Regulation of trabecular meshwork cell contraction and intraocular pressure by miR-200c

The TGFβ Induced MicroRNAome of the Trabecular Meshwork

Primary open-angle glaucoma (POAG) is a progressive optic neuropathy with a complex, multifactorial aetiology. Raised intraocular pressure (IOP) is the most important clinically modifiable risk factor for POAG. All current pharmacological agents target aqueous humour dynamics to lower IOP. Newer therapeutic agents are required as some patients with POAG show a limited therapeutic response or develop ocular and systemic side effects to topical medication. Elevated IOP in POAG results from cellular and molecular changes in the trabecular meshwork driven by increased levels of transforming growth factor β (TGFβ) in the anterior segment of the eye. Understanding how TGFβ affects both the structural and functional changes in the outflow pathway and IOP is required to develop new glaucoma therapies that target the molecular pathology in the trabecular meshwork. In this study, we evaluated the effects of TGF-β1 and -β2 treatment on miRNA expression in cultured human primary trabecular meshwork cells. Our findings are presented in terms of specific miRNAs (miRNA-centric), but given miRNAs work in networks to control cellular pathways and processes, a pathway-centric view of miRNA action is also reported. Evaluating TGFβ-responsive miRNA expression in trabecular meshwork cells will further our understanding of the important pathways and changes involved in the pathogenesis of glaucoma and could lead to the development of miRNAs as new therapeutic modalities in glaucoma.

Current understanding of genetics and epigenetics in pseudoexfoliation syndrome and glaucoma

Pseudoexfoliation is a complex, progressive, and systemic age-related disorder. The early stage of deposition of extracellular fibrillar material on ocular and extraocular tissues is termed as pseudoexfoliation syndrome (PEXS). The severe advanced stage is known as pseudoexfoliation glaucoma (PEXG), which involves increased intraocular pressure and optic nerve damage. Through genome-wide association and candidate gene studies, PEX has been associated with numerous genetic risk variants in various gene loci. However, the genetic basis of the disease fails to explain certain features of PEX pathology, such as the progressive nature of the disease, asymmetric ocular manifestation, age-related onset, and only a subset of PEXS individuals developing PEXG. Increasing evidence shows an interplay of genetic and epigenetic factors in the pathology of complex, multifactorial diseases. In this review, we have discussed the genetic basis of the disease and the emerging contribution of epigenetic regulations in PEX pathogenesis, focusing on DNA methylation and non-coding RNAs. Aberrant methylation patterns, histone modifications, and post-transcriptional regulation by microRNAs lead to aberrant gene expression changes. We have reviewed these aberrant epigenetic changes in PEX pathology and their effect on molecular pathways associated with PEX. We have further discussed some possible genetic/epigenetic-based diagnoses and therapeutics for PEX. Although studies to understand the role of epigenetic regulations in PEX are just emerging, epigenetic modifications contribute significantly to PEX pathogenesis and may pave the way for better and targeted therapeutics.

Construction of miRNA-mRNA regulatory network indicates potential biomarkers for primary open-angle glaucoma

BACKGROUND

Trabecular meshwork (TM) dysfunction-induced elevation of intraocular pressure has been identified as the main risk factor of irreversible optic nerve injury in Primary open‑angle glaucoma (POAG). Increasing evidences suggest that microRNA (miRNA) plays a vital role in the pathogenesis of POAG. This study aims to construct a miRNA-mRNA regulatory network and identify biomarkers for POAG.

METHODS

miRNAs and mRNAs expression profiling of TM samples from controls and POAG patients were assessed through microarray analysis. Target genes of differentially expressed miRNAs (DEmiRNAs) were predicted by miEAA and miRNet. Then GO and KEGG pathway analysis of differentially expressed mRNAs (DEmRNAs) were performed. PPI of top 30 hub genes was identified and miRNA-mRNA network was established by STRING database and Cytoscape software. GSE27276 and GSE105269 datasets were used to verify the expression of hub genes and to predict potential biomarkers in TM and aqueous humor (AH) for POAG, respectively. Finally, GSEA analysis was conducted to estimate the main signaling pathway of POAG pathogenesis.

RESULTS

A total of 29 up-regulated and 7 down-regulated miRNAs, 923 up-regulated and 887 down-regulated mRNAs were identified in TM of POAG compared with controls. Target genes and DEmRNAs were mainly enriched in nitric oxide biosynthetic process, vasopressin-regulated water reabsorption, and so on. Through miRNA-mRNA network construction, top 30 hub genes were regulated by 24 DEmiRNAs. 8 genes were aberrantly expressed in dataset GSE27276. 3 genes (CREB1, CAPZA2, SLC2A3) and 2 miRNAs (miR-106b-5p, miR-15a-5p) were identified as potential biomarkers for POAG in TM and AH, respectively. GSEA analysis revealed that these 3 genes modulated POAG through different pathways.

CONCLUSION

In this study, construction of miRNA-mRNA network and identification of biomarkers provide a novel insight into the pathogenesis, early diagnosis and treatment for POAG.

Reduction-responsive polymeric micelles for trans-corneal targeted delivery of microRNA-21-5p and glaucoma-specific gene therapy

The therapeutic value of microRNA (miRNA) for the treatment of glaucoma has become a focus of attention. However, naked miRNA cannot cross the corneal barrier and reach the target tissue by itself. Thus, the precise transport of miRNA to the target sites is key to the success of gene therapy. Herein, we selected a miRNA, namely miR-21-5p, based on its unique intraocular pressure (IOP) mechano-sensing property. Moreover, a biocompatible polymeric poly(L-lysine) (PLL) micelle conjugated with collagenase and ABCA1 antibody was judiciously constructed to achieve the trans-corneal and target delivery of miR-21-5p to the trabecular meshwork (TM) and Schlemm's canal (SC) tissues inside the eye. The topically administrated PLL micelles as an eye drop successfully crossed the cornea with the help of collagenase and then preferentially accumulated in the target TM/SC tissues under the guidance of the ABCA1 antibody. When endocytosed by TM/SC cells, the PLL micelles could be decomposed in the reductive lysosomal environment to release miR-21-5p for successfully lowering the IOP by activating the miR-21-5p/eNOS/MMP9 signaling axis, which will open new prospects for glaucoma-specific gene therapy.

The Application of MicroRNAs in Glaucoma Research: A Bibliometric and Visualized Analysis

Glaucoma is similar to a neurodegenerative disorder and leads to global irreversible loss of vision. Despite extensive research, the pathophysiological mechanisms of glaucoma remain unclear, and no complete cure has yet been identified for glaucoma. Recent studies have shown that microRNAs can serve as diagnostic biomarkers or therapeutic targets for glaucoma; however, there are few bibliometric studies that focus on using microRNAs in glaucoma research. Here, we have adopted a bibliometric analysis in the field of microRNAs in glaucoma research to manifest the current tendencies and research hotspots and to present a visual map of the past and emerging tendencies in this field. In this study, we retrieved publications in the Web of Science database that centered on this field between 2007 and 2022. Next, we used VOSviewer, CiteSpace, Scimago Graphica, and Microsoft Excel to present visual representations of a co-occurrence analysis, co-citation analysis, tendencies, hotspots, and the contributions of authors, institutions, journals, and countries/regions. The United States was the main contributor. Investigative Ophthalmology and Visual Science has published the most articles in this field. Over the past 15 years, there has been exponential growth in the number of publications and citations in this field across various countries, organizations, and authors. Thus, this study illustrates the current trends, hotspots, and emerging frontiers and provides new insight and guidance for searching for new diagnostic biomarkers and clinical trials for glaucoma in the future. Furthermore, international collaborations can also be used to broaden and deepen the field of microRNAs in glaucoma research.

Glaucoma: Novel antifibrotic therapeutics for the trabecular meshwork

Glaucoma is a chronic and progressive neurodegenerative disease characterized by the loss of retinal ganglion cells and visual field defects, and currently affects around 1% of the world's population. Elevated intraocular pressure (IOP) is the best-known modifiable risk factor and a key therapeutic target in hypertensive glaucoma. The trabecular meshwork (TM) is the main site of aqueous humor outflow resistance and therefore a critical regulator of IOP. Fibrosis, a reparative process characterized by the excessive deposition of extracellular matrix components and contractile myofibroblasts, can impair TM function and contribute to the pathogenesis of primary open-angle glaucoma (POAG) as well as the failure of minimally invasive glaucoma surgery (MIGS) devices. This paper provides a detailed overview of the current anti-fibrotic therapeutics targeting the TM in glaucoma, along with their anti-fibrotic mechanisms, efficacy as well as the current research progress from pre-clinical to clinical studies.

Roles of non-coding RNAs in eye development and diseases

The prevalence of ocular disorders is dramatically increasing worldwide, especially those that cause visual impairment and permanent loss of vision, including cataract, glaucoma, age-related macular degeneration, and diabetic retinopathy. Extensive evidence has shown that ncRNAs are key regulators in various biogenesis and biological functions, controlling gene expression related to histogenesis and cell differentiation in ocular tissues. Aberrant expression and function of ncRNA can lead to dysfunction of visual system and mediate progression of eye disorders. Here, we mainly offer an overview of the role of precise modulation of ncRNAs in eye development and function in patients with eye diseases. We also highlight the challenges and future perspectives in conducting ncRNA studies, focusing specifically on the role of ncRNAs that may hold expanded promise for their diagnostic and therapeutic applications in various eye diseases. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA in Disease and Development > RNA in Disease RNA in Disease and Development > RNA in Development.

Exosome-based crosstalk in glaucoma pathogenesis: a focus on oxidative stress and neuroinflammation

Exosomes are membrane-bound tiny particles that are released by all live cells that contain multiple signal molecules and extensively participate in numerous normal physical activities and pathologies. In glaucoma, the crucial role of exosome-based crosstalk has been primarily revealed in animal models and ex vivo cell studies in the recent decade. In the aqueous drainage system, exosomes derived from non-pigment ciliary epithelium act in an endocrine manner and specifically regulate the function of the trabecular meshwork to cope with persistent oxidative stress challenges. In the retina, a more complicated regulatory network among microglia, retinal neurons, retinal ganglial cells, retinal pigment epithelium, and other immune effector cells by exosomes are responsible for the elaborate modulation of tissue homeostasis under physical state and the widespread propagation of neuroinflammation and its consequent neurodegeneration in glaucoma pathogenesis. Accumulating evidence indicates that exosome-based crosstalk depends on numerous factors, including the specific cargos they carried (particularly micro RNA), concentration, size, and ionization potentials, which largely remain elusive. In this narrative review, we summarize the latest research focus of exosome-based crosstalk in glaucoma pathogenesis, the current research progress of exosome-based therapy for glaucoma and provide in-depth perspectives on its current research gap.

Advances in targeting the extracellular matrix for glaucoma therapy: current updates

INTRODUCTION

Elevated intraocular pressure (IOP) is a well-recognized risk factor for development of primary open angle glaucoma (POAG), a leading cause of irreversible blindness. Ocular hypertension is associated with excessive extracellular matrix (ECM) deposition in trabecular meshwork (TM) resulting in increased aqueous outflow resistance and elevated IOP. Hence, therapeutic options targeting ECM remodeling in TM to lower IOP in glaucomatous eyes are of considerable importance.

AREAS COVERED

This paper discusses the complex process of ECM regulation in TM and explores promising therapeutic targets. The role of Transforming Growth Factor-β as a central player in ECM deposition in TM is discussed. We elaborate the key regulatory processes involved in its activation, release, signaling, and cross talk with other signaling pathways including Rho GTPase, Wnt, integrin, cytokines, and renin-angiotensin-aldosterone. Further, we summarize the therapeutic agents that have been explored to target ECM dysregulation in TM.

EXPERT OPINION

Targeting molecular pathways to reduce ECM deposition and/or enhance its degradation are of considerable significance for IOP lowering. Challenges lie in pinpointing specific targets and designing drug delivery systems to precisely interact with pathologically active/inactive signaling. Recent advances in monoclonal antibodies, fusion molecules, and vectored nanotechnology offer potential solutions.

FP and EP2 prostanoid receptor agonist drugs and aqueous humor outflow devices for treating ocular hypertension and glaucoma

Prostaglandin (PG) receptors represent important druggable targets due to the many diverse actions of PGs in the body. From an ocular perspective, the discovery, development, and health agency approvals of prostaglandin F (FP) receptor agonists (FPAs) have revolutionized the medical treatment of ocular hypertension (OHT) and glaucoma. FPAs, such as latanoprost, travoprost, bimatoprost, and tafluprost, powerfully lower and control intraocular pressure (IOP), and became first-line therapeutics to treat this leading cause of blindness in the late 1990s to early 2000s. More recently, a latanoprost-nitric oxide (NO) donor conjugate, latanoprostene bunod, and a novel FP/EP3 receptor dual agonist, sepetaprost (ONO-9054 or DE-126), have also demonstrated robust IOP-reducing activity. Moreover, a selective non-PG prostanoid EP2 receptor agonist, omidenepag isopropyl (OMDI), was discovered, characterized, and has been approved in the United States, Japan and several other Asian countries for treating OHT/glaucoma. FPAs primarily enhance uveoscleral (UVSC) outflow of aqueous humor (AQH) to reduce IOP, but cause darkening of the iris and periorbital skin, uneven thickening and elongation of eyelashes, and deepening of the upper eyelid sulcus during chronic treatment. In contrast, OMDI lowers and controls IOP by activation of both the UVSC and trabecular meshwork outflow pathways, and it has a lower propensity to induce the aforementioned FPA-induced ocular side effects. Another means to address OHT is to physically promote the drainage of the AQH from the anterior chamber of the eye of patients with OHT/glaucoma. This has successfully been achieved by the recent approval and introduction of miniature devices into the anterior chamber by minimally invasive glaucoma surgeries. This review covers the three major aspects mentioned above to highlight the etiology of OHT/glaucoma, and the pharmacotherapeutics and devices that can be used to combat this blinding ocular disease.

MicroRNA expression profiling of endocrine sensitive and resistant breast cancer cell lines

Background

Methods

Results

Conclusions

•

Around 50–60% of microRNAs were significantly differentially expressed between ER- and ER + breast cancer cell lines.

•

Transfection of miR-200c-3p mimic into ER -ve cells induced MET and reduced cell motility.

•

Transfecting of miR-449a inhibitor into ER -ve cells reduced cell invasion but did not induce EMT.

Mechanistic Effects of Baicalein on Aqueous Humor Drainage and Intraocular Pressure

Elevated intraocular pressure (IOP) is a major risk factor for glaucoma that results from impeded fluid drainage. The increase in outflow resistance is caused by trabecular meshwork (TM) cell dysfunction and excessive extracellular matrix (ECM) deposition. Baicalein (Ba) is a natural flavonoid and has been shown to regulate cell contraction, fluid secretion, and ECM remodeling in various cell types, suggesting the potential significance of regulating outflow resistance and IOP. We demonstrated that Ba significantly lowered the IOP by about 5 mmHg in living mice. Consistent with that, Ba increased the outflow facility by up to 90% in enucleated mouse eyes. The effects of Ba on cell volume regulation and contractility were examined in primary human TM (hTM) cells. We found that Ba (1–100 µM) had no effect on cell volume under iso-osmotic conditions but inhibited the regulatory volume decrease (RVD) by up to 70% under hypotonic challenge. In addition, Ba relaxed hTM cells via reduced myosin light chain (MLC) phosphorylation. Using iTRAQ-based quantitative proteomics, 47 proteins were significantly regulated in hTM cells after a 3-h Ba treatment. Ba significantly increased the expression of cathepsin B by 1.51-fold and downregulated the expression of D-dopachrome decarboxylase and pre-B-cell leukemia transcription factor-interacting protein 1 with a fold-change of 0.58 and 0.40, respectively. We suggest that a Ba-mediated increase in outflow facility is triggered by cell relaxation via MLC phosphorylation along with inhibiting RVD in hTM cells. The Ba-mediated changes in protein expression support the notion of altered ECM homeostasis, potentially contributing to a reduction of outflow resistance and thereby IOP.

Degeneration of retina-brain components and connections in glaucoma: Disease causation and treatment options for eyesight preservation

Eyesight is the most important of our sensory systems for optimal daily activities and overall survival. Patients who experience visual impairment due to elevated intraocular pressure (IOP) are often those afflicted with primary open-angle glaucoma (POAG) which slowly robs them of their vision unless treatment is administered soon after diagnosis. The hallmark features of POAG and other forms of glaucoma are damaged optic nerve, retinal ganglion cell (RGC) loss and atrophied RGC axons connecting to various brain regions associated with receipt of visual input from the eyes and eventual decoding and perception of images in the visual cortex. Even though increased IOP is the major risk factor for POAG, the disease is caused by many injurious chemicals and events that progress slowly within all components of the eye-brain visual axis. Lowering of IOP mitigates the damage to some extent with existing drugs, surgical and device implantation therapeutic interventions. However, since multifactorial degenerative processes occur during aging and with glaucomatous optic neuropathy, different forms of neuroprotective, nutraceutical and electroceutical regenerative and revitalizing agents and processes are being considered to combat these eye-brain disorders. These aspects form the basis of this short review article.

Emerging Evidence of Noncoding RNAs in Bleb Scarring after Glaucoma Filtration Surgery

Purpose: To conduct a narrative review of research articles on the potential anti- and pro-fibrotic mechanisms of noncoding RNAs following glaucoma filtration surgery. Methods: Keyword searches of PubMed, and Medline databases were conducted for articles discussing post-glaucoma filtration surgeries and noncoding RNA. Additional manual searches of reference lists of primary articles were performed. Results: Fifteen primary research articles were identified. Four of the included papers used microarrays and qRT-PCR to identify up- or down-regulated microRNA (miRNA, miR) profiles and direct further study, with the remainder focusing on miRNAs or long noncoding RNAs (lncRNAs) based on previous work in other organs or disease processes. The results of the reviewed papers identified miR-26a, -29b, -139, -155, and -200a as having anti-fibrotic effects. In contrast, miRs-200b and -216b may play pro-fibrotic roles in filtration surgery fibrosis. lncRNAs including H19, NR003923, and 00028 have demonstrated pro-fibrotic effects. Conclusions: Noncoding RNAs including miRNAs and lncRNAs are emerging and promising therapeutic targets in the prevention of post-glaucoma filtration surgery fibrosis.

The role of microRNAs in glaucoma

In this review, we aim to provide a comprehensive summary of the various microRNAs (miRNAs) shown to be involved in glaucoma and intraocular pressure regulation. miRNAs are short, single-stranded, and noncoding RNAs that regulate gene expression in a number of physiological conditions and human diseases, including glaucoma. Numerous miRNAs display differential expression in glaucoma-affected tissues, such as aqueous humor, tears, trabecular meshwork, and retina analyzed from patients and animal models, suggesting their potential involvement in glaucoma pathogenesis. Several studies summarized here have also investigated the challenge of delivering intact miRNAs to target tissues in order to develop miRNA-based glaucoma therapies. We extend these reports by conducting an additional layer of analysis that integrates the interaction between glaucoma-related miRNAs and glaucoma-associated genes. We conclude with a comprehensive discussion of the therapeutic potential of miRNAs, the cellular pathways that link these miRNAs together, and the most promising miRNAs for future glaucoma research.

Tear miRNA expression analysis reveals miR-203 as a potential regulator of corneal epithelial cells

Background

microRNAs (miRNAs) are small noncoding RNAs that negatively regulate gene expression. They are found within cells and in body fluids. Extracellular miRNAs have been shown to associate with the surrounding tissues. Therefore, we predicted that miRNAs in tears may contribute to regulate corneal epithelial cell function. However, information on the miRNA expression profile of tears is limited and the specific functions of tear miRNAs for corneal epithelial cells are still unknown. To study the role of tear miRNAs, we determined which miRNAs are highly expressed in tears and examined the involvement of miRNAs in corneal epithelial cell viability.

Methods

miRNAs extracted from monkey tears and sera were subjected to microarray analysis. miRNAs of which expression levels were higher in tears than in sera were selected, and their expression levels were quantified by quantitative polymerase chain reaction (qPCR). To examine miRNA function, mimics and inhibitors of miRNAs were transfected into human corneal epithelial (HCE-T) cells and incubated for 24 or 48 h. After transfection of miRNA mimics and inhibitors, the viability of HCE-T cells was measured using the water soluble tetrazolium salt (WST) assay, and microarray analysis and qPCR were performed using total RNA extracted from HCE-T cells. siRNAs of the candidate targets for miR-203 were transfected into HCE-T cells and the WST assay was performed. To determine a direct target gene for miR-203, a dual luciferase reporter assay was performed in HCE-T cells using a luciferase reporter plasmid containing 3′-UTR of human IGFBP5.

Results

Microarray and qPCR analyses showed that miR-184 and miR-203 were expressed significantly more highly in tears than in sera (165,542.8- and 567.8-fold, respectively, p < 0.05). Of these two miRNAs, transfection of a miR-203 mimic significantly reduced the viability of HCE-T cells (p < 0.05), while a miR-203 inhibitor significantly increased this viability (p < 0.05). miR-203 mimic downregulated insulin-like growth factor-binding protein 5 (IGFBP5) and nuclear casein kinase and cyclin-dependent kinase substrate 1 (NUCKS1), while miR-203 inhibitor upregulated these two genes. Transfection of IGFBP5-siRNA decreased the viability of HCE-T cells. miR-203 mimic significantly diminished the luciferase reporter activity.

Conclusions

In this study, we identified miRNAs that are highly expressed in tears, and the inhibition of miR-203 increases the viability of corneal epithelial cells. Our results suggest that miR-203 contributes to regulating the homeostasis of corneal epithelial cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-02141-9.

Fundamental Biomaterial Considerations in the Development of a 3D Model Representative of Primary Open Angle Glaucoma

Glaucoma is a leading cause of irreversible blindness globally, with primary open angle glaucoma (POAG) being the most common subset. Raised intraocular pressure is an important risk factor for POAG and is caused by a reduction in aqueous humour (AqH) outflow due to dysfunctional cellular and matrix dynamics in the eye’s main drainage site, the trabecular meshwork (TM) and Schlemm’s canal (SC). The TM/SC are highly specialised tissues that regulate AqH outflow; however, their exact mechanisms of AqH outflow control are still not fully understood. Emulating physiologically relevant 3D TM/S in vitro models poses challenges to accurately mimic the complex biophysical and biochemical cues that take place in healthy and glaucomatous TM/SC in vivo. With development of such models still in its infancy, there is a clear need for more well-defined approaches that will accurately contrast the two central regions that become dysfunctional in POAG; the juxtacanalicular tissue (JCT) region of the TM and inner wall endothelia of the Schlemm’s canal (eSC). This review will discuss the unique biological and biomechanical characteristics that are thought to influence AqH outflow and POAG progression. Further consideration into fundamental biomaterial attributes for the formation of a biomimetic POAG/AqH outflow model will also be explored for future success in pre-clinical drug discovery and disease translation.

The Future of Stem Cells and Their Derivates in the Treatment of Glaucoma. A Critical Point of View

This review focuses on the clinical translation of preclinical studies, especially those that have used stem cells in the treatment of glaucoma, with an emphasis on optic nerve regeneration. The studies referred to in the review aim to treat optic nerve atrophy, while cell therapies targeting other sites in the eye, such as the trabecular meshwork, have not been addressed. Such complex and varied pathophysiological mechanisms that lead to glaucoma may explain the fact that although stem cells have a high capacity of neuronal regeneration, the treatments performed did not have the expected results and the promise offered by animal studies was not achieved. By analyzing the facts associated with failure, important lessons are to be learned: the type of stem cells that are used, the route of administration, the selection of patients eligible for these treatments, additional therapies that support stem cells transplantation and their mode of action, methods of avoiding the host’s immune response. Many of these problems could be solved using exosomes (EV), but also miRNA, which allows more targeted approaches with minimal side effects.

Therapeutic Drugs and Devices for Tackling Ocular Hypertension and Glaucoma, and Need for Neuroprotection and Cytoprotective Therapies

Damage to the optic nerve and the death of associated retinal ganglion cells (RGCs) by elevated intraocular pressure (IOP), also known as glaucoma, is responsible for visual impairment and blindness in millions of people worldwide. The ocular hypertension (OHT) and the deleterious mechanical forces it exerts at the back of the eye, at the level of the optic nerve head/optic disc and lamina cribosa, is the only modifiable risk factor associated with glaucoma that can be treated. The elevated IOP occurs due to the inability of accumulated aqueous humor (AQH) to egress from the anterior chamber of the eye due to occlusion of the major outflow pathway, the trabecular meshwork (TM) and Schlemm’s canal (SC). Several different classes of pharmaceutical agents, surgical techniques and implantable devices have been developed to lower and control IOP. First-line drugs to promote AQH outflow via the uveoscleral outflow pathway include FP-receptor prostaglandin (PG) agonists (e.g., latanoprost, travoprost and tafluprost) and a novel non-PG EP2-receptor agonist (omidenepag isopropyl, Eybelis^®). TM/SC outflow enhancing drugs are also effective ocular hypotensive agents (e.g., rho kinase inhibitors like ripasudil and netarsudil; and latanoprostene bunod, a conjugate of a nitric oxide donor and latanoprost). One of the most effective anterior chamber AQH microshunt devices is the Preserflo^® microshunt which can lower IOP down to 10–13 mmHg. Other IOP-lowering drugs and devices on the horizon will be also discussed. Additionally, since elevated IOP is only one of many risk factors for development of glaucomatous optic neuropathy, a treatise of the role of inflammatory neurodegeneration of the optic nerve and retinal ganglion cells and appropriate neuroprotective strategies to mitigate this disease will also be reviewed and discussed.

Endogenous dual stimuli-activated NO generation in the conventional outflow pathway for precision glaucoma therapy

High intraocular pressure (IOP) has been regarded as a predominant risk factor for glaucoma. Nitric oxide (NO) is shown to lower IOP, but the magnitude and duration of IOP reduction are not satisfying due to the poor cornea penetration of NO drugs and limited NO generation in the trabecular meshwork (TM)/Schlemm's canal (SC) area. Herein, we introduce deep cornea penetrating biodegradable hollow mesoporous organosilica (HOS) nanocapsules for the efficient co-delivery of hydrophobic JS-K (J_R) and hydrophilic l-Arginine (L_O). The resulting HOS-J_RL_O can be reduced and oxidized by the ascorbic acid (AA) and catalysis of endothelial nitric oxide synthase (eNOS) in the TM/SC microenvironment to release NO for inducing appreciable IOP reduction in various glaucoma mouse models. In addition to developing an endogenous stimuli-responsive NO nanotherapeutic, this study is also expected to establish a versatile, non-invasive, and efficacious treatment paradigm for precision glaucoma therapy.

The Role of MicroRNAs in Mitochondria-Mediated Eye Diseases

The retina is among the most metabolically active tissues with high-energy demands. The peculiar distribution of mitochondria in cells of retinal layers is necessary to assure the appropriate energy supply for the transmission of the light signal. Photoreceptor cells (PRs), retinal pigment epithelium (RPE), and retinal ganglion cells (RGCs) present a great concentration of mitochondria, which makes them particularly sensitive to mitochondrial dysfunction. To date, visual loss has been extensively correlated to defective mitochondrial functions. Many mitochondrial diseases (MDs) show indeed neuro-ophthalmic manifestations, including retinal and optic nerve phenotypes. Moreover, abnormal mitochondrial functions are frequently found in the most common retinal pathologies, i.e., glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy (DR), that share clinical similarities with the hereditary primary MDs. MicroRNAs (miRNAs) are established as key regulators of several developmental, physiological, and pathological processes. Dysregulated miRNA expression profiles in retinal degeneration models and in patients underline the potentiality of miRNA modulation as a possible gene/mutation-independent strategy in retinal diseases and highlight their promising role as disease predictive or prognostic biomarkers. In this review, we will summarize the current knowledge about the participation of miRNAs in both rare and common mitochondria-mediated eye diseases. Definitely, given the involvement of miRNAs in retina pathologies and therapy as well as their use as molecular biomarkers, they represent a determining target for clinical applications.

Altered Expression of Extracellular Vesicles miRNAs from Primary Human Trabecular Meshwork Cells Induced by Transforming Growth Factor-β2

Primary open-angle glaucoma (POAG) is tightly related with extracellular matrix (ECM) remodeling of human trabecular meshwork cells (HTMCs). Transforming growth factor-β2 (TGF-β2) can induce ECM remodeling. The aim of the study was to investigate the microRNAs (miRNAs) expression changes of extracellular vesicles (EVs) derived from HTMCs treated with TGF-β2. EVs were isolated from HTMCs supernatant cultured for 24 h with TGF-β2. The morphology of EVs pellets was examined by transmission electron microscopy. Nanoparticle tracking analysis used to demonstrate the particle size distribution. Total EVs RNAs were extracted for subsequent miRNA gene chip analysis to investigate differentially expressed miRNAs between the controls and treatment cells. Gene Ontology (GO) annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were used to predict potential target and validate possible functions of the miRNAs. There were 23 miRNAs upregulated and 3 miRNAs downregulated and 469,102, and 94 GO terms involved in biological processes, cellular components, and molecular function for the possible functions of the 26 miRNAs. These findings indicate that TGF-β2 may alter EVs miRNAs expression to participate in the pathogenesis of POAG. They may provide significant information for potential biomarkers for POAG diagnosis and treatment.

The lysophosphatidic acid axis in fibrosis: Implications for glaucoma

Glaucoma is a common progressive optic neuropathy that results in visual field defects and can lead to irreversible blindness. The pathophysiology of glaucoma involves dysregulated extracellular matrix remodelling in both the trabecular meshwork in the anterior chamber and in the lamina cribrosa of the optic nerve head. Fibrosis in these regions leads to raised intraocular pressure and retinal ganglion cell degeneration, respectively. Lysophosphatidic acid (LPA) is a bioactive lipid mediator which acts via six G-protein coupled receptors on the cell surface to activate intracellular pathways that promote cell proliferation, transcription and survival. LPA signalling has been implicated in both normal wound healing and pathological fibrosis. LPA enhances fibroblast proliferation, migration and contraction, and induces expression of pro-fibrotic mediators such as connective tissue growth factor. The LPA axis plays a major role in diseases such as idiopathic pulmonary fibrosis, where it has been identified as an important pharmacological target. In glaucoma, LPA is present in high levels in the aqueous humour, and its signalling has been found to increase resistance to aqueous humour outflow through altered trabecular meshwork cellular contraction and extracellular matrix deposition. LPA signalling may, therefore, also represent an attractive target for treatment of glaucoma. In this review we wish to describe the role of LPA and its related proteins in tissue fibrosis and glaucoma.

MicroRNAs in the aqueous humor of patients with different types of glaucoma

Purpose

The aim of the study was to compare the frequency and the level of expression of selected miRNAs in the aqueous humor of patients with various types of glaucoma.

Methods

The studied group consisted of 42 patients with glaucoma: 19 with primary open-angle glaucoma (POAG), 14 with pseudoexfoliation glaucoma (PEXG), 9 with primary angle closure glaucoma (PACG), and the control group of 36 patients with senile cataract without glaucoma. The real-time polymerase chain reaction method was used to analyze the expression of miRNAs.

Results

There were no significant differences in the frequency and the level of miRNA expression between various types of glaucoma. There was a tendency for hsa-miR-6722-3p and hsa-miR-184 to be expressed more frequently in PEXG and hsa-miR-1260b in POAG. The expression levels of hsa-miR-1260b and hsa-miR-6515-3p were correlated with age in POAG. Target annotation and functional analyses showed that genes targeted by the most frequently expressed miRNAs (hsa-miR-1202, -1260b, -184, -187-5p, -6515-3p, -6722-3p, and hsa-mir-4634) are involved mainly in response to hypoxia, cardiovascular system development, and apoptosis.

Conclusion

Hsa-miR-1260b was the most abundantly expressed among studied miRNAs and may be a potential biomarker of clinical status in PEXG and PACG.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00417-021-05214-z.

Harnessing the tunable cavity of nanoceria for enhancing Y-27632-mediated alleviation of ocular hypertension

Background: Y-27632 is a potent ophthalmic drug for the treatment of ocular hypertension, a globally prevalent eye disease. However, the sustained delivery of Y-27632 by a therapeutic carrier to lesion sites located in the inner segments of the eye for effectively treating the ocular disorder still remains challenging.

Methods: To realize the goal, a strategy based on solvothermal-assisted deposition/infiltration in combination with surface modification is utilized to synthesize hollow mesoporous ceria nanoparticles (HMCNs) with tailorable shell thicknesses and drug release profiles. The shell thickness of HMCNs is rationally exploited for achieving sustained drug release and advanced therapeutic benefits.

Results: The shell thickness can regulate release profiles of Y-27632, displaying that thick and thin (~40 nm and ~10 nm) shelled HMCNs reveal burst release characteristics (within 2 days) or limited drug loading content (~10% for the 40 nm thick). As a compromise, the HMCNs with moderate shell thickness (~20 nm) possess the most sustained drug release over a period of 10 days. In a rabbit model of glaucoma, a single instillation of the optimized Y-27632-loaded HMCNs can effectively treat glaucoma for 10 days via simultaneously repairing the defected cornea (recovery of ~93% ATP1A1 mRNA levels), restoring the reduced thickness of outer nuclear layer to normal (~64 µm), and restoring ~86% of the impaired photoreceptor cells.

Conclusion: A comprehensive study on the importance of HMCN shell thickness in developing long-acting nano eye drops for the efficient management of glaucoma is proposed. The findings suggest a central role of nanobiomaterial structural engineering in developing the long-life eye drops for pharmacological treatment of intraocular diseases.

Airborne particulate matter (PM2.5) triggers ocular hypertension and glaucoma through pyroptosis

Background

Particulate matter (PM) is strongly linked to human health and has detrimental effects on the eye. Studies have, however, focused on the ocular surface, with limited research on the impact of PM_2.5 on intraocular pressure (IOP).

Methods

To investigate the impact of PM_2.5 on IOP and the associated mechanism, C57BL/6 mouse eyes were topically exposed to a PM_2.5 suspension for 3 months, and human trabecular meshwork (HTM) cells were subjected to various PM_2.5 concentrations in vitro. Cell viability, NLRP3/caspase-1, IL-1β, and GSDMD expression, reactive oxygen species (ROS) production and cell contractility were measured by western blot, ELISA, cell counting kit-8, ROS assay kit or a cell contractility assay. ROS scavenger N-acetyl-L-cysteine (NAC) and caspase-1 inhibitor VX-765 were used to intervene in PM_2.5-induced damages.

Results

The results revealed that the IOP increased gradually after PM_2.5 exposure, and upregulations of the NLRP3 inflammasome, caspase-1, IL-1β, and GSDMD protein levels were observed in outflow tissues. PM_2.5 exposure decreased HTM cell viability and affected contraction. Furthermore, elevated ROS levels were observed as well as an activation of the NLRP3 inflammasome and downstream inflammatory factors caspase-1 and IL-1β. NAC improved HTM cell viability, inhibited the activation of the NLRP3 inflammasome axis, and HTM cell contraction by scavenging ROS. VX-765 showed similar protection against the PM_2.5 induced adverse effects.

Conclusion

This study provides novel evidence that PM_2.5 has a direct toxic effect on intraocular tissues and may contribute to the initiation and development of ocular hypertension and glaucoma. This occurs as a result of increased oxidative stress and the subsequent induction of NLRP3 inflammasome mediated pyroptosis in trabecular meshwork cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00403-4.

Crosstalk between MicroRNA and Oxidative Stress in Primary Open-Angle Glaucoma

Reactive oxygen species (ROS) plays a key role in the pathogenesis of primary open-angle glaucoma (POAG), a chronic neurodegenerative disease that damages the trabecular meshwork (TM) cells, inducing apoptosis of the retinal ganglion cells (RGC), deteriorating the optic nerve head, and leading to blindness. Aqueous humor (AH) outflow resistance and intraocular pressure (IOP) elevation contribute to disease progression. Nevertheless, despite the existence of pharmacological and surgical treatments, there is room for the development of additional treatment approaches. The following review is aimed at investigating the role of different microRNAs (miRNAs) in the expression of genes and proteins involved in the regulation of inflammatory and degenerative processes, focusing on the delicate balance of synthesis and deposition of extracellular matrix (ECM) regulated by chronic oxidative stress in POAG related tissues. The neutralizing activity of a couple of miRNAs was described, suggesting effective downregulation of pro-inflammatory and pro-fibrotic signaling pathways, including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB), transforming growth factor-beta 2 (TGF-β2), Wnt/β-Catenin, and PI3K/AKT. In addition, with regards to the elevated IOP in many POAG patients due to increased outflow resistance, Collagen type I degradation was stimulated by some miRNAs and prevented ECM deposition in TM cells. Mitochondrial dysfunction as a consequence of oxidative stress was suppressed following exposure to different miRNAs. In contrast, increased oxidative damage by inhibiting the mTOR signaling pathway was described as part of the action of selected miRNAs. Summarizing, specific miRNAs may be promising therapeutic targets for lowering or preventing oxidative stress injury in POAG patients.

Pathogenesis and prospects for therapeutic clinical application of noncoding RNAs in glaucoma: Systematic perspectives

Noncoding ribonucleic acids (ncRNAs) are an increasingly studied class of RNA molecules with extensive biological activities, including important roles in human development, health, and disease. Glaucoma is a neurodegenerative disease of the retina, and one of the leading causes of blindness worldwide. However, the specific roles of ncRNAs in the development and progression of glaucoma are unclear, and related reports are fragmented. An in‐depth understanding of ncRNAs participating in the pathogenesis and progression of glaucoma would be helpful for opening up new avenues to facilitate the early diagnosis and clinical treatment. Therefore, in this review, we aimed to discuss the current research progress, the potentialfuture clinical applications and the research limitations of three critical classes of ncRNAs in glaucoma, namely microRNAs, long noncoding RNAs, and circular RNAs.

The vital role for nitric oxide in intraocular pressure homeostasis

Catalyzed by endothelial nitric oxide (NO) synthase (eNOS) activity, NO is a gaseous signaling molecule maintaining endothelial and cardiovascular homeostasis. Principally, NO regulates the contractility of vascular smooth muscle cells and permeability of endothelial cells in response to either biochemical or biomechanical cues. In the conventional outflow pathway of the eye, the smooth muscle-like trabecular meshwork (TM) cells and Schlemm's canal (SC) endothelium control aqueous humor outflow resistance, and therefore intraocular pressure (IOP). The mechanisms by which outflow resistance is regulated are complicated, but NO appears to be a key player as enhancement or inhibition of NO signaling dramatically affects outflow function; and polymorphisms in NOS3, the gene that encodes eNOS modifies the relation between various environmental exposures and glaucoma. Based upon a comprehensive review of past foundational studies, we present a model whereby NO controls a feedback signaling loop in the conventional outflow pathway that is sensitive to changes in IOP and its oscillations. Thus, upon IOP elevation, the outflow pathway tissues distend, and the SC lumen narrows resulting in increased SC endothelial shear stress and stretch. In response, SC cells upregulate the production of NO, relaxing neighboring TM cells and increasing permeability of SC's inner wall. These IOP-dependent changes in the outflow pathway tissues reduce the resistance to aqueous humor drainage and lower IOP, which, in turn, diminishes the biomechanical signaling on SC. Similar to cardiovascular pathogenesis, dysregulation of the eNOS/NO system leads to dysfunctional outflow regulation and ocular hypertension, eventually resulting in primary open-angle glaucoma.

An update: mechanisms of microRNA in primary open-angle glaucoma

Glaucoma is a disease with characteristic optic neuropathy and loss of vision, leading to blindness, and primary open-angle glaucoma (POAG) is the most common glaucoma type throughout the world. Genetic susceptibility is the main factor in POAG, and most susceptibility genes cause changes in microRNA expression and function, thereby leading to POAG occurrence and development. Increasing evidence indicates that many microRNAs are involved in the regulation of intraocular pressure (IOP) and play an important role in the increase in IOP in POAG. Additionally, microRNA is closely related to optic nerve damage factors (mechanical stress, hypoxia and inflammation). This review discusses the effect of single-nucleotide polymorphisms in POAG-related genes on microRNA and the value of microRNA in the diagnosis and treatment of POAG.

miR-21-5p: A viable therapeutic strategy for regulating intraocular pressure

Lowering intraocular pressure (IOP) is the most effective treatment of glaucoma, however most of the current available glaucoma drugs target a single molecule. MicroRNAs (miRNAs) are noncoding RNAs that target a network of molecules. This study aims to investigate the role of miR-21-5p in regulating IOP and the mechanism of function. miR-21-5p mimics was topically applied to C57/BL6 mouse eyes, which significantly increased miR-21-5p expression in the conventional outflow tissue and reduced IOP by a maximum of 17.77% at 24 h after treatment. The conventional outflow facility measured by ex vivo moue eye perfusion of miR-21-5p was significantly increased by 60.14%. Moreover, miR-21-5p overexpression significantly reduced the transendothelial electrical resistance in porcine angular aqueous plexus cells. Transcriptome analysis and further quantification by Western blot and PCR revealed that SMAD7 and FGF18 might be the downstream target of miR-21-5p in regulating aqueous humor outflow. The predicted functional pathways PTEN/eNOS, RhoB/pMLC and TIMP3/MMP9 were significantly altered after miR-21-5p transfection. Dual luciferase assay verified the direct targets of miR-21-5p. In conclusion, miR-21-5p seems to regulate IOP by modulating multiple genes that are associated with aqueous humor outflow, including genes those regulating cell adhesion, cytoskeletal dynamics and extracellular matrix turnover. Thus, miR-21-5p represents a new therapeutic strategy for glaucoma and a viable alternative to existing multidrug regimens.

Optogenetic stimulation of phosphoinositides reveals a critical role of primary cilia in eye pressure regulation

Glaucoma is a group of progressive optic neuropathies that cause irreversible vision loss. Although elevated intraocular pressure (IOP) is associated with the development and progression of glaucoma, the mechanisms for its regulation are not well understood. Here, we have designed CIBN/CRY2-based optogenetic constructs to study phosphoinositide regulation within distinct subcellular compartments. We show that stimulation of CRY2-OCRL, an inositol 5-phosphatase, increases aqueous humor outflow and lowers IOP in vivo, which is caused by a calcium-dependent actin rearrangement of the trabecular meshwork cells. Phosphoinositide stimulation also rescues defective aqueous outflow and IOP in a Lowe syndrome mouse model but not in IFT88^fl/fl mice that lack functional cilia. Thus, our study is the first to use optogenetics to regulate eye pressure and demonstrate that tight regulation of phosphoinositides is critical for aqueous humor homeostasis in both normal and diseased eyes.

Oxidative stress and antioxidants in the trabecular meshwork

Glaucoma is an age-dependent disease closely related to oxidative stress and is regarded as the second leading cause of irreversible blindness worldwide. In recent years, many studies have shown that morphological and functional abnormalities of the trabecular meshwork (TM) are closely related to glaucoma, especially with respect to oxidative stress. In this review, the mechanisms of oxidative stress in the TM and treatment strategies for this condition, including strategies involving antioxidants, noncoding RNAs and exogenous compounds, are discussed. Although many questions remain to be answered, the reviewed findings provide insights for further research on oxidative stress alleviation in glaucoma and suggest new targets for glaucoma prevention.

MicroRNA Regulation of the Autotaxin-Lysophosphatidic Acid Signaling Axis

The revelation that microRNAs (miRNAs) exist within the human genome uncovered an underappreciated mechanism of gene expression. For cells to regulate expression of their genes, miRNA molecules and argonaute proteins bind to mRNAs and interfere with efficient translation of the RNA transcript. Although miRNAs have important roles in normal tissues, miRNAs may adopt aberrant functions in malignant cells depending on their classification as either a tumor suppressor or oncogenic miRNA. Within this review, the current status of miRNA regulation is described in the context of signaling through the lysophosphatidic acid receptors, including the lysophosphatidic acid-producing enzyme, autotaxin. Thus far, research has revealed miRNAs that increase in response to lysophosphatidic acid stimulation, such as miR-21, miR-30c-2-3p, and miR-122. Other miRNAs inhibit the translation of lysophosphatidic acid receptors, such as miR-15b, miR-23a, and miR200c, or proteins that are downstream of lysophosphatidic acid signaling, such as miR-146 and miR-21. With thousands of miRNAs still uncharacterized, it is anticipated that the complex regulation of lysophosphatidic acid signaling by miRNAs will continue to be elucidated. RNA-based therapeutics have entered the clinic with enormous potential in precision medicine. This exciting field is rapidly emerging and it will be fascinating to witness its expansion in scope.

Identification of Candidate miRNA Biomarkers for Glaucoma

Purpose

Glaucoma, a leading cause of blindness worldwide, often remains undetected until irreversible vision loss has occurred. Treatments focus on lowering intraocular pressure (IOP), the only modifiable and readily measurable risk factor. However, IOP can vary and does not always predict disease progression. MicroRNAs (miRNAs) are promising biomarkers. They are abundant and stable in biological fluids, including plasma and aqueous humor (AqH). We aimed to identify differentially expressed miRNAs in AqH and plasma from glaucoma, exfoliation syndrome (XFS), and control subjects.

Methods

Plasma and AqH from two ethnic cohorts were harvested from glaucoma or XFS (often associated with glaucoma, n = 33) and control (n = 31) patients undergoing elective surgery. A custom miRNA array measured 372 miRNAs. Molecular target prediction and pathway analysis were performed with Ingenuity Pathway Analysis (IPA) and DIANA bioinformatical tools.

Results

Levels of miRNAs in plasma, a readily accessible biomarker source, correlated with miRNA levels in AqH. Twenty circulating miRNAs were at least 1.5-fold higher in glaucoma or XFS patients than in controls across two ethnic cohorts: miR-4667-5p (P = 4.1 × 10⁻⁵), miR-99b-3p (P = 4.8 × 10⁻⁵), miR-637 (P = 5.1 × 10⁻⁵), miR-4490 (P = 5.7 × 10⁻⁵), miR-1253 (P = 6.0 × 10⁻⁵), miR-3190-3p (P = 3.1 × 10⁻⁴), miR-3173-3p (P = 0.001), miR-608 (P = 0.001), miR-4725-3p (P = 0.002), miR-4448 (P = 0.002), and miR-323b-5p (P = 0.002), miR-4538 (P = 0.003), miR-3913-3p (P = 0.003), miR-3159 (P = 0.003), miR-4663 (P = 0.003), miR-4767 (P = 0.003), miR-4724-5p (P = 0.003), miR-1306-5p (P = 0.003), miR-181b-3p (P = 0.004), and miR-433-3p (P = 0.004). miR-637, miR-1306-5p, and miR-3159, in combination, allowed discrimination between glaucoma patients and control subjects (AUC = 0.91 ± 0.008, sensitivity 85.0%, specificity 87.5%).

Conclusions

These results identify specific miRNAs as potential biomarkers and provide insight into the molecular processes underlying glaucoma.

Impact of pigment dispersion on trabecular meshwork cells

PURPOSE

Dysfunction of the trabecular meshwork (TM) in pigmentary glaucoma contributes to increased aqueous humor outflow resistance and intraocular pressure. In this study, we investigated the effect of pigment dispersion on trabecular meshwork cells.

METHODS

Porcine TM cells from ab interno trabeculectomy specimens were exposed to pigment dispersion, then, analyzed for changes in morphology, immunostaining, and ultrastructure. Their abilities to phagocytose migrate, and contraction was quantified. An expression microarray, using 23,937 probes, and a pathway analysis were performed.

RESULTS

Stress fiber formation was increased in the pigment dispersion group (P) (60.1 ± 0.3%, n = 10) compared to control (C) (38.4 ± 2.5%, n = 11, p < 0.001). Phagocytosis declined (number of cells with microspheres in P = 37.0 ± 1.1% and in C = 68.7 ± 1.3%, n = 3, p < 0.001) and migration was reduced after 6 h (cells within the visual field over 6 h in P = 28.0.1 ± 2.3 (n = 12) and in C = 40.6 ± 3.3 (n = 13), p < 0.01). Pigment induced contraction at 24 h onwards (p < 0.01). Microarray analysis revealed that Rho signaling was central to these responses.

CONCLUSION

Exposure of TM cells to pigment dispersion resulted in reduced phagocytosis and migration, as well as increased stress fiber formation and cell contraction. The Rho signaling pathway played a central and early role, suggesting that its inhibitors could be used as a specific intervention in treatment of pigmentary glaucoma.

Lysophosphatidic Acid Induces ECM Production via Activation of the Mechanosensitive YAP/TAZ Transcriptional Pathway in Trabecular Meshwork Cells

Purpose

Lysophosphatidic acid (LPA), a bioactive lipid, has been shown to increase resistance to aqueous humor outflow (AH) through the trabecular meshwork (TM). The molecular basis for this response of the TM to LPA, however, is not completely understood. In this study, we explored the possible involvement of mechanosensitive Yes-associated protein (YAP) and its paralog, transcriptional coactivator with PDZ-binding domain (TAZ), transcriptional activation in extracellular matrix (ECM) production by LPA-induced contractile activity in human TM cells (HTM).

Methods

The responsiveness of genes encoding LPA receptors (LPARs), LPA hydrolyzing lipid phosphate phosphatases (LPPs), and the LPA-generating autotaxin (ATX) to cyclic mechanical stretch in HTM cells, was evaluated by RT-quantitative (q)PCR. The effects of LPA and LPA receptor antagonists on actomyosin contractile activity, activation of YAP/TAZ, and levels of connective tissue growth factor (CTGF), and Cyr61 and ECM proteins in HTM cells were determined by immunoblotting, mass spectrometry, and immunofluorescence analyses.

Results

Cyclic mechanical stretch significantly increased the expression of several types of LPARs, LPP1, and ATX in HTM cells. LPA and LPA receptor–dependent contractile activity led to increases in both, the protein levels and activation of YAP/TAZ, and increased the levels of CTGF, Cyr61, α-smooth muscle actin (α–SMA), and ECM proteins in HTM cells.

Conclusions

The results of this study reveal that LPA and its receptors stimulate YAP/TAZ transcriptional activity in HTM cells by modulating cellular contractile tension, and augment expression of CTGF that in turn leads to increased production of ECM. Therefore, YAP/TAZ-induced increases in CTGF and ECM production could be an important molecular mechanism underlying LPA-induced resistance to AH outflow and ocular hypertension.

TGF-β-induced IOP elevations are mediated by RhoA in the early but not the late fibrotic phase of open angle glaucoma

Purpose

Elevations in intraocular pressure (IOP) are associated with the development of glaucoma and loss of sight. High transforming growth factor-β (TGF-β) 1 levels in the eye's anterior chamber can lead to dysfunctional contractions through RhoA signaling in trabecular meshwork (TM) cells and IOP spikes. Sustained high TGF-β levels leads to TM fibrosis and sustained increases in IOP. We investigated whether inhibiting RhoA, using a siRNA-mediated RhoA (siRhoA), controls IOP by altering TM expression of fibrosis and contractility-related proteins in a rodent model of glaucoma.

Methods

TGF-β was injected intracamerally twice a week into adult Sprague Dawley rats, and IOP was recorded with tonometry. Animals were euthanized on day 7 and 35 with TM expression of fibrosis and contractility-related proteins, as well as survival of retinal ganglion cells (RGCs) assessed with immunohistochemistry. siRNA against RhoA or enhanced green fluorescent protein (EGFP) was also injected intracamerally into select animals. Successful RhoA knockdown was determined with quantitative reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry, and the effects of the knockdown on the parameters above analyzed.

Results

TGF-β caused increased TM contractile proteins and IOP spikes by day 7, sustained increases in IOP from day 15, and TM fibrosis at day 35. siRhoA abolished the transient 7 day IOP rise but not the later sustained IOP increase (due to fibrosis). At 35 days, TGF-β-related RGC loss was not prevented with siRhoA treatment.

Conclusions

We conclude that RhoA signaling mediates the early IOP rise induced by TM cellular changes associated with contractility but not the sustained IOP elevation caused by TM fibrosis. Thus, RhoA therapies offer a clinically relevant opportunity for IOP management, likely through the modulation of TM contractility, but appear to be ineffective in the amelioration of fibrosis.

Micro RNA-1298 opposes the effects of chronic oxidative stress on human trabecular meshwork cells via targeting on EIF4E3

OBJECTIVE

This study aimed to investigate the effect and potential mechanism of miR-1298 in the progression of human trabecular meshwork (HTM) cells.

MATERIAL AND METHODS

Expression of miR-1298 was assessed by quantitative real time PCR (qRT-PCR), as well as in HTM-1 and HTM-2 cells. Mature miR-1298 mimic, miR-1298 inhibitor, and si-EIF4E3 and their corresponding controls were transfected into HTM-1 and HTM-2 to obtain stable HTM cells. Luciferase reporter assay was used to verify regulation between miR-1298 and EIF4E3. Cytotoxicity and Oxidative damage were assessed using commercial kits, and apoptosis was determined using flow cytometry. ECM and apoptosis related factors were determined using qRT-PCR and western blotting, as well as the pathway related factors.

RESULTS

The expression of miR-1298 was significantly decreased both in glaucoma and HTM cells. MiR-1298 mimic could significantly inhibit the increase of cytotoxicity, apoptosis, accumulation of carbonylated proteins and ECM induced by COS, but miR-1298 inhibitor could obviously promote the increase effects caused by COS in HTM cells. EIF4E3 was a downstream target of miR-1298. Sliced EIF4E3 could significantly inhibit the increase effects induced miR-1298 inhibitor in HTM cells under COS. The expression levels of TGF-β2 and Smad4 were significantly increased, and Wnt3a and β-cantenin were obviously decreased under COS, and miR-1298 inhibitor could markedly promote this increase effect, while sliced EIF4E3 could reverse the effect of miR-1298 under COS.

CONCLUSIONS

miR-1298 could protect HTM cells to against damage caused by COS via inhibiting TGF-β2/Smad4 pathway and activating canonical Wnt pathway.

HDAC Inhibitor-Mediated Epigenetic Regulation of Glaucoma-Associated TGFβ2 in the Trabecular Meshwork

Purpose

Elevated intraocular pressure (IOP) in primary open-angle glaucoma (POAG) results from glaucomatous damage to the trabecular meshwork (TM). The glaucoma-associated factor TGFβ2 is increased in aqueous humor and TM of POAG patients. We hypothesize that histone acetylation has a role in dysregulated TGFβ2 expression.

Methods

Protein acetylation was compared between nonglaucomatous TM (NTM) and glaucomatous TM (GTM) cells using Western immunoblotting (WB). Nonglaucomatous TM cells were treated with 10 nM thailandepsin-A (TDP-A), a potent histone deacetylase inhibitor for 4 days. Total and nuclear proteins, RNA, and nuclear protein-DNA complexes were harvested for WB, quantitative PCR (qPCR), and chromatin immunoprecipitation (ChIP) assays, respectively. Paired bovine eyes were perfused with TDP-A versus DMSO, or TDP-A versus TDP-A plus the TGFβ pathway inhibitor LY364947 for 5 to 9 days. Intraocular pressure, TM, and perfusate proteins were compared.

Results

We found increased acetylated histone 3 and total protein acetylation in the GTM cells and TDP-A treated NTM cells. Chromatin immunoprecipitation assays showed that TDP-A induced histone hyperacetylation associated with the TGFβ2 promoter. This change of acetylation significantly increased TGFβ2 mRNA and protein expression in NTM cells. In perfusion-cultured bovine eyes, TDP-A increased TGFβ2 in the perfusate as well as elevated IOP. Histologic and immunofluorescent analyses showed increased extracellular matrix and cytoskeletal proteins in the TM of TDP-A treated bovine eyes. Cotreatment with the TGFβ pathway inhibitor LY364947 blocked TDP-A–induced ocular hypertension.

Conclusions

Our results suggest that histone acetylation has an important role in increased expression of the glaucoma-associated factor TGFβ2. Histone hyperacetylation may be the initiator of glaucomatous damage to the TM.

Regulation of intraocular pressure by microRNA cluster miR-143/145

Glaucoma is a major cause of irreversible blindness worldwide. Elevated intraocular pressure (IOP), which causes optic nerve damage and retinal ganglion cell death, is the primary risk factor for blindness in glaucoma patients. IOP is controlled by the balance between aqueous humor secretion from the ciliary body (CB) and its drainage through the trabecular meshwork (TM). How microRNAs (miRs) regulate IOP and glaucoma in vivo is largely unknown. Here we show that miR-143 and miR-145 expression is enriched in the smooth muscle and trabecular meshwork in the eye. Targeted deletion of miR-143/145 in mice results in significantly reduced IOP, consistent with an ~2-fold increase in outflow facilities. However, aqueous humor production in the same mice appears to be normal based on a microbeads-induced glaucoma model. Mechanistically, we found that miR-143/145 regulates actin dynamics and the contractility of TM cells, consistent with its regulation of actin-related protein complex (ARPC) subunit 2, 3, and 5, as well as myosin light chain kinase (MLCK) in these cells. Our data establish miR-143/145 as important regulators of IOP, which may have important therapeutic implications in glaucoma.

Expression of lens-related microRNAs in transparent infant lenses and congenital cataract

AIM

To identify the expression of lens-related microRNAs (miRNAs) in the central epithelium of transparent infant lenses and congenital cataract.

METHODS

Lens-related miRNAs were retrieved from PubMed database. The expression levels of these miRNAs in transparent infant lenses and congenital cataract were determined by stem-loop reverse transcription-polymerase chain reaction (RT-PCR). miRanda algorithm was used to predict the target genes of these differentially expressed miRNAs. The target mRNA was validated.

RESULTS

Six lens-related miRNAs were retrieved from screening PubMed database. The most abundant miRNA in transparent infant lenses according to stem-loop RT-PCR was miR-184. miR-182 was up-regulated in congenital cataract. Contrarily, miR-204 and miR-124 was down-regulated. miR-204 exhibited a more significant decrease in expression than miR-124. In addition, Meis2 was predicted to be the target of miR-204 using miRanda algorithm. miR-204 mimic/antagomir transfection experiments suggested the negative correlation between the expression of miR-204 and Meis2.

CONCLUSION

The expression levels of miR-182, miR-204 and miR-124 differ between the central epithelium of transparent infant lens and congenital cataract, suggesting their involvement in the pathogenesis of congenital cataract. miR-204 may act via silencing Meis2 to regulate lens development and congenital cataract formation.

MicroRNA‑93 is overexpressed and induces apoptosis in glaucoma trabecular meshwork cells

Glaucoma is an optic neuropathy and a major cause of blindness globally. Trabecular meshwork cells are important in maintaining aqueous humor flow, the dysfunction of which tends to induce glaucoma. As important regulators of gene expression, microRNAs may be crucial in regulating trabecular meshwork cells. The present study aimed to reveal the effect of microRNA‑93 (miR‑93) on glaucoma trabecular meshwork (GTM) cell apoptosis. The expression levels of miR‑93 were compared between human trabecular meshwork (HTM) cells and GTM cells. The expression of miR‑93 was inhibited and increased by transfecting the cells with a lentivirus containing its specific inhibitor sponge and expression vector to investigate changes in GTM cell viability and apoptosis. Alterations in the protein expression of nuclear factor erythroid 2‑like 2 (NFE2L2) were also examined to elucidate the possible mechanism underlying the effects of miR‑93. The results showed a marked promotion in the expression of miR‑93 in the GTM cells, compared with the HTM cells (P<0.01). GTM cell viability was increased and its apoptosis was inhibited by transfection with the miR‑93 sponge (P<0.01 and P<0.001, respectively), whereas the overexpression of miR‑93 abrogated these effects (P<0.05 and P<0.0001, respectively). The expression of NFE2L2, a possible target of miR‑93, was promoted by transfection with the miR‑93 sponge (P<0.01) and was inhibited in the cells overexpressing miR‑93 (P<0.01). Therefore, miR‑93 was capable of inhibiting viability and inducing apoptosis of the GTM cells, which was achieved via the suppression of NFE2L2. These results elucidated the pro‑apoptotic effects of miR‑93 in GTM cells and its possible functional mechanism, providing potential therapeutic targets for the treatment of glaucoma.

Role of the Rho GTPase/Rho kinase signaling pathway in pathogenesis and treatment of glaucoma: Bench to bedside research

Glaucoma is a leading cause of irreversible blindness worldwide. Elevated intraocular pressure (IOP) is considered to be a predominant risk factor for primary open angle glaucoma, the most prevalent form of glaucoma. Although the etiological mechanisms responsible for increased IOP are not completely clear, impairment in aqueous humor (AH) drainage through the conventional or trabecular pathway is recognized to be a primary cause in glaucoma patients. Importantly, lowering of IOP has been demonstrated to reduce progression of vision loss and is a mainstay of treatment for all types of glaucoma. Currently however, there are limited therapeutic options available for lowering IOP especially as it relates to enhancement of AH outflow through the trabecular pathway. Towards addressing this challenge, bench and bedside research conducted over the course of the last decade and a half has identified the significance of inhibiting Rho kinase for lowering IOP. Rho kinase is a downstream effector of Rho GTPase signaling that regulates actomyosin dynamics in numerous cell types. Studies from several laboratories have demonstrated that inhibition of Rho kinase lowers IOP via relaxation of the trabecular meshwork which enhances AH outflow. By contrast, activation of Rho GTPase/Rho kinase signaling in the trabecular outflow pathway increases IOP by altering the contractile, cell adhesive and permeability barrier characteristics of the trabecular meshwork and Schlemm's canal tissues, and by influencing extracellular matrix production and fibrotic activity. This article, written in honor of the late David Epstein, MD, summarizes findings from both basic and clinical studies that have been instrumental for recognition of the importance of the Rho/Rho kinase signaling pathway in regulation of AH outflow, and in the development of Rho kinase inhibitors as promising IOP- lowering agents for glaucoma treatment.

A Common Variant in MIR182 Is Associated With Primary Open-Angle Glaucoma in the NEIGHBORHOOD Consortium

PURPOSE

Noncoding microRNAs (miRNAs) have been implicated in the pathogenesis of glaucoma. We aimed to identify common variants in miRNA coding genes (MIR) associated with primary open-angle glaucoma (POAG).

METHODS

Using the NEIGHBORHOOD data set (3853 cases/33,480 controls with European ancestry), we first assessed the relation between 85 variants in 76 MIR genes and overall POAG. Subtype-specific analyses were performed in high-tension glaucoma (HTG) and normal-tension glaucoma subsets. Second, we examined the expression of miR-182, which was associated with POAG, in postmortem human ocular tissues (ciliary body, cornea, retina, and trabecular meshwork [TM]), using miRNA sequencing (miRNA-Seq) and droplet digital PCR (ddPCR). Third, miR-182 expression was also examined in human aqueous humor (AH) by using miRNA-Seq. Fourth, exosomes secreted from primary human TM cells were examined for miR-182 expression by using miRNA-Seq. Fifth, using ddPCR we compared miR-182 expression in AH between five HTG cases and five controls.

RESULTS

Only rs76481776 in MIR182 gene was associated with POAG after adjustment for multiple comparisons (odds ratio [OR] = 1.23, 95% confidence interval [CI]: 1.11-1.42, P = 0.0002). Subtype analysis indicated that the association was primarily in the HTG subset (OR = 1.26, 95% CI: 1.08-1.47, P = 0.004). The risk allele T has been associated with elevated miR-182 expression in vitro. Data from ddPCR and miRNA-Seq confirmed miR-182 expression in all examined ocular tissues and TM-derived exosomes. Interestingly, miR-182 expression in AH was 2-fold higher in HTG patients than nonglaucoma controls (P = 0.03) without controlling for medication treatment.

CONCLUSIONS

Our integrative study is the first to associate rs76481776 with POAG via elevated miR-182 expression.

MicroRNAs in glaucoma and neurodegenerative diseases

MicroRNAs (miRNAs) constitute a class of short, non-coding RNAs, which have important role in post-transcriptional regulation of genes expression by base-pairing with their target messenger RNA (mRNA). In recent years, miRNAs biogenesis, gene silencing mechanism and implication in various diseases have been thoroughly investigated. Many scientific findings indicate the altered expression of specific miRNA in the brains of patients affected by neurodegenerative diseases (NDs) such as Alzheimer's disease, Parkinson's disease and Huntington disease. The progressive optic nerve neuropathy associated with changed miRNA profile was also observed during glaucoma development. This suggests that the miRNAs may have a crucial role in these disorders, contributing to the neuronal cell death. A better understanding of molecular mechanism of these disorders will open a new potential way of ND treatment. In this review, the miRNAs role in particular neurodegenerative disorders and their possible application in medicine was discussed.

Tissue-based multiphoton analysis of actomyosin and structural responses in human trabecular meshwork

The contractile trabecular meshwork (TM) modulates aqueous humor outflow resistance and intraocular pressure. The primary goal was to visualize and quantify human TM contractile state by analyzing actin polymerization (F-actin) by 2-photon excitation fluorescence imaging (TPEF) in situ. A secondary goal was to ascertain if structural extracellular matrix (ECM) configuration changed with contractility. Viable ex vivo human TM was incubated with latrunculin-A (Lat-A) or vehicle prior to Alexa-568-phalloidin labeling and TPEF. Quantitative image analysis was applied to 2-dimensional (2D) optical sections and 3D image reconstructions. After Lat-A exposure, (a) the F-actin network reorganized as aggregates; (b) F-actin-associated fluorescence intensity was reduced by 48.6% (mean; p = 0.007; n = 8); (c) F-actin 3D distribution was reduced by 68.9% (p = 0.040); (d) ECM pore cross-sectional area and volume were larger by 36% (p = 0.032) and 65% (p = 0.059) respectively and pores appeared more interconnected; (e) expression of type I collagen and elastin, key TM structural ECM proteins, were unaltered (p = 0.54); and (f) tissue viability was unchanged (p = 0.39) relative to vehicle controls. Thus Lat-A-induced reduction of actomyosin contractility was associated with TM porous expansion without evidence of reduced structural ECM protein expression or cellular viability. These important subcellular-level dynamics could be visualized and quantified within human tissue by TPEF.