Publications by authors named "Vijaykrishna Raghunathan"

Neurodegeneration in glaucoma patients is clinically identified through longitudinal assessment of structure-function changes, including intraocular pressure, cup-to-disc ratios from fundus images, and optical coherence tomography imaging of the retinal nerve fiber layer. Use of human post-mortem ocular tissue for basic research is rising in the glaucoma field, yet there are challenges in assessing disease stage and severity, since tissue donations with informed consent are often unaccompanied by detailed pre-mortem clinical information. Further, the interpretation of disease severity based solely on anatomical and morphological assessments by histology can be affected by differences in death-to-preservation time and tissue processing.

View Article and Find Full Text PDF

Intraocular pressure (IOP) elevation is the primary risk factor and currently the main treatable factor for progression of glaucomatous optic neuropathy. In addition to direct clinical and living animal in vivo studies, ex vivo perfusion of anterior segments and whole eyes is a key technique for studying conventional outflow function as it is responsible for IOP regulation. We present well-tested experimental details, protocols, considerations, advantages, and limitations of several ex vivo model systems for studying IOP regulation.

View Article and Find Full Text PDF
Article Synopsis
  • The study investigates how the extracellular matrix (ECM) interacts with trabecular meshwork (TM) cells in the eye, particularly focusing on its role in causing ocular hypertension and glaucoma-like changes due to dexamethasone treatment.
  • Researchers created an in vitro model using primary TM cells isolated from non-glaucoma donors and analyzed gene expression after treating these cells with ECM derived from dexamethasone-treated cultures.
  • They identified 402 differentially expressed genes related to glaucoma pathogenesis, which are involved in inflammation, signaling, matrix remodeling, and angiogenesis, highlighting the complex cellular interactions that can lead to increased eye pressure.
View Article and Find Full Text PDF

The trabecular meshwork within the conventional outflow apparatus is critical in maintaining intraocular pressure homeostasis. studies employing primary cell cultures of the human trabecular meshwork (hTM) have conventionally served as surrogates for investigating the pathobiology of TM dysfunction. Despite its abundant use, translation of outcomes from studies to and/or studies remains a challenge.

View Article and Find Full Text PDF

Purpose: Biophysical and biochemical attributes of the extracellular matrix are major determinants of cell fate in homeostasis and disease. Ocular hypertension and glaucoma are diseases where the trabecular meshwork tissue responsible for aqueous humor egress becomes stiffer accompanied by changes in its matrisome in a segmental manner with regions of high or low flow. Prior studies demonstrate these alterations in the matrix are dynamic in response to age and pressure changes.

View Article and Find Full Text PDF

Biophysical and biochemical attributes of the extracellular matrix are major determinants of cell fate in homeostasis and disease. Ocular hypertension and glaucoma are diseases where the trabecular meshwork tissue responsible for aqueous humor egress becomes stiffer accompanied by changes in its matrisome in a segmental manner with regions of high or low flow. Prior studies demonstrate these alterations in the matrix are dynamic in response to age and pressure changes.

View Article and Find Full Text PDF

Purpose: Fuchs endothelial corneal dystrophy (FECD) is a progressive corneal disease that impacts the structure and stiffness of the Descemet's membrane (DM), the substratum for corneal endothelial cells (CECs). These structural alterations of the DM could contribute to the loss of the CECs resulting in corneal edema and blindness. Oxidative stress and transforming growth factor-β (TGF-β) pathways have been implicated in endothelial cell loss and endothelial to mesenchymal transition of CECs in FECD.

View Article and Find Full Text PDF

Fabrication of conductive and bioactive microdevices has garnered tremendous attention in the emerging biomedical fields, particularly organic bioelectronics and biosensing. Direct laser 3D printing based on two-photon polymerization (TPP) has shown great promise in construction of well-defined and multi-functional microdevices. Herein, we present a novel photosensitive resin for fabrication of highly conductive and bioactive microstructures via TPP.

View Article and Find Full Text PDF

Primary open-angle glaucoma progression is associated with increased human trabecular meshwork (HTM) stiffness and elevated transforming growth factor beta 2 (TGFβ2) levels in the 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 cell dysfunction. Yet, the detailed mechanisms underlying YAP/TAZ modulation in HTM cells in response to alterations in extracellular matrix (ECM) stiffness and TGFβ2 levels are not well understood.

View Article and Find Full Text PDF

Due to their similarities in anatomy, physiology, and pharmacology to humans, mice are a valuable model system to study the generation and mechanisms modulating conventional outflow resistance and thus intraocular pressure. In addition, mouse models are critical for understanding the complex nature of conventional outflow homeostasis and dysfunction that results in ocular hypertension. In this review, we describe a set of minimum acceptable standards for developing, characterizing, and utilizing mouse models of open-angle ocular hypertension.

View Article and Find Full Text PDF
Article Synopsis
  • - Re-epithelialization is essential for wound healing, but conventional topical methods of delivering growth factors, like ointments, have limited effectiveness due to their short duration on wounds.
  • - The study shows that covalently immobilizing epidermal growth factor (EGF) onto the wound surfaces of genetically diabetic mice allows for sustained release and improved healing outcomes.
  • - This method resulted in a 20% increase in wound closure compared to topical treatment and required significantly less EGF, with no observed adverse effects, highlighting its potential for treating difficult wounds.
View Article and Find Full Text PDF

The transformation of quiescent keratocytes to activated fibroblasts and myofibroblasts (KFM transformation) largely depends on transforming growth factor beta (TGFβ) signaling. Initiation of the TGFβ signaling cascade results from binding of TGFβ to the labile type I TGFβ receptor (TGFβRI), which is stabilized by the 90 kDa heat shock protein (Hsp90). Since myofibroblast persistence within the corneal stroma can result in stromal haze and corneal fibrosis in patients undergoing keratorefractive therapy, modulation of TGFβ signaling through Hsp90 inhibition would represent a novel approach to prevent myofibroblast persistence.

View Article and Find Full Text PDF

Purpose: Lysophosphatidic acid (LPA) and soluble interleukin-6 receptor (sIL6R) are elevated in primary open angle glaucoma (POAG). LPA and IL6 modulate in response to biomechanical stimuli and converge on similar fibrotic phenotypes. Thus, we determined whether LPA and IL6 trans-signaling (IL6/sIL6R) interact via Yes-associated protein (YAP)/Transcriptional coactivator with a PDZ-binding motif (TAZ) or Signal transducer and activator of transcription 3 (STAT3) pathways in human trabecular meshwork (hTM) cells.

View Article and Find Full Text PDF

Purpose: To determine the temporal effects of dexamethasone (DEX) and glucocorticoid-induced matrix (GIM) on integrins/integrin adhesomes, caveolins, cytoskeletal-related proteins, and stiffness in human trabecular meshwork (hTM) cells.

Methods: Primary hTM cells were plated on plastic dishes (TCP), treated with vehicle (Veh) or 100 nM DEX in 1% serum media for 1, 3, 5, and 7 day(s). Concurrently, hTM cells were also plated on vehicle control matrices (VehMs) and GIMs for similar time points; VehMs and GIMs had been generated from chronic cultures of Veh-/DEX-stimulated hTM cells and characterized biochemically.

View Article and Find Full Text PDF

The underlying pathological mechanisms of glaucomatous trabecular meshwork (TM) damage and elevation of intraocular pressure (IOP) are poorly understood. Here, we report that the chronic endoplasmic reticulum (ER) stress-induced ATF4-CHOP-GADD34 pathway is activated in TM of human and mouse glaucoma. Expression of ATF4 in TM promotes aberrant protein synthesis and ER client protein load, leading to TM dysfunction and cell death.

View Article and Find Full Text PDF

Glaucoma remains only partially understood, particularly at the level of intraocular pressure (IOP) regulation. Trabecular meshwork (TM) and Schlemm's canal inner wall endothelium (SCE) are key to IOP regulation and their characteristics and behavior are the focus of much investigation. This is becoming more apparent with time.

View Article and Find Full Text PDF

Purpose: Wnt is a spatiotemporally regulated signaling pathway whose inhibition is associated with glaucoma, elevated intraocular pressure (IOP), and cell stiffening. Whether such changes are permanent or may be reversed is unclear. Here, we determine if activation of Wnt pathway after inhibition reverses the pathologic phenotype.

View Article and Find Full Text PDF

Segmental flow in the human trabecular meshwork is a well-documented phenomenon but in depth mechanistic investigations of high flow (HF) and low flow (LF) regions are restricted due to the small amount of tissue available from a single donor. To address this issue we have generated and characterized multiple paired HF and LF cell strains. Here paired HF and LF cell strains were generated from single donors.

View Article and Find Full Text PDF

Ocular hypertension has been attributed to increased resistance to aqueous outflow often as a result of changes in trabecular meshwork (TM) extracellular matrix (ECM) using in vivo animal models (for example, by genetic manipulation) and ex vivo anterior segment perfusion organ cultures. These are, however, complex and difficult in dissecting molecular mechanisms and interactions. In vitro approaches to mimic the underlying substrate exist by manipulating either ECM topography, mechanics, or chemistry.

View Article and Find Full Text PDF

Reactive molecular oxygen (O) plays important roles in bioenergetics and metabolism and is implicated in biochemical pathways underlying angiogenesis, fertilization, wound healing and regeneration. Here we describe how to use the scanning micro-optrode technique (SMOT) to measure extracellular fluxes of dissolved O. The self-referencing O-specific micro-optrode (also termed micro-optode and optical fiber microsensor) is a tapered optical fiber with an O-sensitive fluorophore coated onto the tip.

View Article and Find Full Text PDF

Elevated intraocular pressure (IOP) is the primary risk factor for glaucoma and is the only treatable feature of the disease. There is a correlation between elevated pressure and homeostatic reductions in the aqueous humor outflow resistance via changes in the extracellular matrix of the trabecular meshwork. It is unclear how these extracellular matrix changes affect segmental patterns of aqueous humor outflow, nor do we understand their causal relationship.

View Article and Find Full Text PDF

Redox state sustained by reactive oxygen species (ROS) is crucial for regeneration; however, the interplay between oxygen (O), ROS and hypoxia-inducible factors (HIF) remains elusive. Here we observe, using an optic-based probe (optrode), an elevated and steady O influx immediately upon amputation. The spatiotemporal O influx profile correlates with the regeneration of Xenopus laevis tadpole tails.

View Article and Find Full Text PDF

Purpose: To develop a mechanical model in which a contact lens is swept over ocular surface cells under conditions that mimic the force and speed of the blink, and to investigate the resulting biological changes.

Methods: A computer controlled mechanical instrument was developed to hold a dish containing 3D cultured stratified human ocular surface epithelial cells, across which an arm bearing a contact lens was swept back and forth repeatedly at a speed and force mimicking the human blink. Cells were subjected to repeated sweep cycles for up to 1 h at a speed of 120 mm/s with or without an applied force of 19.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

The posterior face of the cornea consists of the corneal endothelium, a monolayer of cuboidal cells that secrete and attach to Descemet's membrane, an exaggerated basement membrane. Dysfunction of the endothelium compromises the barrier and pump functions of this layer that maintain corneal deturgesence. A large number of corneal endothelial dystrophies feature irregularities in Descemet's membrane, suggesting that cells create and respond to the biophysical signals offered by their underlying matrix.

View Article and Find Full Text PDF