Human small intestinal organotypic culture model for drug permeation, inflammation, and toxicity assays

The gastrointestinal tract (GIT), in particular, the small intestine, plays a significant role in food digestion, fluid and electrolyte transport, drug absorption and metabolism, and nutrient uptake. As the longest portion of the GIT, the small intestine also plays a vital role in protecting the host against pathogenic or opportunistic microbial invasion. However, establishing polarized intestinal tissue models in vitro that reflect the architecture and physiology of the gut has been a challenge for decades and the lack of translational models that predict human responses has impeded research in the drug absorption, metabolism, and drug-induced gastrointestinal toxicity space. Often, animals fail to recapitulate human physiology and do not predict human outcomes. Also, certain human pathogens are species specific and do not infect other hosts. Concerns such as variability of results, a low throughput format, and ethical considerations further complicate the use of animals for predicting the safety and efficacy xenobiotics in humans. These limitations necessitate the development of in vitro 3D human intestinal tissue models that recapitulate in vivo–like microenvironment and provide more physiologically relevant cellular responses so that they can better predict the safety and efficacy of pharmaceuticals and toxicants. Over the past decade, much progress has been made in the development of in vitro intestinal models (organoids and 3D-organotypic tissues) using either inducible pluripotent or adult stem cells. Among the models, the MatTek’s intestinal tissue model (EpiIntestinal™ Ashland, MA) has been used extensively by the pharmaceutical industry to study drug permeation, metabolism, drug-induced GI toxicity, pathogen infections, inflammation, wound healing, and as a predictive model for a clinical adverse outcome (diarrhea) to pharmaceutical drugs. In this paper, our review will focus on the potential of in vitro small intestinal tissues as preclinical research tool and as alternative to the use of animals.

Human 3D Gastrointestinal Microtissue Barrier Function As a Predictor of Drug-Induced Diarrhea

Drug-induced gastrointestinal toxicities (GITs) rank among the most common clinical side effects. Preclinical efforts to reduce incidence are limited by inadequate predictivity of in vitro assays. Recent breakthroughs in in vitro culture methods support intestinal stem cell maintenance and continual differentiation into the epithelial cell types resident in the intestine. These diverse cells self-assemble into microtissues with in vivo-like architecture. Here, we evaluate human GI microtissues grown in transwell plates that allow apical and/or basolateral drug treatment and 96-well throughput. Evaluation of assay utility focused on predictivity for diarrhea because this adverse effect correlates with intestinal barrier dysfunction which can be measured in GI microtissues using transepithelial electrical resistance (TEER). A validation set of widely prescribed drugs was assembled and tested for effects on TEER. When the resulting TEER inhibition potencies were adjusted for clinical exposure, a threshold was identified that distinguished drugs that induced clinical diarrhea from those that lack this liability. Microtissue TEER assay predictivity was further challenged with a smaller set of drugs whose clinical development was limited by diarrhea that was unexpected based on 1-month animal studies. Microtissue TEER accurately predicted diarrhea for each of these drugs. The label-free nature of TEER enabled repeated quantitation with sufficient precision to develop a mathematical model describing the temporal dynamics of barrier damage and recovery. This human 3D GI microtissue is the first in vitro assay with validated predictivity for diarrhea-inducing drugs. It should provide a platform for lead optimization and offers potential for dose schedule exploration.

In vitro demonstration of intestinal absorption mechanisms of different sugars using 3D organotypic tissues in a fluidic device

Intestinal permeability is crucial in regulating the bioavailability and, consequently, the biological effects of drugs and compounds. However, systematic and quantitative studies of the absorption of molecules are quite limited due to a lack of reliable experimental models able to mimic human in vivo responses. In this work, we present an in vitro perfused model of the small intestinal barrier using a 3D reconstructed intestinal epithelium integrated into a fluid-dynamic biore­actor (MIVO®) resembling the physiological stimuli of the intestinal environment. This platform was investigated in both healthy and induced pathological conditions by monitoring the absorption of two non-metabolized sugars, lactulose and mannitol, frequently used as indicators of intestinal barrier dysfunctions. In healthy conditions, an in vivo-like plateau of the percentage of absorbed sugars was reached, where mannitol absorption was much greater than lactulose absorption. Moreover, a model of pathologically altered intestinal permeability was generated by depleting extracellular Ca2+, using a calcium-specific chelator. After calcium depletion, the pattern of sugar passage observed under pathological conditions was reversed only in dynamic conditions in the MIVO® chamber, due to the dynamic fluid flow beneath the membrane, but not in static conditions. Therefore, the combination of the MIVO® with the EpiIntestinal™ platform can rep­resent a reliable in vitro model to study the passage of molecules across the healthy or pathological small intestinal barrier by discriminating the two main mechanisms of intestinal absorption.

Human Primary Cell-Based Organotypic Microtissues for Modeling Small Intestinal Drug Absorption

PURPOSE

The study evaluates the use of new in vitro primary human cell-based organotypic small intestinal (SMI) microtissues for predicting intestinal drug absorption and drug-drug interaction.

METHODS

The SMI microtissues were reconstructed using human intestinal fibroblasts and enterocytes cultured on a permeable support. To evaluate the suitability of the intestinal microtissues to model drug absorption, the permeability coefficients across the microtissues were determined for a panel of 11 benchmark drugs with known human absorption and Caco-2 permeability data. Drug-drug interactions were examined using efflux transporter substrates and inhibitors.

RESULTS

The 3D-intestinal microtissues recapitulate the structural features and physiological barrier properties of the human small intestine. The microtissues also expressed drug transporters and metabolizing enzymes found on the intestinal wall. Functionally, the SMI microtissues were able to discriminate between low and high permeability drugs and correlated better with human absorption data (r2 = 0.91) compared to Caco-2 cells (r2 = 0.71). Finally, the functionality of efflux transporters was confirmed using efflux substrates and inhibitors which resulted in efflux ratios of >2.0 fold and by a decrease in efflux ratios following the addition of inhibitors.

CONCLUSION

The SMI microtissues appear to be a useful pre-clinical tool for predicting drug bioavailability of orally administered drugs.

Systematic review of e-learning for surgical training

BACKGROUND

Internet and software-based platforms (e-learning) have gained popularity as teaching tools in medical education. Despite widespread use, there is limited evidence to support their effectiveness for surgical training. This study sought to evaluate the effectiveness of e-learning as a teaching tool compared with no intervention and other methods of surgical training.

METHODS

A systematic literature search of bibliographical databases was performed up to August 2015. Studies were included if they were RCTs assessing the effectiveness of an e-learning platform for teaching any surgical skill, compared with no intervention or another method of training.

RESULTS

From 4704 studies screened, 87 were included with 7871 participants enrolled, comprising medical students (52 studies), trainees (51 studies), qualified surgeons (2 studies) and nurses (6 studies). E-learning tools were used for teaching cognitive (71 studies), psychomotor (36 studies) and non-technical (8 studies) skills. Tool features included multimedia (84 studies), interactive learning (60 studies), feedback (27 studies), assessment (26 studies), virtual patients (22 studies), virtual reality environment (11 studies), spaced education (7 studies), community discussions (2 studies) and gaming (2 studies). Overall, e-learning showed either greater or similar effectiveness compared with both no intervention (29 and 4 studies respectively) and non-e-learning interventions (29 and 22 studies respectively).

CONCLUSION

Despite significant heterogeneity amongst platforms, e-learning is at least as effective as other methods of training.

Effects of topiramate and gabapentin on cognitive abilities in healthy volunteers

OBJECTIVE

To evaluate the cognitive effects of topiramate (TPM) and gabapentin (GBP).

METHODS

Forty healthy volunteers were randomized to a 12-week course of TPM, GBP, or placebo. Doses were gradually escalated over 10 weeks to a maximum of 400 mg/day of TPM or 3,600 mg/day of GBP or to the highest tolerated dose. Subjects were interviewed and examined biweekly. Cognitive testing was performed prior to initiating the drug and again 12 weeks later, at least 2 weeks after achieving plateau dosing. For each subject and cognitive measure, test-retest Z scores were calculated based on regression equations derived from 73 healthy volunteers. Group comparisons utilized the Wilcoxon test.

RESULTS

There were significant TPM vs GBP and TPM vs placebo differences in test-retest Z scores for four of six target cognitive measures (Digit Symbol, Story Recall, Selective Reminding, Controlled Oral Word Association), always indicating worse retest performance for subjects receiving TPM. Overall, 12 of 24 cognitive measures were similarly affected. TPM effects were large, and several target measures averaged >2 SD of negative change. One measure was significantly affected by GBP.

CONCLUSIONS

Topiramate (TPM) impaired cognitive test performance, whereas gabapentin had minimal effects. The effects of TPM were of sufficient magnitude potentially to affect daily and occupational function.

Evaluation of travoprost as adjunctive therapy in patients with uncontrolled intraocular pressure while using timolol 0.5%

PURPOSE

To evaluate the intraocular pressure-lowering efficacy and safety of travoprost 0.0015% and 0.004%, dosed daily in the evening compared with vehicle, in patients with open-angle glaucoma or ocular hypertension, whose intraocular pressure was not adequately controlled on timolol 0.5% twice daily (twice daily).

METHODS

Subjects who qualified at screening began a run-in period dosing timolol twice daily for 3 weeks. If the subjects had an intraocular pressure of 24 to 36 mm Hg at 8 AM and 21 to 36 mm Hg at 10 AM and 4 pm in at least one eye on timolol, they were randomized to one of two concentrations of travoprost (0.0015% or 0.004%) or vehicle solution every day and were followed for 6 months. Four hundred twenty-six subjects were randomized. The mean intraocular pressure at 8 AM, 10 AM, and 4 PM in the patient's eye with the higher intraocular pressure was used for the analysis.

RESULTS

Mean baseline values (25 mm Hg) for subjects at eligibility (while maintained on timolol) were not significantly different (P <.0001) among the treatment groups. The intraocular pressure was lowered an additional -5.7 to -7.2 mm Hg and -5.1 to -6.7 mm Hg in the travoprost 0.004% and 0.0015% concentrations, respectively. These changes were significantly (P < or =.0001) different from the vehicle group (-1.3 to -2.8 mm Hg). The intraocular pressure range on treatment at all visit times over the 6-month treatment period ranged from 17.9 to 19.2 mm Hg for travoprost 0.004% and 18.3 to 20.1 mm Hg for travoprost 0.0015% compared with 22.4 to 24.1 mm Hg for vehicle. Average hyperemia scores ranged from trace to mild (mean 0.5 on a scale of 0 = none/trace; 1= mild; 2 = moderate; 3 = severe) for all treatment groups. No iris pigmentation changes were observed in any patient during this study. There were no clinically or statistically significant changes from baseline in visual acuity, ocular cells and flare, fundus parameter, cup-to-disk ratio and visual field between the treatment groups. There were no serious adverse events reported for any treatment group.

CONCLUSIONS

Travoprost produced clinically relevant and statistically significant additional intraocular pressure reductions from baseline when used adjunctively with timolol in subjects with open-angle glaucoma or ocular hypertension.

Travoprost compared with latanoprost and timolol in patients with open-angle glaucoma or ocular hypertension

PURPOSE

This study evaluated the safety and intraocular pressure-lowering efficacy of two concentrations of travoprost (0.0015% and 0.004%) compared with latanoprost 0.005% and timolol 0.5% in patients with open-angle glaucoma or ocular hypertension.

METHODS

Eight hundred one patients with open-angle glaucoma or ocular hypertension were randomly assigned to travoprost 0.0015%, travoprost 0.004%, latanoprost 0.005%, or timolol 0.5%. The efficacy and safety of travoprost (0.0015% and 0.004%) daily was compared with latanoprost daily and timolol twice daily for a period of 12 months.

RESULTS

Travoprost was equal or superior to latanoprost and superior to timolol with mean intraocular pressure over visits and time of day ranging from 17.9 to 19.1 mm Hg (travoprost 0.0015%), 17.7 to 19.1 mm Hg (travoprost 0.004%), 18.5 to 19.2 mm Hg (latanoprost), and 19.4 to 20.3 mm Hg (timolol). For all visits pooled, the mean intraocular pressure at 4 PM for travoprost was 0.7 mm Hg (0.0015%, P =.0502) and 0.8 mm Hg (0.004%, P =.0191) lower than for latanoprost. Travoprost 0.004% was more effective than latanoprost and timolol in reducing intraocular pressure in black patients by up to 2.4 mm Hg (versus latanoprost) and 4.6 mm Hg (versus timolol). Based on a criterion of 30% or greater intraocular pressure reduction from diurnal baseline or intraocular pressure 17 mm Hg or less, travoprost 0.0015% and 0.004% had an overall response to treatment of 49.3% and 54.7%, respectively, compared with 49.6% for latanoprost and 39.0% for timolol. Iris pigmentation change was observed in 10 of 201 of patients (5.0%) receiving travoprost 0.0015%, six of 196 of patients (3.1%) receiving travoprost 0.004%, 10 of 194 of patients (5.2%) receiving latanoprost, and none of the patients receiving timolol (0 of 196). The average ocular hyperemia score was less than 1 on a scale of 0 to 3, indicating that on average patients experienced between none/trace and mild for all treatment groups. There were no serious, unexpected, related adverse events reported for any therapy.

CONCLUSIONS

Travoprost (0.0015% and 0.004%), a highly selective, potent prostaglandin F (FP) receptor agonist, is equal or superior to latanoprost and superior to timolol in lowering intraocular pressure in patients with open-angle glaucoma or ocular hypertension. In addition, travoprost 0.004% is significantly better than either latanoprost or timolol in lowering intraocular pressure in black patients. Travoprost is safe and generally well tolerated in the studied patient population.

In vivo skin decontamination of methylene bisphenyl isocyanate (MDI): soap and water ineffective compared to polypropylene glycol, polyglycol-based cleanser, and corn oil

In the home and workplace, decontamination of a chemical from skin is traditionally done with a soap-and-water wash, although some workplaces may have emergency showers. It has been assumed that these procedures are effective, yet workplace illness and even death occur from chemical contamination. Water, or soap and water, may not be the most effective means of skin decontamination, particularly for fat-soluble materials. This study was undertaken to help determine whether there are more effective means of removing methylene bisphenyl isocyanate (MDI), a potent contact sensitizer, from the skin. MDI is an industrial chemical for which skin decontamination, using traditional soap and water and nontraditional polypropylene glycol, a polyglycol-based cleanser (PG-C), and corn oil were all tried in vivo on the rhesus monkey, over 8 h. Water, alone and with soap (5% and 50% soap), were partially effective in the first h after exposure, removing 51-69% of the applied dose. However, decontamination fell to 40-52% at 4 h and 29-46% by 8 h. Thus, the majority of MDI was not removed by the traditional soap-and-water wash; skin tape stripping after washing confirmed that MDI was still on the skin. In contrast, polypropylene glycol, PG-C, and corn oil all removed 68-86% of the MDI in the first h, 74-79% at 4 h, and 72-86% at 8 h. Statistically, polypropylene glycol, PG-C, and corn oil were all better (p < 0.05) than soap and water at 4 and 8 h after dose application. These results indicate that a traditional soap-and-water wash and the emergency water shower are relatively ineffective at removing MDI from the skin. More effective decontamination procedures, as shown here, are available. These procedures are consistent with the partial miscibility of MDI in corn oil and polyglycols.

Les parasites de l'alose d'été (Alosa aestivalis) et du gaspareau (Alosa pseudoharengus) de la rivière Miramichi, Nouveau-Brunswick

The parasite fauna of blueback herring (Alosa aestivalis) and alewife (Alosa pseudoharengus) were examined to determine their usefulness as biological indicators in the differentiation of these two sympatric species. Thirteen parasite species were identified from 100 specimens each of blueback herring and alewife from the main estuary of the Miramichi River, New Brunswick, of which 11 and 8, respectively, represent new host records. Significant differences (p < 0.05) in the counts of Mazocraeoides sp., Diplostomum spathaceum (metacercaria), Derogenes varicus, Anisakis simplex (larvae), and Echinorhynchus gadi between alewives and blueback herring reflect differences of physiological and ecological order between these two host species.

Methylmercury and the skeletal muscle receptor

Methylmercury at bath concentration of 2 X 10(-5) M was capable of inhibiting muscular contractions of the isolated rat phrenic-nerve hemidiaphragm preparation. At the height of inhibition, nerve action potential could still be recorded and the muscles continued to respond to direct stimulation. The inhibition was not reversible with L-cysteine or D-penicillamine but limited protection was possible by prior treatment with (+)-tubocurarine. Treatment of frog rectus muscles with methylmercury (0-2 mM for 15 min) resulted in a shift to the right of 1 log unit in the dose response curve to acetylcholine and a reduction in the maximum response of the tissue. The observed inhibitory action of methylmercury on neuromuscular transmission may be explained by an action on the disulphide bond believed to be present on a cholinergic receptor.