Suitability of different reconstructed human skin models in the skin and liver Chip2 microphysiological model to investigate the kinetics and first-pass skin metabolism of the hair dye, 4-amino-2-hydroxytoluene

The HUMIMIC skin-liver Chip2 microphysiological systems model using the epidermal model, EpiDerm™, was reported previously to mimic application route-dependent metabolism of the hair dye, 4-amino-2-hydroxytoluene (AHT). Therefore, we evaluated the use of alternative skin models-SkinEthic™, EpiDermFT™ and PhenionFT™-for the same purpose. In static incubations, AHT permeation was similar using SkinEthic™ and EpiDerm™ models. Older Day 21 (D21) SkinEthic™ models with a thicker stratum corneum did not exhibit a greater barrier to AHT (overall permeation was the same in D17 and D21 models). All epidermal models metabolised AHT, with the EpiDerm™ exhibiting higher N-acetylation than SkinEthic™ models. AHT metabolism by D21 SkinEthic™ models was lower than that by D17 SkinEthic™ and EpiDerm™ models, thus a thicker stratum corneum was associated with fewer viable cells and a lower metabolic activity. AHT permeation was much slower using PhenionFT™ compared to epidermal models and better reflected permeation of AHT through native human skin. This model also extensively metabolised AHT to N-acetyl-AHT. After a single topical or systemic application of AHT to Chip2 model with PhenionFT™, medium was analysed for parent and metabolites over 5 days. The first-pass metabolism of AHT was demonstrated, and the introduction of a wash step after 30 min decreased the exposure to AHT and its metabolites by 33% and 40%-43%, respectively. In conclusion, epidermal and FT skin models used in the Chip2 can mimic the first-pass skin metabolism of AHT. This highlights the flexibility of the Chip2 to incorporate different skin models according to the purpose.

Application of a skin and liver Chip2 microphysiological model to investigate the route-dependent toxicokinetics and toxicodynamics of consumer-relevant doses of genistein

The HUMMIC skin-liver Chip2 microphysiological system using EpiDerm™ and HepaRG and stellate liver spheroids was used to evaluate the route-specific metabolism and toxicodynamic effects of genistein. Human-relevant exposure levels were compared: 60 nM representing the plasma concentration expected after topical application of a cosmetic product and 1 μM representing measured plasma concentrations after ingesting soya products. Genistein was applied as single and repeated topical and/or systemic doses. The kinetics of genistein and its metabolites were measured over 5 days. Toxicodynamic effects were measured using transcriptional analyses of skin and liver organoids harvested on Days 2 and 5. Route-specific differences in genistein's bioavailability were observed, with first-pass metabolism (sulfation) occurring in the skin after topical application. Only repeated application of 1 μM, resembling daily oral intake of soya products, induced statistically significant changes in gene expression in liver organoids only. This was concomitant with a much higher systemic concentration of genistein which was not reached in any other dosing scenario. This suggests that single or low doses of genistein are rapidly metabolised which limits its toxicodynamic effects on the liver and skin. Therefore, by facilitating longer and/or repeated applications, the Chip2 can support safety assessments by linking relevant gene modulation with systemically available parent or metabolite(s). The rate of metabolism was in accordance with the short half-life observed in in vivo in humans, thus supporting the relevance of the findings. In conclusion, the skin-liver Chip2 provides route-specific information on metabolic fate and toxicodynamics that may be relevant to safety assessment.

Development of a microphysiological skin-liver-thyroid Chip3 model and its application to evaluate the effects on thyroid hormones of topically applied cosmetic ingredients under consumer-relevant conditions

All cosmetic ingredients registered in Europe must be evaluated for their safety using non-animal methods. Microphysiological systems (MPS) offer a more complex higher tier model to evaluate chemicals. Having established a skin and liver HUMIMIC Chip2 model demonstrating how dosing scenarios impact the kinetics of chemicals, we investigated whether thyroid follicles could be incorporated to evaluate the potential of topically applied chemicals to cause endocrine disruption. This combination of models in the HUMIMIC Chip3 is new; therefore, we describe here how it was optimized using two chemicals known to inhibit thyroid production, daidzein and genistein. The MPS was comprised of Phenion^® Full Thickness skin, liver spheroids and thyroid follicles co-cultured in the TissUse HUMIMIC Chip3. Endocrine disruption effects were determined according to changes in thyroid hormones, thyroxine (T₄) and 3,3',5-triiodothyronine (T₃). A main part of the Chip3 model optimization was the replacement of freshly isolated thyroid follicles with thyrocyte-derived follicles. These were used in static incubations to demonstrate the inhibition of T₄ and T₃ production by genistein and daidzein over 4 days. Daidzein exhibited a lower inhibitory activity than genistein and both inhibitory activities were decreased after a 24 h preincubation with liver spheroids, indicating metabolism was via detoxification pathways. The skin-liver-thyroid Chip3 model was used to determine a consumer-relevant exposure to daidzein present in a body lotion based on thyroid effects. A "safe dose" of 0.235 μg/cm² i.e., 0.047% applied in 0.5 mg/cm² of body lotion was the highest concentration of daidzein which does not result in changes in T₃ and T₄ levels. This concentration correlated well with the value considered safe by regulators. In conclusion, the Chip3 model enabled the incorporation of the relevant exposure route (dermal), metabolism in the skin and liver, and the bioactivity endpoint (assessment of hormonal balance i.e., thyroid effects) into a single model. These conditions are closer to those in vivo than 2D cell/tissue assays lacking metabolic function. Importantly, it also allowed the assessment of repeated doses of chemical and a direct comparison of systemic and tissue concentrations with toxicodynamic effects over time, which is more realistic and relevant for safety assessment.

A multi-organ-chip co-culture of liver and testis equivalents: a first step toward a systemic male reprotoxicity model

STUDY QUESTION

Is it possible to co-culture and functionally link human liver and testis equivalents in the combined medium circuit of a multi-organ chip?

SUMMARY ANSWER

Multi-organ-chip co-cultures of human liver and testis equivalents were maintained at a steady-state for at least 1 week and the co-cultures reproduced specific natural and drug-induced liver-testis systemic interactions.

WHAT IS KNOWN ALREADY

Current benchtop reprotoxicity models typically do not include hepatic metabolism and interactions of the liver-testis axis. However, these are important to study the biotransformation of substances.

STUDY DESIGN, SIZE, DURATION

Testicular organoids derived from primary adult testicular cells and liver spheroids consisting of cultured HepaRG cells and hepatic stellate cells were loaded into separate culture compartments of each multi-organ-chip circuit for co-culture in liver spheroid-specific medium, testicular organoid-specific medium or a combined medium over a week. Additional multi-organ-chips (single) and well plates (static) were loaded only with testicular organoids or liver spheroids for comparison. Subsequently, the selected type of medium was supplemented with cyclophosphamide, an alkylating anti-neoplastic prodrug that has demonstrated germ cell toxicity after its bioactivation in the liver, and added to chip-based co-cultures to replicate a human liver-testis systemic interaction in vitro. Single chip-based testicular organoids were used as a control. Experiments were performed with three biological replicates unless otherwise stated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The metabolic activity was determined as glucose consumption and lactate production. The cell viability was measured as lactate dehydrogenase activity in the medium. Additionally, immunohistochemical and real-time quantitative PCR end-point analyses were performed for apoptosis, proliferation and cell-specific phenotypical and functional markers. The functionality of Sertoli and Leydig cells in testicular spheroids was specifically evaluated by measuring daily inhibin B and testosterone release, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

Co-culture in multi-organ chips with liver spheroid-specific medium better supported the metabolic activity of the cultured tissues compared to other media tested. The liver spheroids did not show significantly different behaviour during co-culture compared to that in single culture on multi-organ-chips. The testicular organoids also developed accordingly and produced higher inhibin B but lower testosterone levels than the static culture in plates with testicular organoid-specific medium. By comparison, testosterone secretion by testicular organoids cultured individually on multi-organ-chips reached a similar level as the static culture at Day 7. This suggests that the liver spheroids have metabolised the steroids in the co-cultures, a naturally occurring phenomenon. The addition of cyclophosphamide led to upregulation of specific cytochromes in liver spheroids and loss of germ cells in testicular organoids in the multi-organ-chip co-cultures but not in single-testis culture.

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The number of biological replicates included in this study was relatively small due to the limited availability of individual donor testes and the labour-intensive nature of multi-organ-chip co-cultures. Moreover, testicular organoids and liver spheroids are miniaturised organ equivalents that capture key features, but are still simplified versions of the native tissues. Also, it should be noted that only the prodrug cyclophosphamide was administered. The final concentration of the active metabolite was not measured.

WIDER IMPLICATIONS OF THE FINDINGS

This co-culture model responds to the request of setting up a specific tool that enables the testing of candidate reprotoxic substances with the possibility of human biotransformation. It further allows the inclusion of other human tissue equivalents for chemical risk assessment on the systemic level.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by research grants from the Scientific Research Foundation Flanders (FWO), Universitair Ziekenhuis Brussel (scientific fund Willy Gepts) and the Vrije Universiteit Brussel. Y.B. is a postdoctoral fellow of the FWO. U.M. is founder, shareholder and CEO of TissUse GmbH, Berlin, Germany, a company commercializing the Multi-Organ-Chip platform systems used in the study. The other authors have no conflict of interest to declare.

Demonstration of the first-pass metabolism in the skin of the hair dye, 4-amino-2-hydroxytoluene, using the Chip2 skin-liver microphysiological model

We used TissUse's HUMIMIC Chip2 microfluidic model, incorporating reconstructed skin models and liver spheroids, to investigate the impact of consumer-relevant application scenarios on the metabolic fate of the hair dye, 4-amino-2-hydroxytoluene (AHT). After a single topical or systemic application of AHT to Chip2 models, medium was analysed for parent and metabolites over 5 days. The metabolic profile of a high dose (resulting in a circuit concentration of 100 μM based on 100% bioavailability) of AHT was the same after systemic and topical application to 96-well EpiDerm™ models. Additional experiments indicated that metabolic capacity of EpiDerm™ models were saturated at this dose. At 2.5 μM, concentrations of AHT and several of its metabolites differed between application routes. Topical application resulted in a higher C_max and a 327% higher area under the curve (AUC) of N-acetyl-AHT, indicating a first-pass effect in the EpiDerm™ models. In accordance with in vivo observations, there was a concomitant decrease in the C_max and AUC of AHT-O-sulphate after topical, compared with systemic application. A similar alteration in metabolite ratios was observed using a 24-well full-thickness skin model, EpiDermFT™, indicating that a first-pass effect was also possible to detect in a more complex model. In addition, washing the EpiDermFT™ after 30 min, thus reflecting consumer use, decreased the systemic exposure to AHT and its metabolites. In conclusion, the skin-liver Chip2 model can be used to (a) recapitulate the first-pass effect of the skin and alterations in the metabolite profile of AHT observed in vivo and (b) provide consumer-relevant data regarding leave-on/rinse-off products.

Characterization of application scenario-dependent pharmacokinetics and pharmacodynamic properties of permethrin and hyperforin in a dynamic skin and liver multi-organ-chip model

Microphysiological systems (MPS) aim to mimic the dynamic microenvironment and the interaction between tissues. While MPS exist for investigating pharmaceuticals, the applicability of MPS for cosmetics ingredients is yet to be evaluated. The HUMIMIC Chip2 ("Chip2″), is the first multi-organ chip technology to incorporate skin models, allowing for the topical route to be tested. Therefore, we have used this model to analyze the impact of different exposure scenarios on the pharmacokinetics and pharmacodynamics of two topically exposed chemicals, hyperforin and permethrin. The Chip2 incorporated reconstructed human epidermis models (EpiDerm™) and HepaRG-stellate spheroids. Initial experiments using static incubations of single organoids helped determine the optimal dose. In the Chip2 studies, parent and metabolites were analyzed in the circuit over 5 days after application of single and repeated topical or systemic doses. The gene expression of relevant xenobiotic metabolizing enzymes in liver spheroids was measured to reflect toxicodynamics effects of the compounds in liver. The results show that 1) metabolic capacities of EpiDerm™ and liver spheroids were maintained over five days; 2) EpiDerm™ model barrier function remained intact; 3) repeated application of compounds resulted in higher concentrations of parent chemicals and most metabolites compared to single application; 4) compound-specific gene induction e.g. induction of CYP3A4 by hyperforin depended on the application route and frequency; 5) different routes of application influenced the systemic concentrations of both parents and metabolites in the chip over the course of the experiment; 6) there was excellent intra- and inter-lab reproducibility. For permethrin, a process similar to the excretion in a human in vivo study could be simulated which was remarkably comparable to the in vivo situation. These results support the use of the Chip2 model to provide information on parent and metabolite disposition that may be relevant to risk assessment of topically applied cosmetics ingredients.

Organ-on-a-Chip

Limitations of the current tools used in the drug development process, cell cultures, and animal models have highlighted the need for a new powerful tool that can emulate the human physiology in vitro. Advances in the field of microfluidics have made the realization of this tool closer than ever. Organ-on-a-chip platforms have been the first step forward, leading to the combination and integration of multiple organ models in the same platform with human-on-a-chip being the ultimate goal. Despite the current progress and technological developments, there are still several unmet engineering and biological challenges curtailing their development and widespread application in the biomedical field. The potentials, challenges, and current work on this unprecedented tool are being discussed in this chapter.

Abstract LB-027: Evaluation of EGFR induced on-target and target-mediated adverse effects in a 3D human lung tumour/skin microphysiological co-culture system

Organs-on-a-chip or microphysiological systems (MPS) are increasingly contributing to the preclinical characterization of mode of action and adverse events of drug candidates. The recent advent of robust human multi-organ-chip systems enables the establishment of co-cultures of human drug target tissues with healthy organ equivalents prone to off-target effects of the respective drug. The prediction of side effects, such as those occurring in the skin during cancer therapies with antibodies against the epithelial growth factor receptor (EGFR), is currently not possible in conventional in vitro systems and limited in existing animal models due to phylogenetic differences between species.

Here we present a chip-based 5-day co-culture of human lung tumour spheroids (mucoepidermoid carcinoma H292) and human skin equivalents. We investigated the impact of repeated cetuximab exposure, an antibody against the EGF receptor to the co-culture and compared it with the effects on individual tissue cultures. Cetuximab showed an increased pro-apoptotic related gene expression in the tumor microtissues, and, simultaneously, proliferative keratinocytes in the basal layer of the skin microtissues were eliminated. Additionally, we compared the tumor-target related antibody effects with response data for afatinib - a small molecule EGFR inhibitor. Cetuximab showed an increased pro-apoptotic related gene expression in the tumor microtissues, and, simultaneously, proliferative keratinocytes in the basal layer of the skin microtissues were eliminated.

The described MPS has the potential to provide a single platform for in vitro evaluation of the therapeutic window of drug candidates.

Citation Format: Juliane Huebner, Marian Raschke, Katharina Schimek, Isabel Ruetschle, Sarah Graessle, Susanne Schnurre, Roland Lauster, Ilka Maschmeyer, Thomas Steger-Hartmann, Uwe Marx. Evaluation of EGFR induced on-target and target-mediated adverse effects in a 3D human lung tumour/skin microphysiological co-culture system [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-027.

Simultaneous evaluation of anti-EGFR-induced tumour and adverse skin effects in a microfluidic human 3D co-culture model

Antibody therapies targeting the epithelial growth factor receptor (EGFR) are being increasingly applied in cancer therapy. However, increased tumour containment correlates proportionally with the severity of well-known adverse events in skin. The prediction of the latter is not currently possible in conventional in vitro systems and limited in existing laboratory animal models. Here we established a repeated dose “safficacy” test assay for the simultaneous generation of safety and efficacy data. Therefore, a commercially available multi-organ chip platform connecting two organ culture compartments was adapted for the microfluidic co-culture of human H292 lung cancer microtissues and human full-thickness skin equivalents. Repeated dose treatment of the anti-EGFR-antibody cetuximab showed an increased pro-apoptotic related gene expression in the tumour microtissues. Simultaneously, proliferative keratinocytes in the basal layer of the skin microtissues were eliminated, demonstrating crucial inhibitory effects on the physiological skin cell turnover. Furthermore, antibody exposure modulated the release of CXCL8 and CXCL10, reflecting the pattern changes seen in antibody-treated patients. The combination of a metastatic tumour environment with a miniaturized healthy organotypic human skin equivalent make this “safficacy” assay an ideal tool for evaluation of the therapeutic index of EGFR inhibitors and other promising oncology candidates.

Biology-inspired microphysiological system approaches to solve the prediction dilemma of substance testing

The recent advent of microphysiological systems - microfluidic biomimetic devices that aspire to emulate the biology of human tissues, organs and circulation in vitro - is envisaged to enable a global paradigm shift in drug development. An extraordinary US governmental initiative and various dedicated research programs in Europe and Asia have led recently to the first cutting-edge achievements of human single-organ and multi-organ engineering based on microphysiological systems. The expectation is that test systems established on this basis would model various disease stages, and predict toxicity, immunogenicity, ADME profiles and treatment efficacy prior to clinical testing. Consequently, this technology could significantly affect the way drug substances are developed in the future. Furthermore, microphysiological system-based assays may revolutionize our current global programs of prioritization of hazard characterization for any new substances to be used, for example, in agriculture, food, ecosystems or cosmetics, thus, replacing laboratory animal models used currently. Thirty-six experts from academia, industry and regulatory bodies present here the results of an intensive workshop (held in June 2015, Berlin, Germany). They review the status quo of microphysiological systems available today against industry needs, and assess the broad variety of approaches with fit-for-purpose potential in the drug development cycle. Feasible technical solutions to reach the next levels of human biology in vitro are proposed. Furthermore, key organ-on-a-chip case studies, as well as various national and international programs are highlighted. Finally, a roadmap into the future is outlined, to allow for more predictive and regulatory-accepted substance testing on a global scale.

A four-organ-chip for interconnected long-term co-culture of human intestine, liver, skin and kidney equivalents

Systemic absorption and metabolism of drugs in the small intestine, metabolism by the liver as well as excretion by the kidney are key determinants of efficacy and safety for therapeutic candidates. However, these systemic responses of applied substances lack in most in vitro assays. In this study, a microphysiological system maintaining the functionality of four organs over 28 days in co-culture has been established at a minute but standardized microsystem scale. Preformed human intestine and skin models have been integrated into the four-organ-chip on standard cell culture inserts at a size 100,000-fold smaller than their human counterpart organs. A 3D-based spheroid, equivalent to ten liver lobules, mimics liver function. Finally, a barrier segregating the media flow through the organs from fluids excreted by the kidney has been generated by a polymeric membrane covered by a monolayer of human proximal tubule epithelial cells. A peristaltic on-chip micropump ensures pulsatile media flow interconnecting the four tissue culture compartments through microfluidic channels. A second microfluidic circuit ensures drainage of the fluid excreted through the kidney epithelial cell layer. This four-organ-chip system assures near to physiological fluid-to-tissue ratios. In-depth metabolic and gene analysis revealed the establishment of reproducible homeostasis among the co-cultures within two to four days, sustainable over at least 28 days independent of the individual human cell line or tissue donor background used for each organ equivalent. Lastly, 3D imaging two-photon microscopy visualised details of spatiotemporal segregation of the two microfluidic flows by proximal tubule epithelia. To our knowledge, this study is the first approach to establish a system for in vitro microfluidic ADME profiling and repeated dose systemic toxicity testing of drug candidates over 28 days.

The multi-organ chip--a microfluidic platform for long-term multi-tissue coculture

The ever growing amount of new substances released onto the market and the limited predictability of current in vitro test systems has led to a high need for new solutions for substance testing. Many drugs that have been removed from the market due to drug-induced liver injury released their toxic potential only after several doses of chronic testing in humans. However, a controlled microenvironment is pivotal for long-term multiple dosing experiments, as even minor alterations in extracellular conditions may greatly influence the cell physiology. We focused within our research program on the generation of a microengineered bioreactor, which can be dynamically perfused by an on-chip pump and combines at least two culture spaces for multi-organ applications. This circulatory system mimics the in vivo conditions of primary cell cultures better and assures a steadier, more quantifiable extracellular relay of signals to the cells.

For demonstration purposes, human liver equivalents, generated by aggregating differentiated HepaRG cells with human hepatic stellate cells in hanging drop plates, were cocultured with human skin punch biopsies for up to 28 days inside the microbioreactor. The use of cell culture inserts enables the skin to be cultured at an air-liquid interface, allowing topical substance exposure. The microbioreactor system is capable of supporting these cocultures at near physiologic fluid flow and volume-to-liquid ratios, ensuring stable and organotypic culture conditions. The possibility of long-term cultures enables the repeated exposure to substances. Furthermore, a vascularization of the microfluidic channel circuit using human dermal microvascular endothelial cells yields a physiologically more relevant vascular model.

Chip-based human liver-intestine and liver-skin co-cultures--A first step toward systemic repeated dose substance testing in vitro

Systemic repeated dose safety assessment and systemic efficacy evaluation of substances are currently carried out on laboratory animals and in humans due to the lack of predictive alternatives. Relevant international regulations, such as OECD and ICH guidelines, demand long-term testing and oral, dermal, inhalation, and systemic exposure routes for such evaluations. So-called "human-on-a-chip" concepts are aiming to replace respective animals and humans in substance evaluation with miniaturized functional human organisms. The major technical hurdle toward success in this field is the life-like combination of human barrier organ models, such as intestine, lung or skin, with parenchymal organ equivalents, such as liver, at the smallest biologically acceptable scale. Here, we report on a reproducible homeostatic long-term co-culture of human liver equivalents with either a reconstructed human intestinal barrier model or a human skin biopsy applying a microphysiological system. We used a multi-organ chip (MOC) platform, which provides pulsatile fluid flow within physiological ranges at low media-to-tissue ratios. The MOC supports submerse cultivation of an intact intestinal barrier model and an air-liquid interface for the skin model during their co-culture with the liver equivalents respectively at (1)/100.000 the scale of their human counterparts in vivo. To increase the degree of organismal emulation, microfluidic channels of the liver-skin co-culture could be successfully covered with human endothelial cells, thus mimicking human vasculature, for the first time. Finally, exposure routes emulating oral and systemic administration in humans have been qualified by applying a repeated dose administration of a model substance - troglitazone - to the chip-based co-cultures.