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

Three-Dimensional Extracellular Matrix Protein Hydrogels for Human Trabecular Meshwork Cell Studies

The extracellular microenvironment plays a crucial role in regulating a wide range of cell behaviors. Biopolymer hydrogels are ideally suited to present a realistic three-dimensional extracellular milieu to cells in vitro. Here, we describe the fabrication and use of soft tissue-mimetic extracellular matrix protein hydrogels for investigations of human trabecular meshwork cell biology.

The role of YAP/TAZ mechanosignaling in trabecular meshwork and Schlemm's canal cell dysfunction

This focused review highlights the importance of yes-associated protein (YAP)/transcriptional coactivator with PDZ binding motif (TAZ) mechanosignaling in human trabecular meshwork and Schlemm's canal cells in response to glaucoma-associated extracellular matrix stiffening and cyclic mechanical stretch, as well as biochemical pathway modulators (with signaling crosstalk) including transforming growth factor beta 2, glucocorticoids, Wnt, lysophosphatidic acid, vascular endothelial growth factor, and oxidative stress. We provide a comprehensive overview of relevant literature from the last decade, highlight intriguing research avenues with translational potential, and close with an outlook on future directions.

3D printed gelatin methacryloyl hydrogels for perfusion culture of human trabecular meshwork cells and glaucoma studies

Glaucoma, a progressive eye disease leading to irreversible blindness, currently affects over 70 million people globally. Elevated intraocular pressure (IOP) is implicated in its development. IOP is carefully regulated by the trabecular meshwork (TM). However, studying TM behavior has been limited to traditional tissue culture studies or costly ex vivo cultures of animal and donor eyes. Developing novel functional TM models could enhance cell/tissue behavior understanding and aid therapeutic development for glaucoma. In this study, we 3D printed a simplified and reproducible model of the human TM (hTM) and studied hTM cell behavior under static and dynamic cultures. Gelatin Methacryloyl bioinks proved suitable for printing with viable and proliferative hTM cells expressing crucial marker genes in response to glucocorticoid induction. This, to our knowledge, is the first functional 3D printed hTM model and aims to facilitate TM research. Moreover, this easily reproducible model could also be applicable in the study of numerous other cell types throughout the body.

ECM biomaterials for modeling of outflow cell biology in health and disease

This review highlights the importance of extracellular matrix (ECM) biomaterials in understanding the biology of human trabecular meshwork (TM) and Schlemm's canal (SC) cells under normal and simulated glaucoma-like conditions. We provide an overview of recent progress in the development and application of state-of-the-art 3D ECM biomaterials including cell-derived ECM, ECM scaffolds, Matrigel, and ECM hydrogels for studies of TM and SC cell (patho)biology. Such bioengineered platforms enable accurate and reliable modeling of tissue-like cell-cell and cell-ECM interactions. They bridge the gap between conventional 2D approaches and in vivo/ex vivo models, and have the potential to aid in the identification of the causal mechanism(s) for outflow dysfunction in ocular hypertensive glaucoma. We discuss each model's benefits and limitations, and close with an outlook on future directions.

Targeting YAP/TAZ mechanosignaling to ameliorate stiffness-induced Schlemm's canal cell pathobiology

Pathological alterations in the biomechanical properties of the Schlemm's canal (SC) inner wall endothelium and its immediate vicinity are strongly associated with ocular hypertension in glaucoma due to decreased outflow facility. Specifically, the underlying trabecular meshwork is substantially stiffer in glaucomatous eyes compared with that from normal eyes. This raises the possibility of a critical involvement of mechanotransduction processes in driving SC cell dysfunction. Yes-associated protein (YAP) has emerged as a key contributor to glaucoma pathogenesis. However, the molecular underpinnings of SC cell mechanosignaling via YAP and transcriptional coactivator with PDZ-binding motif (TAZ) in response to glaucomatous extracellular matrix (ECM) stiffening are not well understood. Using a novel biopolymer hydrogel that facilitates dynamic and reversible stiffness tuning, we investigated how ECM stiffening modulates YAP/TAZ activity in primary human SC cells, and whether disruption of YAP/TAZ mechanosignaling attenuates SC cell pathobiology and increases ex vivo outflow facility. We demonstrated that ECM stiffening drives pathologic YAP/TAZ activation and cytoskeletal reorganization in SC cells, which was fully reversible by matrix softening in a distinct time-dependent manner. Furthermore, we showed that pharmacologic or genetic disruption of YAP/TAZ mechanosignaling abrogates stiffness-induced SC cell dysfunction involving altered cytoskeletal and ECM remodeling. Finally, we found that perfusion of the clinically used, small molecule YAP/TAZ inhibitor verteporfin (without light activation) increases ex vivo outflow facility in normal mouse eyes. Collectively, our data provide new evidence for a pathologic role of aberrant YAP/TAZ mechanosignaling in SC cell dysfunction and suggest that YAP/TAZ inhibition has therapeutic value for treating ocular hypertension in glaucoma.NEW & NOTEWORTHY Pathologically altered biomechanical properties of the Schlemm's canal (SC) inner wall microenvironment were recently validated as the cause for increased outflow resistance in ocular hypertensive glaucoma. However, the involvement of specific mechanotransduction pathways in these disease processes is largely unclear. Here, we demonstrate that Yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) are central regulators of glaucoma-like SC cell dysfunction in response to extracellular matrix stiffening and that targeted disruption of YAP/TAZ mechanosignaling attenuates SC cell pathobiology and enhances outflow function.

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.

Sigma-1 Receptor Activation Is Protective against TGFβ2-Induced Extracellular Matrix Changes in Human Trabecular Meshwork Cells

The trabecular meshwork (TM) route is the principal outflow egress of the aqueous humor. Actin cytoskeletal remodeling in the TM and extracellular matrix (ECM) deposition increase TM stiffness, outflow resistance, and elevate intraocular pressure (IOP). These alterations are strongly linked to transforming growth factor-β2 (TGFβ2), a known profibrotic cytokine that is markedly elevated in the aqueous humor of glaucomatous eyes. Sigma-1 receptor (S1R) has been shown to have neuroprotective effects in the retina, but data are lacking about its role in the TM. In this study, we identified the presence of S1R in mouse TM tissue and investigated the effect of an S1R agonist fluvoxamine (FLU) on TGFβ2-induced human TM cells regarding cell proliferation; ECM-related functions, including F-actin reorganization; and the accumulation of ECM elements. TGFβ2 increased the proliferation, cytoskeletal remodeling, and protein levels of fibronectin, collagen type IV, and connective tissue growth factor, and decreased the level of matrix metalloproteinase-2. Most importantly, FLU reversed all these effects of TGFβ2, suggesting that S1R agonists could be potential candidates for preserving TM function and thus maintaining normal IOP.

MAPK Pathways in Ocular Pathophysiology: Potential Therapeutic Drugs and Challenges

Mitogen-activated protein kinase (MAPK) pathways represent ubiquitous cellular signal transduction pathways that regulate all aspects of life and are frequently altered in disease. Once activated through phosphorylation, these MAPKs in turn phosphorylate and activate transcription factors present either in the cytoplasm or in the nucleus, leading to the expression of target genes and, as a consequence, they elicit various biological responses. The aim of this work is to provide a comprehensive review focusing on the roles of MAPK signaling pathways in ocular pathophysiology and the potential to influence these for the treatment of eye diseases. We summarize the current knowledge of identified MAPK-targeting compounds in the context of ocular diseases such as macular degeneration, cataract, glaucoma and keratopathy, but also in rare ocular diseases where the cell differentiation, proliferation or migration are defective. Potential therapeutic interventions are also discussed. Additionally, we discuss challenges in overcoming the reported eye toxicity of some MAPK inhibitors.

Berberine Depresses Inflammation and Adjusts Smooth Muscle to Ameliorate Ulcerative Colitis of Cats by Regulating Gut Microbiota

Intestinal microbiota dysbiosis is a well established characteristic of ulcerative colitis (UC). Regulating the gut microbiota is an effective UC treatment strategy. Berberine (BBR), an alkaloid extracted from several Chinese herbs, is a common traditional Chinese medicine. To establish the efficacy and mechanism of action of BBR, we constructed a UC model using healthy adult shorthair cats to conduct a systematic study of colonic tissue pathology, inflammatory factor expression, and gut microbiota structure. We investigated the therapeutic capacity of BBR for regulating the gut microbiota and thus work against UC in cats using 16S rRNA genes amplicon sequencing technology. Our results revealed that dextran sulfate sodium (DSS)-induced cat models of UC showed weight loss, diarrhea accompanied by mucous and blood, histological abnormalities, and shortening of the colon, all of which were significantly alleviated by supplementation with BBR. A 16S rRNA gene-based microbiota analysis demonstrated that BBR could significantly benefit gut microbiota. Western blot, quantitative PCR, and enzyme-linked immunosorbent assays (ELISAs) showed that in DSS-induced cat models, the expression of the inflammatory factors was increased, activating the JAK2/STAT3 signaling pathway, and treatment with BBR reversed this effect. The myosin light chain (MLC) phosphorylation in the smooth muscle of the intestines is associated with motility of inflammation-related diarrhea in cats. This study used gut flora analyses to demonstrate the anti-UC effects of BBR and its potential therapeutic mechanisms and offers novel insights into the prevention of inflammatory diseases using natural products. IMPORTANCE Ulcerative colitis (UC) is common in clinics. Intestinal microbiota disorder is correlated with ulcerative colitis. Although there are many studies on ulcerative colitis in rats, there are few studies on colitis in cats. Therefore, this study explored the possibility of the use of BBR as a safe and efficient treatment for colitis in cats. The results demonstrated the therapeutic effects of BBR on UC based on the state of the intestinal flora. The study found BBR supplementation to be effective against dextran sulfate sodium (DSS)-induced colitis, smooth muscle damage, and gut microbiota dysbiosis.

YAP/TAZ Mediate TGFβ2-Induced Schlemm's Canal Cell Dysfunction

Purpose

Elevated transforming growth factor beta2 (TGFβ2) levels in the aqueous humor have been linked to glaucomatous outflow tissue dysfunction. Potential mediators of dysfunction are the transcriptional coactivators, Yes-associated protein (YAP) and transcriptional coactivator with PDZ binding motif (TAZ). However, the molecular underpinnings of YAP/TAZ modulation in Schlemm's canal (SC) cells under glaucomatous conditions are not well understood. Here, we investigate how TGFβ2 regulates YAP/TAZ activity in human SC (HSC) cells using biomimetic extracellular matrix hydrogels, and examine whether pharmacological YAP/TAZ inhibition would attenuate TGFβ2-induced HSC cell dysfunction.

Methods

Primary HSC cells were seeded atop photo-cross-linked extracellular matrix hydrogels, made of collagen type I, elastin-like polypeptide and hyaluronic acid, or encapsulated within the hydrogels. HSC cells were induced with TGFβ2 in the absence or presence of concurrent actin destabilization or pharmacological YAP/TAZ inhibition. Changes in actin cytoskeletal organization, YAP/TAZ activity, extracellular matrix production, phospho-myosin light chain levels, and hydrogel contraction were assessed.

Results

TGFβ2 significantly increased YAP/TAZ nuclear localization in HSC cells, which was prevented by either filamentous-actin relaxation or depolymerization. Pharmacological YAP/TAZ inhibition using verteporfin without light stimulation decreased fibronectin expression and actomyosin cytoskeletal rearrangement in HSC cells induced by TGFβ2. Similarly, verteporfin significantly attenuated TGFβ2-induced HSC cell-encapsulated hydrogel contraction.

Conclusions

Our data provide evidence for a pathologic role of aberrant YAP/TAZ signaling in HSC cells under simulated glaucomatous conditions and suggest that pharmacological YAP/TAZ inhibition has promising potential to improve outflow tissue dysfunction.

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.