Associations between clinical signs and pathological findings in toxicity testing

Animal testing for toxicity assessment of chemicals and pharmaceuticals must take the 3R principles into consideration. During toxicity testing in vivo, clinical signs are used to monitor animal welfare and to inform about potential toxicity. This study investigated possible associations between clinical signs, body weight change and histopathological findings observed after necropsy. We hypothesized that clinical signs and body weight loss observed during experiments could be used as early markers of organ toxicity. This represents a potential for refinement in terms of improved study man­agement and decreasing of pain and distress experienced during animal experiments. Data from three sequential toxicity studies of an anti-cancer drug candidate in rats were analyzed using the multivariate partial least squares (PLS) regression method. Associations with a predictive value over 80% were found between the occurrence of mild to severe clinical signs and histopathological findings in the thymus, testes, epididymides and bone marrow. Piloerection, eyes half shut and slightly decreased motor activity were most strongly associated with the pathological findings. A 5% body weight loss was found to be a strong empirical predictor of pathological findings but could also be predicted accurately by clinical signs. Thus, we suggest using mild clinical signs and a 5% body weight loss as toxicity markers and as a non-invasive surveillance tool to monitor research animal welfare in toxicity testing. These clinical signs may also enable reduction of animal use due to their informative potential to support scientific decisions regarding drug candidate selection, dose setting, study design, and toxicity assessment.

Fungal Pigments: Potential Coloring Compounds for Wide Ranging Applications in Textile Dyeing

Synthetic pigments/non-renewable coloring sources used normally in the textile industry release toxic substances into the environment, causing perilous ecological challenges. To be safer from such challenges of synthetic colorants, academia and industries have explored the use of natural colorants such as microbial pigments. Such explorations have created a fervent interest among textile stakeholders to undertake the dyeing of textile fabrics, especially with fungal pigments. The biodegradable and sustainable production of natural colorants from fungal sources stand as being comparatively advantageous to synthetic dyes. The prospective scope of fungal pigments has emerged in the opening of many new avenues in textile colorants for wide ranging applications. Applying the biotechnological processes, fungal pigments like carotenoids, melanins, flavins, phenazines, quinones, monascins, violacein, indigo, etc. could be extracted on an industrial scale. This review appraises the studies and applications of various fungal pigments in dyeing textile fabrics and is furthermore shedding light on the importance of toxicity testing, genetic manipulations of fungal pigments, and their future perspectives under biotechnological approaches.

In vitro toxicity model: Upgrades to bridge the gap between preclinical and clinical research

The Centers for Disease Control and Prevention (CDC) provides extensive data that indicate our need for drugs to maintain human population health. Despite the substantial availability of drugs on the market, many patients lack specific drugs. New drugs are required to tackle this issue. Moreover, we need more reliable models for testing drug toxicity, as too many drug approval failures occur with the current models. This article briefly describes various approaches of the currently used models for toxicity screening, to justify the selection of in vitro cell-based models. Cell-based toxicity models have the best potential to reliably predict drug toxicity in humans, as they are developed using the cells of the target organism. However, currently, a large gap exists between in vitro cell-based approach to toxicity testing and the clinical approach, which may be contributing to drug approval failures. We propose improvements to in vitro cell-based toxicity models, which is often an insight approach, to better match this approach with the clinical homeostatic approach. This should enable a more accurate comparison of data between the preclinical as well as clinical models and provide a more comprehensive understanding of human physiology and biological effects of drugs.

Toxicity testing is evolving!

The efficient management of the continuously increasing number of chemical substances used in today's society is assuming greater importance than ever before. Toxicity testing plays a key role in the regulatory decisions of agencies and governments that aim to protect the public and the environment from the potentially harmful or adverse effects of these multitudinous chemicals. Therefore, there is a critical need for reliable toxicity-testing methods to identify, assess and interpret the hazardous properties of any substance. Traditionally, toxicity-testing approaches have been based on studies in experimental animals. However, in the last 20 years, there has been increasing concern regarding the sustainability of these methodologies. This has created a real need for the development of new approach methodologies (NAMs) that satisfy the regulatory requirements and are acceptable and affordable to society. Numerous initiatives have been launched worldwide in attempts to address this critical need. However, although the science to support this is now available, the legislation and the pace of NAMs acceptance is lagging behind. This review will consider some of the various initiatives in Europe to identify NAMs to replace or refine the current toxicity-testing methods for pharmaceuticals. This paper also presents a novel systematic approach to support the desired toxicity-testing methodologies that the 21st century deserves.

Translational Toxicology in Zebrafish

A major goal of translational toxicology is to identify adverse chemical effects and determine whether they are conserved or divergent across experimental systems. Translational toxicology encompasses assessment of chemical toxicity across multiple life stages, determination of toxic mode-of-action, computational prediction modeling, and identification of interventions that protect or restore health following toxic chemical exposures. The zebrafish is increasingly used in translational toxicology because it combines the genetic and physiological advantages of mammalian models with the higher-throughput capabilities and genetic manipulability of invertebrate models. Here, we review recent literature demonstrating the power of the zebrafish as a model for addressing all four activities of translational toxicology. Important data gaps and challenges associated with using zebrafish for translational toxicology are also discussed.

Human Cell-Based in vitro Phenotypic Profiling for Drug Safety-Related Attrition

Ensuring the safety of new drugs is critically important to regulators, pharmaceutical researchers and patients alike. Even so, unexpected toxicities still account for 20–30% of clinical trial failures, in part due to the persistence of animal testing as the primary approach for de-risking new drugs. Clearly, improved methods for safety attrition that incorporate human-relevant biology are needed. This recognition has spurred interest in non-animal alternatives or new approach methodologies (NAMs) including in vitro models that utilize advances in the culture of human cell types to provide greater clinical relevance for assessing risk. These phenotypic assay systems use human primary and induced pluripotent stem cell-derived cells in various formats, including co-cultures and advanced cellular systems such as organoids, bioprinted tissues, and organs-on-a-chip. Despite the promise of these human-based phenotypic approaches, adoption of these platforms into drug discovery programs for reducing safety-related attrition has been slow. Here we discuss the value of large-scale human cell-based phenotypic profiling for incorporating human-specific biology into the de-risking process. We describe learnings from our experiences with human primary cell-based assays and analysis of clinically relevant reference datasets in developing in vitro-based toxicity signatures. We also describe how Adverse Outcome Pathway (AOP) frameworks can be used to integrate results from diverse platforms congruent with weight-of-evidence approaches from risk assessment to improve safety-related decisions in early discovery.

Using Proales similis (Rotifera) for toxicity assessment in marine waters

There is a need to develop more animal species for assessing toxicity in marine environments. Cyst-based toxicity tests using invertebrates are especially fast, technically simple, cost-effective, and sensitive to a variety of toxicants. Over the past 30 years, a variety of toxicity endpoints have been measured using the marine rotifer Brachionus plicatilis hatched from cysts, including mortality, reproduction, ingestion, swimming, enzyme activity, and gene expression. A consensus has developed that the most ecologically relevant toxicity measurements should be made using more than one species. Furthermore, it has been noted that the rotifer species toxicant sensitivity distribution is much broader than which endpoint is measured. This implies that toxicity should be measured with the simplest, fastest, least expensive test available on as many species as feasible. If a battery of test species is to be used to estimate toxicity, diapause egg-based toxicity tests that do not require culturing of test animals will be key. In this paper, we describe how diapause eggs of a new marine rotifer, Proales similis, can be produced, stored and hatched under controlled conditions to produce animals for toxicity tests. Methods are described for quantifying the toxicity of copper, mercury and cadmium based on mortality, ingestion, reproduction, and diapause egg hatching endpoints. We found that reproduction and ingestion endpoints were generally more sensitive to the metals than mortality or diapause egg hatching. When the copper sensitivity of P. similis was compared to Brachionus manjavacas and B. plicatilis using an ingestion test, similar EC50s were observed. In contrast, the B. rotundiformis ingestion EC50 for copper was about 4× more sensitive. Although diapause egg hatching was not the most sensitive endpoint, it is the most ecologically relevant for assessing sediment toxicity. Our discovery of diapausing eggs in the P. similis life cycle has created a conundrum. We have not observed males or sex in P. similis populations, which is a direct contradiction to the orthodox view of the monogonont rotifer life cycle. Work is needed to clarify how diapause egg production is accomplished by P. similis and whether sexual reproduction is involved.

Conceptual Design of Micro-Bioreactors and Organ-on-Chips for Studies of Cell Cultures

Engineering design of microbioreactors (MBRs) and organ-on-chip (OoC) devices can take advantage of established design science theory, in which systematic evaluation of functional concepts and user requirements are analyzed. This is commonly referred to as a conceptual design. This review article compares how common conceptual design principles are applicable to MBR and OoC devices. The complexity of this design, which is exemplified by MBRs for scaled-down cell cultures in bioprocess development and drug testing in OoCs for heart and eye, is discussed and compared with previous design solutions of MBRs and OoCs, from the perspective of how similarities in understanding design from functionality and user purpose perspectives can more efficiently be exploited. The review can serve as a guideline and help the future design of MBR and OoC devices for cell culture studies.

Toxicity Assay for Citrinin, Zearalenone and Zearalenone-14-Sulfate Using the Nematode Caenorhabditis elegans as Model Organism

To keep pace with the rising number of detected mycotoxins, there is a growing need for fast and reliable toxicity tests to assess potential threats to food safety. Toxicity tests with the bacterial-feeding nematode Caenorhabditis elegans as the model organism are well established. In this study the C. elegans wildtype strain N2 (var. Bristol) was used to investigate the toxic effects of the food-relevant mycotoxins citrinin (CIT) and zearalenone-14-sulfate (ZEA-14-S) and zearalenone (ZEA) on different life cycle parameters including reproduction, thermal and oxidative stress resistance and lifespan. The metabolization of the mycotoxins by the nematodes in vivo was investigated using HPLC-MS/MS. ZEA was metabolized in vivo to the reduced isomers α-zearalenol (α-ZEL) and β-ZEL. ZEA-14-S was reduced to α-/β-ZEL-14-sulfate and CIT was metabolized to mono-hydroxylated CIT. All mycotoxins tested led to a significant decrease in the number of nematode offspring produced. ZEA and CIT displayed negative effects on stress tolerance levels and for CIT an additional shortening of the mean lifespan was observed. In the case of ZEA-14-S, however, the mean lifespan was prolonged. The presented study shows the applicability of C. elegans for toxicity testing of emerging food mycotoxins for the purpose of assigning potential health threats.

Advances in acute toxicity testing: strengths, weaknesses and regulatory acceptance

Safety assessment of chemicals, pharmaceuticals, food and food ingredients, cosmetics, industrial products is very crucial prior to their approval for human uses. Since the commencement of toxicity testing (about 500 years ago, since 1520), significant advances have been made with respect to the 3Rs (reduction, refinement and replacement) alternative approaches. This review is focused on the update in acute systemic toxicity testing of chemicals. Merits and demerits of these advances were also highlighted. Traditional LD50 test methods are being suspended while new methods are developed and endorsed by the regulatory body. Based on the refinement and reduction approaches, the regulatory body has approved fixed dose procedure (FDP), acute toxic class (ATC) method and up and down procedure (UDP) which involves few numbers of animals. In terms of replacement approach, the regulatory body approved 3T3 neutral red uptake (NRU), the normal human keratinocyte (NHK), and the 3T3 neutral red uptake (NRU) phototoxicity test for acute phototoxicity. However, other promising replacement alternatives such as organ on chip seeded with human cells for acute systemic toxicity and 3T3 neutral red uptake (NRU) cytotoxicity test for identifying substances not requiring classification, as well as the in silico approaches are yet to receive regulatory approval. With this backdrop, a collaborative effort is required from the academia, industries, regulatory agencies, government and scientific organizations to ensure speedily regulatory approval of the prospective alternatives highlighted.

Safety Aspects of Bio-Based Nanomaterials

Moving towards a bio-based and circular economy implies a major focus on the responsible and sustainable utilization of bio-resources. The emergence of nanotechnology has opened multiple possibilities, not only in the existing industrial sectors, but also for completely novel applications of nanoscale bio-materials, the commercial exploitation of which has only begun during the last few years. Bio-based materials are often assumed not to be toxic. However, this pre-assumption is not necessarily true. Here, we provide a short overview on health and environmental aspects associated with bio-based nanomaterials, and on the relevant regulatory requirements. We also discuss testing strategies that may be used for screening purposes at pre-commercial stages. Although the tests presently used to reveal hazards are still evolving, regarding modifi­cations required for nanomaterials, their application is needed before the upscaling or commercialization of bio-based nanomaterials, to ensure the market potential of the nanomaterials is not delayed by uncertainties about safety issues.

Nanomaterials in food contact materials; considerations for risk assessment

Nanotechnology applications in the food industry, including food contact materials, offer many potential benefits for consumers and manufacturers alike. The article discusses the migration of nanoparticles from food contact materials and the possible health risks associated with in the context of insufficient knowledge of the potential exposure to nanomaterial. The importance of gaps in the general knowledge on the behaviour and biological interactions of nanomaterials in biological systems becomes crucial for risk assessment. The article also discussed numerous doubts concerning the measurements of biological reactions in animal tests and the need for new approaches in the interpretation of data from nanoparticles studies in vivo. The article underlines the need to develop predictive and validated toxicological tests that can be used to screen for potential hazards, and also to develop new methodology for measuring nanoparticles in biological matrices to assess human exposure. Further studies should focus on understanding the mechanisms of action. Nanoparticles exhibit chemical and physical properties that significantly differ from those substances at a large size. Different properties of nanoparticles may lead to different toxicological properties. From that reason nanoparticles, in each case, are individually assessed by the European Food Standard Agency (EFSA) in terms of health risk before the European Commission authorizes them to be used in food contact materials.

Evaluation of sampling methods for toxicological testing of indoor air particulate matter

There is a need for toxicity tests capable of recognizing indoor environments with compromised air quality, especially in the context of moisture damage. One of the key issues is sampling, which should both provide meaningful material for analyses and fulfill requirements imposed by practitioners using toxicity tests for health risk assessment. We aimed to evaluate different existing methods of sampling indoor particulate matter (PM) to develop a suitable sampling strategy for a toxicological assay. During three sampling campaigns in moisture-damaged and non-damaged school buildings, we evaluated one passive and three active sampling methods: the Settled Dust Box (SDB), the Button Aerosol Sampler, the Harvard Impactor and the National Institute for Occupational Safety and Health (NIOSH) Bioaerosol Cyclone Sampler. Mouse RAW264.7 macrophages were exposed to particle suspensions and cell metabolic activity (CMA), production of nitric oxide (NO) and tumor necrosis factor (TNFα) were determined after 24 h of exposure. The repeatability of the toxicological analyses was very good for all tested sampler types. Variability within the schools was found to be high especially between different classrooms in the moisture-damaged school. Passively collected settled dust and PM collected actively with the NIOSH Sampler (Stage 1) caused a clear response in exposed cells. The results suggested the higher relative immunotoxicological activity of dust from the moisture-damaged school. The NIOSH Sampler is a promising candidate for the collection of size-fractionated PM to be used in toxicity testing. The applicability of such sampling strategy in grading moisture damage severity in buildings needs to be developed further in a larger cohort of buildings.

Assigning ethical weights to clinical signs observed during toxicity testing

Reducing the number of laboratory animals used and refining experimental procedures to enhance animal welfare are fundamental questions to be considered in connection with animal experimentation. Here, we explored the use of cardinal ethical weights for clinical signs and symptoms in rodents by conducting trade-off interviews with members of Swedish Animal Ethics Committees in order to derive such weights for nine typical clinical signs of toxicity. The participants interviewed represent researchers, politically nominated political nominees and representatives of animal welfare organizations. We observed no statistically significant differences between these groups with respect to the magnitude of the ethical weights assigned, though the political nominees tended to assign lower weights. Overall, hunched posture was considered the most severe clinical sign and body weight loss the least severe. The ethical weights assigned varied considerably between individuals, from zero to infinite value, indicating discrepancies in prioritization of reduction and refinement. Cardinal ethical weights may be utilized to include both animal welfare refinement and reduction of animal use in designing as well as in retrospective assessment of animal experiments. Such weights may also be used to estimate ethical costs of animal experiments.

In Vitro Cell Models for Ophthalmic Drug Development Applications

Tissue engineering is a rapidly expanding field that aims to establish feasible techniques to fabricate biologically equivalent replacements for diseased and damaged tissues/organs. Emerging from this prospect is the development of in vitro representations of organs for drug toxicity assessment. Due to the ever-increasing interest in ocular drug delivery as a route for administration as well as the rise of new ophthalmic therapeutics, there is a demand for physiologically accurate in vitro models of the eye to assess drug delivery and safety of new ocular medicines. This review summarizes current existing ocular models and highlights the important factors and limitations that need to be considered during their use.

Morphological and Functional Characterization and Assessment of iPSC-Derived Hepatocytes for In Vitro Toxicity Testing

Drug-induced liver injury (DILI) remains a great challenge and a major concern during late-stage drug development. Induced pluripotent stem cells (iPSC) represent an exciting alternative in vitro model system to explore the role of genetic diversity in DILI, especially when derived from patients who have experienced drug-induced hepatotoxicity. The development and validation of the iPSC-derived hepatocytes as an in vitro cell-based model of DILI is an essential first step in creating more predictive tools for understanding patient-specific hepatotoxic responses to drug treatment. In this study, we performed extensive morphological and functional analyses on iPSC-derived hepatocytes from a commercial source. iPSC-derived hepatocytes exhibit many of the key morphological and functional features of primary hepatocytes, including membrane polarity and production of glycogen, lipids, and key hepatic proteins, such as albumin, asialoglycoprotein receptor and α1-antitrypsin. They maintain functional activity for many drug-metabolizing enzyme pathways and possess active efflux capacity of marker substrates into bile canalicular compartments. Whole genome-wide array analysis of multiple batches of iPSC-derived cells showed that their transcriptional profiles are more similar to those from neonatal and adult hepatocytes than those from fetal liver. Results from experiments using prototype DILI compounds, such as acetaminophen and trovafloxacin, indicate that these cells are able to reproduce key characteristic metabolic and adaptive responses attributed to the drug-induced hepatotoxic effects in vivo. Overall, this novel system represents a promising new tool for understanding the underlying mechanisms of idiosyncratic DILI and for screening new compounds for DILI-related liabilities.

Effects of alendronate and pamidronate on apoptosis and cell proliferation in cultured primary human gingival fibroblasts

Data arising from the recent literature directed the researchers to study on the degree and extent of bisphosphonate toxicity on oral mucosa in further detail. The aim of this study is to determine the half maximal inhibitory concentration of pamidronate (PAM) and alendronate (ALN) on human gingival fibroblasts in vitro using 3-[4.5-thiazol-2-yl]-2.5-diphenyltetrazolium bromide (MTT) assay and to evaluate the effects of both agents on the proliferation and apoptotic indices. Cells used in the study were generated from human gingival specimens and divided into alendronate (n = 240), PAM (n = 240), and control groups (n = 60). Based on the MTT assay results, 10(-4), 10(-5), 10(-6), and 10(-7) M concentrations of both drugs were administered and the effects were evaluated for 6, 12, 24, 48, or 72 h periods. An indirect immunofluorescence technique was used to evaluate apoptotic (anti-caspase 3) and proliferation (anti-Ki67) indices. Toxicity of both PAM and ALN was found to be the most potent at 10(-4)-10(-5) M range. The apoptotic index of PAM group was found to be significantly higher than ALN group for all concentrations especially at 24 h incubation time (p < 0.05). The decrease in the proliferation index was found similar in first 48 h for both drugs; however, after 72 h of incubation decrease in proliferation index in PAM group was found to be significantly higher (p < 0.05). Micromolar concentrations of not only PAM but also ALN rapidly affect cells generated from human oral gingival tissue by inducing apoptosis together with inhibition of proliferation. Cytotoxic effects of both ALN and PAM on primary human gingival fibroblasts, which cause significant changes in apoptotic and proliferative indices as shown in this in vitro study, suggests that the defective epithelialization of oral mucosa is possibly a major factor on the onset of bisphosphonate-related osteonecrosis of the jaw cases.

Acute toxicity studies of a novel excipient arabinoxylan isolated from Ispaghula (Plantago ovata) husk

PURPOSE

The arabinoxylan from Ispaghula (Plantago ovata) husk has been proven scientifically as potential excipient. However, toxicity study of the arabinoxylan is still lacking. The present study was done to investigate the acute toxicity of arabinoxylan in two animal species.

METHODS

The mice were exposed to (1 g/kg, 5 g/kg, 10 g/kg) and rabbits (2.5 g/kg, 5 g/kg) of arabinoxylan orally and observed for a period of 14 days. On day 15 hematology, serum biochemistry and necropsy was performed in mice relative organ weight calculated and histological examination was carried out. Primary dermal and eye irritation tests were carried out. Cardiac effects of isolated arabinoxylan were studied on frog heart.

RESULTS

The acute administration of the arabinoxylan did not produce mortality or significant changes in, water and food consumption however body weights of mice and rabbits decreased initially with a gradual increase till day 14. Internal organs relative weights were found to be normal. Hematological biochemical and histopathological examination did not show any significant (p < 0.05) change. Primary dermal and eye irritation was not observed in treated rabbits. No change in heart rate and vascular contraction was observed in frog heart.

CONCLUSION

This study has shown that acute administration of arabinoxylan may be safe.

Functional toxicology: tools to advance the future of toxicity testing

The increased presence of chemical contaminants in the environment is an undeniable concern to human health and ecosystems. Historically, by relying heavily upon costly and laborious animal-based toxicity assays, the field of toxicology has often neglected examinations of the cellular and molecular mechanisms of toxicity for the majority of compounds—information that, if available, would strengthen risk assessment analyses. Functional toxicology, where cells or organisms with gene deletions or depleted proteins are used to assess genetic requirements for chemical tolerance, can advance the field of toxicity testing by contributing data regarding chemical mechanisms of toxicity. Functional toxicology can be accomplished using available genetic tools in yeasts, other fungi and bacteria, and eukaryotes of increased complexity, including zebrafish, fruit flies, rodents, and human cell lines. Underscored is the value of using less complex systems such as yeasts to direct further studies in more complex systems such as human cell lines. Functional techniques can yield (1) novel insights into chemical toxicity; (2) pathways and mechanisms deserving of further study; and (3) candidate human toxicant susceptibility or resistance genes.

They see a rat, we seek a cure for diseases: the current status of animal experimentation in medical practice

The objective of this review article was to examine current and prospective developments in the scientific use of laboratory animals, and to find out whether or not there are still valid scientific benefits of and justification for animal experimentation. The PubMed and Web of Science databases were searched using the following key words: animal models, basic research, pharmaceutical research, toxicity testing, experimental surgery, surgical simulation, ethics, animal welfare, benign, malignant diseases. Important relevant reviews, original articles and references from 1970 to 2012 were reviewed for data on the use of experimental animals in the study of diseases. The use of laboratory animals in scientific research continues to generate intense public debate. Their use can be justified today in the following areas of research: basic scientific research, use of animals as models for human diseases, pharmaceutical research and development, toxicity testing and teaching of new surgical techniques. This is because there are inherent limitations in the use of alternatives such as in vitro studies, human clinical trials or computer simulation. However, there are problems of transferability of results obtained from animal research to humans. Efforts are on-going to find suitable alternatives to animal experimentation like cell and tissue culture and computer simulation. For the foreseeable future, it would appear that to enable scientists to have a more precise understanding of human disease, including its diagnosis, prognosis and therapeutic intervention, there will still be enough grounds to advocate animal experimentation. However, efforts must continue to minimize or eliminate the need for animal testing in scientific research as soon as possible.

The Tox21 robotic platform for the assessment of environmental chemicals--from vision to reality

Since its establishment in 2008, the US Tox21 inter-agency collaboration has made great progress in developing and evaluating cellular models for the evaluation of environmental chemicals as a proof of principle. Currently, the program has entered its production phase (Tox21 Phase II) focusing initially on the areas of modulation of nuclear receptors and stress response pathways. During Tox21 Phase II, the set of chemicals to be tested has been expanded to nearly 10,000 (10K) compounds and a fully automated screening platform has been implemented. The Tox21 robotic system combined with informatics efforts is capable of screening and profiling the collection of 10K environmental chemicals in triplicate in a week. In this article, we describe the Tox21 screening process, compound library preparation, data processing, and robotic system validation.

A simple, sensitive and accurate method for rat paw volume measurement and its expediency in preclinical animal studies

Several methods are used to evaluate the inflammatory changes. Measurement of edema is the most commonly used method for evaluating artificially induced inflammation in rat model. In this context, we present a method for the measurement of volume of rat paw, in which two glass columns containing fluid are connected by a glass tube. Paw is immersed in one column and the other column is placed on weighing balance. Upon immersion of paw, equal volume of fluid displaced applies a force F, which shows specific and proportional increment in the level of fluid in both the columns, which could then be detected by weighing balance, as 'Force = Weight' of displaced fluid, using the specific gravity of the fluid and the volume of paw, and thus the change in the volume of paw can be calculated. The rat paw immersed in column without touching the wall of the column facilitates the accurate measurement of volume of paw when measured several times. Present method is validated for its accuracy and reproducibility when internal radii of both the columns were same or different. Presented method is also cost-effective and hence can be used for the academic and the commercial animal research purpose, without compromising the precision of the evaluation.

A multi-scale modeling framework for individualized, spatiotemporal prediction of drug effects and toxicological risk

In this study, we focus on a novel multi-scale modeling approach for spatiotemporal prediction of the distribution of substances and resulting hepatotoxicity by combining cellular models, a 2D liver model, and whole body model. As a case study, we focused on predicting human hepatotoxicity upon treatment with acetaminophen based on in vitro toxicity data and potential inter-individual variability in gene expression and enzyme activities. By aggregating mechanistic, genome-based in silico cells to a novel 2D liver model and eventually to a whole body model, we predicted pharmacokinetic properties, metabolism, and the onset of hepatotoxicity in an in silico patient. Depending on the concentration of acetaminophen in the liver and the accumulation of toxic metabolites, cell integrity in the liver as a function of space and time as well as changes in the elimination rate of substances were estimated. We show that the variations in elimination rates also influence the distribution of acetaminophen and its metabolites in the whole body. Our results are in agreement with experimental results. What is more, the integrated model also predicted variations in drug toxicity depending on alterations of metabolic enzyme activities. Variations in enzyme activity, in turn, reflect genetic characteristics or diseases of individuals. In conclusion, this framework presents an important basis for efficiently integrating inter-individual variability data into models, paving the way for personalized or stratified predictions of drug toxicity and efficacy.

Organotypic liver culture models: meeting current challenges in toxicity testing

Prediction of chemical-induced hepatotoxicity in humans from in vitro data continues to be a significant challenge for the pharmaceutical and chemical industries. Generally, conventional in vitro hepatic model systems (i.e. 2-D static monocultures of primary or immortalized hepatocytes) are limited by their inability to maintain histotypic and phenotypic characteristics over time in culture, including stable expression of clearance and bioactivation pathways, as well as complex adaptive responses to chemical exposure. These systems are less than ideal for longer-term toxicity evaluations and elucidation of key cellular and molecular events involved in primary and secondary adaptation to chemical exposure, or for identification of important mediators of inflammation, proliferation and apoptosis. Progress in implementing a more effective strategy for in vitro-in vivo extrapolation and human risk assessment depends on significant advances in tissue culture technology and increasing their level of biological complexity. This article describes the current and ongoing need for more relevant, organotypic in vitro surrogate systems of human liver and recent efforts to recreate the multicellular architecture and hemodynamic properties of the liver using novel culture platforms. As these systems become more widely used for chemical and drug toxicity testing, there will be a corresponding need to establish standardized testing conditions, endpoint analyses and acceptance criteria. In the future, a balanced approach between sample throughput and biological relevance should provide better in vitro tools that are complementary with animal testing and assist in conducting more predictive human risk assessment.

In vitro assessment of developmental neurotoxicity: use of microelectrode arrays to measure functional changes in neuronal network ontogeny

Because the Developmental Neurotoxicity Testing Guidelines require large numbers of animals and is expensive, development of in vitro approaches to screen chemicals for potential developmental neurotoxicity is a high priority. Many proposed approaches for screening are biochemical or morphological, and do not assess function of neuronal networks. In this study, microelectrode arrays (MEAs) were used to determine if chemical-induced changes in function could be detected by assessing the development of spontaneous network activity. MEAs record individual action potential spikes as well as groups of spikes (bursts) in neuronal networks, and activity can be assessed repeatedly over days in vitro (DIV). Primary cultures of rat cortical neurons were prepared on MEAs and spontaneous activity was assessed on DIV 2, 6, 9, 13, and 20 to determine the in vitro developmental profile of spontaneous spiking and bursting in cortical networks. In addition, 5 μM of the protein kinase C inhibitor bisindolylmaleamide-1 (Bis-1) was added to MEAs (n = 9–18) on DIV 5 to determine if changes in spontaneous activity could be detected in response to inhibition of neurite outgrowth. A clear profile of in vitro activity development occurred in control MEAs, with the number of active channels increasing from 0/MEA on DIV 2 to 37 ± 5/MEA by DIV 13; the rate of increase was most rapid between DIV 6 and 9, and activity declined by DIV 20. A similar pattern was observed for the number of bursting channels, as well as the total number of bursts. Bis-1 decreased the number of active channels/MEA and the number of bursting channels/MEA. Burst characteristics, such as burst duration and the number of spikes in a burst, were unchanged by Bis-1. These results demonstrate that MEAs can be used to assess the development of functional neuronal networks in vitro, as well as chemical-induced dysfunction.