Assessment of nanomaterial-induced hepatotoxicity using a 3D human primary multi-cellular microtissue exposed repeatedly over 21 days - the suitability of the in vitro system as an in vivo surrogate

Microplastic-induced hepatic adverse effects evaluated in advanced quadruple cell human primary models following three weeks of repeated exposure

Nano and microplastics are defined as particles smaller than 100 nm and 5 mm respectively. The widespread production and use of plastics in everyday life has resulted in significant accumulation of plastic debris in the environment. Over the last two decades there are increased concerns regarding the potential entry and accumulation of plastics in the human body with ingestion being one of the most important routes of exposure. However, the magnitude and nature of potential toxic effects of plastic exposure to human health is not yet fully understood. The liver is the body's principal detoxification organ and critically to this study recognized as the main accumulation site for particulates. In this study as the first of its kind the health impacts of long term low repeated polystyrene microplastics (1 and 5 μm) exposure was investigated in a functionally active 3D liver microtissue model, composed of primary human hepatocytes, Kupffer cells, sinusoidal endothelial cells and hepatic stellate cells. The highlight from the data includes microplastic-induced dose (3.125-25 μg/ml) and time dependent (up to 504 h) increase in cell death and inflammation manifested by enhanced release of IL6, IL8 and TNF-α. The exposure to repeated dosing of the plastics also resulted in notable pathology manifested as aberrant tissue architecture, such as dilated bile canaliculi and large lipid droplets inside the hepatic cells. This toxicity matched extremely well to the accumulation of the materials with the cells of microtissue predominately in the organ macrophages. This study highlights the real issue and danger of microplastic exposure with potential for long-term accumulation and adverse effects of non-biodegradable plastics within the liver.

Next Generation Risk Assessment approaches for advanced nanomaterials: Current status and future perspectives

This manuscript discusses the challenges of applying New Approach Methodologies (NAMs) for safe by design and regulatory risk assessment of advanced nanomaterials (AdNMs). The authors propose a framework for Next Generation Risk Assessment of AdNMs involving NAMs that is aligned to the conventional risk assessment paradigm. This framework is exposure-driven, endpoint-specific, makes best use of pre-existing information, and can be implemented in tiers of increasing specificity and complexity of the adopted NAMs. The tiered structure of the approach, which effectively combines the use of existing data with targeted testing will allow safety to be assessed cost-effectively and as far as possible with even more limited use of vertebrates. The regulatory readiness of state-of-the-art emerging NAMs is assessed in terms of Transparency, Reliability, Accessibility, Applicability, Relevance and Completeness, and their appropriateness for AdNMs is discussed in relation to each step of the risk assessment paradigm along with providing perspectives for future developments in the respective scientific and regulatory areas.

Assessing the transferability and reproducibility of 3D in vitro liver models from primary human multi-cellular microtissues to cell-line based HepG2 spheroids

To reduce, replace, and refine in vivo testing, there is increasing emphasis on the development of more physiologically relevant in vitro test systems to improve the reliability of non-animal-based methods for hazard assessment. When developing new approach methodologies, it is important to standardize the protocols and demonstrate the methods can be reproduced by multiple laboratories. The aim of this study was to assess the transferability and reproducibility of two advanced in vitro liver models, the Primary Human multicellular microtissue liver model (PHH) and the 3D HepG2 Spheroid Model, for nanomaterial (NM) and chemical hazard assessment purposes. The PHH model inter-laboratory trial showed strong consistency across the testing sites. All laboratories evaluated cytokine release and cytotoxicity following exposure to titanium dioxide (TiO₂) and zinc oxide (ZnO) nanoparticles. No significant difference was observed in cytotoxicity or IL-8 release for the test materials. The data were reproducible with all three laboratories with control readouts within a similar range. The PHH model ZnO induced the greatest cytotoxicity response at 50.0 μg/mL and a dose-dependent increase in IL-8 release. For the 3D HepG2 spheroid model, all test sites were able to construct the model and demonstrated good concordance in IL-8 cytokine release and genotoxicity data. This trial demonstrates the successful transfer of new approach methodologies across multiple laboratories, with good reproducibility for several hazard endpoints.

Determination of the nanoparticle- and cell-specific toxicological mechanisms in 3D liver spheroids using scRNAseq analysis

Engineered nanomaterials (ENMs) are commonly used in consumer products, allowing exposure to target organs such as the lung, liver, and skin that could lead to adverse health effects in humans. To better reflect on toxicological effects in liver cells, it is important to consider the contribution of hepatocyte morphology, function, and intercellular interactions in a dynamic 3D microenvironment. Herein, we used a 3D liver spheroid model containing hepatocyte and Kupffer cells (KCs) to study the effects of three different material compositions, namely vanadium pentoxide (V2O5), titanium dioxide (TiO2), or graphene oxide (GO). Additionally, we used single-cell RNA sequencing (scRNAseq) to determine the nanoparticle (NP) and cell-specific toxicological responses. A general finding was that hepatocytes exhibit more variation in gene expression and adaptation of signaling pathways than KCs. TNF-α production tied to the NF-κB pathway was a commonly affected pathway by all NPs while impacts on the metabolic function of hepatocytes were unique to V2O5. V2O5 NPs also showed the largest number of differentially expressed genes in both cell types, many of which are related to pro-inflammatory and apoptotic response pathways. There was also evidence of mitochondrial ROS generation and caspase-1 activation after GO and V2O5 treatment, in association with cytokine production. All considered, this study provides insight into the impact of nanoparticles on gene responses in key liver cell types, providing us with a scRNAseq platform that can be used for high-content screening of nanomaterial impact on the liver, for use in biosafety and biomedical applications.

The application of existing genotoxicity methodologies for grouping of nanomaterials: towards an integrated approach to testing and assessment

The incorporation of nanomaterials (NMs) in consumer products has proven to be highly valuable in many sectors. Unfortunately, however, the same nano specific physicochemical properties, which make these material attractive, might also contribute to hazards for people exposed to these materials. The physicochemical properties of NMs will impact their interaction with biological surroundings and influence their fate and their potential adverse effects such as genotoxicity. Due to the large and expanding number of NMs produced, their availability in different nanoforms (NFs) and their utilization in various formats, it is impossible for risk assessment to be conducted on an individual NF basis. Alternative methods, such as grouping are needed for streamlining hazard assessment. The GRACIOUS Framework provides a logical and science evidenced approach to group similar NFs, allowing read-across of hazard information from source NFs (or non-NFs) with adequate hazard data to target NFs that lack such data. Here, we propose a simple three-tiered testing strategy to gather evidence to determine whether different NFs are sufficiently similar with respect to their potential to induce genotoxicity, in order to be grouped. The tiered testing strategy includes simple in vitro models as well as a number of alternative more complex multi-cellular in vitro models to allow for a better understanding of secondary NM-induced DNA damage, something that has been more appropriate in vivo until recently.

The Road to Achieving the European Commission's Chemicals Strategy for Nanomaterial Sustainability-A PATROLS Perspective on New Approach Methodologies

The European Green Deal outlines ambitions to build a more sustainable, climate neutral, and circular economy by 2050. To achieve this, the European Commission has published the Chemicals Strategy for Sustainability: Towards a Toxic-Free Environment, which provides targets for innovation to better protect human and environmental health, including challenges posed by hazardous chemicals and animal testing. The European project PATROLS (Physiologically Anchored Tools for Realistic nanOmateriaL hazard aSsessment) has addressed multiple aspects of the Chemicals Strategy for Sustainability by establishing a battery of new approach methodologies, including physiologically anchored human and environmental hazard assessment tools to evaluate the safety of engineered nanomaterials. PATROLS has delivered and improved innovative tools to support regulatory decision-making processes. These tools also support the need for reducing regulated vertebrate animal testing; when used at an early stage of the innovation pipeline, the PATROLS tools facilitate the safe and sustainable development of new nano-enabled products before they reach the market.

Understanding Nanomaterial-Liver Interactions to Facilitate the Development of Safer Nanoapplications

Nanomaterials (NMs) are widely used in commercial and medical products, such as cosmetics, vaccines, and drug carriers. Exposure to NMs via various routes such as dermal, inhalation, and ingestion has been shown to gain access to the systemic circulation, resulting in the accumulation of NMs in the liver. The unique organ structures and blood flow features facilitate the liver sequestration of NMs, which may cause adverse effects in the liver. Currently, most in vivo studies are focused on NMs accumulation at the organ level and evaluation of the gross changes in liver structure and functions, however, cell-type-specific uptake and responses, as well as the molecular mechanisms at cellular levels leading to effects at organ levels are lagging. Herein, the authors systematically review diverse interactions of NMs with the liver, specifically on major liver cell types including Kupffer cells (KCs), liver sinusoidal endothelial cells (LSECs), hepatic stellate cells (HSCs), and hepatocytes as well as the detailed molecular mechanisms involved. In addition, the knowledge gained on nano-liver interactions that can facilitate the development of safer nanoproducts and nanomedicine is also reviewed.

Acute hazard assessment of silver nanoparticles following intratracheal instillation, oral and intravenous injection exposures

With ever-increasing production and use of nanoparticles (NPs), there is a necessity to evaluate the probability of consequential adverse effects in individuals exposed to these particles. It is now understood that a proportion of NPs can translocate from primary sites of exposure to a range of secondary organs, with the liver, kidneys and spleen being some of the most important. In this study, we carried out a comprehensive toxicological profiling (inflammation, changes in serum biochemistry, oxidative stress, acute phase response and histopathology) of Ag NP induced adverse effects in the three organs of interest following acute exposure of the materials at identical doses via intravenous (IV), intratracheal (IT) instillation and oral administration. The data clearly demonstrated that bioaccumulation and toxicity of the particles were most significant following the IV route of exposure, followed by IT. However, oral exposure to the NPs did not result in any changes that could be interpreted as toxicity in any of the organs of interest within the confines of this investigation. The finding of this study clearly indicates the importance of the route of exposure in secondary organ hazard assessment for NPs. Finally, we identify Connexin 32 (Cx32) as a novel biomarker of NP-mediated hepatic damage which is quantifiable both (in vitro) and in vivo following exposure of physiologically relevant doses.

Particulate and drug-induced toxicity assessed in novel quadruple cell human primary hepatic disease models of steatosis and pre-fibrotic NASH

In an effort to replace, reduce and refine animal experimentation, there is an unmet need to advance current in vitro models that offer features with physiological relevance and enhanced predictivity of in vivo toxicological output. Hepatic toxicology is key following chemical, drug and nanomaterials (NMs) exposure, as the liver is vital in metabolic detoxification of chemicals as well as being a major site of xenobiotic accumulation (i.e., low solubility particulates). With the ever-increasing production of NMs, there is a necessity to evaluate the probability of consequential adverse effects, not only in health but also in clinically asymptomatic liver, as part of risk stratification strategies. In this study, two unique disease initiation and maintenance protocols were developed and utilised to mimic steatosis and pre-fibrotic NASH in scaffold-free 3D liver microtissues (MT) composed of primary human hepatocytes, hepatic stellate cells, Kupffer cells and sinusoidal endothelial cells. The characterized diseased MT were utilized for the toxicological assessment of a panel of xenobiotics. Highlights from the study included: 1. Clear experimental evidence for the pre-existing liver disease is important in the augmentation of xenobiotic-induced hepatotoxicity and 2. NMs are able to activate stellate cells. The data demonstrated that pre-existing disease is vital in the intensification of xenobiotic-induced liver damage. Therefore, it is imperative that all stages of the wide spectrum of liver disease are incorporated in risk assessment strategies. This is of significant consequence, as a substantial number of the general population suffer from sub-clinical liver injury without any apparent or diagnosed manifestations.

Organoid Technology: A Reliable Developmental Biology Tool for Organ-Specific Nanotoxicity Evaluation

Engineered nanomaterials are bestowed with certain inherent physicochemical properties unlike their parent materials, rendering them suitable for the multifaceted needs of state-of-the-art biomedical, and pharmaceutical applications. The log-phase development of nano-science along with improved "bench to beside" conversion carries an enhanced probability of human exposure with numerous nanoparticles. Thus, toxicity assessment of these novel nanoscale materials holds a key to ensuring the safety aspects or else the global biome will certainly face a debacle. The toxicity may span from health hazards due to direct exposure to indirect means through food chain contamination or environmental pollution, even causing genotoxicity. Multiple ways of nanotoxicity evaluation include several in vitro and in vivo methods, with in vitro methods occupying the bulk of the "experimental space." The underlying reason may be multiple, but ethical constraints in in vivo animal experiments are a significant one. Two-dimensional (2D) monoculture is undoubtedly the most exploited in vitro method providing advantages in terms of cost-effectiveness, high throughput, and reproducibility. However, it often fails to mimic a tissue or organ which possesses a defined three-dimensional structure (3D) along with intercellular communication machinery. Instead, microtissues such as spheroids or organoids having a precise 3D architecture and proximate in vivo tissue-like behavior can provide a more realistic evaluation than 2D monocultures. Recent developments in microfluidics and bioreactor-based organoid synthesis have eased the difficulties to prosper nano-toxicological analysis in organoid models surpassing the obstacle of ethical issues. The present review will enlighten applications of organoids in nanotoxicological evaluation, their advantages, and prospects toward securing commonplace nano-interventions.

Human Embryos, Induced Pluripotent Stem Cells, and Organoids: Models to Assess the Effects of Environmental Plastic Pollution

For a long time, animal models were used to mimic human biology and diseases. However, animal models are not an ideal solution due to numerous interspecies differences between humans and animals. New technologies, such as human-induced pluripotent stem cells and three-dimensional (3D) cultures such as organoids, represent promising solutions for replacing, refining, and reducing animal models. The capacity of organoids to differentiate, self-organize, and form specific, complex, biologically suitable structures makes them excellent in vitro models of development and disease pathogenesis, as well as drug-screening platforms. Despite significant potential health advantages, further studies and considerable nuances are necessary before their clinical use. This article summarizes the definition of embryoids, gastruloids, and organoids and clarifies their appliance as models for early development, diseases, environmental pollution, drug screening, and bioinformatics.

Understanding the impact of more realistic low-dose, prolonged engineered nanomaterial exposure on genotoxicity using 3D models of the human liver

BACKGROUND

With the continued integration of engineered nanomaterials (ENMs) into everyday applications, it is important to understand their potential for inducing adverse human health effects. However, standard in vitro hazard characterisation approaches suffer limitations for evaluating ENM and so it is imperative to determine these potential hazards under more physiologically relevant and realistic exposure scenarios in target organ systems, to minimise the necessity for in vivo testing. The aim of this study was to determine if acute (24 h) and prolonged (120 h) exposures to five ENMs (TiO2, ZnO, Ag, BaSO4 and CeO2) would have a significantly different toxicological outcome (cytotoxicity, (pro-)inflammatory and genotoxic response) upon 3D human HepG2 liver spheroids. In addition, this study evaluated whether a more realistic, prolonged fractionated and repeated ENM dosing regime induces a significantly different toxicity outcome in liver spheroids as compared to a single, bolus prolonged exposure.

RESULTS

Whilst it was found that the five ENMs did not impede liver functionality (e.g. albumin and urea production), induce cytotoxicity or an IL-8 (pro-)inflammatory response, all were found to cause significant genotoxicity following acute exposure. Most statistically significant genotoxic responses were not dose-dependent, with the exception of TiO2. Interestingly, the DNA damage effects observed following acute exposures, were not mirrored in the prolonged exposures, where only 0.2-5.0 µg/mL of ZnO ENMs were found to elicit significant (p ≤ 0.05) genotoxicity. When fractionated, repeated exposure regimes were performed with the test ENMs, no significant (p ≥ 0.05) difference was observed when compared to the single, bolus exposure regime. There was < 5.0% cytotoxicity observed across all exposures, and the mean difference in IL-8 cytokine release and genotoxicity between exposure regimes was 3.425 pg/mL and 0.181%, respectively.

CONCLUSION

In conclusion, whilst there was no difference between a single, bolus or fractionated, repeated ENM prolonged exposure regimes upon the toxicological output of 3D HepG2 liver spheroids, there was a difference between acute and prolonged exposures. This study highlights the importance of evaluating more realistic ENM exposures, thereby providing a future in vitro approach to better support ENM hazard assessment in a routine and easily accessible manner.

In Vitro Three-Dimensional Liver Models for Nanomaterial DNA Damage Assessment

Whilst the liver possesses the ability to repair and restore sections of damaged tissue following acute injury, prolonged exposure to engineered nanomaterials (ENM) may induce repetitive injury leading to chronic liver disease. Screening ENM cytotoxicity using 3D liver models has recently been performed, but a significant challenge has been the application of such in vitro models for evaluating ENM associated genotoxicity; a vital component of regulatory human health risk assessment. This review considers the benefits, limitations, and adaptations of specific in vitro approaches to assess DNA damage in the liver, whilst identifying critical advancements required to support a multitude of biochemical endpoints, focusing on nano(geno)toxicology (e.g., secondary genotoxicity, DNA damage, and repair following prolonged or repeated exposures).

iPSC-derived hepatocytes generated from NASH donors provide a valuable platform for disease modeling and drug discovery

Non-alcoholic fatty liver disease (NAFLD) affects 30-40% of adults and 10% of children in the US. About 20% of people with NAFLD develop non-alcoholic steatohepatitis (NASH), which may lead to cirrhosis and liver cancer, and is projected to be a leading cause of liver transplantation in the near future. Human induced pluripotent stem cells (iPSC) from NASH patients are useful for generating a large number of hepatocytes for NASH modeling applications and identification of potential drug targets. We developed a novel defined in vitro differentiation process to generate cryopreservable hepatocytes using an iPSC panel of NASH donors and apparently healthy normal (AHN) controls. iPSC-derived hepatocytes displayed stage specific phenotypic markers, hepatocyte morphology, with bile canaliculi. Importantly, both fresh and cryopreserved definitive endoderm and hepatoblasts successfully differentiated to pure and functional hepatocytes with increased CYP3A4 activity in response to rifampicin and lipid accumulation upon fatty acid (FA) treatment. End-stage hepatocytes integrated into three-dimensional (3D) liver organoids and demonstrated increased levels of albumin secretion compared to aggregates consisting of hepatocytes alone. End-stage hepatocytes derived from NASH donors demonstrated spontaneous lipidosis without FA supplementation, recapitulating a feature of NASH hepatocytes in vivo Cryopreserved hepatocytes generated by this protocol across multiple donors will provide a critical cell source to facilitate the fundamental understanding of NAFLD/NASH biology and potential high throughput screening applications for preclinical evaluation of therapeutic targets.

Hepatotoxicity induced by nanomaterials: mechanisms and in vitro models

The unique physicochemical properties of materials at nanoscale have opened a plethora of opportunities for applications in the pharmaceutical and medical field, but also in consumer products from food and cosmetics industries. As a consequence, daily human exposure to nanomaterials through distinct routes is considerable and, therefore, may raise health concerns. Many nanomaterials have been described to accumulate and induce adversity in the liver. Among these, silica and some types of metallic nanoparticles are the most broadly used in consumer products and, therefore, the most studied and reported. The reviewed literature was collected from PubMed.gov during the month of March 2020 using the search words "nanomaterials induced hepatotoxicity", which yielded 181 papers. This present paper reviews the hepatotoxic effects of nanomaterials described in in vitro and in vivo studies, with emphasis on the underlying mechanisms. The induction of oxidative stress and inflammation are the manifestations of toxicity most frequently reported following exposure of cells or animal models to different nanomaterials. Furthermore, the available in vitro models for the evaluation of the hepatotoxic effects of nanomaterials are discussed, highlighting the continuous interest in the development of more advanced and reliable in vitro models for nanotoxicology.

A review of hepatic nanotoxicology - summation of recent findings and considerations for the next generation of study designs

The liver is one of the most important multi-functional organs in the human body. Amongst various crucial functions, it is the main detoxification center and predominantly implicated in the clearance of xenobiotics potentially including particulates that reach this organ. It is now well established that a significant quantity of injected, ingested or inhaled nanomaterials (NMs) translocate from primary exposure sites and accumulate in liver. This review aimed to summarize and discuss the progress made in the field of hepatic nanotoxicology, and crucially highlight knowledge gaps that still exist.Key considerations include In vivo studies clearly demonstrate that low-solubility NMs predominantly accumulate in the liver macrophages the Kupffer cells (KC), rather than hepatocytes.KCs lining the liver sinusoids are the first cell type that comes in contact with NMs in vivo. Further, these macrophages govern overall inflammatory responses in a healthy liver. Therefore, interaction with of NM with KCs in vitro appears to be very important.Many acute in vivo studies demonstrated signs of toxicity induced by a variety of NMs. However, acute studies may not be that meaningful due to liver's unique and unparalleled ability to regenerate. In almost all investigations where a recovery period was included, the healthy liver was able to recover from NM challenge. This organ's ability to regenerate cannot be reproduced in vitro. However, recommendations and evidence is offered for the design of more physiologically relevant in vitro models.Models of hepatic disease enhance the NM-induced hepatotoxicity.The review offers a number of important suggestions for the future of hepatic nanotoxicology study design. This is of great significance as its findings are highly relevant due to the development of more advanced in vitro, and in silico models aiming to improve physiologically relevant toxicological testing strategies and bridging the gap between in vitro and in vivo experimentation.

Nanomaterials and Their Negative Effects on Human Health

Mesostructured silica, dendrimers, and allotropes of carbon were exhaustively used in biomedical, cosmetics, semiconductors, and food industry applications. Considering the huge prospect of nanomaterials, their potential hazards on exposure to humans and their related ecotoxicological effects needs to be summarized. Nanoparticles with size below 100 nm could pass into the lung and then to blood through inhalation, ingestion, and skin contact. As nanotechnology innovation is expected to achieve $ 2231 million by 2025, humans will be exposed ever increasingly in day-to-day life and in industries. In this review, the latest synthetic methodology of silica, dendrimers, and CNTs, their biological applications (in vitro and in vivo) related to toxicity were discussed. In terms of structured silica, the toxic and non-toxic effect induced by specific templates (cetylpyridinium bromide, cetyltrimethylammonium bromide, dipalmitoylphosphatidylcholine, C16L-tryptophan, C16-L-histidine, and C16-L-poline) that are used to generate mesoporous silica, silica nanoparticle sizes (25, 50, 60, 115, and 500 nm), and silane functionalization (NH₂ and COOH) were discussed. The recent applications of different generations (G3, G4, G5, and G6) of amphiphilic Janus dendrimers were discussed along with toxicity effect of different charged dendrimers (cationic and anionic) and effect of PEGylation. Recent synthesis, advantages, and disadvantages of carbon nanotubes (CNTs) were presented for structures like single walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs). The influence of diameter of SWCNTs (linear and short), thickness (thin and thick), effect of oxidation, metal oxide species (TiO₂, Fe, and Au), and biocompatible polymers (polyethylene glycol, bisphosphonate, and alendronate) were shown in relation to molecular pathways in animal cells.