Biology subjects

Ganapathy, P. S.

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

4 recordsLinked to original sources

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↗