Biology subjects

Stamer, W. D.

Publications and source records attributed to Stamer, W. D..

At least 19 recordsLinked to original sources

bioRxiv2026

Transcriptomic profiling of normal and glaucomatous trabecular meshwork cells in a tissue-like soft ECM environment

Purpose. Trabecular meshwork (TM) dysfunction contributes to the elevated intraocular pressure in primary open-angle glaucoma. To better understand the molecular signature distinguishing glaucomatous from normal TM cells, we interrogated their genome-wide transcriptomic differences in a tissue-like soft extracellular matrix (ECM) microenvironment. Methods. Primary human glaucomatous and normal TM cell strains (N = 5 each) from three independent laboratories were plated on bioengineered collagen type I/hyaluronic acid/elastin-like polypeptide ECM hydrogels in 10% FBS media for 4-5 days, then serum-free media for 2 days. Cell-laden hydrogels were homogenized in TRIzol for RNA isolation, quality assessment, and library preparation, followed by paired-end 100-bp Illumina sequencing. Differential expression was assessed using DESeq2, including glaucoma status, originating laboratory, and donor age/sex in the model. Differentially expressed genes (DEGs) were defined as p < 0.05 and |fold change| [≥] 2, followed by Gene Ontology (GO) enrichment and QIAGEN Ingenuity Pathway Analysis (IPA). Results. In total, 588 DEGs distinguished the glaucomatous from the normal TM transcriptome (393 up-regulated in glaucomatous TM; 195 up-regulated in normal TM, i.e., down-regulated in glaucomatous TM). GO and IPA causal analyses revealed three coordinated disease programs: (i) TGF-{beta}/Wnt-driven ECM remodeling and fibrosis, (ii) NF-{kappa}B-associated inflammation, and (iii) a hypoxia/metabolic-stress program linked to p300/CREBBP chromatin co-activation. Conclusions. These data define a transcriptomic signature of glaucomatous TM cells when cultured in a soft physiologic ECM microenvironment, independent of the originating laboratory, with three mechanistic axes (ECM/fibrosis, inflammation, hypoxia/metabolism), and nominate p300 (encoded by EP300) as a candidate upstream node integrating these programs.

cell biology↗

bioRxiv2026

Molecular profiling implicates immune-driven adaptive homeostasis in maintaining intraocular pressure with age

Aging and ocular hypertension are primary risk factors for glaucoma - a major cause of blindness worldwide. Ocular hypertension results from dysfunction in the outflow tissues - the trabecular meshwork (TM) and Schlemm's canal (SC), which are key regulators of intraocular pressure (IOP) homeostasis. Despite lifelong multifaceted stress to the outflow pathway, ocular hypertension sufficient to develop glaucoma occurs in only a minority of individuals. The mechanisms that preserve physiological IOP with aging in most individuals remain poorly understood. Using single-cell RNA sequencing and protein validation in mouse outflow tissues, we found that aging is accompanied by subtype-specific changes in TM cells, including altered extracellular matrix maintenance, reduced trophic signaling to SC, and increased profibrotic signaling. Coincident with these changes, we observed age-dependent immune remodeling, marked by increased macrophage abundance in outflow tissues. Our model predicts that macrophages maintain SC homeostasis via VEGFA signaling - normally supplied by the TM and required for normal SC function, but impaired with age. This pattern supports a paradigm in which adaptive immune remodeling contributes to preserving IOP homeostasis despite progressive aging-associated cellular dysfunction. More broadly, we identify the TM/SC outflow pathway as a model for understanding how aging tissues preserve physiological function through coordinated structural, trophic, and adaptive immune remodeling.

cell biology↗

bioRxiv2026

Transcriptomic Profiling of High vs. Low Flow Regions of Mouse and Human Trabecular Meshwork

PurposeAqueous humor outflow through the trabecular meshwork (TM) is segmental, demonstrating high flow (HF) and low flow (LF) regions. Here, we investigate transcriptomic differences between flow regions in naive mouse and non-glaucomatous human TM tissue to better understand intraocular pressure (IOP) regulation. MethodsHuman eyes (<6 hours postmortem) from two donors were perfused with a fluorescent tracer to identify HF and LF regions and fixed. In parallel, one pair of 8-month-old C57Bl/6J mouse eyes were similarly processed. Sagittal sections from HF and LF regions underwent whole-transcriptome spatial profiling. Differential expression and gene set variation analysis were conducted to identify transcript and pathway-level differences between HF vs. LF TM. Selected targets were validated by immunolabeling. ResultsGenes with relevance to TM outflow were identified as significantly differentially expressed in the human dataset, including ADAM metallopeptidase domain 15 (ADAM15), vimentin (VIM), chitinase 3-like 1 (CHI3L1), and several transcription factors (e.g., FOS, JUNB, ESR1). Pathways related to epigenetic modifications were also differentially enriched in human eyes. In both human and mouse eyes, myocilin was significantly upregulated in HF regions, despite greater protein labeling in LF regions of human eyes. In both species, rho-kinase signaling pathways showed increased enrichment in LF regions, while cell stress pathways, and TNF- signaling were increased in HF TM. ConclusionsHF regions maintain a more active stress response that facilitates greater outflow, whereas LF regions exhibit more matrix accumulation and contractility. This characterization of segmental flow regions can inform future studies to target trabecular outflow and lower IOP.

bioengineering↗

bioRxiv2026

Microtubule stability modulates Schlemm's canal cell mechanobiology and outflow facility in glaucoma

PurposeThe inner wall of Schlemms canal (SC) is a mechanosensitive endothelial monolayer that provides resistance to conventional aqueous humor drainage, a process dependent on pore formation. This study examined how microtubule (MT) stability affects SC cell mechanobiology, transcellular pore formation, and aqueous humor outflow dynamics. MethodsMT stability in cultured SC cells from normal and glaucomatous human donors was manipulated pharmacologically. Changes in MT acetylation, phosphorylated myosin light chain, and F-actin were assessed by immunofluorescence and immunoblotting. GEF-H1 was knocked down using siRNA. Cellular stiffness was measured by atomic force microscopy. Transcellular pore formation was quantified using an established pore formation assay. Outflow facility was measured in enucleated mouse eyes using the iPerfusion system. ResultsMT stabilization in normal SC cells decreased actomyosin contractility and cellular stiffness, whereas MT destabilization increased contractility and stiffness; these effects involved the MT-associated Rho guanine nucleotide exchange factor GEF-H1. MT stability was also mechano-responsive to substrate stiffness. Furthermore, SC cells derived from glaucomatous donors exhibited reduced MT stability compared with normal SC cells. MT stabilization increased transcellular pore formation in both normal and glaucomatous SC cells. In ex vivo mouse eyes, paclitaxel perfusion to stabilize MTs significantly increased outflow facility relative to contralateral control eyes. ConclusionsOur data suggest that MT stability influences SC cell contractility, stiffness, and transcellular pore formation and can alter aqueous humor outflow facility. These findings identify MT-dependent cytoskeletal remodeling as an important contributor to the biomechanics of the conventional outflow pathway and suggest that MT-associated pathways may represent potential targets for improving outflow function in glaucoma.

cell biology↗

bioRxiv2026

Segmental outflow and trabecular meshwork stiffness in an ocular hypertensive mouse model

PurposeElevated intraocular pressure (IOP) due to increased outflow resistance through the trabecular meshwork (TM) is a major risk factor for primary open-angle glaucoma. Outflow through the TM is segmental, consisting of high flow (HF) and low flow (LF) regions. Here, we investigate how ocular hypertension impacts segmental outflow using a dexamethasone (DEX) mouse model and compare TM stiffness between HF and LF regions. MethodsNanoparticles containing DEX or vehicle were injected twice weekly in 2-4-month-old C57BL/6J mice (n=14), and IOP was measured weekly. At week 4, mouse eyes were perfused in vivo with fluorescent nanospheres to assess flow patterns and the circumferential percentage of high, intermediate, and low flow regions in each eye. Sagittal sections were collected from HF and LF regions, and atomic force microscopy (AFM) was used to measure tissue stiffness. Immunofluorescent labeling was used to compare fibronectin and -SMA protein levels. ResultsDEX treatment significantly elevated IOP by an average of 33.3% and altered tracer distribution but not the percentage of HF and LF regions around the circumference. No significant differences in TM stiffness were detected between DEX-treated and control mice, or between HF and LF regions. Increased fibronectin in LF regions of DEX-treated eyes suggested subtle TM structural changes that were not detected by AFM. ConclusionsDexamethasone alters segmental flow distribution and may impact cell contractility rather than ECM stiffness to cause IOP elevation in young mice. These findings better characterize the nature of segmental outflow and TM mechanics in this model of steroid-induced glaucoma.

bioengineering↗

bioRxiv2025

Interdependent regulation of trabecular meshwork cell physiology and intraocular pressure by KALRN and TMCO1

Glaucoma is a leading cause of irreversible blindness. Primary open-angle glaucoma (POAG) is its most common form. Higher intraocular pressure (IOP), resulting from impaired aqueous humour outflow, is the cardinal mediating factor, and all proven treatments aim to lower IOP. POAG is a complex genetic disease with numerous loci linked to POAG and higher IOP. The mechanisms by which risk alleles cause disease remain unclear. Here, using primary trabecular meshwork (TM) cells, a cell type controlling outflow, and mice, we found that the POAG-associated gene KALRN encodes an endoplasmic reticulum (ER)-associated Rac regulator essential for TM homeostasis and normal IOP. KALRN loss caused widespread disruption from ER to calcium homeostasis and energy metabolism, leading to induction of cell senescence. KALRN-depletion also led to suppression of the ER translocase and calcium regulator TMCO1, encoded by a gene at one of the most significantly associated genomic loci for POAG. TMCO1-depletion in vitro and in vivo phenocopied KALRN-induced phenotypes, and reduced KALRN expression. These findings establish KALRN and TMCO1 as interdependent regulators of TM homeostasis and IOP, that link regulation of ER and intracellular calcium homeostasis to cell and tissue physiology, and illustrate how different genes linked to glaucoma can form regulatory pathways.

cell biology↗

bioRxiv2025

TRPV4 modulates substrate stiffness mechanosensing and transcellular pore formation in human Schlemm's canal cells

Pathological changes in the biomechanical environment of Schlemms canal (SC) inner wall cells, such as substrate stiffening and increased cellular stretch, are associated with ocular hypertension, a key risk factor for the development of glaucoma. Cell membrane stretch can trigger the activation of transient receptor potential vanilloid 4 (TRPV4) mechanosensitive ion channels, allowing calcium influx and initiating downstream signaling. However, the precise role of TRPV4 in SC cell mechanobiology remains unclear. Here, we demonstrate that sustained inhibition of TRPV4 activity modulates substrate stiffness mechanosensing to thereby affect the remodeling of the actin cytoskeleton and extracellular matrix of SC cells. This is accompanied by a reduction in cell stiffness and an increase in transcellular pore forming ability, potentially lowing outflow resistance and risk of ocular hypertension. Conversely, acute activation of TRPV4 channels induces Ca2+ influx, increasing transcellular pore formation in SC cells. Notaly, reduced TRPV4 mechanosensing was observed in glaucomatous SC cells, resulting in reduced transcellular pore forming ability. These findings suggest novel potential strategies based on targeting TRPV4 in SC cells for the treatment of ocular hypertension in glaucoma.

cell biology↗

bioRxiv2025

Intracameral Puncture Lowers Intraocular Pressure and Triggers an Immune Response in the Conventional Outflow Tract

PurposeIntracameral injection is an effective delivery method for biomedical agents and therapeutics to conventional outflow tract tissues. However, the effect of intracameral injections on intraocular pressure and aqueous dynamics has not been well characterized, warranting further investigation. MethodsWild type 3-5-month-old C57BL/6 mice were subjected to intracameral puncture (ICP, without injection of any material). Following ICP, intraocular pressure (IOP), outflow facility, aqueous production, episcleral vessel diameter, and macrophage densities were measured. ResultsOn day 1, IOP was significantly reduced by 30% (p < 0.0001; n=25) while outflow facility (p = 0.306; n=15) and aqueous production (p = 0.163; n=9) were unchanged. As well, Schlemms canal filtration area was unchanged, however distal vessels were dilated (p < 0.001) at day 1 post ICP. Correspondingly, macrophage density was significantly increased around episcleral vessels (p < 0.0005) at day 1. Macrophage densities in Schlemms canal and trabecular meshwork, while unchanged at day 1, were significantly increased by day 3 (p < 0.0001). ConclusionsCoincident with significantly reduced IOP one day after ICP, there was an influx of macrophages into the distal portion of the conventional outflow tissues and a dilation of episcleral vessels, likely reducing distal outflow resistance. Our study demonstrates the importance of considering the drug delivery method to the eye due to its effects on the immune response and conventional outflow homeostasis.

physiology↗

bioRxiv2025

Resident Tissue Macrophages Govern Intraocular Pressure Homeostasis

Intraocular pressure is tightly regulated by the conventional outflow tissues, preventing ocular hypertension that leads to neurodegeneration of the optic nerve, or glaucoma. Although macrophages reside throughout the conventional outflow tract, their role in regulating intraocular pressure remains unknown. Using macrophage lineage tracing approaches, we uncovered a dual macrophage ontogeny with distinct spatial organizations across the mouse lifespan. Long-lived, resident tissue macrophages concentrated in the trabecular meshwork and Schlemms canal, whereas short-lived monocyte-derived macrophages, instead, were abundant around distal vessels. Specific depletion of resident tissue macrophages triggered elevated intraocular pressure and outflow resistance, linked to aberrant extracellular matrix turnover in the resistance-generating tissues of the trabecular meshwork. This dysregulated physiology and tissue remodeling were not observed when we depleted monocyte-derived macrophages. Results show ontogeny and tissue-specific macrophage function within the outflow tract, uncovering the integral homeostatic role of resident tissue macrophages in resistance-generating tissues whose dysfunction is responsible for glaucoma.

immunology↗

bioRxiv2024

Single-cell profiling of trabecular meshwork identifies mitochondrial dysfunction in a glaucoma model that is protected by vitamin B3 treatment

Since the trabecular meshwork (TM) is central to intraocular pressure (IOP) regulation and glaucoma, a deeper understanding of its genomic landscape is needed. We present a multimodal, single-cell resolution analysis of mouse limbal cells (includes TM). In total, we sequenced 9,394 wild-type TM cell transcriptomes. We discovered three TM cell subtypes with characteristic signature genes validated by immunofluorescence on tissue sections and whole-mounts. The subtypes are robust, being detected in datasets for two diverse mouse strains and in independent data from two institutions. Results show compartmentalized enrichment of critical pathways in specific TM cell subtypes. Distinctive signatures include increased expression of genes responsible for 1) extracellular matrix structure and metabolism (TM1 subtype), 2) secreted ligand signaling to support Schlemms canal cells (TM2), and 3) contractile and mitochondrial/metabolic activity (TM3). ATAC-sequencing data identified active transcription factors in TM cells, including LMX1B. Mutations in LMX1B cause high IOP and glaucoma. LMX1B is emerging as a key transcription factor for normal mitochondrial function and its expression is much higher in TM3 cells than other limbal cells. To understand the role of LMX1B in TM function and glaucoma, we single-cell sequenced limbal cells from Lmx1bV265D/+mutant mice (2,491 TM cells). In V265D/+ mice, TM3 cells were uniquely affected by pronounced mitochondrial pathway changes. Mitochondria in TM cells of V265D/+ mice are swollen with a reduced cristae area, further supporting a role for mitochondrial dysfunction in the initiation of IOP elevation in these mice. Importantly, treatment with vitamin B3 (nicotinamide), to enhance mitochondrial function and metabolic resilience, significantly protected Lmx1b mutant mice from IOP elevation.

molecular biology↗

bioRxiv2024

Endothelial cell stiffness and type drive the formation of biomechanically-induced transcellular pores

Formation of transcellular pores facilitates the transport of materials across endothelial barriers. In Schlemms canal (SC) endothelium, impaired pore formation is associated with glaucoma. However, our understanding of the cellular processes responsible for pore formation is limited by lack of in vitro assays. Here, we present a novel platform for studying transcellular pore formation in human endothelial cells. We induced pores in SC cells by seeding them atop micron-sized magnetic beads followed by application of a magnetic field to subject cells to a basal to apical force, mimicking in vivo biomechanical forces. The pore formation process was dynamic, with pores opening and closing. Glaucomatous cells exhibited impaired pore formation that correlated with their increased stiffness. We further discovered that application of forces from the apical to basal direction did not induce pores in SC cells but resulted in formation of pores in other types of endothelial cells. Our studies reveal the central role of cell mechanics in formation of transcellular pores in endothelial cells, and provide a new approach for investigating their associated underlying mechanism/s.

bioengineering↗

bioRxiv2024

In vivo quantification of anterior and posterior chamber volumes in mice: implications for aqueous humor dynamics

PurposeAqueous humor inflow rate, a key parameter influencing aqueous humor dynamics, is typically measured by fluorophotometery. Analyzing fluorophotometric data depends, inter alia, on the volume of aqueous humor in the anterior, but not the posterior, chamber. Previous fluorophotometric studies of aqueous inflow rate in mice have assumed the ratio of anterior:posterior volumes in mice to be similar to those in humans. Our goal was to measure anterior and posterior chamber volumes in mice to facilitate better estimates of aqueous inflow rates. MethodsWe used standard near-infrared optical coherence tomography (OCT) and robotic visible-light OCT (vis-OCT) to visualize, reconstruct and quantify the volumes of the anterior and posterior chambers of the mouse eye in vivo. We used histology and micro-CT scans to validate relevant landmarks from ex vivo tissues to facilitate in vivo measurement. ResultsPosterior chamber volume is 1.1 times the anterior chamber volume in BALB/cAnNCrl mice, i.e. the anterior chamber constitutes about 47% of the total aqueous humor volume, which is very dissimilar to the situation in humans. Anterior chamber volumes in 2-month-old BALB/cAnNCrl and 7-month-old C57BL6/J mice were 1.55 {+/-} 0.36 {micro}L (n=10) and 2.41 {+/-} 0.29 {micro}L (n=8), respectively. This implies that previous studies likely over-estimated aqueous inflow rate by approximately two-fold. ConclusionsIt is necessary to reassess previously reported estimates of aqueous inflow rates, and thus aqueous humor dynamics in the mouse. For example, we now estimate that only 0-15% of aqueous humor drains via the pressure-independent (unconventional) route, similar to that seen in humans and monkeys.

physiology↗

bioRxiv2024

Magnetically Steered Cell Therapy For Functional Restoration Of Intraocular Pressure Control In Open-Angle Glaucoma

Trabecular meshwork (TM) cell therapy has been proposed as a next-generation treatment for elevated intraocular pressure (IOP) in glaucoma, the most common cause of irreversible blindness. Using a magnetic cell steering technique with excellent efficiency and tissue-specific targeting, we delivered two types of cells into a mouse model of glaucoma: either human adipose-derived mesenchymal stem cells (hAMSCs) or induced pluripotent cell derivatives (iPSC-TM cells). We observed a 4.5 [3.1, 6.0] mmHg or 27% reduction in intraocular pressure (IOP) for nine months after a single dose of only 1500 magnetically-steered hAMSCs, explained by increased outflow through the conventional pathway and associated with an higher TM cellularity. iPSC-TM cells were also effective, but less so, showing only a 1.9 [0.4, 3.3] mmHg or 13% IOP reduction and increased risk of tumorigenicity. In both cases, injected cells remained detectable in the iridocorneal angle three weeks post-transplantation. Based on the locations of the delivered cells, the mechanism of IOP lowering is most likely paracrine signaling. We conclude that magnetically-steered hAMSC cell therapy has potential for long-term treatment of ocular hypertension in glaucoma. One Sentence SummaryA novel magnetic cell therapy provided effective intraocular pressure reduction in a mouse model, motivating future translational studies.

bioengineering↗

bioRxiv2023

Aging and intraocular pressure homeostasis in mice

Age and elevated intraocular pressure (IOP) are the two primary risk factors for glaucoma, an optic neuropathy that is the leading cause of irreversible blindness. In most people, IOP is tightly regulated over a lifetime by the conventional outflow tissues. However, the mechanistic contributions of age to conventional outflow dysregulation, elevated IOP and glaucoma are unknown. To address this gap in knowledge, we studied how age affects the morphology, biomechanical properties and function of conventional outflow tissues in C57BL/6 mice, which have an outflow system similar to humans. As reported in humans, we observed that IOP in mice was maintained within a tight range over their lifespan. Remarkably, despite a constellation of age-related changes to the conventional outflow tissues that would be expected to hinder aqueous drainage and impair homeostatic function (decreased cellularity, increased pigment accumulation, increased cellular senescence and increased stiffness), outflow facility, a measure of conventional outflow tissue fluid conductivity, was stable with age. We conclude that the murine conventional outflow system has significant functional reserve in healthy eyes. However, these age-related changes, when combined with other underlying factors, such as genetic susceptibility, are expected to increase risk for ocular hypertension and glaucoma.

physiology↗

bioRxiv2023

A Histomorphometric and Computational Investigation of the Stabilizing Role of Pectinate Ligaments in the Aqueous Outflow Pathway

Murine models are commonly used to study glaucoma, the leading cause of irreversible blindness. Glaucoma is associated with elevated intraocular pressure (IOP), which is regulated by the tissues of the aqueous outflow pathway. In particular, pectinate ligaments (PLs) connect the iris and trabecular meshwork (TM) at the anterior chamber angle, with an unknown role in maintenance of the biomechanical stability of the aqueous outflow pathway, thus motivating this study. We conducted histomorphometric analysis and optical coherence tomography-based finite element (FE) modeling on three cohorts of C57BL/6 mice: young (2-6 months), middle-aged (11-16 months), and elderly (25-32 months). We evaluated the age-specific morphology of the outflow pathway tissues. Further, because of the known pressure-dependent Schlemms canal (SC) narrowing, we assessed the dependence of the SC lumen area to varying IOPs in age-specific FE models over a physiological range of TM/PL stiffness values. We found age-dependent changes in morphology of outflow tissues; notably, the PLs were more developed in older mice compared to younger ones. In addition, FE modeling demonstrated that murine SC patency is highly dependent on the presence of PLs, and that increased IOP caused SC collapse only with sufficiently low TM/PL stiffness values. Moreover, the elderly model showed more susceptibility to SC collapse compared to the younger models. In conclusion, our study elucidated the previously unexplored role of PLs in the aqueous outflow pathway, indicating their function in supporting TM and SC under elevated IOP.

bioengineering↗

bioRxiv2023

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

Pathologic alterations in the biomechanical properties of the Schlemms 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 to 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 YAP mechanosignaling 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 activity in primary human SC cells, and whether disruption of YAP mechanosignaling attenuates SC cell pathobiology and increases ex vivo outflow facility. We demonstrated that ECM stiffening drives pathologic YAP 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 mechanosignaling abrogates stiffness-induced SC cell dysfunction involving altered cytoskeletal and ECM remodeling. Lastly, we found that perfusion of the clinically-used, small molecule YAP 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 mechanosignaling in SC cell dysfunction and suggest that YAP inhibition has therapeutic value for treating ocular hypertension in glaucoma.

cell biology↗

bioRxiv2023

Polarized Desmosome and Hemidesmosome Shedding via Exosomes is an Early Indicator of Outer Blood-Retina Barrier Dysfunction

The retinal pigmented epithelium (RPE) constitutes the outer blood-retinal barrier, enables photoreceptor function of the eye, and is constantly exposed to oxidative stress. As such, dysfunction of the RPE underlies pathology leading to development of age-related macular degeneration (AMD), the leading cause of vision loss among the elderly in industrialized nations. A major responsibility of the RPE is to process photoreceptor outer segments, which relies on the proper functioning of its endocytic pathways and endosomal trafficking. Exosomes and other extracellular vesicles from RPE are an essential part of these pathways and may be early indicators of cellular stress. To test the role of exosomes that may underlie the early stages of AMD, we used a polarized primary RPE cell culture model under chronic subtoxic oxidative stress. Unbiased proteomic analyses of highly purified basolateral exosomes from oxidatively stressed RPE cultures revealed changes in proteins involved in epithelial barrier integrity. There were also significant changes in proteins accumulating in the basal-side sub-RPE extracellular matrix during oxidative stress, that could be prevented with an inhibitor of exosome release. Thus, chronic subtoxic oxidative stress in primary RPE cultures induces changes in exosome content, including basal-side specific desmosome and hemidesmosome shedding via exosomes. These findings provide novel biomarkers of early cellular dysfunction and opportunity for therapeutic intervention in age-related retinal diseases, (e.g., AMD) and broadly from blood-CNS barriers in other neurodegenerative diseases.

cell biology↗

bioRxiv2022

YAP/TAZ mediate TGFβ2-induced Schlemm's canal cell dysfunction

PurposeElevated transforming growth factor beta2 (TGF{beta}2) levels in the aqueous humor have been linked to glaucomatous outflow tissue dysfunction. Potential mediators of dysfunction are the transcriptional co-activators, Yes-associated protein (YAP) and transcriptional coactivator with PDZ binding motif (TAZ). However, the molecular underpinnings of YAP/TAZ modulation in Schlemms Canal (SC) cells under glaucomatous conditions are not well understood. Here, we investigate how TGF{beta}2 regulates YAP/TAZ activity in human SC (HSC) cells using biomimetic extracellular matrix (ECM) hydrogels, and examine whether pharmacologic YAP/TAZ inhibition would attenuate TGF{beta}2-induced HSC cell dysfunction. MethodsPrimary HSC cells were seeded atop photocrosslinked ECM hydrogels, made of collagen type I, elastin-like polypeptide and hyaluronic acid, or encapsulated within the hydrogels. HSC cells were induced with TGF{beta}2 in the absence or presence of concurrent actin destabilization or pharmacologic YAP/TAZ inhibition. Changes in actin cytoskeletal organization, YAP/TAZ activity, ECM production, phospho-myosin light chain levels, and hydrogel contraction were assessed. ResultsTGF{beta}2 significantly increased YAP/TAZ nuclear localization in HSC cells, which was prevented by either filamentous (F)-actin relaxation or depolymerization. Pharmacologic YAP/TAZ inhibition using verteporfin without light stimulation decreased fibronectin expression and reduced actomyosin cytoskeletal rearrangement in HSC cells induced by TGF{beta}2. Similarly, verteporfin significantly attenuated TGF{beta}2-induced HSC cell-encapsulated hydrogel contraction. ConclusionsOur data provide evidence for a pathologic role of aberrant YAP/TAZ signaling in HSC cells under simulated glaucomatous conditions, and suggest that pharmacologic YAP/TAZ inhibition has promising potential to improve outflow tissue dysfunction.

cell biology↗