Biology subjects

Ganapathy, P. S.

Publications and source records attributed to Ganapathy, P. S..

10 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↗

bioRxiv2025

Harnessing cell-encapsulated hydrogels to study astrocyte mechanoresponse in 4D

In glaucoma, the optic nerve head (ONH) is exposed to increased biomechanical strain, impacting the resident astrocytes that maintain neural homeostasis. During disease progression astrocytes exhibit morphologic and metabolic shifts; however, the specific impact of glaucoma-related biomechanical strains on astrocyte behavior remains poorly understood. To address this, we used our previously established 3D cell-encapsulated extracellular matrix (ECM) hydrogel to investigate ONH astrocyte cellular and transcriptomic responses to varying biomechanical strain levels over time. Murine ONH astrocyte were encapsulated within an ECM hydrogel made from photocrosslinkable collagen type I and hyaluronic acid, and subjected to 0, 3, or 10% cyclic compression for 4h and 24h. We found significant restructuring of cytoskeletal morphology, metabolic dysregulation, and astrocyte-mediated ECM modulation that were strain-, duration- and hydrogel subregion-dependent. These phenotypic alterations were associated with diverse transcriptional changes in genes related to cell cycle and morphology, inflammation, metabolism and matrix remodeling that were driven by compressive strain intensity and duration. Our work reveals the direct role of compressive strain in eliciting a complex astrocyte response, supports targeting mechanosensation to prevent these pathologic astrocyte responses, and establishes ECM-based hydrogels as a platform to test mechanisms driving astrocyte mechanodysfunction. Altogether, our study offers new insights into astrocyte responses to biomechanical insult and demonstrates the use of a tunable 3D ECM hydrogel for future mechanistic studies of neurodegeneration. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/660800v2_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@f355fborg.highwire.dtl.DTLVardef@191e096org.highwire.dtl.DTLVardef@2fae32org.highwire.dtl.DTLVardef@55913c_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

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↗

bioRxiv2022

YAP/TAZ inactivation with simvastatin attenuates glucocorticoid-induced human trabecular meshwork cell dysfunction

PurposeImpairment 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 YAP/TAZ inactivation with simvastatin attenuates glucocorticoid-induced human TM (HTM) cell dysfunction. MethodsPrimary 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. ResultsSimvastatin 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 extracellular fibronectin deposition. Sequential treatment was similarly effective but did not match clinically-used Rho kinase inhibition. ConclusionsYAP/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.

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↗

bioRxiv2022

Engineering a 3D hydrogel system to study optic nerve head astrocyte morphology and behavior in response to glaucomatous insult

In glaucoma, astrocytes within the optic nerve head (ONH) rearrange their actin cytoskeleton, while becoming reactive and upregulating intermediate filament glial fibrillary acidic protein (GFAP). Increased transforming growth factor beta 2 (TGF{beta}2) levels have been implicated in glaucomatous ONH dysfunction. A key limitation of using conventional 2D culture to study ONH astrocyte behavior is the inability to faithfully replicate the in vivo ONH microenvironment. Here, we engineer a 3D ONH astrocyte hydrogel to better mimic in vivo mouse ONH astrocyte (MONHA) morphology, and test induction of MONHA reactivity using TGF{beta}2. Primary MONHAs were isolated from C57BL/6J mice and cell purity confirmed. To engineer 3D cell-laden hydrogels, MONHAs were mixed with photoactive extracellular matrix components (collagen type I, hyaluronic acid) and crosslinked for 5 minutes using a photoinitiator (0.025% riboflavin) and UV light (405-500 nm, 10.3 mW/cm2). MONHA-encapsulated hydrogels were cultured for 3 weeks, and then treated with TGF{beta}2 (2.5, 5.0 or 10 ng/ml) for 7 days to assess for reactivity. Following encapsulation, MONHA retained high cell viability in hydrogels and continued to proliferate over 4 weeks as determined by live/dead staining and MTS assays. Sholl analysis demonstrated that MONHAs within hydrogels developed increasing process complexity with longer process length over time. Cell processes connected with neighboring cells, coinciding with Connexin43 expression within astrocytic processes. Treatment with TGF{beta}2 induced reactivity in MONHA-encapsulated hydrogels as determined by altered F-actin cytoskeletal morphology, increased GFAP expression, and elevated fibronectin and collagen IV deposition. Our data sets the stage for future use of this 3D biomimetic ONHA-encapsulated hydrogel to investigate ONHA behavior in response to glaucomatous insult.

bioengineering↗

bioRxiv2021

Extracellular matrix stiffness and TGFβ2 regulate YAP/TAZ activity in human trabecular meshwork cells

Primary open-angle glaucoma progression is associated with increased human trabecular meshwork (HTM) stiffness and elevated transforming growth factor beta 2 (TGF{beta}2) levels in aqueous humor. Increased transcriptional activity of Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), central players in mechanotransduction, are implicated in glaucomatous HTM (GTM) cell dysfunction. Yet, the detailed mechanisms underlying YAP/TAZ modulation in HTM cells in response to alterations in extracellular matrix (ECM) stiffness and TGF{beta}2 levels are not well understood. Using biomimetic ECM hydrogels with tunable stiffness, here we show that increased ECM stiffness elevates YAP/TAZ transcriptional activity potentially through modulating focal adhesions and cytoskeletal rearrangement. Furthermore, TGF{beta}2 increased YAP/TAZ nuclear localization in both normal and glaucomatous HTM cells, which was prevented by inhibiting extracellular-signal-regulated kinase and Rho-associated kinase signaling pathways. Filamentous (F)-actin depolymerization reversed TGF{beta}2-induced YAP/TAZ nuclear localization. YAP/TAZ depletion using siRNA or verteporfin decreased focal adhesions, ECM remodeling and cell contractile properties. Similarly, YAP/TAZ inactivation with verteporfin partially blocked TGF{beta}2-induced HTM/GTM hydrogel contraction and stiffening. Collectively, our data provide evidence for a pathologic role of aberrant YAP/TAZ signaling in glaucomatous HTM cell dysfunction, and may help inform strategies for the development of novel multifactorial approaches to prevent progressive ocular hypertension in glaucoma.

cell biology↗

bioRxiv2021

TGFβ2 regulates human trabecular meshwork cell contractility via ERK and ROCK pathways with distinct signaling crosstalk dependent on the culture substrate

Transforming growth factor beta 2 (TGF{beta}2) is a major contributor to the pathologic changes occurring in human trabecular meshwork (HTM) cells in primary open-angle glaucoma. Receptor binding of TGF{beta}2 activates non-canonical extracellular-signal-regulated kinase (ERK) and Rho-associated kinase (ROCK) signaling pathways, both broadly affecting HTM cell behavior. However, exactly how these signaling pathways converge to regulate pathologic HTM cell contractility associated with glaucomatous dysfunction is unclear. Here, we investigated the molecular mechanism underlying TGF{beta}2-induced pathologic HTM cell contractility, and the crosstalk between ERK and ROCK signaling pathways. We compared soft biomimetic hydrogels composed of collagen type I, elastin-like polypeptide, and hyaluronic acid with conventional stiff glass coverslips. Results show that HTM cell morphology and filamentous (F)-actin organization was affected by the underlying culture substrate: TGF{beta}2 increased HTM cell contractility via ERK and ROCK signaling pathways by differentially regulating F-actin, -smooth muscle actin, fibronectin, and phospho-myosin light chain in cells grown on hydrogels compared to glass. Importantly, we showed that ERK inhibition further increased TGF{beta}2-induced phospho-myosin light chain levels in HTM cells on hydrogels, but not on glass, which translated into hypercontractility of three-dimensional (3D) HTM cell-laden hydrogels. ROCK inhibition had precisely the opposite effects and potently relaxed the TGF{beta}2-induced hydrogels. This suggests that ERK signaling negatively regulates ROCK-mediated HTM cell contractility, and that impairment of this crosstalk balance contributes to the pathologic contraction associated with the glaucomatous stressor TGF{beta}2. These findings emphasize the critical importance of using 3D tissue-mimetic extracellular matrix substrates for investigating HTM cell physiology and glaucomatous pathophysiology in vitro.

cell biology↗

bioRxiv2021

Mechanosensitive channel inhibition attenuates TGFβ2-induced actin cytoskeletal remodeling and reactivity in mouse optic nerve head astrocytes.

Astrocytes within the optic nerve head undergo actin cytoskeletal rearrangement early in glaucoma, which coincides with astrocyte reactivity and extracellular matrix (ECM) deposition. Elevated transforming growth factor beta 2 (TGF{beta}2) levels within astrocytes have been described in glaucoma, and TGF{beta} signaling induces actin cytoskeletal remodeling and ECM deposition in many tissues. A key mechanism by which astrocytes sense and respond to external stimuli is via mechanosensitive ion channels. Here, we tested the hypothesis that inhibition of mechanosensitive channels will attenuate TGF{beta}2-mediated optic nerve head astrocyte actin cytoskeletal remodeling, reactivity, and ECM deposition. Primary optic nerve head astrocytes were isolated from C57BL/6J mice and cell purity was confirmed by immunostaining. Astrocytes were treated with vehicle control, TGF{beta}2 (5 ng/ml), GsMTx4 (a mechanosensitive channel inhibitor; 500 nM), or TGF{beta}2 (5 ng/ml) + GsMTx4 (500 nM) for 48 h. FITC-phalloidin staining was used to assess the formation of f-actin stress fibers and to quantify the presence of crosslinked actin networks (CLANs). Cell reactivity was determined by immunostaining for GFAP. Levels of fibronectin deposition were also quantified. Primary optic nerve head astrocytes were positive for the astrocyte marker GFAP and negative for markers for microglia (Iba1) and oligodendrocytes (OSP1). Significantly increased %CLAN-positive cells were observed after 48-h treatment with TGF{beta}2 vs. control in a dose-dependent manner. Co-treatment with GsMTx4 significantly decreased %CLAN-positive cells vs. TGF{beta}2 treatment and the presence of f-actin stress fibers. TGF{beta}2 treatment significantly increased GFAP and fibronectin fluorescence intensity, which were decreased with GsMTx4 treatment. Our data suggest inhibition of mechanosensitive channel activity as a potential therapeutic strategy to modulate actin cytoskeletal remodeling within the optic nerve head in glaucoma.

cell biology↗

bioRxiv2020

A tissue-engineered human trabecular meshwork hydrogel for advanced glaucoma disease modeling

PurposeAbnormal human trabecular meshwork (HTM) cell function and extracellular matrix (ECM) remodeling contribute to HTM stiffening in primary open-angle glaucoma (POAG). Most current cellular HTM model systems do not sufficiently replicate the complex native three dimensional (3D) cell-ECM interface, which makes them less than ideal to investigate POAG pathology. Tissue-engineered protein-based hydrogels are ideally positioned to overcome shortcomings of current models. Here, we report a novel biomimetic HTM hydrogel and test its utility as a POAG disease model. MethodsHTM hydrogels were engineered by mixing normal donor-derived HTM cells with collagen type I, elastin-like polypeptide and hyaluronic acid, each containing photoactive functional groups, followed by UV light-activated free-radical crosslinking. Glaucomatous conditions were induced with dexamethasone (DEX), and therapeutic effects of the Rho-associated kinase (ROCK) inhibitor Y27632 on cytoskeletal organization and tissue-level function, contingent on HTM cell-ECM interactions, were assessed. ResultsDEX exposure increased HTM hydrogel contractility, f-actin and alpha smooth muscle actin abundance and rearrangement, ECM remodeling, and fibronectin and collagen type IV deposition, all contributing to HTM hydrogel condensation and stiffening consistent with recent data from normal vs. glaucomatous HTM tissue. Y27632 treatment produced precisely the opposite effects and attenuated the DEX-induced pathologic changes, resulting in HTM hydrogel relaxation and softening. ConclusionsWe have developed a biomimetic HTM hydrogel model for detailed investigation of 3D cell-ECM interactions under normal and simulated glaucomatous conditions. Its bidirectional responsiveness to pharmaceutical challenge and rescue suggests promising potential to serve as screening platform for new POAG treatments with focus on HTM biomechanics.

bioengineering↗