Effect of benzalkonium chloride on trabecular meshwork cells in a new in vitro 3D trabecular meshwork model for glaucoma

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.

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.

Preservatives and ocular surface disease: A review

Ocular surface disease (OSD) is a complex condition that can cause a range of symptoms (e.g, dryness, irritation, and pain) and can significantly impact the quality of life of affected individuals. Iatrogenic OSD, a common finding in patients with glaucoma who receive chronic therapy with topical ocular antihypertensive drugs containing preservatives such as benzalkonium chloride (BAK), has been linked to damage to the ocular surface barrier, corneal epithelial cells, nerves, conjunctival goblet cells, and trabecular meshwork. Chronic BAK exposure activates inflammatory pathways and worsens symptoms, compromising the success of subsequent filtration surgery in an exposure-dependent manner. In eyes being treated for glaucoma, symptomatic treatment of OSD may provide some relief, but addressing the root cause of the OSD often necessitates reducing or, ideally, eliminating BAK toxicity. Strategies to decrease BAK exposure in patients with glaucoma encompass the use of preservative-free formulations or drugs with alternative and less toxic preservatives such as SofZia®, Polyquad, potassium sorbate, or Purite®. Though the benefits of these alternative preservatives are largely unproven, they might be considered when financial constraints prevent the use of preservative-free versions. For patients receiving multiple topical preserved drugs, the best practice is to switch to nonpreserved equivalents wherever feasible, regardless of OSD severity. Furthermore, nonpharmacological approaches, including laser or incisional procedures, should be considered. This review explores the effects of BAK on the ocular surface and reviews strategies for minimizing or eliminating BAK exposure in patients with glaucoma in order to significantly improve their quality of life and prevent complications associated with chronic exposure to BAK.

RNA-seq transcriptomic profiling of TGF-β2-exposed human trabecular meshwork explants: Advancing insights beyond conventional cell culture models

Primary open-angle glaucoma (POAG), a leading cause of irreversible vision loss, is closely linked to increased intraocular pressure (IOP), with the trabecular meshwork (TM) playing a critical role in its regulation. The TM, located at the iridocorneal angle, acts as a sieve, filtering the aqueous humor from the eye into the collecting ducts, thus maintaining proper IOP levels. The transforming growth factor-beta 2 (TGF-β2) signaling pathway has been implicated in the pathophysiology of primary open-angle glaucoma POAG particularly, in the dysfunction of the TM. This study utilizes human TM explants to closely mimic in vivo conditions, thereby minimizing transcriptional changes that could arise from cell culture enabling an exploration of the transcriptomic impacts of TGF-β2. Through bulk RNA sequencing and immunohistological analysis, we identified distinct gene expression patterns and morphological changes induced by TGF-β2 exposure (5 ng/ml for 48 h). Bulk RNA sequencing identified significant upregulation in genes linked to extracellular matrix (ECM) regulation and fibrotic signaling. Immunohistological analysis further elucidated the morphological alterations, including cytoskeletal rearrangements and ECM deposition, providing a visual confirmation of the transcriptomic data. Notably, the enrichment analysis unveils TGF-β2's influence on both bone morphogenic protein (BMP) and Wnt signaling pathways, suggesting a complex interplay of molecular mechanisms contributing to TM dysfunction in glaucoma. This characterization of the transcriptomic modifications on an explant model of TM obtained under the effect of this profibrotic cytokine involved in glaucoma is crucial in order to develop and test new molecules that can block their signaling pathways.

Application of Single Cell Type-Derived Spheroids Generated by Using a Hanging Drop Culture Technique in Various In Vitro Disease Models: A Narrow Review

Cell culture methods are indispensable strategies for studies in biological sciences and for drug discovery and testing. Most cell cultures have been developed using two-dimensional (2D) culture methods, but three-dimensional (3D) culture techniques enable the establishment of in vitro models that replicate various pathogenic conditions and they provide valuable insights into the pathophysiology of various diseases as well as more precise results in tests for drug efficacy. However, one difficulty in the use of 3D cultures is selection of the appropriate 3D cell culture technique for the study purpose among the various techniques ranging from the simplest single cell type-derived spheroid culture to the more sophisticated organoid cultures. In the simplest single cell type-derived spheroid cultures, there are also various scaffold-assisted methods such as hydrogel-assisted cultures, biofilm-assisted cultures, particle-assisted cultures, and magnet particle-assisted cultures, as well as non-assisted methods, such as static suspension cultures, floating cultures, and hanging drop cultures. Since each method can be differently influenced by various factors such as gravity force, buoyant force, centrifugal force, and magnetic force, in addition to non-physiological scaffolds, each method has its own advantages and disadvantages, and the methods have different suitable applications. We have been focusing on the use of a hanging drop culture method for modeling various non-cancerous and cancerous diseases because this technique is affected only by gravity force and buoyant force and is thus the simplest method among the various single cell type-derived spheroid culture methods. We have found that the biological natures of spheroids generated even by the simplest method of hanging drop cultures are completely different from those of 2D cultured cells. In this review, we focus on the biological aspects of single cell type-derived spheroid culture and its applications in in vitro models for various diseases.

Artificial Trabecular Meshwork Structure Combining Melt Electrowriting and Solution Electrospinning

The human trabecular meshwork (HTM) is responsible for regulating intraocular pressure (IOP) by means of gradient porosity. Changes in its physical properties, like increases in stiffness or alterations in the extracellular matrix (ECM), are associated with increases in the IOP, which is the primary cause of glaucoma. The complexity of its structure limits the engineered models to one-layered and simple approaches, which do not accurately replicate the biological and physiological cues related to glaucoma. Here, a combination of melt electrowriting (MEW) and solution electrospinning (SE) is explored as a biofabrication technique used to produce a gradient porous scaffold that mimics the multi-layered structure of the native HTM. Polycaprolactone (PCL) constructs with a height of 20-710 µm and fiber diameters of 0.7-37.5 µm were fabricated. After mechanical characterization, primary human trabecular meshwork cells (HTMCs) were seeded over the scaffolds within the subsequent 14-21 days. In order to validate the system's responsiveness, cells were treated with dexamethasone (Dex) and the rho inhibitor Netarsudil (Net). Scanning electron microscopy and immunochemistry staining were performed to evaluate the expected morphological changes caused by the drugs. Cells in the engineered membranes exhibited an HTMC-like morphology and a correct drug response. Although this work demonstrates the utility of combining MEW and SE in reconstructing complex morphological features like the HTM, new geometries and dimensions should be tested, and future works need to be directed towards perfusion studies.

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.

Comparing the effect of benzalkonium chloride-preserved, polyquad-preserved, and preservative-free prostaglandin analogue eye drops on cultured human conjunctival goblet cells

PURPOSE

To investigate the effect of benzalkonium chloride (BAK)-preserved latanoprost and bimatoprost, polyquad (PQ)-preserved travoprost, and preservative-free (PF) latanoprost and tafluprost, all prostaglandin analogues (PGAs), on human conjunctival goblet cell (GC) survival. Furthermore, to investigate the effect of BAK-preserved and PF latanoprost on the cytokine secretion from GC.

METHODS

Primary human conjunctival GCs were cultivated from donor tissue. Lactate dehydrogenase (LDH) and tetrazolium dye colorimetric (MTT) assays were used for the assessment of GC survival. A cytometric bead array was employed for measuring secretion of interleukin (IL)-6 and IL-8 from GC.

RESULTS

BAK-preserved latanoprost and bimatoprost reduced cell survival by 28% (p = 0.0133) and 20% (p = 0.0208), respectively, in the LDH assay compared to a negative control. BAK-preserved latanoprost reduced cell proliferation by 54% (p = 0.003), BAK-preserved bimatoprost by 45% (p = 0.006), PQ-preserved travoprost by 16% (p = 0.0041), and PF latanoprost by 19% (p = 0.0001), in the MTT assay compared to a negative control. Only PF tafluprost did not affect the GCs in either assay. BAK-preserved latanoprost caused an increase in the secretion of pro-inflammatory IL-6 and IL-8 (p = 0.0001 and p = 0.0019, respectively) compared to a negative control, which PF latanoprost did not.

CONCLUSION

BAK-preserved PGA eye drops were more cytotoxic to GCs than PQ-preserved and PF PGA eye drops. BAK-preserved latanoprost induced an inflammatory response in GC. Treatment with PF and PQ-preserved PGA eye drops could mean better tolerability and adherence in glaucoma patients compared to treatment with BAK-preserved PGA eye drops.

The use of benzalkonium chloride in topical glaucoma treatment: An investigation of the efficacy and safety of benzalkonium chloride-preserved intraocular pressure-lowering eye drops and their effect on conjunctival goblet cells

ENGLISH SUMMARY

Glaucoma is a leading cause of the global prevalence of irreversible blindness. The pathogenesis of glaucoma is not entirely known, but the major risk factors include advancing age, genetic predisposition, and increased intraocular pressure (IOP). The only evidence-based treatment is a lowering of IOP through the use of eye drops, laser procedures, or surgical interventions. Although laser treatment is gaining recognition as a first-choice treatment option, the most common approach for managing glaucoma is IOP-lowering eye drops. A major challenge in the treatment is the occurrence of adverse events and poor adherence. In this context, the ocular surface is an area of great concern, as most glaucoma patients have dry eye disease (DED), which is largely caused by eye drops. Preservation with benzalkonium chloride (BAK) is a controversial topic due to its potential role as a significant cause of DED. A systematic review and meta-analyses investigate potential differences in efficacy and safety between BAK-preserved and BAK-free anti-glaucomatous eye drops (I). Many of the included studies report on ocular surface damage caused by the application of BAK-preserved eye drops. However, the meta-analyses addressing hyperemia, number of ocular adverse events, and tear break-up time did not identify any significant differences. The latter is likely due to varying measurement methods, different endpoints, and study durations. It is, therefore, possible that the large variations between the studies conceal differences in the safety profiles. The efficacy meta-analysis finds that there are no differences in the IOP-lowering effect between BAK-preserved and BAK-free eye drops, indicating that BAK is not necessary for the effectiveness of eye drops. To promote more homogeneous choices of endpoints and methods when evaluating BAK-preserved and BAK-free glaucoma treatments, a Delphi consensus statement was performed. In this study, glaucoma experts and ocular surface disease experts reached consensus on the key factors to consider when designing such studies (II). The hope is to have more studies with comparable endpoints that can systematically show the potentially adverse effects of BAK. The preclinical studies in the current Ph.D. research focus on conjunctival goblet cells (GCs). GCs are important for the ocular surface because they release the mucin MUC5AC, which is an essential component of the inner layer of the tear film. BAK preservation may damage the GCs and result in a low GC density, leading to an unstable tear film and DED. The most commonly used IOP-lowering drugs are prostaglandin analogs (PGAs). Thus, the conducted studies investigate the effect of PGAs preserved in different ways on GCs. BAK-preserved latanoprost is cytotoxic to primary cultured human conjunctival GCs and results in a scattered expression of MUC5AC, in contrast to negative controls, where MUC5AC is localized around the cell nucleus (III). Preservative-free (PF) latanoprost is not cytotoxic and does not affect the MUC5AC expression pattern. Furthermore, BAK-preserved travoprost is found to be cytotoxic in a time-dependent manner, while Polyquad®-preserved travoprost does not affect GC survival at any measured time point (IV). Both Polyquad and BAK induce scattered expression of MUC5AC. The cytotoxicity of BAK-preserved PGA eye drops is higher compared to the safer profile of PF and Polyquad-preserved PGA eye drops (V). Additionally, PF latanoprost does not increase the release of the inflammatory markers interleukin (IL)-6 and IL-8, unlike BAK-preserved latanoprost. A review highlights the active and inactive components of IOP-lowering eye drops (VI). Several preclinical and clinical studies have identified adverse effects of BAK. Although other components, such as the active drug and phosphates, can also cause adverse events, the review clearly states that BAK alone is a major source of decreased tolerability. The conclusion of this thesis is that BAK preservation is unnecessary and harmful to the ocular surface. The preclinical studies demonstrate that GCs die when exposed to BAK. Furthermore, they find that BAK induces a pro-inflammatory response. The review included in the thesis concludes that BAK should be phased out of eye drops for chronic use. Overall, the inclusion of BAK poses a risk of developing DED and poor adherence, which can ultimately lead to disease progression and blindness.

An Overview of Current Glaucomatous Trabecular Meshwork Models

PURPOSE

To provide an overview of the existing alternative models for studying trabecular meshwork (TM).

METHODS

Literature review.

RESULTS

The TM is a complex tissue that regulates aqueous humor outflow from the eye. Dysfunction of the TM is a major contributor to the pathogenesis of open-angle glaucoma, a leading cause of irreversible blindness worldwide. The TM is a porous structure composed of trabecular meshwork cells (TMC) within a multi-layered extracellular matrix (ECM). Although dysregulation of the outflow throughout the TM represents the first step in the disease process, the underlying mechanisms of TM degeneration associate cell loss and accumulation of ECM, but remain incompletely understood, and drugs targeting the TM are limited. Therefore, experimental models of glaucomatous trabeculopathy are necessary for preclinical screening, to advance research on this disease's pathophysiology, and to develop new therapeutic strategies targeting the TM. Traditional animal models have been used extensively, albeit with inherent limitations, including ethical concerns and limited translatability to humans. Consequently, there has been an increasing focus on developing alternative in vitro models to study the TM. Recent advancements in three-dimensional cell culture and tissue engineering are still in their early stages and do not yet fully reflect the complexity of the outflow pathway. However, they have shown promise in reducing reliance on animal experimentation in certain aspects of glaucoma research.

CONCLUSION

This review provides an overview of the existing alternative models for studying TM and their potential for advancing research on the pathophysiology of open-angle glaucoma and developing new therapeutic strategies.

Nanofibrous PCL-Based Human Trabecular Meshwork for Aqueous Humor Outflow Studies

Primary open-angle glaucoma is characterized by the progressive degeneration of the optic nerve, with the high intraocular pressure (IOP) being one of the main risk factors. The human trabecular meshwork (HTM), specifically the juxtacanalicular tissue (JCT), is responsible for placing resistance to the aqueous humor (AH) outflow and the resulting IOP control. Currently, the lack of a proper in vitro JCT model and the complexity of three-dimensional models impede advances in understanding the relationship between AH outflow and HTM degeneration. Therefore, we design an in vitro JCT model using a polycaprolactone (PCL) nanofibrous scaffold, which supports cells to recapitulate the functional JCT morphology and allow the study of outflow physiology. Mechanical and morphological characterizations of the electrospun membranes were performed, and human trabecular meshwork cells were seeded over the scaffolds. The engineered JCT was characterized by scanning electron microscopy, quantitative real-time polymerase chain reaction, and immunochemistry assays staining HTM cell markers and proteins. A pressure-sensitive perfusion system was constructed and used for the investigation of the outflow facility of the polymeric scaffold treated with dexamethasone (a glucocorticoid) and netarsudil (a novel IOP lowering the rho inhibitor). Cells in the in vitro model exhibited an HTM-like morphology, expression of myocilin, fibronectin, and collagen IV, genetic expression, outflow characteristics, and drug responsiveness. Altogether, the present work develops an in vitro JCT model to better understand HTM cell biology and the relationship between the AH outflow and the HTM and allow further drug screening of pharmacological agents that affect the trabecular outflow facility.

The molecular aspect of anti-glaucomatous eye drops - are we harming our patients?

Glaucoma is one of the leading causes of irreversible blindness. Progression is halted with a reduction in intraocular pressure (IOP), which is most often achieved with eye drops. A major challenge in the topical treatment of glaucoma patients is the many side effects and the resulting reduced adherence. Side effects may of course be due to the molecular properties of the active pharmaceutical ingredients (APIs). There are currently six different APIs available: prostaglandin analogues, β-adrenergic inhibitors, α-adrenergic agonists, carbonic anhydrase inhibitors, rho-kinase inhibitors and muscarinic 3 agonists. But the additives used in eye drops are also known to cause damage to the ocular surface and to some extent also to the deeper tissues. Said additives are considered inactive molecular components and are added to secure for instance viscosity and pH value, and to prevent contamination. There has been an increasing focus on the harmful effects of preservatives, with the most commonly used preservative benzalkonium chloride (BAK) being particularly controversial. BAK has long been recognized as a toxin that increases the risk of ocular discomfort. This can affect the adherence and ultimately result in lack of disease control. Other issues include the addition of certain buffers, such as phosphates, and varying pH values. This review will address the different molecular components of the IOP-lowering eye drops and what to be aware of when prescribing topical glaucoma treatment.

Selective laser trabeculoplasty is safe and effective in patients previously treated with prostaglandin analogs: An evidence-based review

PURPOSE

Prostaglandin analogs (PGAs) are first-line treatments for ocular hypertension (OHT) and open-angle glaucoma (OAG). However, frequent side effects and high costs hinder patient's compliance resulting in disease progression. Evidence suggests selective laser trabeculoplasty (SLT) may be considered a first-line treatment for OHT and OAG due to its safety profile, minor side effects, and reduced costs. Considering that PGAs and SLT share action mechanisms, it is hypothesized that previous PGA therapy may affect subsequent SLT efficacy. Therefore, we analyzed if PGAs reduce SLT efficacy.

METHODS

An evidence-based review was performed to assess the safety and efficacy of SLT in patients previously treated with PGAs. For this purpose, we performed an extensive literature search using the National Library of Medicine's PubMed and Google Scholar database for all English language articles published until May 2021.

RESULTS

There is evidence of non-superiority of PGAs therapy versus SLT for OHT and OAG. A multicenter, randomized, observer-masked clinical trial (RCT) of untreated OHT and OAG patients concluded that SLT should be offered as the first-line treatment for these patients. This study was supported by a meta-analysis of RCTs, comparing SLT efficacy versus antiglaucoma drugs only, with the advantage of an SLT lower rate of adverse effects.

CONCLUSIONS

Cost-effectiveness, patient compliance, and antiglaucoma drugs' side effects, including higher surgical failure, favor consideration of SLT as first-line therapy for OAG and OHT. Furthermore, SLT efficacy does not seem to be affected by prior PGA administration; however, larger cohort, comparative, multicenter RCTs are necessary to answer this question.

Technological advances in ocular trabecular meshwork in vitro models for glaucoma research

Glaucoma is the leading cause of irreversible blindness worldwide and is characterized by the progressive degeneration of the optic nerve. Intraocular pressure (IOP), which is considered to be the main risk factor for glaucoma development, builds up in response to the resistance (resistance to what?) provided by the trabecular meshwork (TM) to aqueous humor (AH) outflow. Although the TM and its relationship to AH outflow have remained at the forefront of scientific interest, researchers remain uncertain regarding which mechanisms drive the deterioration of the TM. Current tissue-engineering fabrication techniques have come up with promising approaches to successfully recreate the TM. Nonetheless, more accurate models are needed to understand the factors that make glaucoma arise. In this review, we provide a chronological evaluation of the technological milestones that have taken place in the field of glaucoma research, and we conduct a comprehensive comparison of available TM fabrication technologies. Additionally, we also discuss AH perfusion platforms, since they are essential for the validation of these scaffolds, as well as pressure-outflow relationship studies and the discovery of new IOP-reduction therapies.

Citicoline Eye Drops Protect Trabecular Meshwork Cells from Oxidative Stress Injury in a 3D In Vitro Glaucoma Model

Intraocular pressure (IOP) is considered an important modifiable risk factor for glaucoma, which is known as the second leading cause of blindness worldwide. However, lowering the IOP is not always sufficient to preserve vision due to other non-IOP-dependent mechanisms being involved. To improve outcomes, adjunctive therapies with IOP-independent targets are required. To date, no studies have shown the effect of citicoline on the trabecular meshwork (TM), even though it is known to possess neuroprotective/enhancement properties and multifactorial mechanisms of action. Given that reactive oxygen species seem to be involved in glaucomatous cascade, in this present study, an advanced millifluidic in vitro model was used to evaluate if citicoline could exert a valid TM protection against oxidative stress. To this end, the cellular behavior, in terms of viability, apoptosis, mitochondrial state, senescence and pro-inflammatory cytokines, on 3D human TM cells, treated either with H2O2 alone or cotreated with citicoline, was analyzed. Our preliminary in vitro results suggest a counteracting effect of citicoline eye drops against oxidative stress on TM cells, though further studies are necessary to explore citicoline's potential as a TM-target therapy.

Benzalkonium Chloride, Even at Low Concentrations, Deteriorates Intracellular Metabolic Capacity in Human Conjunctival Fibroblasts

The objective of this study was to clarify the effects of benzalkonium chloride (BAC) on two-dimensional (2D) and three-dimensional (3D) cultures of human conjunctival fibroblast (HconF) cells, which are in vitro models replicating the epithelial barrier and the stromal supportive functions of the human conjunctiva. The cultured HconF cells were subjected to the following analyses in the absence and presence of 10⁻⁵% or 10⁻⁴% concentrations of BAC; (1) the barrier function of the 2D HconF monolayers, as determined by trans-endothelial electrical resistance (TEER) and FITC dextran permeability, (2) real-time metabolic analysis using an extracellular Seahorse flux analyzer, (3) the size and stiffness of 3D HconF spheroids, and (4) the mRNA expression of genes that encode for extracellular matrix (ECM) molecules including collagen (COL)1, 4 and 6, and fibronectin (FN), α-smooth muscle actin (α-SMA), ER stress related genes including the X-box binding protein-1 (XBP1), the spliced XBP1 (sXBP1) glucose regulator protein (GRP)78, GRP94, and the CCAAT/enhancer-binding protein homologous protein (CHOP), hypoxia inducible factor 1α (HIF1α), and Peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α). In the presence of BAC, even at low concentrations at 10⁻⁵% or 10⁻⁴%, the maximal respiratory capacity, mitochondrial respiratory reserve, and glycolytic reserve of HconF cells were significantly decreased, although the barrier functions of 2D HconF monolayers, the physical properties of the 3D HconF spheroids, and the mRNA expression of the corresponding genes were not affected. The findings reported herein highlight the fact that BAC, even such low concentrations, may induce unfavorable adverse effects on the cellular metabolic capacity of the human conjunctiva.

Melt Electrowriting of Graded Porous Scaffolds to Mimic the Matrix Structure of the Human Trabecular Meshwork

The permeability of the human trabecular meshwork (HTM) regulates eye pressure via a porosity gradient across its thickness modulated by stacked layers of matrix fibrils and cells. Changes in HTM porosity are associated with increases in intraocular pressure and the progress of diseases such as glaucoma. Engineered HTMs could help to understand the structure-function relation in natural tissues and lead to new regenerative solutions. Here, melt electrowriting (MEW) is explored as a biofabrication technique to produce fibrillar, porous scaffolds that mimic the multilayer, gradient structure of native HTM. Poly(caprolactone) constructs with a height of 125-500 μm and fiber diameters of 10-12 μm are printed. Scaffolds with a tensile modulus between 5.6 and 13 MPa and a static compression modulus in the range of 6-360 kPa are obtained by varying the scaffold design, that is, the density and orientation of the fibers and number of stacked layers. Primary HTM cells attach to the scaffolds, proliferate, and form a confluent layer within 8-14 days, depending on the scaffold design. High cell viability and cell morphology close to that in the native tissue are observed. The present work demonstrates the utility of MEW for reconstructing complex morphological features of natural tissues.

Noninferiority Study Comparing Latanoprost 0.005% Without Versus With Benzalkonium Chloride in Open-Angle Glaucoma or Ocular Hypertension

OBJECTIVES

To evaluate the noninferiority of intraocular pressure (IOP)-lowering latanoprost without benzalkonium chloride (BAK) versus latanoprost with BAK (for treatment of open-angle glaucoma or ocular hypertension).

METHODS

Overall, 578 patients were randomized 1:1 to latanoprost without BAK or latanoprost with BAK once daily in the affected eye(s) for 12 weeks. The primary efficacy endpoint was IOP, measured on days 0, 7, 28, 56, and 84 (8 am, 10 am, and 4 pm). Noninferiority was established if the following criteria were met: 95% confidence interval (CI) of the mean difference between treatments included 0 mm Hg for all time points (N1), 95% CI upper limit less than 1.5 mm Hg (N2), and less than 1 mm Hg for≥7 of 12 time points (N3). Primary efficacy analysis was performed on the intent-to-treat population. Safety measurements included ocular and systemic adverse event (AE).

RESULTS

The 95% CI included 0 mm Hg for 7/12 time points (N1), 95% CI upper limit was less than 1.5 mm Hg for 12/12 time points (N2), and less than 1.0 mm Hg for 4/7 time points (N3). AEs were mild and similarly distributed between groups.

CONCLUSIONS

Latanoprost without BAK did not meet two of three criteria for noninferiority and showed a similar safety profile relative to latanoprost with BAK.

The Dual Effect of Rho-Kinase Inhibition on Trabecular Meshwork Cells Cytoskeleton and Extracellular Matrix in an In Vitro Model of Glaucoma

The trabecular meshwork (TM) is the main site of drainage of the aqueous humor, and its dysfunction leads to intraocular pressure elevation, which is one of the main risk factors of glaucoma. We aimed to compare the effects on cytoskeleton organization and extracellular matrix (ECM) of latanoprost (LT) and a Rho-kinase inhibitor (ROCKi) on a transforming growth factor beta2 (TGF-β2)-induced glaucoma-like model developed from primary culture of human TM cells (pHTMC). The TGF-β2 stimulated pHTMC were grown and incubated with LT or a ROCKi (Y-27632) for 24 h. The expression of alpha-smooth muscle actin (αSMA) and fibronectin (FN), and phosphorylation of the myosin light chain (MLC-P) and Cofilin (Cofilin-P) were evaluated using immunofluorescence and Western blot. The architectural modifications were studied in a Matrigel^TM 3D culture. TGF-β2 increased the expression of αSMA and FN in pHTMC and modified the cytoskeleton with cross-linked actin network formation. LT did not alter the expression of αSMA but decreased FN deposition. The ROCKi decreased TGF-β2-induced αSMA and FN expression, as well as MLC-P and Cofilin-P, and stimulated the cells to recover a basal cytoskeletal arrangement. In the preliminary 3D study, pHTMC organized in a mesh conformation showed the widening of the TM under the effect of Y-27632. By simultaneously modifying the organization of the cytoskeleton and the ECM, with fibronectin deposition and overexpression, TGF-β2 reproduced the trabecular degeneration described in glaucoma. The ROCKi was able to reverse the TGF-β2-induced cytoskeletal and ECM rearrangements. LT loosened the extracellular matrix but had no action on the stress fibers.

Cytokine and Growth Factor Analysis in Exfoliation Syndrome and Glaucoma

Purpose

We compared cytokines, chemokines, and growth factors in the aqueous humor (AH) of patients with exfoliation syndrome (XFS), with exfoliation glaucoma (XFG), with primary open angle glaucoma (POAG), and healthy controls.

Methods

AH samples were collected from 21 patients with XFS, 28 with XFG, 14 with POAG, and 17 healthy controls during routine cataract surgery. The protein levels of 21 cytokines and growth factors, together with TGF-β1, 2, and 3, were quantified using the multiplex immunoassay. The levels of each protein in the four groups were compared using the Kruskal-Wallis test.

Results

Among the 24 cytokines and growth factors, 16 were out of the detectable range in >50% of samples in at least one group; the remaining 8 cytokines and growth factors (IL-8, MIP-1α, fractalkine, Flt3 ligand, PDGF-AA, VEGF, TGF-β1, and TGF-β2) were included in the analysis. TGF-β1 and TGF-β2 levels were the highest in patients with XFG and those with POAG, respectively. Expression levels of the inflammatory chemokines IL-8, MIP-1α, and fractalkine, as well as levels of the immune cell growth factor Flt3 ligand, were significantly higher in the XFG group than in the other groups. The protein levels of PDGF-AA and VEGF were not significantly different among the 4 groups.

Conclusions

Both TGF-β1 and inflammatory cytokines were highly expressed in the AH of patients with XFG. Considering that the levels of these cytokines are increased by oxidative stress and that they regulate the extracellular matrix, they may also play a role in intraocular pressure elevation in XFG.

An Innovative In Vitro Open-Angle Glaucoma Model (IVOM) Shows Changes Induced by Increased Ocular Pressure and Oxidative Stress

Primary Open-Angle Glaucoma (POAG) is a neurodegenerative disease, and its clinical outcomes lead to visual field constriction and blindness. POAG's etiology is very complex and its pathogenesis is mainly explained through both mechanical and vascular theories. The trabecular meshwork (TM), the most sensitive tissue of the eye anterior segment to oxidative stress (OS), is the main tissue involved in early-stage POAG, characterized by an increase in pressure. Preclinical assessments of neuroprotective drugs on animal models have not always shown correspondence with human clinical studies. In addition, intra-ocular pressure management after a glaucoma diagnosis does not always prevent blindness. Recently, we have been developing an innovative in vitro 3Dadvanced human trabecular cell model on a millifluidicplatform as a tool to improve glaucoma studies. Herein, we analyze the effects of prolonged increased pressure alone and, in association with OS, on such in vitro platform. Moreover, we verify whethersuch damaged TM triggers apoptosis on neuron-like cells. The preliminary results show that TM cells are less sensitive to pressure elevation than OS, and OS-damaging effects were worsened by the pressure increase. The stressed TM releases harmful signals, which increase apoptosis stimuli on neuron-like cells, suggesting its pivotal role in the glaucoma cascade.

Fundamental Biomaterial Considerations in the Development of a 3D Model Representative of Primary Open Angle Glaucoma

Glaucoma is a leading cause of irreversible blindness globally, with primary open angle glaucoma (POAG) being the most common subset. Raised intraocular pressure is an important risk factor for POAG and is caused by a reduction in aqueous humour (AqH) outflow due to dysfunctional cellular and matrix dynamics in the eye’s main drainage site, the trabecular meshwork (TM) and Schlemm’s canal (SC). The TM/SC are highly specialised tissues that regulate AqH outflow; however, their exact mechanisms of AqH outflow control are still not fully understood. Emulating physiologically relevant 3D TM/S in vitro models poses challenges to accurately mimic the complex biophysical and biochemical cues that take place in healthy and glaucomatous TM/SC in vivo. With development of such models still in its infancy, there is a clear need for more well-defined approaches that will accurately contrast the two central regions that become dysfunctional in POAG; the juxtacanalicular tissue (JCT) region of the TM and inner wall endothelia of the Schlemm’s canal (eSC). This review will discuss the unique biological and biomechanical characteristics that are thought to influence AqH outflow and POAG progression. Further consideration into fundamental biomaterial attributes for the formation of a biomimetic POAG/AqH outflow model will also be explored for future success in pre-clinical drug discovery and disease translation.

Impact of dorzolamide, benzalkonium-preserved dorzolamide and benzalkonium-preserved brinzolamide on selected biomarkers of oxidative stress in the tear film

Background

Long-term use of topical, especially benzalkonium chloride (BAC)-preserved, antiglaucoma medications can cause a negative impact on the ocular surface. The aim of the study was to assess the effect of topical carbonic anhydrase inhibitors (CAIs) on selected oxidative stress biomarkers in the tear film.

Methods

The patients were divided into four sex-matched groups: group C (n = 25) – control group – subjects who did not use topical antiglaucoma medications, group DL (n = 14) – patients using preservative-free dorzolamide, group DL + BAC (n = 16) – patients using topical BAC-preserved dorzolamide, group BL + BAC (n = 17) – patients using BAC-preserved brinzolamide. Subjects in all the study groups have been using the eye drops two times daily for 6–12 months. The oxidative stress biomarkers in the tear film samples were measured: total protein (TP) concentration, advanced oxidation protein products (AOPP) content, total sulfhydryl (-SH) groups content, the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), as well as Total Oxidant Status (TOS), Total Antioxidant Response (TAR), and Oxidative Stress Index (OSI).

Results

The advanced oxidation protein products content, Total Oxidant Status as well as superoxide dismutase and catalase activities in the group DL + BAC and BL + BAC were higher in comparison with the group C. The total sulfhydryl groups content was lower in the group DL + BAC and BL + BAC when compared to group C. Oxidative Stress Index was higher in the groups DL + BAC and BL + BAC in comparison with the groups DL and C.

Conclusions

Use of topical benzalkonium chloride-preserved carbonic anhydrase inhibitors increases oxidative stress in the tear film.

Preserved Versus Preservative-Free Latanoprost for the Treatment of Glaucoma and Ocular Hypertension: A Post Hoc Pooled Analysis

Introduction

To compare the tolerability and efficacy of a preservative-containing latanoprost (PCL) to a preservative-free formulation of latanoprost (PFL) in patients with open-angle glaucoma or ocular hypertension.

Methods

A pooled analysis was performed of data from five published studies. The primary outcome was tolerability as evaluated by the severity of hyperemia. The secondary objectives were patient tolerance based on a composite ocular surface disease (OSD) score arising from ocular signs and symptoms, patient and investigator satisfaction, and a comparison of IOP-lowering efficacy.

Results

There were three randomized controlled trials and two observational studies included in the analysis. Conjunctival hyperemia improved significantly in 25.6% (388) of patients switched to the PFL group versus 11.7% (117) of patients switched to the PCL group (p < 0.001). PFL was two times superior to PCL in reducing ocular hyperemia (odds ratio = 1.96; p < 0.001). The mean OSD composite score decreased by 32.2% in patients switched to the PFL group and 14.1% in the PCL group (p < 0.001). At 3 months, the mean IOP was similar between groups (p = 0.312).

Conclusion

This post hoc pooled analysis confirmed the findings of the individual studies that PFL is as efficacious at reducing IOP as PCL but better tolerated. After switching to PFL, there was twice the improvement in the OSD composite score. PFL was twice as effective at reducing ocular hyperemia and other ocular signs. These findings suggest that PFL has features that may improve patient compliance, thereby potentially improving the IOP-lowering efficacy on a long-term basis.

Preservatives in eye drops for glaucoma can cause side effects such as stinging and eye redness. These side effects can cause some patients to reduce the frequency of the drops as prescribed or stop using the drops. One of the most common drops for glaucoma is latanoprost. This study evaluated whether a preservative-free latanoprost (PFL) is as effective as preservative-containing latanoprost (PCL) for reducing eye pressure and whether PFL is better tolerated in patients with glaucoma. The results of the study indicated that PFL was as effective as PCL for reducing eye pressure. The results also indicated PFL was much better at reducing the side effects related to PCL. For example PFL reduces eye redness up to twofold compared to PCL. By reducing the side effects associated with PCL patients may continue to take their glaucoma drops as directed and thereby reduce the risk of vision loss from glaucoma.

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

Abnormal 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, limiting their use for investigating POAG pathology. Tissue-engineered 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. HTM 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 crosslinking. Glaucomatous conditions were induced with dexamethasone (DEX), and effects of the Rho-associated kinase (ROCK) inhibitor Y27632 on cytoskeletal organization and tissue-level function, contingent on HTM cell-ECM interactions, were assessed. DEX exposure increased HTM hydrogel contractility, f-actin and alpha smooth muscle actin abundance and rearrangement, ECM remodeling, and fibronectin deposition - all contributing to HTM hydrogel condensation and stiffening consistent with glaucomatous HTM tissue behavior. Y27632 treatment produced precisely the opposite effects and attenuated the DEX-induced pathologic changes, resulting in HTM hydrogel relaxation and softening. For model validation, confirmed glaucomatous HTM (GTM) cells were encapsulated; GTM hydrogels showed increased contractility, fibronectin deposition, and stiffening vs. normal HTM hydrogels despite reduced GTM cell proliferation. We 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 pharmacological challenge and rescue suggests promising potential to serve as screening platform for new POAG treatments with focus on HTM biomechanics.

The treatment of glaucoma using topical preservative-free agents: an evaluation of safety and tolerability

Introduction: Preservative-free (PF) medications represent a valuable treatment strategy in the lifelong management of glaucoma. By removing preservative toxicity, PF formulations provide tangible clinical benefits to glaucoma patients worldwide. They improve tolerability and adherence, leading to a positive impact in long-term intraocular pressure (IOP) control.Areas covered: A critical review of the subject is provided, including selected evidence on the safety and tolerability of currently available topical PF formulations. Cumulative evidence confirms that topical PF medications are at least equally efficacious to their preserved equivalents. There is convincing short-term evidence for superior tolerability and safety of PF formulations compared to preserved medications. The long-term benefits and success of PF therapy requires further elucidation.Expert opinion: Successful stepwise administration of medical therapy for glaucoma remains elusive. There is a greater risk for ocular toxicity and therapy failure with preserved topical glaucoma therapy. Currently available and emerging PF therapy options potentially optimize lifelong stepwise glaucoma therapy and may enhance outcome. To avert complications from preservatives leading to poor adherence, ideally, future antiglaucoma therapy should become 100% PF. There are still key aspects of PF therapy that warrant further investigation.

Topical preservative-free ophthalmic treatments: an unmet clinical need

Introduction: The main role of preservatives in eyedrops is to ensure sterility and microbiological integrity of the drug, and to facilitate the penetration of active compounds into the eye. However, several studies documented significant toxic effects induced by preservatives, especially on the ocular surface. Consequently, most of the ophthalmic medications became progressively available in preservative-free (PF) formulations.Areas covered: We analyzed pre-clinical and clinical studies on PF eyedrops with particular attention to common chronic diseases such as dry eye and glaucoma. We discussed about the pros and cons of using PF eyedrops, in terms of efficacy, safety, and social-economic aspects.Expert opinion: There are still unresolved issues that make hard for PF medications to definitively conquer the drug market. Despite robust pre-clinical evidences of less toxicity, the low number of randomized clinical trials does not permit to state that PF eyedrops have, in clinical practice, a similar efficacy or a higher safety compared to preserved forms. These aspects limit their use to chronic diseases requiring long-term therapies with multiple daily instillations, especially in the presence of concomitant ophthalmic diseases that expose to a risk of ocular surface worsening.

Three-Dimensional Human Cell Culture Models to Study the Pathophysiology of the Anterior Eye

In recent decades, the establishment of complex three-dimensional (3D) models of tissues has allowed researchers to perform high-quality studies and to not only advance knowledge of the physiology of these tissues but also mimic pathological conditions to test novel therapeutic strategies. The main advantage of 3D models is that they recapitulate the spatial architecture of tissues and thereby provide more physiologically relevant information. The eye is an extremely complex organ that comprises a large variety of highly heterogeneous tissues that are divided into two asymmetrical portions: the anterior and posterior segments. The anterior segment consists of the cornea, conjunctiva, iris, ciliary body, sclera, aqueous humor, and the lens. Different diseases in these tissues can have devastating effects. To study these pathologies and develop new treatments, the use of cell culture models is instrumental, and the better the model, the more relevant the results. Thus, the development of sophisticated 3D models of ocular tissues is a significant challenge with enormous potential. In this review, we present a comprehensive overview of the latest advances in the development of 3D in vitro models of the anterior segment of the eye, with a special focus on those that use human primary cells.

A 3D Model of Human Trabecular Meshwork for the Research Study of Glaucoma

Glaucoma is a multifactorial syndrome in which the development of pro-apoptotic signals are the causes for retinal ganglion cell (RGC) loss. Most of the research progress in the glaucoma field have been based on experimentally inducible glaucoma animal models, which provided results about RGC loss after either the crash of the optic nerve or IOP elevation. In addition, there are genetically modified mouse models (DBA/2J), which make the study of hereditary forms of glaucoma possible. However, these approaches have not been able to identify all the molecular mechanisms characterizing glaucoma, possibly due to the disadvantages and limits related to the use of animals. In fact, the results obtained with small animals (i.e., rodents), which are the most commonly used, are often not aligned with human conditions due to their low degree of similarity with the human eye anatomy. Although the results obtained from non-human primates are in line with human conditions, they are little used for the study of glaucoma and its outcomes at cellular level due to their costs and their poor ease of handling. In this regard, according to at least two of the 3Rs principles, there is a need for reliable human-based in vitro models to better clarify the mechanisms involved in disease progression, and possibly to broaden the scope of the results so far obtained with animal models. The proper selection of an in vitro model with a "closer to in vivo" microenvironment and structure, for instance, allows for the identification of the biomarkers involved in the early stages of glaucoma and contributes to the development of new therapeutic approaches. This review summarizes the most recent findings in the glaucoma field through the use of human two- and three-dimensional cultures. In particular, it focuses on the role of the scaffold and the use of bioreactors in preserving the physiological relevance of in vivo conditions of the human trabecular meshwork cells in three-dimensional cultures. Moreover, data from these studies also highlight the pivotal role of oxidative stress in promoting the production of trabecular meshwork-derived pro-apoptotic signals, which are one of the first marks of trabecular meshwork damage. The resulting loss of barrier function, increase of intraocular pressure, as well the promotion of neuroinflammation and neurodegeneration are listed as the main features of glaucoma. Therefore, a better understanding of the first molecular events, which trigger the glaucoma cascade, allows the identification of new targets for an early neuroprotective therapeutic approach.

A Biomimetic, Stem Cell-Derived In Vitro Ocular Outflow Model

Age-related human trabecular meshwork (HTM) cell loss is suggested to affect its ability to regulate aqueous humor outflow in the eye. In addition, disease-related HTM cell loss is suggested to lead to elevated intraocular pressure in glaucoma. Induced pluripotent stem cell (iPSC)-derived trabecular meshwork (TM) cells are promising autologous cell sources that can be used to restore the declining TM cell population and function. Previously, an in vitro HTM model is bioengineered for understanding HTM cell biology and screening of pharmacological or biological agents that affect trabecular outflow facility. In this study, it is demonstrated that human iPSC-derived TM cells cultured on SU-8 scaffolds exhibit HTM-like cell morphology, extracellular matrix deposition, and drug responsiveness to dexamethasone treatment. These findings suggest that iPSC-derived TM cells behave like primary HTM cells and can thus serve as reproducible and scalable cell sources when using this in vitro system for glaucoma drug screening and further understanding of outflow pathway physiology, leading to personalized medicine.

[The trabecular meshwork: Structure, function and clinical implications. A review of the littérature (French translation of the article)]

Glaucoma is a blinding optic neuropathy, the main risk factor for which is increased intraocular pressure (IOP). The trabecular meshwork, located within the iridocorneal angle, is the main pathway for drainage of aqueous humor (AH) out of the eye, and its dysfunction is responsible for the IOP elevation. The trabecular meshwork is a complex, fenestrated, three-dimensional structure composed of trabecular meshwork cells (TMC) interdigitated into a multilayered organization within the extracellular matrix (ECM). The purpose of this literature review is to provide an overview of current understanding of the trabecular meshwork and its pathophysiology in glaucoma. Thus, we will present the main anatomical and cellular bases for the regulation of aqueous humor outflow resistance, the pathophysiological mechanisms involved in trabecular dysfunction in the various types of glaucoma, as well as current and future therapeutic strategies targeting the trabecular meshwork.

Human trabecular meshwork cell behavior is influenced by collagen scaffold pore architecture and glycosaminoglycan composition

Glaucoma is a degenerative eye disease in which damage to the optic nerve leads to a characteristic loss of vision. The primary risk factor for glaucoma is an increased intraocular pressure that is caused by an imbalance of aqueous humor generation and subsequent drainage through the trabecular meshwork (TM) drainage system. The small size, donor tissue limitations, and high complexity of the TM make it difficult to research the relationship between the TM cells and their immediate environment. Thus, a biomaterial-based approach may be more appropriate for research manipulations and in vitro drug development platforms. In this work, human TM (hTM) cells were cultured on various collagen scaffolds containing different glycosaminoglycans (GAGs) and different pore architectures to better understand how hTM cells respond to changes in their extracellular environment. Cellular response was measured by quantifying cellular proliferation and expression of an important extracellular matrix protein, fibronectin. The pore architecture of the scaffolds was altered using freeze-casting technique to make both large and small pores that were aligned or with a non-aligned random structure. The composition of the scaffolds was altered with the addition of chondroitin sulfate and/or hyaluronic acid. It was found that the hTM cells grown on large pore scaffolds proliferate more than those grown on small pores. There was an increase in the fibronectin expression with the incorporation of GAGs, and its morphology was changed by the underlying pore architecture. This work will help provide an insight into the behavior of hTM cells when introducing changes in their microenvironment.

Tissue-Engineered Models for Glaucoma Research

Glaucoma is a group of optic neuropathies characterized by the progressive degeneration of retinal ganglion cells (RGCs). Patients with glaucoma generally experience elevations in intraocular pressure (IOP), followed by RGC death, peripheral vision loss and eventually blindness. However, despite the substantial economic and health-related impact of glaucoma-related morbidity worldwide, the surgical and pharmacological management of glaucoma is still limited to maintaining IOP within a normal range. This is in large part because the underlying molecular and biophysical mechanisms by which glaucomatous changes occur are still unclear. In the present review article, we describe current tissue-engineered models of the intraocular space that aim to advance the state of glaucoma research. Specifically, we critically evaluate and compare both 2D and 3D-culture models of the trabecular meshwork and nerve fiber layer, both of which are key players in glaucoma pathophysiology. Finally, we point out the need for novel organ-on-a-chip models of glaucoma that functionally integrate currently available 3D models of the retina and the trabecular outflow pathway.

The trabecular meshwork: Structure, function and clinical implications. A review of the literature

Glaucoma is a blinding optic neuropathy, the main risk factor for which is increased intraocular pressure (IOP). The trabecular meshwork, located within the iridocorneal angle, is the main pathway for drainage of aqueous humor (AH) out of the eye, and its dysfunction is responsible for the IOP elevation. The trabecular meshwork is a complex, fenestrated, three-dimensional structure composed of trabecular meshwork cells (TMC) interdigitated into a multilayered organization within the extracellular matrix (ECM). The purpose of this literature review is to provide an overview of current understanding of the trabecular meshwork and its pathophysiology in glaucoma. Thus, we will present the main anatomical and cellular bases for the regulation of aqueous humor outflow resistance, the pathophysiological mechanisms involved in trabecular dysfunction in the various types of glaucoma, as well as current and future therapeutic strategies targeting the trabecular meshwork.

Mitochondrial Dysfunctions May Be One of the Major Causative Factors Underlying Detrimental Effects of Benzalkonium Chloride

Benzalkonium chloride (BAC) is currently the most commonly used antimicrobial preservative in ophthalmic solutions, nasal sprays, and cosmetics. However, a large number of clinical and experimental investigations showed that the topical administration of BAC-containing eye drops could cause a variety of ocular surface changes, from ocular discomfort to potential risk for future glaucoma surgery. BAC-containing albuterol may increase the risk of albuterol-related systemic adverse effects. BAC, commonly present in personal care products, in cosmetic products can induce irritation and dose-dependent changes in the cell morphology. The cationic nature of BAC (it is a quaternary ammonium) suggests that one of the major targets of BAC in the cell may be mitochondria, the only intracellular compartment charged negatively. However, the influence of BAC on mitochondria has not been clearly understood. Here, the effects of BAC on energy parameters of rat liver mitochondria as well as on yeast cells were examined. BAC, being a "weaker" uncoupler, potently inhibited respiration in state 3, diminished the mitochondrial membrane potential, caused opening of the Ca2+/Pi-dependent pore, blocked ATP synthesis, and promoted H₂O₂ production by mitochondria. BAC triggered oxidative stress and mitochondrial fragmentation in yeast cells. BAC-induced oxidative stress in mitochondria and yeast cells was almost totally prevented by the mitochondria-targeted antioxidant SkQ1; the protective effect of SkQ1 on mitochondrial fragmentation was only partial. Collectively, these data showed that BAC acts adversely on cell bioenergetics (especially on ATP synthesis) and mitochondrial dynamics and that its prooxidant effect can be partially prevented by the mitochondria-targeted antioxidant SkQ1.

An injectable peptide hydrogel for reconstruction of the human trabecular meshwork

Glaucoma is a leading cause of irreversible blindness worldwide. Current treatments of glaucoma involve lowering the IOP by means of decreasing aqueous humor production or increasing non-trabecular aqueous humor outflow with the help of IOP-lowering eye drops, nanotechnology enabled glaucoma drainage implants, and trabeculectomy. However, there is currently no effective and permanent cure for this disease. In order to investigate new therapeutic strategies, three dimensional (3D) biomimetic trabecular meshwork (TM) models are in demand. Therefore, we adapted MAX8B, a peptide hydrogel system to bioengineer a 3D trabecular meshwork scaffold. We assessed mechanical and bio-instructive properties of this engineered tissue matrix by using rheological analysis, 3D cell culture and imaging techniques. The scaffold material exhibited shear-thinning ability and biocompatibility for proper hTM growth and proliferation indicating a potential utilization as an injectable implant. Additionally, by using a perfusion system, MAX8B scaffold was tested as an in vitro platform for investigating the effect of Dexamethasone (Dex) on trabecular meshwork outflow facility. The physiological response of hTM cells within the scaffold to Dex treatment clearly supported the effectiveness of this 3D model as a drug-testing platform, which can accelerate discovery of new therapeutic targets for glaucoma. STATEMENT OF SIGNIFICANCE: Artificial 3D-TM (3-dimentional Trabecular Meshwork) developed here with hTM (human TM) cells seeded on peptide-hydrogel scaffolds exhibits the mechanical strength and physiological properties mimicking the native TM tissue. Besides serving a novel and effective 3D-TM model, the MAX8B hydrogel could potentially function as an injectable trabecular meshwork implant.

Novel in situ gelling ophthalmic drug delivery system based on gellan gum and hydroxyethylcellulose: Innovative rheological characterization, in vitro and in vivo evidence of a sustained precorneal retention time

Achieving drug delivery at the ocular level encounters many challenges and obstacles. In situ gelling delivery systems are now widely used for topical ocular administration and recognized as a promising strategy to improve the treatment of a wide range of ocular diseases. The present work describes the formulation and evaluation of a mucoadhesive and ion-activated in situ gelling delivery system based on gellan gum and hydroxyethylcellulose for the delivery of phenylephrine and tropicamide. First, physico-chemical characteristics were assessed to ensure suitable properties regarding ocular administration. Then, rheological properties such as viscosity and gelation capacity were determined. Gelation capacity of the formulations and the effect of hydroxyethylcellulose on viscosity were demonstrated. A new rheological method was developed to assess the gel resistance under simulated eye blinking. Afterward, mucoadhesion was evaluated using tensile strength test and rheological synergism method in both rotational and oscillatory mode allowing mucoadhesive properties of hydroxyethylcellulose to be point out. Finally, residence time on the ocular surface was investigated in vivo, using cyanine 5.5 dye as a fluorescent marker entrapped in the in situ gelling delivery systems. Residence performance was studied by non-invasive optical imaging on vigilant rabbits, allowing eye blinking and nasolacrimal drainage to occur physiologically. Fluorescence intensity profiles pointed out a prolonged residence time on the ocular surface region for the developed formulations compared to conventional eye drops, suggesting in vitro / in vivo correlations between rheological properties and in vivo residence performances.

Human Trabecular Meshwork Progenitors

Trabecular meshwork (TM) cells are a group of progenitors that have the ability to become adipocytes, chondrocytes and endothelial cells. Therefore, those adult corneal progenitors may be used as an effective therapy for trabecular meshwork diseases such as glaucoma, corneal endothelial dysfunctions such as blindness due to corneal endothelial dysfunction, and similar diseases. In order to promote the understanding of human trabecular meshwork progenitors, this article reviews human trabecular meshwork progenitor therapy and discusses its potential applications for curing human eye blindness.

Preservative-Free Prostaglandin Analogs and Prostaglandin/Timolol Fixed Combinations in the Treatment of Glaucoma: Efficacy, Safety and Potential Advantages

Glaucoma therapy-related ocular surface disease (OSD) is a serious pathology with a broad spectrum of insidious clinical presentations and complex pathogenesis that undermines long-term glaucoma care. Preservatives, especially benzalkonium chloride (BAK), contained in topical intraocular pressure-lowering medications frequently cause or aggravate OSD in glaucoma. Management of these patients is challenging, and to date often empirical due to the scarcity of controlled long-term clinical trials. Most of the available data are extracted from case series and retrospective analysis. Preservative-free prostaglandins and prostaglandin/timolol fixed combinations are novel options developed to remove the harmful impact of preservatives, especially BAK, upon ocular tissues. Based on what is currently known on the value of preservative-free antiglaucoma therapies it is tempting to speculate how these new therapies may affect the future medical management of all glaucoma patients. This article provides a comprehensive and critical review of the current literature on preservative-free prostaglandins and preservative-free prostaglandin/timolol fixed combinations.