CD11c, CD68, and CD3 positive cells. Corneal epithelial debridement experiments in young ACE2‐deficient mice showed normal appearing corneas, devoid of haze. We hypothesized, however, that these mice are “primed” for a corneal inflammatory response, which once initiated, would persist. In vitro studies reveal that interleukins (IL‐1a, IL‐1b), chemokines (CCL2, CXCL8), and TNF‐α, are all significantly elevated, resulting in a cytokine storm‐like phenotype. This phenotype could be partially rescued by treatment with the AngII type 1 receptor (AT1R) antagonist, losartan, suggesting that the observed effect was mediated by AngII acting on its main receptor. Since the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) utilizes human ACE2 as the receptor for entry with subsequent downregulation of ACE2, corneal inflammation in Ace2−/− mice may have a similar mechanism with that in COVID‐19 patients. Thus the Ace2−/− cornea, because of easy accessibility, may provide an attractive model to explore the molecular mechanisms, immunological changes, and treatment modalities in patients with COVID‐19.

Yan Huo* Qun Wang* Ying Liu Junyi Wang Qian Li Zongyuan Li Yan Dong Yifei Huang Liqiang Wang 1Department of Ophthalmology, The 1st Medical Center Of Chinese PLA General Hospital, Beijing 100853, People’s Republic of China; 2The Institutional Animal Care and Use Committee of National Beijing Center for Drug Safety Assessment, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing 100850, People’s Republic of China