Heparanase Overexpresses in Keratoconic Cornea and Tears Depending on the Pathologic Grade

Identification of hub genes and molecular pathways in keratoconus by integrating bioinformatics and literature mining at the RNA level

OBJECTIVE

Keratoconus (KC) is a condition characterized by progressive corneal steepening and thinning. However, its pathophysiological mechanism remains vague. We mainly performed literature mining to extract bioinformatic and related data on KC at the RNA level. The objective of this study was to explore the potential pathological mechanisms of KC by identifying hub genes and key molecular pathways at the RNA level.

METHODS

We performed an exhaustive search of the PubMed database and identified studies that pertained to gene transcripts derived from diverse corneal layers in patients with KC. The identified differentially expressed genes were intersected, and overlapping genes were extracted for further analyses. Significantly enriched genes were screened using "Gene Ontology" (GO) and "Kyoto Encyclopedia of Genes and Genomes" (KEGG) analysis with the "Database for Annotation, Visualization, and Integrated Discovery" (DAVID) database. A protein-protein interaction (PPI) network was constructed for the significantly enriched genes using the STRING database. The PPI network was visualized using the Cytoscape software, and hub genes were screened via betweenness centrality values. Pathways that play a critical role in the pathophysiology of KC were discovered using the GO and KEGG analyses of the hub genes.

RESULTS

68 overlapping genes were obtained. Fifty genes were significantly enriched in 67 biological processes, and 16 genes were identified in 7 KEGG pathways. Moreover, 14 nodes and 32 edges were identified via the PPI network constructed using the STRING database. Multiple analyses identified 4 hub genes, 12 enriched biological processes, and 6 KEGG pathways. GO enrichment analysis showed that the hub genes are mainly involved in the positive regulation of apoptotic process, and KEGG analysis showed that the hub genes are primarily associated with the interleukin-17 (IL-17) and tumor necrosis factor (TNF) pathways. Overall, the matrix metalloproteinase 9, IL-6, estrogen receptor 1, and prostaglandin-endoperoxide synthase 2 were the potential important genes associated with KC.

CONCLUSION

Four genes, matrix metalloproteinase 9, IL-6, estrogen receptor 1, and prostaglandin endoperoxide synthase 2, as well as IL-17 and TNF pathways, are critical in the development of KC. Inflammation and apoptosis may contribute to the pathogenesis of KC.

A multi-ancestry GWAS of Fuchs corneal dystrophy highlights the contributions of laminins, collagen, and endothelial cell regulation

Fuchs endothelial corneal dystrophy (FECD) is a leading indication for corneal transplantation, but its molecular etiology remains poorly understood. We performed genome-wide association studies (GWAS) of FECD in the Million Veteran Program followed by multi-ancestry meta-analysis with the previous largest FECD GWAS, for a total of 3970 cases and 333,794 controls. We confirm the previous four loci, and identify eight novel loci: SSBP3, THSD7A, LAMB1, PIDD1, RORA, HS3ST3B1, LAMA5, and COL18A1. We further confirm the TCF4 locus in GWAS for admixed African and Hispanic/Latino ancestries and show an enrichment of European-ancestry haplotypes at TCF4 in FECD cases. Among the novel associations are low frequency missense variants in laminin genes LAMA5 and LAMB1 which, together with previously reported LAMC1, form laminin-511 (LM511). AlphaFold 2 protein modeling, validated through homology, suggests that mutations at LAMA5 and LAMB1 may destabilize LM511 by altering inter-domain interactions or extracellular matrix binding. Finally, phenome-wide association scans and colocalization analyses suggest that the TCF4 CTG18.1 trinucleotide repeat expansion leads to dysregulation of ion transport in the corneal endothelium and has pleiotropic effects on renal function.

Multi-ancestry GWAS of Fuchs corneal dystrophy highlights roles of laminins, collagen, and endothelial cell regulation

Fuchs endothelial corneal dystrophy (FECD) is a leading indication for corneal transplantation, but its molecular pathophysiology remains poorly understood. We performed genome-wide association studies (GWAS) of FECD in the Million Veteran Program (MVP) and meta-analyzed with the previous largest FECD GWAS, finding twelve significant loci (eight novel). We further confirmed the TCF4 locus in admixed African and Hispanic/Latino ancestries, and found an enrichment of European-ancestry haplotypes at TCF4 in FECD cases. Among the novel associations are low frequency missense variants in laminin genes LAMA5 and LAMB1 which, together with previously reported LAMC1, form laminin-511 (LM511). AlphaFold 2 protein modeling suggests that mutations at LAMA5 and LAMB1 may destabilize LM511 by altering inter-domain interactions or extracellular matrix binding. Finally, phenome-wide association scans and co-localization analyses suggest that the TCF4 CTG18.1 trinucleotide repeat expansion leads to dysregulation of ion transport in the corneal endothelium and has pleiotropic effects on renal function.

The research progress on the molecular mechanism of corneal cross-linking in keratoconus treatment

Keratoconus (KC) is a corneal anomaly that is manifested in a limited cone-like bulge with corneal thinning. Many molecules in the cornea change during the development of KC, including various components of the extracellular matrix, cytokines, cell connection, and cell adhesion-related proteins. Several treatment options are available, with corneal cross-linking (CXL) being the treatment of choice for early KC. However, postoperative complications have been reported in some CXL patients, mainly caused by corneal epithelial resection. Despite the fact that some novel approaches have helped to reduce some of the initial post-operative issues, their effectiveness seems to be inferior to that of the original CXL. To keep effectiveness while avoiding these negative effects, it is necessary to study the mechanism of CXL in KC treatment at the molecular level. This article provides a review of the molecular mechanism of CXL in the treatment of KC from four aspects: enzyme activity, signal transduction pathway, corneal-related proteins, and other KC-related molecules, further confirming the feasibility of CXL treatment of KC, providing new ideas for improving CXL.

Exosomes Released by Corneal Stromal Cells Show Molecular Alterations in Keratoconus Patients and Induce Different Cellular Behavior

Exosomes have been related to various disorders, but their study in relation to ocular pathologies has been limited. In this article, we analyze exosomes produced by corneal stromal cells from healthy individuals and from patients with keratoconus. The proteomic study allowed for the identification of 14 new proteins with altered expression, related to molecules previously associated with the pathology. miRNA analysis detected 16 altered species, including miR-184, responsible for familial severe keratoconus. The prediction of its potential biological targets identified 1121 genes, including some related to this pathology. Exosomes produced by keratoconic cells induced a marked increase in the migration of stromal cells and corneal epithelium, while those produced by healthy cells had no effect on stromal cells. Both types of nanovesicles reduced the proliferation of stromal and corneal cells, but those produced by healthy cells had less effect. Exosomes produced by healthy cells had concentration-dependent effects on the transcription of genes encoding proteoglycans by keratoconus cells, with a relative normalization observed at concentrations of 240 µg/mL. These results show the alteration of stromal exosomes in keratoconus and suggest an influence on the development of the pathology, although the use of healthy exosomes could also have therapeutic potential.

Assessment of the Retinal Vessels in Keratoconus: An OCT Angiography Study

This study investigated vascular density and foveal avascular zone (FAZ) parameters using optical coherence tomography angiography (OCT-A) in patients with keratoconus (KC). Participants with KC and healthy controls were included and underwent best-corrected visual acuity (BCVA), keratometry, anterior segment OCT, and macular OCT-A examinations. Of the 70 subjects (mean age 42.9 ± 15.31 years), 79 KC and 47 healthy eyes were included. Significant reductions in the KC group were recorded for the FAZ area, with a mean (±SD) of 0.19 ± 0.12 vs. 0.25 ± 0.09 mm2 p < 0.001. Central vascular density in KC patients was lower compared with the controls: 6.78 ± 4.74 vs. 8.44 ± 3.33 mm−1 p = 0.049; the inner density was also decreased in the study group (13.64 ± 5.13 vs. 16.54 ± 2.89 mm−1, p = 0.002), along with the outer density (14.71 ± 4.12 vs. 16.88 ± 2.42 mm−1, p = 0.004) and full density (14.25 ± 4.30 vs. 16.57 ± 2.48) p = 0.003. Furthermore, BCVA was positively correlated with central vascular density (R = 0.42 p = 0.004, total R = 0.40, p = 0.006) and inner density (R = 0.44, p = 0.002) in patients with KC but not in controls. Additionally, we found a correlation between K2 and inner vascular density (R = −0.30, p = 0.043) and central epithelium thickness and outer density (R = 0.03, p = 0.046). KC patients had lower macular vascular density and a smaller FAZ than healthy participants. The BCVA in KC patients was correlated with the vascular density.

Biochemical and molecular alterations and potential clinical applications of biomarkers in keratoconus

Keratoconus (KC) is a complex multifactorial corneal ectatic disorder, with disease onset commonly in the second-third decades significantly affecting quantity, quality of vision, and quality of life. Several pathways and factors such as eye rubbing, inflammatory, oxidative, metabolic, genetic, and hormonal among others have been studied in the last two decades. However, the management of KC is still based on a few "one-size fits all" approaches and is predominantly guided by topo/tomographic parameters. Consideration of the several novel factors which have the potential to be biomarkers in addressing several unanswered questions in the disease process could help in the better predictive ability of progression or vision loss and customization of treatment options. This article delves into the understanding of these novel factors or biomarkers based on the pathogenesis of KC and features a special focus on their potential clinical applications and their future role in personalized medicine.

Systematically Displaying the Pathogenesis of Keratoconus via Multi-Level Related Gene Enrichment-Based Review

Keratoconus (KC) is an etiologically heterogeneous corneal ectatic disorder. To systematically display the pathogenesis of keratoconus (KC), this study reviewed all the reported genes involved in KC, and performed an enrichment analysis of genes identified at the genome, transcription, and protein levels respectively. Combined analysis of multi-level results revealed their shared genes, gene ontology (GO), and pathway terms, to explore the possible pathogenesis of KC. After an initial search, 80 candidate genes, 2,933 transcriptional differential genes, and 947 differential proteins were collected. The candidate genes were significantly enriched in extracellular matrix (ECM) related terms, Wnt signaling pathway and cytokine activities. The enriched GO/pathway terms of transcription and protein levels highlight the importance of ECM, cell adhesion, and inflammatory once again. Combined analysis of multi-levels identified 13 genes, 43 GOs, and 12 pathways. The pathogenic relationships among these overlapping factors maybe as follows. The gene mutations/variants caused insufficient protein dosage or abnormal function, together with environmental stimulation, leading to the related functions and pathways changes in the corneal cells. These included response to the glucocorticoid and reactive oxygen species; regulation of various signaling (P13K-AKT, MAPK and NF-kappaB), apoptosis and aging; upregulation of cytokines and collagen-related enzymes; and downregulation of collagen and other ECM-related proteins. These undoubtedly lead to a reduction of extracellular components and induction of cell apoptosis, resulting in the loosening and thinning of corneal tissue structure. This study, in addition to providing information about the genes involved, also provides an integrated insight into the gene-based etiology and pathogenesis of KC.

Keratoconus patients exhibit a distinct ocular surface immune cell and inflammatory profile

Inflammatory factors have been considered to contribute to keratoconus (KC) pathogenesis. This study aims to determine the immune cells subsets and soluble inflammatory factor profile on the ocular surface of KC patients. 32 KC subjects (51 eyes) across different grades of severity and 15 healthy controls (23 eyes) were included in the study. Keratometry and pachymetry measurements were recorded. Ocular surface immune cells (collected by ocular surface wash) immunophenotyped using flow cytometry include leukocytes, neutrophils, macrophages, natural killer (NK) cells, pan-T cells, gamma delta T (γδT) cells and NKT cells. Tear fluid collected using Schirmer's strip was used to measure 50 soluble factors by multiplex ELISA. Proportions of activated neutrophils, NK cells and γδT cells were significantly increased in KC patients. Significantly higher levels of tear fluid IL-1β, IL-6, LIF, IL-17A, TNFα, IFNα/β/γ, EPO, TGFβ1, PDGF-BB, sVCAM, sL-selectin, granzyme-B, perforin, MMP2, sFasL and IgE, along with significantly lower levels of IL-1α and IL-9 were observed in KC patients. Alterations observed in few of the immuno-inflammatory parameters correlated with grades of disease, allergy, eye rubbing and keratometry or pachymetry measurements. The observation implies a distinct immuno-inflammatory component in KC pathogenesis and its potential as an additional therapeutic target in KC management.

Biochemical Markers and Alterations in Keratoconus

Keratoconus (KC) is a corneal ectatic condition characterized by focal structural changes, resulting in progressive thinning, biomechanical weakening, and steeping of the cornea that can lead to worsening visual acuity due to irregular astigmatism and corneal scarring in more advanced cases. It is a relatively common ectatic disease of the cornea predominantly affecting the younger population. Despite its worldwide prevalence, its incidence is rather varied with a higher incidence among the Middle Eastern and South Asian population. Dysregulated corneal extracellular matrix remodeling underlies KC pathogenesis. However, a lack of absolute clarity regarding the factors that initiate and drive progression poses a significant challenge in its prevention and management. KC is a complex multifactorial disease as it is associated with a wide variety of etiological factors such as environmental stimuli/insults, oxidative stress, genetic predisposition, comorbidities, and eye rubbing. A series of studies using corneal tissues (epithelium, stroma), cultured corneal fibroblasts/keratocytes, tear fluid, aqueous humor, and blood from KC subjects has reported significant alterations in various biochemical factors such as extracellular matrix components, cellular homeostasis regulators, inflammatory factors, hormones, metabolic products, and chemical elements. It has become apparent that alterations in the biochemical mediators (related to various etiologies) could contribute to KC pathogenesis by altering the dynamics of extracellular matrix remodeling events such as collagen deposition, degradation, and cross-linking in the cornea. Determining key disease contributing biochemical mediators would aid in disease monitoring, prediction or abatement of disease progression, and development of targeted therapeutics to improve disease prognosis.

Heparanase in Acute Kidney Injury

Recent years have brought about fledgling realization of the role played by heparanase in the pathogenesis of diverse diseases including kidney diseases and, specifically, acute kidney injury. Human heparanase-1 is critically and uniquely engaged in cleavage of heparan sulfate, an integral part of glycocalyx and extracellular matrix where it harbors distinct growth factors, cytokines, and other biologically active molecules. The enzyme is induced and activated in acute kidney injury regardless of its causes, ischemic, nephrotoxic, septic or transplantation-related. This event unleashes a host of sequelae characteristic of the pathogenesis of acute kidney injury, such as induction and reinforcement of innate immune responses, predisposition to thrombosis, activation of monocytes/macrophages and remodeling of the extracellular matrix, thus setting up the stage for future fibrotic complications and development of chronic kidney disease. We briefly discuss the emerging therapeutic strategies of inhibiting heparanase, as well as the diagnostic value of detecting products of heparanase activity for prognostication and treatment.

New Advances of Heparanase in Human Diseases

OBJECTIVE

This mini-review aims to discuss research works about heparanase published in 2016, 2017, 2018 and 2019 and provide a direction for therapy methods targeting heparanase.

PATIENTS AND METHODS

The relevant data were searched by using keywords "heparanase" "function", "diseases" and "inhibitors" in "PubMed", "Web of Science" and "China Knowledge Resource Integrated databases (CNKI)", and a hand-search was done to acquire peer-reviewed articles and reports about heparanase.

RESULTS

Except for tumor progression, pathological processes including procoagulant activities, preeclamptic placentas, inflammation and so on are all verified to be associated with heparanase activity. Also, these newly-found functions are closely related to certain cellular activities, including epithelial to Mesenchymal Transition (EMT).

CONCLUSION

It could be concluded that heparanase would be a potential and valuable therapy target.

New Advances of Heparanase and Heparanase-2 in Human Diseases

As we all know, heparanase plays an important role in human diseases. As a kind of endo-β-glucuronidase, heparanase is the known only enzyme in mammals which could degrade heparan sulfate(HS) specifically. HS is a vital component of extracellular matrix(ECM). Heparanase takes effect by cleaving theβ(1,4)-glycosidic between glucosamine residue and glucuronic acid of HS. This cleavage will cause ECM remodelling and HS-linked biological molecules release, including cytokines, growth factors and a lot of biological molecules regulating various pathological activities. Experiments already proved that heparanase gene over-expresses in cancers of gastrointestinal tract, esophagus, breast and so on. Various studies have demonstrated the heparanase's pro-metastatic function and the reduced survival rate of patients could be indicated by high heparanase levels. Besides, pathological processes including procoagulant activities, preeclamptic placentas and inflammation are all verified to be associated with heparanase activity. In recent years, many functions other than pro-tumor effect was found in heparanase and worldwide researchers conducted varieties of experiments to identify the new function of this significant enzyme. Also, these newly-found functions are closely connected to certain cellular activities, for example epithelial to mesenchymal transition (EMT). It has already been demonstrated that EMT is related to some clinical disorders, like renal diseases. Given that heparanase is the only enzyme capable of this function, it could be concluded that heparanase would be a potential and valuable therapy target. This mini-review aims to retrospect literatures about heparanase published in 2017 and 2018 and provide a direction for therapy methods targeting heparanase.

Changes in tear biomarker levels in keratoconus after corneal collagen crosslinking

Purpose

The purpose of this work was to analyze the expressions of matrix metalloproteinase 9 (MMP-9), calcyclin (S100A6), and cystatin S (CST4) in the tears of keratoconus (KC) patients. The correlations between the expressions of these proteins and the values of various ocular surface parameters were examined after accelerated corneal crosslinking (A-CXL) with pulsed ultraviolet light.

Methods

This prospective, observational study enrolled patients with different grades of KC, scheduled to undergo the A-CXL procedure, as well as healthy subjects. Tear samples were analyzed by employing customized antibody microarray assays for MMP-9, S100A6, and CST4 proteins. The keratometry readings at the maximum keratometry (Kmax) and the simulated keratometry (SimK) values were obtained for examining the postoperative evolution of corneal topography. The state of the ocular surface was evaluated using the results of the Ocular Surface Disease Index (OSDI) questionnaire, tear osmolarity (OSM) test, Schirmer test (SCH), Tear Break Up Time (TBUT), tear clearance (CLR), and fluorescein (FLUO) and lissamine green (LG) corneal staining.

Results

A total of 18 patients (22 eyes) and 10 healthy subjects were studied. The concentrations of MMP-9 and S100A6 decreased in tears, from 104.5 ± 78.98 ng/ml and 350.20 ± 478.08 ng/ml before the surgery to 48.7 ± 24.20 ng/ml and 55.70 ± 103.62 ng/ml, respectively, after 12 months of follow up. There were no changes in the CST4 concentration after 12 months of follow up (2202.75 ± 2863.70 versus 2139.68 ±2719.89 ng/ml). When the patients were divided into three groups according to the evolutive stage of KC, the trends for the three biomarkers in each group were the same as in the general group. Basal concentrations of MMP-9 and S100A6 from healthy subjects and KC patients were compared. The levels of MMP-9 and S100A6 in tears were (9.8 ± 5.11 and 104.55 ± 78.98 ng/ml, p<0.01; and 11.35 ± 3.18 and 350.26 ± 478.06 ng/ml, respectively, p<0.01). This was not the case for CST4, which did not exhibit statistically significant differences between the two groups (2261.94 ± 510.65 and 2176.73 ± 2916.27 ng/ml respectively, p=0.07).

Conclusions

A-CXL promoted a decrease in the concentrations of MMP-9 and S100A6 in the tear film. This effect may be related to the restoration of corneal homeostasis and the consequent repair of the tissue damage caused by KC. Moreover, the A-CXL treatment did not produce lasting alterations in the ocular surface, and the values of the evaluated clinical parameters did not change significantly.