Development of In Vitro Corneal Models: Opportunity for Pharmacological Testing

In-vitro safety assessment of meropenem on human retinal pigment epithelium (RPE)

Purpose

Endophthalmitis is a severe infection accompanied by inflammation that affects the anterior and posterior parts of the eye. It is typically treated with a combination of antibiotics that cover various microorganisms. However, retinal pigment epithelium (RPE) cells are highly susceptible to damage from intravitreal injection therapy. This study aimed to investigate the impact of clinically relevant concentrations of meropenem (alone or in combination with vancomycin) on the viability and inflammation of RPE cells.

Design

In-vitro Study.

Methods

RPE cells from passages 5-7 were treated with different concentrations of meropenem (1/4x, x, and 4x; [x = 16 mg/L]), vancomycin (30 mg/L), and meropenem (x) plus vancomycin for 24 h. The morphology assessment and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay were performed to evaluate cytotoxicity due to drug treatment. Real-time PCR was used to measure the relative expression of apoptotic genes (BCL-2 and BAX) and inflammation biomarkers (IL-1b and IL-6).

Results

Meropenem (alone or in combination with vancomycin) did not have any significant effect on RPE cell morphology, density, and viability. Gene expression analysis confirmed these results, showing no significant changes in the BCL-2/BAX ratio in drug-treated RPE cells compared to controls. Treatment with meropenem significantly induced the expression of IL-1b at all studied concentrations. Additionally, at concentrations of x and 4x, it also significantly increased the expression of IL-6, which was dose-dependent. However, this effect was not observed with vancomycin alone or in combination with meropenem.

Conclusions

The results of this study suggest that meropenem, either alone or in combination with vancomycin, does not induce RPE cytotoxicity. There was an upregulation of IL-1b and IL-6 in meropenem monotherapy, the clinical implication of which should be elucidated in future in-vivo or clinical studies.

Identifying gene variants underlying the pathogenesis of diabetic retinopathy based on integrated genomic and transcriptomic analysis of clinical extreme phenotypes

Diabetic retinopathy (DR) is a common complication and the leading cause of blindness in patients with type 2 diabetes. DR has been shown to be closely correlated with blood glucose levels and the duration of diabetes. However, the onset and progression of DR also display clinical heterogeneity. We applied whole-exome sequencing and RNA-seq approaches to study the gene mutation and transcription profiles in three groups of diabetic patients with extreme clinical phenotypes in DR onset, timing, and disease progression, aiming to identify genetic variants that may play roles in the pathogenesis of DR. We identified 23 putatively pathogenic genes, and ingenuity pathway analysis of these mutated genes reveals their functional association with glucose metabolism, diabetic complications, neural system activity, and dysregulated immune responses. In addition, ten potentially protective genes were also proposed. These findings shed light on the mechanisms underlying the pathogenesis of DR and may provide potential targets for developing new strategies to combat DR.

Supporting discovery and development of medical countermeasures for chemical injury to eye and skin

Vesicants, from vesica (Latin for blister), can cause local and systemic toxicity. They include the chemotherapy drug nitrogen mustard and chemical warfare agents sulfur mustard, Lewisite, and phosgene oxime. These agents are commonly released in vapor form and consequently, eyes and skin are the most vulnerable. The ocular and cutaneous injuries can be acute, subacute, or chronic, and can predispose casualties to secondary deleterious effects. Underlying these broad organ responses are shared and tissue-specific cellular and molecular biological cascades that attempt to counteract such chemical injuries. Depending on the severity of the chemical insult, biological responses often lead to inadequate wound healing and result in long-term pathology instead. Exposure to other toxic industrial chemicals such as acrolein, chloropicrin, and hydrogen fluoride, can also cause prominent eye and skin damage. There are currently no FDA-approved drugs to counteract these injuries. Hence, the possibility of a mass casualty emergency involving these chemicals is a major public health concern. Recognizing this critical challenge, the United States Department of Health and Human Services (HHS) is committed to the development of medical countermeasures to advance national health and medical preparedness against these highly toxic chemicals. Here, we provide an overview of various HHS funding and scientific opportunities available in this space, emphasizing parallels between eye and skin response to chemical injury. We also discuss a main limitation of existing data and suggest ways to overcome it.

Mucus-producing 3D cell culture models

In vitro cell-based models have been used for a long time since they are normally easily obtained and have an advantageous cost-benefit. Besides, they can serve a variety of ends, from studying drug absorption and metabolism to disease modeling. However, some in vitro models are too simplistic, not accurately representing the living tissues. It has been shown, mainly in the last years, that fully mimicking a tissue composition and architecture can be paramount for cellular behavior and, consequently, for the outcomes of the studies using such models. Because of this, 3D in vitro cell models have been gaining much attention, since they are able to better replicate the in vivo environment. In this review we focus on 3D models that contain mucus-producing cells, as mucus can play a pivotal role in drug absorption. Being frequently overlooked, this viscous fluid can have an impact on drug delivery. Thus, the aim of this review is to understand to which extent can mucus affect mucosal drug delivery and to provide a state-of-the-art report on the existing 3D cell-based mucus models.

Pharmacological evaluation of innovative eye drop formulations containing TS-polysaccaride, hyaluronic acid and glycyrrhizin for irritative ocular diseases using in vitro reconstituted human corneal epithelium model

In vitro reconstructed human corneal tissue models are closer to in vivo human corneal tissue in term of morphology, biochemical and physiological properties, and represent a valid alternative to animal use for evaluating the pharmacological effects ophthalmic topically applied medical devices. In this experimental work the in vitro reconstructed human corneal tissues have been used for assessing the potential beneficial effects of an innovative ophthalmic formulation containing hyaluronic acid, glycyrrhizin and TS-polysaccharide for the treatment of symptomatic states on the eye surface including dry eye, itching, foreign body sensation and redness due allergic reaction. Corneal tissues have been treated with benzalkonium chloride for 24 h to induce cell damage and then treated with the tested items for 16 h. After the incubation period, tissue viability, TNF-α, IL-6 and MMP-9 have been assessed. Diclofenac has been used as reference anti-inflammatory drug. The novel formulation protected the tissues against benzalkonium chloride damage, while exerted a mild but not significant reduction of the anti-inflammatory mediator TNF-α.

An Open-Source Add-On EVOM® Device for Real-Time Transepithelial/Endothelial Electrical Resistance Measurements in Multiple Transwell Samples

This study provides design of a low-cost and open source add-on device that enhances the functionality of the popular EVOM® instrument for transepithelial/endothelial electrical resistance (TEER) measurement. The original EVOM® instrument is designed for measuring TEER in transwell samples manually using a pair of Ag/AgCl electrodes. The inconsistency in electrode placement, temperature variation, and a typically large (12-24 h) time interval between measurements result in large data variabilities. Thus, to solve the current limitation of the EVOM® instrument, we built an add-on device using a custom designed electronic board and a 3D printed electrode holder that allowed automated TEER measurements in multiple transwell samples. To demonstrate the functionality of the device prototype, we monitored TEER in 4 transwell samples containing retinal cells (ARPE-19) for 67 h. Furthermore, by monitoring temperature of the cell culture medium, we were able to detect fluctuations in TEER due to temperature change after the medium change process, and were able to correct the data offset. Although we demonstrated the use of our add-on device on EVOM® instrument only, the concept (multiplexing using digitally controlled relays) and hardware (custom data logger) presented here can be applied to more advanced TEER instruments to improve the performance of those devices.