An emerging treatment option for glaucoma: Rho kinase inhibitors

Simvastatin Attenuates Glucocorticoid-Induced Human Trabecular Meshwork Cell Dysfunction via YAP/TAZ Inactivation

PURPOSE

Impairment of the trabecular meshwork (TM) is the principal cause of increased outflow resistance in the glaucomatous eye. Yes-associated protein (YAP) and transcriptional coactivator with PDZ binding motif (TAZ) are emerging as potential mediators of TM cell/tissue dysfunction. Furthermore, YAP/TAZ activity was recently found to be controlled by the mevalonate pathway in non-ocular cells. Clinically used statins block the mevalonate cascade and were shown to improve TM cell pathobiology; yet, the link to YAP/TAZ signaling was not investigated. In this study, we hypothesized that simvastatin attenuates glucocorticoid-induced human TM (HTM) cell dysfunction via YAP/TAZ inactivation.

METHODS

Primary HTM cells were seeded atop or encapsulated within bioengineered extracellular matrix (ECM) hydrogels. Dexamethasone was used to induce a pathologic phenotype in HTM cells in the absence or presence of simvastatin. Changes in YAP/TAZ activity, actin cytoskeletal organization, phospho-myosin light chain levels, hydrogel contraction/stiffness, and fibronectin deposition were assessed.

RESULTS

Simvastatin potently blocked pathologic YAP/TAZ nuclear localization/activity, actin stress fiber formation, and myosin light chain phosphorylation in HTM cells. Importantly, simvastatin co-treatment significantly attenuated dexamethasone-induced ECM contraction/stiffening and fibronectin mRNA and protein levels. Sequential treatment was similarly effective but did not match clinically-used Rho kinase inhibition.

CONCLUSIONS

YAP/TAZ inactivation with simvastatin attenuates HTM cell pathobiology in a tissue-mimetic ECM microenvironment. Our data may help explain the association of statin use with a reduced risk of developing glaucoma via indirect YAP/TAZ inhibition as a proposed regulatory mechanism.

MiR-18a-5p Targets Connective Tissue Growth Factor Expression and Inhibits Transforming Growth Factor β2-Induced Trabecular Meshwork Cell Contractility

Increased trabecular meshwork (TM) cell and tissue contractility is a driver of the reduced outflow facility and elevation of intraocular pressure (IOP) associated with primary open-angle glaucoma (POAG). Connective tissue growth factor (CTGF) is an established mediator of TM cell contractility, and its expression is increased in POAG due to transforming growth factor β 2 (TGFβ2) signalling. Inhibiting CTGF upregulation using microRNA (miRNA) mimetics could represent a new treatment option for POAG. A combination of in silico predictive tools and a literature review identified a panel of putative CTGF-targeting miRNAs. Treatment of primary human TM cells with 5 ng/mL TGFβ2 for 24 h identified miR-18a-5p as a consistent responder, being upregulated in cells from five different human donors. Transfection of primary donor TM cells with 20 nM synthetic miR-18a-5p mimic reduced TGFβ2-induced CTGF protein expression, and stable lentiviral-mediated overexpression of this miRNA reduced TGFβ2-induced contraction of collagen gels. Together, these findings identify miR-18a-5p as a mediator of the TGFβ2 response and a candidate therapeutic agent for glaucoma via its ability to inhibit CTGF-associated increased TM contractility.

TGFβ2 Regulates Human Trabecular Meshwork Cell Contractility via ERK and ROCK Pathways with Distinct Signaling Crosstalk Dependent on the Culture Substrate

PURPOSE

Transforming growth factor-beta 2 (TGFβ2) is a major contributor to the pathologic changes occurring in human trabecular meshwork (HTM) cells in primary open-angle glaucoma (POAG). TGFβ2 activates extracellular-signal-regulated kinase (ERK) and Rho-associated kinase (ROCK) signaling pathways, both affecting HTM cell behavior. However, exactly how these signaling pathways converge to regulate HTM cell contractility is unclear. Here, we investigated the molecular mechanism underlying TGFβ2-induced pathologic HTM cell contractility, and the crosstalk between ERK and ROCK signaling pathways with different culture substrates.

METHODS

Hydrogels were engineered by mixing collagen type I, elastin-like polypeptide, and hyaluronic acid, each containing photoactive functional groups, followed by UV crosslinking. Primary HTM cells were seeded atop pre-formed hydrogels for comparisons with glass, or encapsulated within the hydrogels. Changes in actin cytoskeleton, extracellular matrix (ECM) production, phospho-myosin light chain (p-MLC) levels, and hydrogel contraction were assessed.

RESULTS

HTM cell morphology and filamentous (F)-actin organization were affected by the underlying culture substrates. TGFβ2 increased HTM cell contractility via ERK and ROCK signaling pathways by differentially regulating F-actin, α-smooth muscle actin (αSMA), fibronectin (FN), and p-MLC in HTM cells. ERK inhibition, even as short as 4 h, further increased TGFβ2-induced p-MLC in HTM cells on hydrogels, but not on glass. This translated into hypercontractility of HTM cell-laden hydrogels. ROCK inhibition had precisely the opposite effects and potently relaxed the TGFβ2-induced hydrogels.

CONCLUSIONS

Our data suggest that ERK signaling negatively regulates ROCK-mediated HTM cell contractility. These findings emphasize the critical importance of using tissue-mimetic ECM substrates for investigating HTM cell physiology and glaucomatous pathophysiology in vitro.

Effects of Netarsudil-Family Rho Kinase Inhibitors on Human Trabecular Meshwork Cell Contractility and Actin Remodeling Using a Bioengineered ECM Hydrogel

Interactions between trabecular meshwork (TM) cells and their extracellular matrix (ECM) are critical for normal outflow function in the healthy eye. Multifactorial dysregulation of the TM is the principal cause of elevated intraocular pressure that is strongly associated with glaucomatous vision loss. Key characteristics of the diseased TM are pathologic contraction and actin stress fiber assembly, contributing to overall tissue stiffening. Among first-line glaucoma medications, the Rho-associated kinase inhibitor (ROCKi) netarsudil is known to directly target the stiffened TM to improve outflow function via tissue relaxation involving focal adhesion and actin stress fiber disassembly. Yet, no in vitro studies have explored the effect of netarsudil on human TM (HTM) cell contractility and actin remodeling in a 3D ECM environment. Here, we use our bioengineered HTM cell-encapsulated ECM hydrogel to investigate the efficacy of different netarsudil-family ROCKi compounds on reversing pathologic contraction and actin stress fibers. Netarsudil and all related experimental ROCKi compounds exhibited significant ROCK1/2 inhibitory and focal adhesion disruption activities. Furthermore, all ROCKi compounds displayed potent contraction-reversing effects on HTM hydrogels upon glaucomatous induction in a dose-dependent manner, relatively consistent with their biochemical/cellular inhibitory activities. At their tailored EC50 levels, netarsudil-family ROCKi compounds exhibited distinct effect signatures of reversing pathologic HTM hydrogel contraction and actin stress fibers, independent of the cell strain used. Netarsudil outperformed the experimental ROCKi compounds in support of its clinical status. In contrast, at uniform EC50-levels using netarsudil as reference, all ROCKi compounds performed similarly. Collectively, our data suggest that netarsudil exhibits high potency to rescue HTM cell pathobiology in a tissue-mimetic 3D ECM microenvironment, solidifying the utility of our bioengineered hydrogel model as a viable screening platform to further our understanding of TM pathophysiology in glaucoma.

The Dual Effect of Rho-Kinase Inhibition on Trabecular Meshwork Cells Cytoskeleton and Extracellular Matrix in an In Vitro Model of Glaucoma

The trabecular meshwork (TM) is the main site of drainage of the aqueous humor, and its dysfunction leads to intraocular pressure elevation, which is one of the main risk factors of glaucoma. We aimed to compare the effects on cytoskeleton organization and extracellular matrix (ECM) of latanoprost (LT) and a Rho-kinase inhibitor (ROCKi) on a transforming growth factor beta2 (TGF-β2)-induced glaucoma-like model developed from primary culture of human TM cells (pHTMC). The TGF-β2 stimulated pHTMC were grown and incubated with LT or a ROCKi (Y-27632) for 24 h. The expression of alpha-smooth muscle actin (αSMA) and fibronectin (FN), and phosphorylation of the myosin light chain (MLC-P) and Cofilin (Cofilin-P) were evaluated using immunofluorescence and Western blot. The architectural modifications were studied in a Matrigel^TM 3D culture. TGF-β2 increased the expression of αSMA and FN in pHTMC and modified the cytoskeleton with cross-linked actin network formation. LT did not alter the expression of αSMA but decreased FN deposition. The ROCKi decreased TGF-β2-induced αSMA and FN expression, as well as MLC-P and Cofilin-P, and stimulated the cells to recover a basal cytoskeletal arrangement. In the preliminary 3D study, pHTMC organized in a mesh conformation showed the widening of the TM under the effect of Y-27632. By simultaneously modifying the organization of the cytoskeleton and the ECM, with fibronectin deposition and overexpression, TGF-β2 reproduced the trabecular degeneration described in glaucoma. The ROCKi was able to reverse the TGF-β2-induced cytoskeletal and ECM rearrangements. LT loosened the extracellular matrix but had no action on the stress fibers.

Exploring a Novel Fasudil-Phospholipid Complex Formulated as Liposomal Thermosensitive in situ Gel for Glaucoma

Purpose

Methods

Results

Conclusion

Genetic Markers PLEKHA7, ABCC5, and KALRN Are Not Associated With the Progression of Primary Angle Closure Glaucoma (PACG) in Malays

Introduction PLEKHA7, ABCC5, and KALRN have been identified as susceptible genetic markers related to glaucoma. We aimed to investigate the association between the identified susceptible genetic markers PLEKHA7 rs11024102, ABCC5 rs17217796, and KALRN rs1392912 in the progression of primary angle-closure glaucoma (PACG) in Malay patients. Methods For this study, 163 Malay patients with PACG were recruited from April 2015 to April 2017 at Hospital Universiti Sains Malaysia and Hospital Raja Perempuan Zainab II, Kota Bharu. Venesection was performed. DNA was extracted using a commercial DNA extraction kit. The primer was optimized for rs11024102, rs17217796, and rs1392912 of the PLEKHA7, ABCC5, and KALRN genes, respectively. Polymerase chain reaction (PCR) was performed, and PCR products were purified. A DNA sequencer was used to identify polymorphisms. Progression was based on the agreement between the Advanced Glaucoma Intervention Study scoring system and the Hodapp-Parrish and Anderson staging system. The scoring was conducted on two reliable consecutive Humphrey visual fields (HVFs) during the recruitment period and two baseline HVFs obtained when the diagnosis was made. Based on the scoring, patients were grouped into progressed and non-progressed. A chi-square test was used to analyze the association between the genetic markers and the progression of PACG. Results One hundred and sixty-three Malay patients with PACG (58 men and 105 women) were recruited. Twenty-nine patients (18%) had visual field progression of PACG after a mean (SD) follow-up of 6.0 (1.0) years. The minor allele frequencies for PLEKHA7 rs11024102 (G/A), ABCC5 rs17217796 (C/G), and KALRN rs1392912 (A/G) were 0.44, 0.08, and 0.48, respectively. We found that rs11024102 (p=0.828), rs17217796 (p=0.865), and rs1392912 (p=0.684) were not associated with PACG progression in the Malay patients. Conclusion Although PLEKHA7 and ABCC5 were found to be genetic markers associated with the risk of PACG, they played no roles in PACG progression in the Malay population. Moreover, KALRN was not significantly associated with PACG progression. Other susceptible genetic markers may be responsible for PACG progression.

Status of Rho kinase inhibitors in glaucoma therapeutics-an overview

Medical management remains the cornerstone of glaucoma management despite advances in the surgical or laser procedures. After a leap of almost two decades of the advent of prostaglandin analogues, recently a new class of drug, Rho kinase (ROCK) inhibitors, has come to limelight because of their varied therapeutic potential in different clinical conditions of eye, especially glaucoma. Their efficacy of lowering intraocular pressure (IOP) by virtue of an entirely different mechanism of decreasing outflow resistance has ignited a series of clinical trials evaluating their potential as monotherapy or as adjunct to existing antiglaucoma medications, and three of them ripasudil, netarsudil and roclatan have even been approved for clinical use in the recent past. There are evidences suggesting their beneficial effects in glaucoma patients even via non-IOP-dependent mechanisms like neuroprotection by improving blood flow to the optic nerve and increasing ganglion cell survival. They can even act as antifibrotic agents and reduce bleb scarring after glaucoma surgery. Hence, their effective role in glaucomatous optic neuropathy is multifaceted primary being improved drainage through the conventional pathway. On the other hand, certain local adverse effects like conjunctival hyperaemia have been reported in substantial proportion of patients, while some others like blepharitis, subconjunctival haemorrhages and cornea verticillata constitute less common side effects. The purpose of this review is to summarize the discovery, evolution and recent update of clinical trials on Rho kinase inhibitors as antiglaucoma medicine and to delineate their role in existing management protocol.

Myocilin-associated Glaucoma: A Historical Perspective and Recent Research Progress

Glaucoma a debilitating disease, is globally the second most common kind of permanent blindness. Primary open-angle glaucoma (POAG) is its most prevalent form and is often linked with alterations in the myocilin gene (MYOC). MYOC encodes the myocilin protein, which is expressed throughout the body, but primarily in trabecular meshwork (TM) tissue in the eyes. TM is principally involved in regulating intraocular pressure (IOP), and elevated IOP is the main risk factor associated with glaucoma. The myocilin protein's function remains unknown; however, mutations compromise its folding and processing inside TM cells, contributing to the glaucoma phenotype. While glaucoma is a complex disease with various molecules and factors as contributing causes, the role played by myocilin has been the most widely studied. The current review describes the present understanding of myocilin and its association with glaucoma and aims to shift the focus toward developing targeted therapies for treating glaucoma patients with variations in MYOC.

Design, synthesis and biological evaluations of a long-acting, hypoxia-activated prodrug of fasudil, a ROCK inhibitor, to reduce its systemic side-effects

ROCK, one of the downstream regulators of Rho, controls actomyosin cytoskeleton organization, stress fiber formation, smooth muscle contraction, and cell migration. ROCK plays an important role in the pathologies of cerebral and coronary vasospasm, hypertension, cancer, and arteriosclerosis. Pharmacological-induced systemic inhibition of ROCK affects both the pathological and physiological functions of Rho-kinase, resulting in hypotension, increased heart rate, decreased lymphocyte count, and eventually cardiovascular collapse. To overcome the adverse effects of systemic ROCK inhibition, we developed a bioreductive prodrug of a ROCK inhibitor, fasudil, that functions selectively under hypoxic conditions. By masking fasudil's active site with a bioreductive 4-nitrobenzyl group, we synthesized a prodrug of fasudil that is inactive in normoxia. Reduction of the protecting group initiated by hypoxia reveals an electron-donating substituent that leads to fragmentation of the parent molecule. Under normoxia the fasudil prodrug displayed significantly reduced activity against ROCK compared to its parent compound, but under severe hypoxia the prodrug was highly effective in suppressing ROCK activity. Under hypoxia the prodrug elicited an antiproliferative effect on disease-afflicted pulmonary arterial smooth muscle cells and pulmonary arterial endothelial cells. The prodrug displayed a long plasma half-life, remained inactive in the blood, and produced no drop in systemic blood pressure when compared with fasudil-treated controls. Due to its selective nature, our hypoxia-activated fasudil prodrug could be used to treat diseases where tissue-hypoxia or hypoxic cells are the pathological basis of the disease.

Evolution of therapies for the corneal endothelium: past, present and future approaches

Corneal endothelial diseases are leading indications for corneal transplantations. With significant advancement in medical science and surgical techniques, corneal transplant surgeries are now increasingly effective at restoring vision in patients with corneal diseases. In the last 15 years, the introduction of endothelial keratoplasty (EK) procedures, where diseased corneal endothelium (CE) are selectively replaced, has significantly transformed the field of corneal transplantation. Compared to traditional penetrating keratoplasty, EK procedures, namely Descemet's stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK), offer faster visual recovery, lower immunological rejection rates, and improved graft survival. Although these modern techniques can achieve high success, there are fundamental impediments to conventional transplantations. A lack of suitable donor corneas worldwide restricts the number of transplants that can be performed. Other barriers include the need for specialized expertise, high cost, and risks of graft rejection or failure. Research is underway to develop alternative treatments for corneal endothelial diseases, which are less dependent on the availability of allogeneic tissues - regenerative medicine and cell-based therapies. In this review, an overview of past and present transplantation procedures used to treat corneal endothelial diseases are described. Potential novel therapies that may be translated into clinical practice will also be presented.

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.

Management of glaucoma in pregnancy - balancing safety with efficacy

Glaucoma and pregnancy is an uncommon combination, but it constitutes a very challenging situation for the treating doctor. The challenge is not only controlling the intraocular pressure and preventing glaucoma progression in the mother, but also having to deal with her mental stress and anxiety regarding the safety of her child. The situation is further worsened by the lack of definite guidelines as to how to deal with such patients. Relative rarity of glaucoma in this population restricts any large prospective randomized clinical trials or any large systematic studies. Moreover, none of the existing anti-glaucoma medications is absolutely safe in pregnancy. Current practice patterns depend on some case reports, a few observational studies and a few animal studies that attempt at determining the safety and efficacy of the available medicines. These are then prescribed on the basis of their relative safety in any particular stage of pregnancy or lactation. Newer medications that were released recently in 2018, such as Vyzulta and Rhopressa, presently have limited data to support their safety for use during pregnancy. Laser trabeculoplasty, conventional filtration surgery (of course without anti-metabolites), and minimally invasive glaucoma surgery represent a few non-pharmacological management options. Surgical procedures such as trabeculectomy and tube-shunts or collagen matrix implants, and newer minimally invasive glaucoma surgery procedures such as the gelatin stents are currently being explored and may prove to be viable solutions for severe glaucoma during pregnancy, although they too have their own inherent drawbacks. Management of glaucoma during pregnancy and lactation requires careful consideration of the disease status, gestational stage, US Food and Drug Administration classification and guidelines, and potential benefits and limitations of the various therapeutic modalities. This review focuses on the importance of a multidisciplinary team approach, starting with preconception planning and counseling, determining the treatment options depending on the stage of glaucoma and of pregnancy, and emphasizes the involvement of the patients, their obstetrician, and pediatrician through active discussion regarding the various medical, laser, or surgical modalities currently available or under exploration for use during pregnancy and lactation. The ultimate aim is to achieve an optimal balance between the risks and benefits of any type of intervention, and to customize treatment on an individual basis in order to achieve the best outcomes for both mother and fetus.

A 3D Model of Human Trabecular Meshwork for the Research Study of Glaucoma

Glaucoma is a multifactorial syndrome in which the development of pro-apoptotic signals are the causes for retinal ganglion cell (RGC) loss. Most of the research progress in the glaucoma field have been based on experimentally inducible glaucoma animal models, which provided results about RGC loss after either the crash of the optic nerve or IOP elevation. In addition, there are genetically modified mouse models (DBA/2J), which make the study of hereditary forms of glaucoma possible. However, these approaches have not been able to identify all the molecular mechanisms characterizing glaucoma, possibly due to the disadvantages and limits related to the use of animals. In fact, the results obtained with small animals (i.e., rodents), which are the most commonly used, are often not aligned with human conditions due to their low degree of similarity with the human eye anatomy. Although the results obtained from non-human primates are in line with human conditions, they are little used for the study of glaucoma and its outcomes at cellular level due to their costs and their poor ease of handling. In this regard, according to at least two of the 3Rs principles, there is a need for reliable human-based in vitro models to better clarify the mechanisms involved in disease progression, and possibly to broaden the scope of the results so far obtained with animal models. The proper selection of an in vitro model with a "closer to in vivo" microenvironment and structure, for instance, allows for the identification of the biomarkers involved in the early stages of glaucoma and contributes to the development of new therapeutic approaches. This review summarizes the most recent findings in the glaucoma field through the use of human two- and three-dimensional cultures. In particular, it focuses on the role of the scaffold and the use of bioreactors in preserving the physiological relevance of in vivo conditions of the human trabecular meshwork cells in three-dimensional cultures. Moreover, data from these studies also highlight the pivotal role of oxidative stress in promoting the production of trabecular meshwork-derived pro-apoptotic signals, which are one of the first marks of trabecular meshwork damage. The resulting loss of barrier function, increase of intraocular pressure, as well the promotion of neuroinflammation and neurodegeneration are listed as the main features of glaucoma. Therefore, a better understanding of the first molecular events, which trigger the glaucoma cascade, allows the identification of new targets for an early neuroprotective therapeutic approach.

Prolonged treatment with Y-27632 promotes the senescence of primary human dermal fibroblasts by increasing the expression of IGFBP-5 and transforming them into a CAF-like phenotype

The Rho-kinases (ROCK) inhibitor Y-27632 has been shown to promote the growth of epidermal cells, however, its potential effects on human dermal fibroblasts (HDFs) need to be clarified. Here we show that prolonged treatment of HDFs with Y-27632 decreased their growth by inducing senescence, which was associated with induction of the senescence markers p16 and p21, and downmodulation of the ERK pathways. The senescent HDFs induced by Y-27632 acquired a cancer-associated-fibroblast (CAF)-like phenotype to promote squamous cell carcinoma (SCC) cell growth in vitro. Expression of a newly identified target of Y-27632 by RNA-seq, insulin growth factor binding protein 5 (IGFBP-5), was dramatically increased after 24 h of treatment with Y-27632. Adding recombinant IGFBP-5 protein to the culture medium produced similar phenotypes of HDFs as did treatment with Y-27632, and knockdown of IGFBP-5 blocked the Y-27632-induced senescence. Furthermore, Y-27632 induced the expression of an IGFBP-5 upstream gene, GATA4, and knockdown of GATA4 also reduced the Y-27632-induced senescence. In summary, these results demonstrate for the first time that Y-27632 promotes cellular senescence in primary HDFs by inducing the expression of IGFBP-5 and that prolonged treatment with Y-27632 potentially transforms primary HDFs into CAF-like cells.

[Medicated prevention of scarring after glaucoma surgery]

Modulation of wound healing is one of the main challenges in glaucoma surgery. Modern antiproliferative agents used to reduce postoperative scarring are either insufficiently effective or inadequate in terms of safety. In the search for novel agents devoid of such drawbacks, specialists directed their attention to selective inhibitors of proinflammatory cytokines and growth factors. The article reviews pathophysiologic basis of wound healing, characteristics of inflammatory mediators affecting fibroblast proliferation and scarring, and provides description of the currently used and new, potentially promising antiproliferative agents.

Fasudil Loaded PLGA Microspheres as Potential Intravitreal Depot Formulation for Glaucoma Therapy

Rho-associated protein kinase (ROCK) inhibitors allow for causative glaucoma therapy. Unfortunately, topically applied ROCK inhibitors suffer from high incidence of hyperemia and low intraocular bioavailability. Therefore, we propose the use of poly (lactide-co-glycolide) (PLGA) microspheres as a depot formulation for intravitreal injection to supply outflow tissues with the ROCK inhibitor fasudil over a prolonged time. Fasudil-loaded microspheres were prepared by double emulsion solvent evaporation technique. The chemical integrity of released fasudil was confirmed by mass spectrometry. The biological activity was measured in cell-based assays using trabecular meshwork cells (TM cells), Schlemm’s canal cells (SC cells), fibroblasts and adult retinal pigment epithelium cells (ARPE-19). Cellular response to fasudil after its diffusion through vitreous humor was investigated by electric cell-substrate impedance sensing. Microspheres ranged in size from 3 to 67 µm. The release of fasudil from microspheres was controllable and sustained for up to 45 days. Released fasudil reduced actin stress fibers in TM cells, SC cells and fibroblasts. Decreased collagen gel contraction provoked by fasudil was detected in TM cells (~2.4-fold), SC cells (~1.4-fold) and fibroblasts (~1.3-fold). In addition, fasudil readily diffused through vitreous humor reaching its target compartment and eliciting effects on TM cells. No negative effects on ARPE-19 cells were observed. Since fasudil readily diffuses through the vitreous humor, we suggest that an intravitreal drug depot of ROCK inhibitors could significantly improve current glaucoma therapy particularly for patients with comorbid retinal diseases.

Rho-kinase (ROCK) Inhibitors - A Neuroprotective Therapeutic Paradigm with a Focus on Ocular Utility

BACKGROUND

Glaucoma is a progressive optic neuropathy causing visual impairment and Retinal Ganglionic Cells (RGCs) death gradually posing a need for neuroprotective strategies to minimize the loss of RGCs and visual field. It is recognized as a multifactorial disease, Intraocular Pressure (IOP) being the foremost risk factor. ROCK inhibitors have been probed for various possible indications, such as myocardial ischemia, hypertension, kidney diseases. Their role in neuroprotection and neuronal regeneration has been suggested to be of value in the treatment of neurological diseases, like spinal-cord injury, Alzheimer's disease and multiple sclerosis but recently Rho-associated Kinase inhibitors have been recognized as potential antiglaucoma agents.

EVIDENCE SYNTHESIS

Rho-Kinase is a serine/threonine kinase with a kinase domain which is constitutively active and is involved in the regulation of smooth muscle contraction and stress fibre formation. Two isoforms of Rho-Kinase, ROCK-I (ROCK β) and ROCK-II (ROCK α) have been identified. ROCK II plays a pathophysiological role in glaucoma and hence the inhibitors of ROCK may be beneficial to ameliorate the vision loss. These inhibitors decrease the intraocular pressure in the glaucomatous eye by increasing the aqueous humour outflow through the trabecular meshwork pathway. They also act as anti-scarring agents and hence prevent post-operative scarring after the glaucoma filtration surgery. Their major role involves axon regeneration by increasing the optic nerve blood flow which may be useful in treating the damaged optic neurons. These drugs act directly on the neurons in the central visual pathway, interrupting the RGC apoptosis and therefore serve as a novel pharmacological approach for glaucoma neuroprotection.

CONCLUSION

Based on the results of high-throughput screening, several Rho kinase inhibitors have been designed and developed comprising of diverse scaffolds exhibiting Rho kinase inhibitory activity from micromolar to subnanomolar ranges. This diversity in the scaffolds with inhibitory potential against the kinase and their SAR development will be intricated in the present review. Ripasudil is the only Rho kinase inhibitor marketed to date for the treatment of glaucoma. Another ROCK inhibitor AR-13324 has recently passed the clinical trials whereas AMA0076, K115, PG324, Y39983 and RKI-983 are still under trials. In view of this, a detailed and updated account of ROCK II inhibitors as the next generation therapeutic agents for glaucoma will be discussed in this review.

Ocular Disease Therapeutics: Design and Delivery of Drugs for Diseases of the Eye

The ocular drug discovery field has evidenced significant advancement in the past decade. The FDA approvals of Rhopressa, Vyzulta, and Roclatan for glaucoma, Brolucizumab for wet age-related macular degeneration (wet AMD), Luxturna for retinitis pigmentosa, Dextenza (0.4 mg dexamethasone intracanalicular insert) for ocular inflammation, ReSure sealant to seal corneal incisions, and Lifitegrast for dry eye represent some of the major developments in the field of ocular therapeutics. A literature survey also indicates that gene therapy, stem cell therapy, and target discovery through genomic research represent significant promise as potential strategies to achieve tissue repair or regeneration and to attain therapeutic benefits in ocular diseases. Overall, the emergence of new technologies coupled with first-in-class entries in ophthalmology are highly anticipated to restructure and boost the future trends in the field of ophthalmic drug discovery. This perspective focuses on various aspects of ocular drug discovery and the recent advances therein. Recent medicinal chemistry campaigns along with a brief overview of the structure-activity relationships of the diverse chemical classes and developments in ocular drug delivery (ODD) are presented.

Treatment of glaucoma by prostaglandin agonists and beta-blockers in combination directly reduces pro-fibrotic gene expression in trabecular meshwork

Prostaglandin analogues (PG), beta-blockers (BB) or their combination (PG+BB) are used primarily to reduce the intraocular pressure (IOP) pathologically associated with glaucoma. Since, fibrosis of the trabecular meshwork (TM) is a major aetiological factor in glaucoma, we studied the effect of these drugs on fibrosis-associated gene expression in TM of primary glaucoma patients. In the present study, TM and iris of primary open-angle (n = 32) and angle-closure (n = 37) glaucoma patients were obtained surgically during trabeculectomy and categorized based on the type of IOP-lowering medications use as PG, BB or PG+BB. mRNA expression of pro-fibrotic and anti-fibrotic genes was quantified using qPCR in these tissues. The gene expression levels of pro-fibrotic genes were significantly lower in PG+BB as compared to other groups. These observations and underlying signalling validated in vitro in human TM cells also showed reduced fibrotic gene and protein expression levels following PG+BB treatment. In conclusion, it is observed that PG+BB combination rather than their lone use renders a reduced fibrotic status in TM. This further suggests that IOP-lowering medications, in combination, would also modulate fibrosis-associated molecular changes in the TM, which may be beneficial for maintaining aqueous out-flow mechanisms over the clinical treatment duration.

Fixed-Dose Combination of Netarsudil and Latanoprost in Ocular Hypertension and Open-Angle Glaucoma: Pooled Efficacy/Safety Analysis of Phase 3 MERCURY-1 and -2

INTRODUCTION

New open-angle glaucoma (OAG) and ocular hypertension (OHT) therapies that reduce treatment burden and improve outcomes relative to currently available agents are needed. Netarsudil, a novel Rho kinase inhibitor approved by the US Food and Drug Administration, reduces intraocular pressure (IOP) by increasing trabecular outflow. Two phase 3 superiority studies compared a fixed-dose combination (FDC) of netarsudil and the prostaglandin latanoprost with each active component for IOP-lowering efficacy.

METHODS

Pooled efficacy and safety data were analyzed from MERCURY-1 and -2 studies in patients with OAG or OHT. Patients instilled one drop of netarsudil (0.02%)/latanoprost (0.005%) FDC (n = 483), netarsudil (0.02%, n = 499), or latanoprost (0.005%, n = 486) into each eye once-daily between 20:00 and 22:00. IOP was measured at 08:00, 10:00, and 16:00 at weeks 2, 6, and the primary endpoint at month 3.

RESULTS

Baseline mean diurnal IOP was 23.6, 23.6, and 23.5 mmHg in netarsudil/latanoprost FDC, netarsudil, and latanoprost groups, respectively. Mean diurnal IOP in each group was 15.3, 18.1, and 17.5 mmHg at week 2, 15.7, 18.4, and 17.4 mmHg at week 6, and 15.8, 18.4, and 17.3 mmHg at week 12. The netarsudil/latanoprost FDC met criteria for superiority compared with each active component (p < 0.0001 for all nine time points). At month 3, among patients randomized to netarsudil/latanoprost FDC or latanoprost, 58.4% vs 37.3% (p < 0.0001) achieved IOP ≤ 16 mmHg. Among patients randomized to netarsudil/latanoprost FDC or netarsudil or latanoprost, 30.9% vs 5.9% (p < 0.0001) vs 8.5% (p < 0.0001) achieved at least a 40% reduction from baseline in mean diurnal IOP. Pooled safety results were consistent with individual MERCURY studies.

CONCLUSION

Once-daily netarsudil/latanoprost FDC produced statistically significant and clinically relevant reductions in mean IOP that were statistically superior to IOP reductions achieved by netarsudil and latanoprost monotherapy. Results of the pooled efficacy and safety analyses were consistent with the individual studies.

TRIAL REGISTRATION

ClinicalTrials.gov identifiers, NCT02558400 and NCT02674854.

Effects of 0.4% ripasudil hydrochloride hydrate on morphological changes in rabbit eyes

We evaluated the cellular structure changes after continuous use of ripasudil hydrochloride hydrate in rabbit eyes which might affect its own efficacy and adverse effects. Two pigmented Dutch rabbits and 1 Japanese white rabbit were instilled with 0.4% ripasudil hydrochloride hydrate to the left eye twice daily. The right eye was observed as the control. Both eyes of all 3 rabbits were then enucleated for histopathologic examination by light and electron microscope at 1mo in 1 of the pigmented Dutch rabbits, 3mo in the other pigmented Dutch rabbit, and in the Japanese white rabbit after instillation. Microscopic observations showed increase intercellular space in trabecular meshwork, ciliary body, and iris stoma, increase pigmented granule number and size in iris epithelial cells, and decrease actin filament in iris muscle fiber cells. Consequently, ripasudil hydrochloride hydrate decreases the intraocular pressure by improving the conventional outflow and may also facilitate the unconventional outflow via intercellular space widening without serious side effects.

The future of canine glaucoma therapy

Canine glaucoma is a group of disorders that are generally associated with increased intraocular pressure (IOP) resulting in a characteristic optic neuropathy. Glaucoma is a leading cause of irreversible vision loss in dogs and may be either primary or secondary. Despite the growing spectrum of medical and surgical therapies, there is no cure, and many affected dogs go blind. Often eyes are enucleated because of painfully high, uncontrollable IOP. While progressive vision loss due to primary glaucoma is considered preventable in some humans, this is mostly not true for dogs. There is an urgent need for more effective, affordable treatment options. Because newly developed glaucoma medications are emerging at a very slow rate and may not be effective in dogs, work toward improving surgical options may be the most rewarding approach in the near term. This Viewpoint Article summarizes the discussions and recommended research strategies of both a Think Tank and a Consortium focused on the development of more effective therapies for canine glaucoma; both were organized and funded by the American College of Veterinary Ophthalmologists Vision for Animals Foundation (ACVO-VAF). The recommendations consist of (a) better understanding of disease mechanisms, (b) early glaucoma diagnosis and disease staging, (c) optimization of IOP-lowering medical treatment, (d) new surgical therapies to control IOP, and (e) novel treatment strategies, such as gene and stem cell therapies, neuroprotection, and neuroregeneration. In order to address these needs, increases in research funding specifically focused on canine glaucoma are necessary.

Trabecular Meshwork Regeneration - A Potential Treatment for Glaucoma

Purpose

In this review, we overview the pathophysiology of primary open-angle glaucoma as it relates to the trabecular meshwork (TM), exploring modes of TM dysfunction and regeneration via stem cell therapies.

Recent Findings

Stem cells from a variety of sources, including trabecular meshwork, mesenchymal, adipose and induced pluripotent stem cells, have shown the potential to differentiate into TM cells in vitro or in vivo and to regenerate the TM in vivo, lowering intraocular pressure (IOP) and reducing glaucomatous retinal ganglion cell damage.

Summary

Stem cell therapies for TM regeneration provide a robust and promising suite of treatments for eventual lowering of IOP and prevention of glaucomatous vision loss in humans in the future. Further investigation into stem cell homing mechanisms and the safety of introducing these cells into human anterior chamber, for instance, are required before clinical applications in treating glaucoma patients.

Probe Sensitivity to Cortical versus Intracellular Cytoskeletal Network Stiffness

In development, wound healing, and pathology, cell biomechanical properties are increasingly recognized as being of central importance. To measure these properties, experimental probes of various types have been developed, but how each probe reflects the properties of heterogeneous cell regions has remained obscure. To better understand differences attributable to the probe technology, as well as to define the relative sensitivity of each probe to different cellular structures, here we took a comprehensive approach. We studied two cell types-Schlemm's canal endothelial cells and mouse embryonic fibroblasts (MEFs)-using four different probe technologies: 1) atomic force microscopy (AFM) with sharp tip, 2) AFM with round tip, 3) optical magnetic twisting cytometry (OMTC), and 4) traction microscopy (TM). Perturbation of Schlemm's canal cells with dexamethasone treatment, α-actinin overexpression, or RhoA overexpression caused increases in traction reported by TM and stiffness reported by sharp-tip AFM as compared to corresponding controls. By contrast, under these same experimental conditions, stiffness reported by round-tip AFM and by OMTC indicated little change. Knockout (KO) of vimentin in MEFs caused a diminution of traction reported by TM, as well as stiffness reported by sharp-tip and round-tip AFM. However, stiffness reported by OMTC in vimentin-KO MEFs was greater than in wild type. Finite-element analysis demonstrated that this paradoxical OMTC result in vimentin-KO MEFs could be attributed to reduced cell thickness. Our results also suggest that vimentin contributes not only to intracellular network stiffness but also cortex stiffness. Taken together, this evidence suggests that AFM sharp tip and TM emphasize properties of the actin-rich shell of the cell, whereas round-tip AFM and OMTC emphasize those of the noncortical intracellular network.

Glaucoma - Next Generation Therapeutics: Impossible to Possible

The future of next generation therapeutics for glaucoma is strong. The recent approval of two novel intraocular pressure (IOP)-lowering drugs with distinct mechanisms of action is the first in over 20 years. However, these are still being administered as topical drops. Efforts are underway to increase patient compliance and greater therapeutic benefits with the development of sustained delivery technologies. Furthermore, innovations from biologics- and gene therapy-based therapeutics are being developed in the context of disease modification, which are expected to lead to more permanent therapies for patients. Neuroprotection, including the preservation of retinal ganglion cells (RGCs) and optic nerve is another area that is actively being explored for therapeutic options. With improvements in imaging technologies and determination of new surrogate clinical endpoints, the therapeutic potential for translation of neuroprotectants is coming close to clinical realization. This review summarizes the aforementioned topics and other related aspects.

RKI-1447, a Rho kinase inhibitor, causes ocular hypotension, actin stress fiber disruption, and increased phagocytosis

PURPOSE

This study investigated the hypotensive effect of RKI-1447, a Rho kinase inhibitor, in a porcine ex vivo pigmentary glaucoma model.

METHODS

Twenty-eight porcine anterior chambers were perfused with medium supplemented with 1.67 × 10⁷ pigment particles/ml for 48 h before treatment with RKI-1447 (n = 16) or vehicle control (n = 12). Intraocular pressure (IOP) was recorded and outflow facility was calculated. Primary trabecular meshwork cells were exposed to RKI-1447 or vehicle control; effects on the cytoskeleton, motility, and phagocytosis were evaluated.

RESULT

Compared to baseline, the perfusion of pigment caused a significant increase in IOP in the RKI-1447 group (P = 0.003) at 48 h. Subsequent treatment with RKI-1447 significantly reduced IOP from 20.14 ± 2.59 to 13.38 ± 0.91 mmHg (P = 0.02). Pigment perfusion reduced the outflow facility from 0.27 ± 0.03 at baseline to 0.18 ± 0.02 at 48 h (P < 0.001). This was partially reversed with RKI-1447. RKI-1447 caused no apparent histological changes in the micro- or macroscopic TM appearance. RKI-1447-treated primary TM cells showed significant disruption of the actin cytoskeleton both in the presence and absence of pigment (P < 0.001) but no effect on TM migration was observed. Pigment-treated TM cells exhibited a reduction in TM phagocytosis, which RKI-1447 reversed.

CONCLUSION

RKI-1447 significantly reduces IOP by disrupting TM stress fibers and increasing TM phagocytosis. These features may make it useful for the treatment of secondary glaucomas with an increased phagocytic load.

The Role of Endogenous Neuroprotective Mechanisms in the Prevention of Retinal Ganglion Cells Degeneration

Retinal neurons are not able to undergo spontaneous regeneration in response to damage. A variety of stressors, i.e., UV radiation, high temperature, ischemia, allergens, and others, induce reactive oxygen species production, resulting in consecutive alteration of stress-response gene expression and finally can lead to cell apoptosis. Neurons have developed their own endogenous cellular protective systems. Some of them are preventing cell death and others are allowing functional recovery after injury. The high efficiency of these mechanisms is crucial for cell survival. In this review we focus on the contribution of the most recently studied endogenous neuroprotective factors involved in retinal ganglion cell (RGC) survival, among which, neurotrophic factors and their signaling pathways, processes regulating the redox status, and different pathways regulating cell death are the most important. Additionally, we summarize currently ongoing clinical trials for therapies for RGC degeneration and optic neuropathies, including glaucoma. Knowledge of the endogenous cellular protective mechanisms may help in the development of effective therapies and potential novel therapeutic targets in order to achieve progress in the treatment of retinal and optic nerve diseases.

Rho-Kinase Inhibition Reduces Myofibroblast Differentiation and Proliferation of Scleral Fibroblasts Induced by Transforming Growth Factor β and Experimental Glaucoma

Purpose

We evaluated prevention of transforming growth factor β (TGFβ)–induced transdifferentiation of cultured scleral fibroblasts to myofibroblasts by rho-associated protein kinase (ROCK) inhibitors. Additionally, we tested whether local delivery of ROCK inhibitors reduced scleral fibroblast proliferation in response to chronic intraocular pressure (IOP) elevation.

Methods

Primary human peripapillary sclera (PPS) fibroblasts were cultured and treated with TGFβ to induce myofibroblast transdifferentiation, as determined by immunoblot assessment of α smooth muscle actin (SMA) levels and collagen gel contraction. Cells were treated with the ROCK inhibitors Y27632, fasudil, and H1152 before TGFβ treatment. ROCK activity in TGFβ-treated fibroblasts and sclera from ocular hypertensive mice was assessed by measuring phosphorylation of the ROCK substrate MYPT1 at Thr696. Fibroblast proliferation following IOP elevation and ROCK inhibitor treatment was assessed by an enzyme-linked immunosorbent (ELISA) assay.

Results

ROCK inhibitors H1152 (10μM), Y27632 (10 μM), and fasudil (5μM) reduced SMA expression 72%, 85%, and 68%, respectively. Collagen gel contraction was reduced by 36% (P < 0.001), 27% (P = 0.0003), and 33% (P = 0.0019) following treatment with fasudil (25 μM), Y27632 (10 μM), and H1152 (10μM). ROCK activity induced by TGFβ rose 4.74 ± 1.9 times over control at 4 hours (P = 0.0004) and 2.4 ± 0.47-fold (P = 0.0016) in sclera after IOP elevation. Proliferation of scleral fibroblasts after chronic IOP elevation was reduced 77% by Y27632 (P = 0.001) and 84% by fasudil (P = 0.0049).

Conclusions

ROCK inhibitors reduce TGFβ-induced myofibroblast transdifferentiation and glaucoma-induced scleral cell proliferation.

Translational Relevance

These findings suggest altered fibroblast activity promoted by ROCK inhibitors could modify scleral biomechanics and be relevant to glaucoma treatment.

Rho Kinase Inhibitors as a Novel Treatment for Glaucoma and Ocular Hypertension

In an elegant example of bench-to-bedside research, a hypothesis that cells in the outflow pathway actively regulate conventional outflow resistance was proposed in the 1990s and systematically pursued, exposing novel cellular and molecular mechanisms of intraocular pressure (IOP) regulation. The critical discovery that pharmacologic manipulation of the cytoskeleton of outflow pathway cells decreased outflow resistance placed a spotlight on the Rho kinase pathway that was known to regulate the cytoskeleton. Ultimately, a search for Rho kinase inhibitors led to the discovery of several molecules of therapeutic interest, leaving us today with 2 new ocular hypotensive agents approved for clinical use: ripasudil in Japan and netarsudil in the United States. These represent members of the first new class of clinically useful ocular hypotensive agents since the US Food and Drug Administration approval of latanoprost in 1996. The development of Rho kinase inhibitors as a class of medications to lower IOP in patients with glaucoma and ocular hypertension represents a triumph in translational research. Rho kinase inhibitors are effective alone or when combined with other known ocular hypotensive medications. They also offer the possibility of neuroprotective activity, a favorable impact on ocular blood flow, and even an antifibrotic effect that may prove useful in conventional glaucoma surgery. Local adverse effects, however, including conjunctival hyperemia, subconjunctival hemorrhages, and cornea verticillata, are common. Development of Rho kinase inhibitors targeted to the cells of the outflow pathway and the retina may allow these agents to have even greater clinical impact. The objectives of this review are to describe the basic science underlying the development of Rho kinase inhibitors as a therapy to lower IOP and to summarize the results of the clinical studies reported to date. The neuroprotective and vasoactive properties of Rho kinase inhibitors, as well as the antifibrotic properties, of these agents are reviewed in the context of their possible role in the medical and surgical treatment of glaucoma.

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.

GCDB: a glaucomatous chemogenomics database for in silico drug discovery

Glaucoma is a group of neurodegenerative diseases that can cause irreversible blindness. The current medications, which mainly reduce intraocular pressure to slow the progression of disease, may have local and systemic side effects. Recently, medications with possible neuroprotective effects have attracted much attention. To assist in the identification of new glaucoma drugs, we created a glaucomatous chemogenomics database (GCDB; http://cadd.pharmacy.nankai.edu.cn/gcdb/home) in which various glaucoma-related chemogenomics data records are assembled, including 275 genes, 105 proteins, 83 approved or clinical trial drugs, 90 206 chemicals associated with 213 093 records of reported bioactivities from 22 324 corresponding bioassays and 5630 references. Moreover, an improved chemical similarity ensemble approach computational algorithm was incorporated in the GCDB to identify new targets and design new drugs. Further, we demonstrated the application of GCDB in a case study screening two chemical libraries, Maybridge and Specs, to identify interactions between small molecules and glaucoma-related proteins. Finally, six and four compounds were selected from the final hits for in vitro human glucocorticoid receptor (hGR) and adenosine A3 receptor (A3AR) inhibitory assays, respectively. Of these compounds, six were shown to have inhibitory activities against hGR, with IC50 values ranging from 2.92-28.43 μM, whereas one compoundshowed inhibitory activity against A3AR, with an IC50 of 6.15 μM. Overall, GCDB will be helpful in target identification and glaucoma chemogenomics data exchange and sharing, and facilitate drug discovery for glaucoma treatment.

Experimental research on the relationship between the stiffness and the expressions of fibronectin proteins and adaptor proteins of rat trabecular meshwork cells

Background

Trabecular meshwork (TM) plays an important role in maintaining normal intraocular pressure (IOP). Studies have shown that glaucomatous TM tissues are stiffer than those of normal tissue. The high expression of fibronectin protein (FN) and adaptor protein (LNK) may be related to high resistance to aqueous humor outflow as well as high IOP. Our concern is what factors lead to the variation of the stiffness of trabecular tissue/cells.

Methods

Atomic force microscope (AFM) and Western blot (WB) analysis were applied to test TM cells of rats cultured with different concentrations of dexamethasone (DEX) and mifepristone (MIF). Rat TM cells were randomly divided into 7 groups, marked as D1, D2, D3 and M1, M2 M3 for different concentrations of DEX and MIF, respectively, and C for blank control.

Results

The elastic modulus of the treated cells were 2.67 ± 0.914 KPa, 2.92 ± 0.986 KPa, 4.52 ± 1.22 KPa for D1, D2, D3, 2.06 ± 0.745 KPa, 1.23 ± 0.462 KPa, 0.467 ± 0.275 KPa for M1, M2, M3, and 2.43 ± 0.713 KPa for C group, respectively. Expressions of FN and LNK increase (decrease) with the increase of the concentrations of DEX (MIF).

Discussion

We focus on the relationship between the stiffness and the expressions of FN and LNK of rat TM cells. We analyzed the correlation between cell stiffness and FN, LNK expression, discussed the relationship between cell stiffness and aqueous humor outflow resistance.

Conclusions

The changes of TM cell stiffness and the expressions of FN and LNK are positively correlated.

Biomechanical, ultrastructural, and electrophysiological characterization of the non-human primate experimental glaucoma model

Laser-induced experimental glaucoma (ExGl) in non-human primates (NHPs) is a common animal model for ocular drug development. While many features of human hypertensive glaucoma are replicated in this model, structural and functional changes in the unlasered portions of trabecular meshwork (TM) of laser-treated primate eyes are understudied. We studied NHPs with ExGl of several years duration. As expected, ExGl eyes exhibited selective reductions of the retinal nerve fiber layer that correlate with electrophysiologic measures documenting a link between morphologic and elctrophysiologic endpoints. Softening of unlasered TM in ExGl eyes compared to untreated controls was observed. The degree of TM softening was consistent, regardless of pre-mortem clinical findings including severity of IOP elevation, retinal nerve fiber layer thinning, or electrodiagnostic findings. Importantly, this softening is contrary to TM stiffening reported in glaucomatous human eyes. Furthermore, microscopic analysis of unlasered TM from eyes with ExGl demonstrated TM thinning with collapse of Schlemm's canal; and proteomic analysis confirmed downregulation of metabolic and structural proteins. These data demonstrate unexpected and compensatory changes involving the TM in the NHP model of ExGl. The data suggest that compensatory mechanisms exist in normal animals and respond to elevated IOP through softening of the meshwork to increase outflow.

ROCK regulates the intermittent mode of interstitial T cell migration in inflamed lungs

Effector T cell migration through tissues can enable control of infection or mediate inflammatory damage. Nevertheless, the molecular mechanisms that regulate migration of effector T cells within the interstitial space of inflamed lungs are incompletely understood. Here, we show T cell migration in a mouse model of acute lung injury with two-photon imaging of intact lung tissue. Computational analysis indicates that T cells migrate with an intermittent mode, switching between confined and almost straight migration, guided by lung-associated vasculature. Rho-associated protein kinase (ROCK) is required for both high-speed migration and straight motion. By contrast, inhibition of Gα_i signaling with pertussis toxin affects speed but not the intermittent migration of lung-infiltrating T cells. Computational modeling shows that an intermittent migration pattern balances both search area and the duration of contacts between T cells and target cells. These data identify that ROCK-dependent intermittent T cell migration regulates tissue-sampling during acute lung injury.

ROCK is associated with T cell movement in lymph nodes. Here the authors use an LPS lung damage model and two-photon imaging to show that CD8⁺ T cells in lung tissue engage in ROCK-dependent fast linear migration alternating with bursts of slower confined migration that together optimize contact with target cells.

Topical treatment of glaucoma: established and emerging pharmacology

INTRODUCTION

Glaucoma is a collection of optic neuropathies consisting of retinal ganglion cell death and corresponding visual field loss. Glaucoma is the leading cause of irreversible vision loss worldwide and is forecasted to precipitously increase in prevalence in the coming decades. Current treatment options aim to lower intraocular pressure (IOP) via topical or oral therapy, laser treatment to the trabecular meshwork or ciliary body, and incisional surgery. Despite increasing use of trabecular laser therapy, topical therapy remains first-line in the treatment of most forms of glaucoma. Areas covered: Novel glaucoma therapies are a long-standing focus of investigational study. More than two decades have passed since the last United States Food and Drug Administration (FDA) approval of a topical glaucoma drug. Here, the authors review established topical glaucoma drops as well as those currently in FDA phase 2 and 3 clinical trial, nearing clinical use. Expert opinion: Current investigational glaucoma drugs lower IOP, mainly through enhanced trabecular meshwork outflow. Although few emerging therapies show evidence of retinal ganglion cell and optic nerve neuroprotection in animal models, emerging drugs are focused on lowering IOP, similar to established medicines.

New Insight of Common Regulatory Pathways in Human Trabecular Meshwork Cells in Response to Dexamethasone and Prednisolone Using an Integrated Quantitative Proteomics: SWATH and MRM-HR Mass Spectrometry

The molecular pathophysiology of corticosteroid-induced ocular hypertension (CIH) is not well understood. To determine the biological mechanisms of CIH, this study investigated protein expression profiles of human trabecular meshwork (hTM) cells in response to dexamethasone and prednisolone treatment. Both discovery-based sequential windowed data independent acquisition of the total high-resolution mass spectra (SWATH-MS) and targeted based high resolution multiple reaction monitoring (MRM-HR) confirmation were applied using a hybrid quadrupole-time-of-flight mass spectrometer. A comprehensive list of 1759 proteins (1% FDR) was generated from the hTM. Quantitative proteomics revealed 20 differentially expressed proteins (p-value ≤ 0.05 and fold-change ≥ 1.5 or ≤ 0.67) commonly induced by prednisolone and dexamethasone, both at 300 nM. These included connective tissue growth factor (CTGF) and thrombospondin-1 (THBS1), two proteins previously implicated in ocular hypertension, glaucoma, and the transforming growth factor-β pathway. Their gene expressions in response to corticosteroids were further confirmed using reverse-transcription polymerase chain reaction. Together with other novel proteins identified in the data sets, additional pathways implicated by these regulated proteins were the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt) signaling pathway, integrin cell surface interaction, extracellular matrix (ECM) proteoglycans, and ECM-receptor interaction. Our results indicated that an integrated platform of SWATH-MS and MRM-HR allows high throughput identification and confirmation of novel and known corticosteroid-regulated proteins in trabecular meshwork cells, demonstrating the power of this technique in extending the current understanding of the pathogenesis of CIH.

Discovery and Preclinical Development of Netarsudil, a Novel Ocular Hypotensive Agent for the Treatment of Glaucoma

PURPOSE

Rho-associated protein kinase (ROCK) inhibitors lower intraocular pressure (IOP) by increasing aqueous outflow through the trabecular meshwork (TM). The preclinical characterization of netarsudil, a new ROCK/norepinephrine transporter (NET) inhibitor currently in clinical development, is presented herein.

METHODS

The kinase inhibitory activity of netarsudil was compared to its esterase metabolite, netarsudil-M1, and 3 other ROCK inhibitors using a commercially available kinase assay kit. Disruption of actin stress fibers was measured in primary porcine TM cells and disruption of focal adhesions in transformed human TM (HTM) cells. Induction of fibrosis markers after exposure to transforming growth factor-β2 (TGF-β2) was conducted in primary HTM cells. Ocular hypotensive activity and tolerability of topical formulations were evaluated in normotensive Dutch Belted rabbits and Formosan Rock monkeys. In vitro corneal metabolism assays were conducted using dog, pig, rabbit, monkey, and human corneas. In vivo ocular pharmacokinetics was studied in Dutch Belted rabbits.

RESULTS

Netarsudil inhibited kinases ROCK1 and ROCK2 with a Ki of 1 nM each, disrupted actin stress fibers and focal adhesions in TM cells with IC50s of 79 and 16 nM, respectively, and blocked the profibrotic effects of TGF-β2 in HTM cells. Netarsudil produced large reductions in IOP in rabbits and monkeys that were sustained for at least 24 h after once daily dosing, with transient, mild hyperemia observed as the only adverse effect.

CONCLUSION

Netarsudil is a novel ROCK/NET inhibitor with high potency in biochemical and cell-based assays, an ability to produce large and durable IOP reductions in animal models, and favorable pharmacokinetic and ocular tolerability profiles.

Targeting Schlemm's Canal in the Medical Therapy of Glaucoma: Current and Future Considerations

Schlemm’s canal (SC) is a unique, complex vascular structure responsible for maintaining fluid homeostasis within the anterior segment of the eye by draining the excess of aqueous humour. In glaucoma, a heterogeneous group of eye disorders afflicting approximately 60 million individuals worldwide, the normal outflow of aqueous humour into SC is progressively hindered, leading to a gradual increase in outflow resistance, which gradually results in elevated intraocular pressure (IOP). By and large available antiglaucoma therapies do not target the site of the pathology (SC), but rather aim to decrease IOP by other mechanisms, either reducing aqueous production or by diverting aqueous flow through the unconventional outflow system. The present review first outlines our current understanding on the functional anatomy of SC. It then summarizes existing research on SC cell properties; first in the context of their role in glaucoma development/progression and then as a target of novel and emerging antiglaucoma therapies. Evidence from ongoing research efforts to develop effective antiglaucoma therapies targeting SC suggests that this could become a promising site of future therapeutic interventions.

Cross-linked actin networks (CLANs) in glaucoma

One of the major causes of decreased vision, irreversible vision loss and blindness worldwide is glaucoma. Increased intraocular pressure (IOP) is a major risk factor associated with glaucoma and its molecular mechanisms are not fully understood. The trabecular meshwork (TM) is the primary site of injury in glaucoma, and its dysfunction results in elevated IOP. The glaucomatous TM has increased extracellular matrix deposition as well as cytoskeletal rearrangements referred to as cross-linked actin networks (CLANs) that consist of dome like structures consisting of hubs and spokes. CLANs are thought to play a role in increased aqueous humor outflow resistance and increased IOP by creating stiffer TM cells and tissue. CLANs are inducible by glucocorticoids (GCs) and TGFβ2 in confluent TM cells and TM tissues. The signaling pathways of these induction agents give insight into the possible mechanisms of CLAN formation, but to date, the mechanism of CLANs regulation by these pathways has yet to be determined. Understanding the role CLANs play in IOP elevation and their mechanisms of induction and regulation may lead to novel treatment options to help prevent or intervene in glaucomatous damage to the trabecular meshwork.

TGFβ2-induced outflow alterations in a bioengineered trabecular meshwork are offset by a rho-associated kinase inhibitor

Members of the transforming growth factor beta (TGFβ) cytokine family have long been associated with affecting several cellular functions, including cell proliferation, differentiation and extracellular matrix (ECM) turnover. Of particular interest to this work, TGFβ2 has been linked to most types of glaucomas as a potential fibrotic agent that can cause elevation of intraocular pressure (IOP). Given that the trabecular meshwork (TM) provides most of aqueous humor outflow resistance in the eye, an in vitro bioengineered human TM (HTM) model has been created and validated by analyzing effects of TGFβ2 on transcellular pressure changes and outflow facility. These changes were correlated with several biological alterations induced by this cytokine, including ECM production and overexpression of HTM-marker myocillin. Furthermore, this TM model has been used to extend current knowledge of gene expression of cytokines involved in TGFβ-induced ECM turnover over time. In particular, the ability for a ROCK-inhibitor to diminish the effect of TGFβ on TM was demonstrated. This work supports the notion that anti-fibrotic activities of ROCK-inhibitors could counteract the elevation of IOP and increased strain observed in glaucomatous TM.

Glaucoma: the retina and beyond

Over 60 million people worldwide are diagnosed with glaucomatous optic neuropathy, which is estimated to be responsible for 8.4 million cases of irreversible blindness globally. Glaucoma is associated with characteristic damage to the optic nerve and patterns of visual field loss which principally involves the loss of retinal ganglion cells (RGCs). At present, intraocular pressure (IOP) presents the only modifiable risk factor for glaucoma, although RGC and vision loss can continue in patients despite well-controlled IOP. This, coupled with the present inability to diagnose glaucoma until relatively late in the disease process, has led to intense investigations towards the development of novel techniques for the early diagnosis of disease. This review outlines our current understanding of the potential mechanisms underlying RGC and axonal loss in glaucoma. Similarities between glaucoma and other neurodegenerative diseases of the central nervous system are drawn before an overview of recent developments in techniques for monitoring RGC health is provided, including recent progress towards the development of RGC specific contrast agents. The review concludes by discussing techniques to assess glaucomatous changes in the brain using MRI and the clinical relevance of glaucomatous-associated changes in the visual centres of the brain.

ROCK Inhibition Promotes Attachment, Proliferation, and Wound Closure in Human Embryonic Stem Cell-Derived Retinal Pigmented Epithelium

Purpose

Nonexudative (dry) age-related macular degeneration (AMD), a leading cause of blindness in the elderly, is associated with the loss of retinal pigmented epithelium (RPE) cells and the development of geographic atrophy, which are areas devoid of RPE cells and photoreceptors. One possible treatment option would be to stimulate RPE attachment and proliferation to replace dying/dysfunctional RPE and bring about wound repair. Clinical trials are underway testing injections of RPE cells derived from pluripotent stem cells to determine their safety and efficacy in treating AMD. However, the factors regulating RPE responses to AMD-associated lesions are not well understood. Here, we use cell culture to investigate the role of RhoA coiled coil kinases (ROCKs) in human embryonic stem cell–derived RPE (hESC-RPE) attachment, proliferation, and wound closure.

Methods

H9 hESC were spontaneously differentiated into RPE cells. hESC-RPE cells were treated with a pan ROCK1/2 or a ROCK2 only inhibitor; attachment, and proliferation and cell size within an in vitro scratch assay were examined.

Results

Pharmacological inhibition of ROCKs promoted hESC-RPE attachment and proliferation, and increased the rate of closure of in vitro wounds. ROCK inhibition decreased phosphorylation of cofilin and myosin light chain, suggesting that regulation of the cytoskeleton underlies the mechanism of action of ROCK inhibition.

Conclusions

ROCK inhibition promotes attachment, proliferation, and wound closure in H9 hESC-RPE cells. ROCK isoforms may have different roles in wound healing.

Translational Relevance

Modulation of the ROCK-cytoskeletal axis has potential in stimulating wound repair in transplanted RPE cells and attachment in cellular therapies.

Trabecular meshwork stiffness in glaucoma

Alterations in stiffness of the trabecular meshwork (TM) may play an important role in primary open-angle glaucoma (POAG), the second leading cause of blindness. Specifically, certain data suggest an association between elevated intraocular pressure (IOP) and increased TM stiffness; however, the underlying link between TM stiffness and IOP remains unclear and requires further study. We here first review the literature on TM stiffness measurements, encompassing various species and based on a number of measurement techniques, including direct approaches such as atomic force microscopy (AFM) and uniaxial tension tests, and indirect methods based on a beam deflection model. We also briefly review the effects of several factors that affect TM stiffness, including lysophospholipids, rho-kinase inhibitors, cytoskeletal disrupting agents, dexamethasone (DEX), transforming growth factor-β₂ (TGF-β₂), nitric oxide (NO) and cellular senescence. We then describe a method we have developed for determining TM stiffness measurement in mice using a cryosection/AFM-based approach, and present preliminary data on TM stiffness in C57BL/6J and CBA/J mouse strains. Finally, we investigate the relationship between TM stiffness and outflow facility between these two strains. The method we have developed shows promise for further direct measurements of mouse TM stiffness, which may be of value in understanding mechanistic relations between outflow facility and TM biomechanical properties.

Topical administration of a Rock/Net inhibitor promotes retinal ganglion cell survival and axon regeneration after optic nerve injury

Intraocular pressure (IOP)-lowering ophthalmic solutions that inhibit Rho-associated protein kinases (Rock) and norepinephrine transporters (Net) are currently under clinical evaluation. Here we evaluate topical application of one such drug for its effects on retinal ganglion cell (RGC) survival and axon regeneration after optic nerve crush injury. We performed unilateral optic nerve crush on young rats (P18) and topically applied Rock/Net inhibitor AR-13324 or placebo 3 times a day for 14 days. IOP was measured starting 3 days before and up to 9 days after injury. On day 12, cholera toxin B (CTB) was injected intravitreally to trace optic nerve regeneration. On day 14, retinas and optic nerves were collected. The retinas were flat-mounted and stained with RBPMS to quantify RGC survival and the optic nerves were sectioned for optic nerve axon quantification using fluorescent and confocal microscopy. Rock phosphorylation targets implicated in axon growth including cofilin and LIMK were examined by fluorescence microscopy and quantitative western blotting. AR-13324 lowered IOP as expected. RGC survival and optic nerve axon regeneration were significantly higher with Rock/Net inhibitor treatment compared with placebo. Furthermore, topical therapy decreased Rock target protein phosphorylation in the retinas and proximal optic nerves. These data suggest that topical administration of a Rock/Net inhibitor promotes RGC survival and regeneration after optic nerve injury, with associated molecular changes indicative of posterior drug activity. Coordinated IOP lowering and neuroprotective or regenerative effects may be advantageous in the treatment of patients with glaucoma.

The progress in optic nerve regeneration, where are we?

Optic nerve regeneration is an important area of research. It can be used to treat patients suffering from optic neuropathy and provides insights into the treatment of numerous neurodegenerative diseases. There are many hurdles impeding optic regeneration in mammals. The mammalian central nervous system is non-permissive to regeneration and intrinsically lacks the capacity for axonal regrowth. Any axonal injury also triggers a vicious cycle of apoptosis. Understanding these hurdles provides us with a rough framework to appreciate the essential steps to bring about optic nerve regeneration: enhancing neuronal survival, axon regeneration, remyelination and establishing functional synapses to the original neuronal targets. In this review article, we will go through current potential treatments for optic nerve regeneration, which includes neurotrophic factor provision, inflammatory stimulation, growth inhibition suppression, intracellular signaling modification and modeling of bridging substrates.

Discovery of Molecular Therapeutics for Glaucoma: Challenges, Successes, and Promising Directions

Glaucoma, a heterogeneous ocular disorder affecting ∼60 million people worldwide, is characterized by painless neurodegeneration of retinal ganglion cells (RGCs), resulting in irreversible vision loss. Available therapies, which decrease the common causal risk factor of elevated intraocular pressure, delay, but cannot prevent, RGC death and blindness. Notably, it is changes in the anterior segment of the eye, particularly in the drainage of aqueous humor fluid, which are believed to bring about changes in pressure. Thus, it is primarily this region whose properties are manipulated in current and emerging therapies for glaucoma. Here, we focus on the challenges associated with developing treatments, review the available experimental methods to evaluate the therapeutic potential of new drugs, describe the development and evaluation of emerging Rho-kinase inhibitors and adenosine receptor ligands that offer the potential to improve aqueous humor outflow and protect RGCs simultaneously, and present new targets and approaches on the horizon.

Rho Kinase (ROCK) Inhibitors and Their Therapeutic Potential

Rho kinases (ROCKs) belong to the serine-threonine family, the inhibition of which affects the function of many downstream substrates. As such, ROCK inhibitors have potential therapeutic applicability in a wide variety of pathological conditions including asthma, cancer, erectile dysfunction, glaucoma, insulin resistance, kidney failure, neuronal degeneration, and osteoporosis. To date, two ROCK inhibitors have been approved for clinical use in Japan (fasudil and ripasudil) and one in China (fasudil). In 1995 fasudil was approved for the treatment of cerebral vasospasm, and more recently, ripasudil was approved for the treatment of glaucoma in 2014. In this Perspective, we present a comprehensive review of the physiological and biological functions for ROCK, the properties and development of over 170 ROCK inhibitors as well as their therapeutic potential, the current status, and future considerations.

Genes, pathways, and animal models in primary open-angle glaucoma

Glaucoma is an optic neuropathy characterized by loss of retinal ganglion cells (RGCs) and consequently visual field loss. It is a complex and heterogeneous disease in which both environmental and genetic factors play a role. With the advent of genome-wide association studies (GWASs), the number of loci associated with primary open-angle glaucoma (POAG) have increased greatly. There has also been major progress in understanding the genes determining the vertical cup-disc ratio (VCDR), disc area (DA), cup area (CA), intraocular pressure (IOP), and central corneal thickness (CCT). In this review, we will update and summarize the genetic loci associated so far with POAG, VCDR, DA, CA, IOP, and CCT. We will describe the pathways revealed and supported by genetic association studies, integrating current knowledge from human and experimental data. Finally, we will discuss approaches for functional genomics and clinical translation.

Dexamethasone Stiffens Trabecular Meshwork, Trabecular Meshwork Cells, and Matrix

PURPOSE

Treatment with corticosteroids can result in ocular hypertension and may lead to the development of steroid-induced glaucoma. The extent to which biomechanical changes in trabecular meshwork (TM) cells and extracellular matrix (ECM) contribute toward this dysfunction is poorly understood.

METHODS

Primary human TM (HTM) cells were cultured for either 3 days or 4 weeks in the presence or absence of dexamethasone (DEX), and cell mechanics, matrix mechanics and proteomics were determined, respectively. Adult rabbits were treated topically with either 0.1% DEX or vehicle over 3 weeks, and mechanics of the TM were determined.

RESULTS

Treatment with DEX for 3 days resulted in a 2-fold increase in HTM cell stiffness, and this correlated with activation of extracellular signal-related kinase 1/2 (ERK1/2) and overexpression of α-smooth muscle actin (αSMA). Further, the matrix deposited by HTM cells chronically treated with DEX is approximately 4-fold stiffer, more organized, and has elevated expression of matrix proteins commonly implicated in glaucoma (decorin, myocilin, fibrillin, secreted frizzle-related protein [SFRP1], matrix-gla). Also, DEX treatment resulted in a 3.5-fold increase in stiffness of the rabbit TM.

DISCUSSION

This integrated approach clearly demonstrates that DEX treatment increases TM cell stiffness concurrent with elevated αSMA expression and activation of the mitogen-activated protein kinase (MAPK) pathway, stiffens the ECM in vitro along with upregulation of Wnt antagonists and fibrotic markers embedded in a more organized matrix, and increases the stiffness of TM tissues in vivo. These results demonstrate glucocorticoid treatment can initiate the biophysical alteration associated with increased resistance to aqueous humor outflow and the resultant increase in IOP.