Matrix metalloproteinases and their inhibitors in Fuchs endothelial corneal dystrophy

Cyanidin prevents cardiomyocyte apoptosis in mice after myocardial infarction

Myocardial infarction is a worldwide disease with high morbidity and mortality and a major cause of chronic heart failure, seriously affecting patients' quality of life. Natural medicine has been used to cure or prevent cardiovascular disease for decades. As a natural flavonoid, anthocyanidin has been used to treat many diseases due to its antioxidative, anti-inflammatory, and other properties. A mouse model (C57BL/6) weighing 30-40 g was utilized to induce myocardial infarction by ligating the left anterior descending coronary artery. Cyanidin (30 mg/kg) was administered orally to mice for four weeks. A variety of assessments were used to evaluate cardiac function. The gene expression was measured using RNAseq and Western blot. Histological changes in myocardial tissue were assessed using staining techniques, including Masson, Hematoxylin Eosin (HE), and transmission electron microscopy. Tunnel staining was implemented as a method to detect cellular apoptosis. For the quantification of B-type natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) in the serum, an enzyme-linked immunosorbent assay (ELISA) was employed. Furthermore, autodock simulation was executed in order to assess the interaction between cyanidin and a subset of genes. Cyanidin treatment inhibited myocardial cell apoptosis, improved cardiac function, and reduced serum concentrations of BNP and atrial natriuretic peptide ANP, as well as mitigated histological cardiac tissue damage. Cyanidin also inhibited the activity of matrix metalloproteinases (MMP2/9) and Fibronectin 1 (Fn1). Cyanidin improves heart function and reduces myocardial damage in mice after MI. Furthermore, cyanidin can prevent cardiomyocyte apoptosis. These effects are most likely caused by suppression of MMP9/2 and control of the Akt signaling pathway, suggesting an appropriate therapeutic target.

Exploring single-cell RNA sequencing as a decision-making tool in the clinical management of Fuchs' endothelial corneal dystrophy

Single-cell RNA sequencing (scRNA-seq) has enabled the identification of novel gene signatures and cell heterogeneity in numerous tissues and diseases. Here we review the use of this technology for Fuchs' Endothelial Corneal Dystrophy (FECD). FECD is the most common indication for corneal endothelial transplantation worldwide. FECD is challenging to manage because it is genetically heterogenous, can be autosomal dominant or sporadic, and progress at different rates. Single-cell RNA sequencing has enabled the discovery of several FECD subtypes, each with associated gene signatures, and cell heterogeneity. Current FECD treatments are mainly surgical, with various Rho kinase (ROCK) inhibitors used to promote endothelial cell metabolism and proliferation following surgery. A range of emerging therapies for FECD including cell therapies, gene therapies, tissue engineered scaffolds, and pharmaceuticals are in preclinical and clinical trials. Unlike conventional disease management methods based on clinical presentations and family history, targeting FECD using scRNA-seq based precision-medicine has the potential to pinpoint the disease subtypes, mechanisms, stages, severities, and help clinicians in making the best decision for surgeries and the applications of therapeutics. In this review, we first discuss the feasibility and potential of using scRNA-seq in clinical diagnostics for FECD, highlight advances from the latest clinical treatments and emerging therapies for FECD, integrate scRNA-seq results and clinical notes from our FECD patients and discuss the potential of applying alternative therapies to manage these cases clinically.

Biomaterials used for tissue engineering of barrier-forming cell monolayers in the eye

Cell monolayers that form a barrier between two structures play an important role for the maintenance of tissue functionality. In the anterior portion of the eye, the corneal endothelium forms a barrier that controls fluid exchange between the aqueous humor of the anterior chamber and the corneal stroma. This monolayer is central in the pathogenesis of Fuchs endothelial corneal dystrophy (FECD). FECD is a common corneal disease, in which corneal endothelial cells deposit extracellular matrix that increases the thickness of its basal membrane (Descemet's membrane), and forms excrescences (guttae). With time, there is a decrease in endothelial cell density that generates vision loss. Transplantation of a monolayer of healthy corneal endothelial cells on a Descemet membrane substitute could become an interesting alternative for the treatment of this pathology. In the back of the eye, the retinal pigment epithelium (RPE) forms the blood-retinal barrier, controlling fluid exchange between the choriocapillaris and the photoreceptors of the outer retina. In the retinal disease dry age-related macular degeneration (dry AMD), deposits (drusen) form between the RPE and its basal membrane (Bruch's membrane). These deposits hinder fluid exchange, resulting in progressive RPE cell death, which in turn generates photoreceptor cell death, and vision loss. Transplantation of a RPE monolayer on a Bruch's membrane/choroidal stromal substitute to replace the RPE before photoreceptor cell death could become a treatment alternative for this eye disease. This review will present the different biomaterials that are proposed for the engineering of a monolayer of corneal endothelium for the treatment of FECD, and a RPE monolayer for the treatment of dry AMD.

The soil and the seed: The relationship between Descemet's membrane and the corneal endothelium

Descemet's membrane (DM), the basement membrane of the corneal endothelium, is formed from the extracellular matrix (ECM) secreted by corneal endothelial cells. The ECM supports the growth and function of the corneal endothelial cells. Changes to DM are central to the diagnosis of the most common corneal endothelial disease, Fuchs endothelial corneal dystrophy (FECD). Changes in DM are also noted in systemic diseases such as diabetes mellitus. In FECD, the DM progressively accumulates guttae, "drop-like deposits" that disrupt the corneal endothelial cell monolayer. While the pathophysiologic changes to corneal endothelial cells in the course of FECD have been well described and reviewed, the changes to DM have received limited attention. The reciprocity of influence between the corneal endothelial cells and DM demands full attention to the latter in our search for novel treatment and preventive strategies. In this review, we discuss what is known about the formation and composition of DM and how it changes in FECD and other conditions. We review characteristics of guttae and the interplay between corneal endothelial cells and guttae, particularly as it might apply to future cell-based and genetic therapies for FECD.

TGF-β-Mediated Modulation of Cell-Cell Interactions in Postconfluent Maturing Corneal Endothelial Cells

Purpose

Transforming growth factor-beta (TGF-β) is known to influence many cell functions. In the corneal endothelium, TGF-β1 exerts contextual effects, promoting endothelial–mesenchymal transition in proliferating cells and enhancing barrier integrity in early confluent maturing cells. Herein, we studied how TGF-β isoforms participate in the formation of corneal endothelial intercellular junctions.

Methods

Corneal endothelial cells (CECs) were cultured using a two-phase media approach. When CECs reached confluence, the proliferation medium was replaced with maturation medium, which was supplemented or not with TGF-β isoforms. The cell morphology (circularity index), intercellular junction protein expression, trans-endothelial electrical resistance (TEER), and permeability of 7-day postconfluent CECs were assessed. Gene transcription and signaling pathways that were activated following maturation in the presence of TGF-β2 were also studied. The beneficial effect of TGF-β2 on CEC maturation was evaluated using ex vivo corneas mounted on a corneal bioreactor.

Results

The results showed increases in circularity index, membrane localization of junction-related proteins, and TEER when TGF-β isoforms were individually added during the maturation phase, and TGF-β2 was the most effective isoform. Gene profiling revealed an increase in extracellular matrix-related gene expression. In ex vivo cell adhesion experiments, CECs that were matured in the presence of TGF-β2 had a higher circularity index and cell density and exhibited cell membrane-localized junction-related protein expression at earlier time points.

Conclusions

These results suggest that TGF-β2 can strengthen cell–cell and cell–substrate adhesion, which accelerates barrier integrity establishment and thus enhances CEC functionality.

Potential role of extracellular granzyme B in wet age-related macular degeneration and fuchs endothelial corneal dystrophy

Age-related ocular diseases are the leading cause of blindness in developed countries and constitute a sizable socioeconomic burden worldwide. Age-related macular degeneration (AMD) and Fuchs endothelial corneal dystrophy (FECD) are some of the most common age-related diseases of the retina and cornea, respectively. AMD is characterized by a breakdown of the retinal pigment epithelial monolayer, which maintains retinal homeostasis, leading to retinal degeneration, while FECD is characterized by degeneration of the corneal endothelial monolayer, which maintains corneal hydration status, leading to corneal edema. Both AMD and FECD pathogenesis are characterized by disorganized local extracellular matrix (ECM) and toxic protein deposits, with both processes linked to aberrant protease activity. Granzyme B (GrB) is a serine protease traditionally known for immune-mediated initiation of apoptosis; however, it is now recognized that GrB is expressed by a variety of immune and non-immune cells and aberrant extracellular localization of GrB substantially contributes to various age-related pathologies through dysregulated cleavage of ECM, tight junction, and adherens junction proteins. Despite growing recognition of GrB involvement in multiple age-related pathologies, its role in AMD and FECD remains poorly understood. This review summarizes the pathophysiology of, and similarities between AMD and FECD, outlines the current knowledge of the role of GrB in AMD and FECD, as well as hypothesizes putative contributions of GrB to AMD and FECD pathogenesis and highlights the therapeutic potential of pharmacologically inhibiting GrB as an adjunctive treatment for AMD and FECD.

Proteases and Their Potential Role as Biomarkers and Drug Targets in Dry Eye Disease and Ocular Surface Dysfunction

Dry eye disease (DED) is a multifactorial disorder that leads to ocular discomfort, visual disturbance, and tear film instability. DED is accompanied by an increase in tear osmolarity and ocular surface inflammation. The diagnosis and treatment of DED still present significant challenges. Therefore, novel biomarkers and treatments are of great interest. Proteases are present in different tissues on the ocular surface. In a healthy eye, proteases are highly regulated. However, dysregulation occurs in various pathologies, including DED. With this review, we provide an overview of the implications of different families of proteases in the development and severity of DED, along with studies involving protease inhibitors as potential therapeutic tools. Even though further research is needed, this review aims to give suggestions for identifying novel biomarkers and developing new protease inhibitors.

Evidence against involvement of kynurenate branch of kynurenine pathway in pathophysiology of Fuchs' dystrophy and keratoconus

Kynurenine aminotransferases (KAT) are enzymes catalyzing formation of kynurenic acid (KYNA) from kynurenine. KYNA is a Janus-faced molecule of high biological activity. On the one hand KYNA was identified as a UV filter and neuroprotectant with free radical scavenging properties, but on the other hand it may contribute to photodamage of lens proteins resulting in cataract formation. Fuchs endothelial corneal dystrophy (FECD) and keratoconus (KC) are common, vision threatening corneal dystrophies whose etiology is not fully understood. In our previous works, we confirmed the presence of KATs in the human cornea together with GPR35, a receptor for KYNA. This prompted us to investigate the potential changes in the expression of three isoforms: KAT I, KAT II, and KAT III in normal and FECD- and KC-affected corneas. Immunohistochemistry accompanied by gene expression data mining revealed that the levels of neither KAT I, KAT II, nor KAT III are affected in FECD and KC. This constitutes evidence against the involvement of KATs in the pathophysiology of FECD and KC.

Matrix metalloproteinase contribution in management of cancer proliferation, metastasis and drug targeting

Matrix metalloproteinases (MMPs) or matrixins, are members of a zinc-dependent endopeptidase family. They cause remodeling of the extracellular matrix (ECM) leading to numerous diseases. MMPs subfamilies possess: collagenases, gelatinases, stromelysins and membrane-type MMPs (MT-MMP). They consist of several domains; pro-peptide, catalytic, linker peptide and the hemopexin (Hpx) domains. MMPs are involved in initiation, proliferation and metastasis of cancer through the breakdown of ECM physical barriers. Overexpression of MMPs is associated with poor prognosis of cancer. This review will discuss both types of MMPs and current inhibitors, which target them in different aspects, including, biosynthesis, activation, secretion and catalytic activity. Several synthetic and natural inhibitors of MMPs (MMPIs) that can bind the catalytic domain of MMPs have been designed including; peptidomimetic, non-peptidomimetic, tetracycline derivatives, off-target MMPI, natural products, microRNAs and monoclonal antibodies.