Effect of Spheroidal Age on Sorafenib Diffusivity and Toxicity in a 3D HepG2 Spheroid Model

Time-course characterization of whole-transcriptome dynamics of HepG2/C3A spheroids and its toxicological implications

Physiologically relevant in vitro models are a priority in predictive toxicology to replace and/or reduce animal experiments. The compromised toxicant metabolism of many immortalized human liver cell lines grown as monolayers as compared to in vivo metabolism limits their physiological relevance. However, recent efforts to culture liver cells in a 3D environment, such as spheroids, to better mimic the in vivo conditions, may enhance the toxicant metabolism of human liver cell lines. In this study, we characterized the dynamic changes in the transcriptome of HepG2/C3A hepatocarcinoma cell spheroids maintained in a clinostat system (CelVivo) to gain insight into the metabolic capacity of this model as a function of spheroid size and culture time. We assessed morphological changes (size, necrotic core), cell health, and proliferation rate from initial spheroid seeding to 35 days of continuous culture in conjunction with a time-course (0, 3, 7, 10, 14, 21, 28 days) of the transcriptome (TempO-Seq, BioSpyder). The phenotypic characteristics of HepG2/C3A growing in spheroids were comparable to monolayer growth until ∼Day 12 (Day 10-14) when a significant decrease in cell doubling rate was noted which was concurrent with down-regulation of cell proliferation and cell cycle pathways over this time period. Principal component analysis of the transcriptome data suggests that the Day 3, 7, and 10 spheroids are pronouncedly different from the Day 14, 21, and 28 spheroids in support of a biological transition time point during the long-term 3D spheroid cultures. The expression of genes encoding cellular components involved in toxicant metabolism and transport rapidly increased during the early time points of spheroids to peak at Day 7 or Day 10 as compared to monolayer cultures with a gradual decrease in expression with further culture, suggesting the most metabolically responsive time window for exposure studies. Overall, we provide baseline information on the cellular and molecular characterization, with a particular focus on toxicant metabolic capacity dynamics and cell growth, of HepG2/C3A 3D spheroid cultures over time.

Bioactive Microgels with Tunable Microenvironment as a 3D Platform to Guide the Complex Physiology of Hepatocellular Carcinoma Spheroids

Miniaturized three-dimensional tissue models, such as spheroids, have become a highly useful and efficient platform to investigate tumor physiology and explore the effect of chemotherapeutic efficacy over traditional two-dimensional monolayer culture, since they can provide more in-depth analysis, especially in regards to intercellular interactions and diffusion. The development of most tumor spheroids relies on the high proliferative capacity and self-aggregation behavior of tumor cells. However, it often disregards the effect of microenvironmental factors mediated by extracellular matrix, which are indispensable components of tissue structure. In this study, hepatocellular carcinoma (HCC) cells are encapsulated in bioactive microgels consisting of gelatin and hyaluronic acid designed to emulate tumor microenvironment in order to induce hepatic tumor spheroid formation. Two different subtypes of HCC's, HepG2 and Hep3B cell lines, are explored. The physicomechanical and biochemical properties of the microgels, controlled by changing the crosslinking density and polymer composition, are clearly shown to have substantial influence over the formation and spheroid formation. Moreover, the spheroids made from different cells and microgel properties display highly variable chemoresistance effects, further highlighting the importance of microenvironmental factors guiding tumor spheroid physiology.

Cytotoxicity of pharmaceuticals and their mixtures toward scaffold-free 3D spheroid cultures of rainbow trout (Oncorhynchus mykiss) hepatocytes

Pharmaceutical residues are widely detected in surface waters all around the world, causing a range of adverse effects on environmental species, such as fish. Besides population level effects (mortality, reproduction), pharmaceutical residues can bioaccumulate in fish tissues resulting in organ-specific toxicities. In this study, we developed in vitro 3D culture models for rainbow trout (Oncorhynchus mykiss) liver cell line (RTH-149) and cryopreserved, primary rainbow trout hepatocytes (RTHEP), and compared their spheroid formation and susceptibility to toxic impacts of pharmaceuticals. The rapidly proliferating, immortalized RTH-149 cells were shown to form compact spheroids with uniform morphology in just three days, thus enabling higher throughput toxicity screening compared with the primary cells that required acclimation times of about one week. In addition, we screened the cytotoxicity of a total of fourteen clinically used human pharmaceuticals toward the 3D cultures of both RTH-149 cells (metabolically inactive) and primary RTHEP cells (metabolically active), to evaluate the impacts of the pharmaceuticals' own metabolism on their hepatotoxicity in rainbow trout in vitro. Among the test substances, the azole antifungals (clotrimazole and ketoconazole) were identified as the most cytotoxic, with hepatic metabolism indicatively amplifying their toxicity, followed by fluoxetine, levomepromazine, and sertraline, which were slightly less toxic toward the metabolically active primary cells than RTH-149 spheroids. Besides individual pharmaceuticals, the 3D cultures were challenged with mixtures of the eight most toxic substances, to evaluate if their combined mixture toxicities can be predicted based on individual substances' half-maximal effect (EC50) concentrations. As a result, the classical concentration addition approach was concluded sufficiently accurate for preliminarily informing on the approximate effect concentrations of pharmaceutical mixtures on a cellular level. However, direct read-across from human data was proven challenging and inexplicit for prediction of hepatotoxicity in fish in vitro.

Reproducible generation of human liver organoids (HLOs) on a pillar plate platform via microarray 3D bioprinting

Human liver organoids (HLOs) hold significant potential for recapitulating the architecture and function of liver tissues in vivo. However, conventional culture methods of HLOs, forming Matrigel domes in 6-/24-well plates, have technical limitations such as high cost and low throughput in organoid-based assays for predictive assessment of compounds in clinical and pharmacological lab settings. To address these issues, we have developed a unique microarray 3D bioprinting protocol of progenitor cells in biomimetic hydrogels on a pillar plate with sidewalls and slits, coupled with a clear bottom, 384-deep well plate for scale-up production of HLOs. Microarray 3D bioprinting, a droplet-based printing technology, was used to generate a large number of small organoids on the pillar plate for predictive hepatotoxicity assays. Foregut cells, differentiated from human iPSCs, were mixed with Matrigel and then printed on the pillar plate rapidly and uniformly, resulting in coefficient of variation (CV) values in the range of 15-18%, without any detrimental effect on cell viability. Despite utilizing 10-50-fold smaller cell culture volume compared to their counterparts in Matrigel domes in 6-/24-well plates, HLOs differentiated on the pillar plate exhibited similar morphology and superior function, potentially due to rapid diffusion of nutrients and oxygen at the small scale. Day 25 HLOs were robust and functional on the pillar plate in terms of their viability, albumin secretion, CYP3A4 activity, and drug toxicity testing, all with low CV values. From three independent trials of in situ assessment, the IC50 values calculated for sorafenib and tamoxifen were 6.2 ± 1.6 μM and 25.4 ± 8.3 μM, respectively. Therefore, our unique 3D bioprinting and miniature organoid culture on the pillar plate could be used for scale-up, reproducible generation of HLOs with minimal manual intervention for high-throughput assessment of compound hepatotoxicity.

Reproducible generation of human liver organoids (HLOs) on a pillar plate platform via microarray 3D bioprinting

Human liver organoids (HLOs) hold significant potential for recapitulating the architecture and function of liver tissues in vivo. However, conventional culture methods of HLOs, forming Matrigel domes in 6-/24-well plates, have technical limitations such as high cost and low throughput in organoid-based assays for predictive assessment of compounds in clinical and pharmacological lab settings. To address these issues, we have developed a unique microarray 3D bioprinting protocol of progenitor cells in biomimetic hydrogels on a pillar plate with sidewalls and slits, coupled with a clear bottom, 384-deep well plate for scale-up production of HLOs. Microarray 3D bioprinting, a droplet-based printing technology, was used to generate a large number of small organoids on the pillar plate for predictive hepatotoxicity assays. Foregut cells, differentiated from human iPSCs, were mixed with Matrigel and then printed on the pillar plate rapidly and uniformly, resulting in coefficient of variation (CV) values in the range of 15 - 18%, without any detrimental effect on cell viability. Despite utilizing 10 - 50-fold smaller cell culture volume compared to their counterparts in Matrigel domes in 6-/24-well plates, HLOs differentiated on the pillar plate exhibited similar morphology and superior function, potentially due to rapid diffusion of nutrients and oxygen at the small scale. Day 25 HLOs were robust and functional on the pillar plate in terms of their viability, albumin secretion, CYP3A4 activity, and drug toxicity testing, all with low CV values. From three independent trials of in situ assessment, the IC50 values calculated for sorafenib and tamoxifen were 6.2 ± 1.6 μM and 25.4 ± 8.3 μM, respectively. Therefore, our unique 3D bioprinting and miniature organoid culture on the pillar plate could be used for scale-up, reproducible generation of HLOs with minimal manual intervention for high-throughput assessment of compound hepatotoxicity.

Investigation of TGF-α-overexpressing mouse hepatocytes (TAMH) cultured as spheroids for use in hepatotoxicity screening of drug candidates

The immortalized mouse liver cell line TAMH has been described as a valuable tool for studying hepatotoxic mechanisms, but until now, it has only been reported to grow as a monolayer in culture. However, culturing hepatocytes as three-dimensional (3D) spheroids has been shown to result in improved liver-specific functions (e.g., metabolic capacity) by better mimicking the in vivo environment. This approach may lead to more reliable detection of drug-induced liver injury (DILI) in the early phase of drug discovery, preventing post-marketing drug withdrawals. Here, we investigated the cultivation of TAMH as 3D spheroids, characterizing them with optical and transmission electron microscopy as well as analyzing their gene expression at mRNA level (especially drug-metabolizing enzymes) compared to TAMH monolayer. In addition, comparisons were made with spheroids grown from the human hepatoblastoma cell line HepG2, another current spheroid model. The results indicate that TAMH spheroids express hepatic structures and show elevated levels of some of the key phase I and II drug-metabolizing enzymes, in contrast to TAMH monolayer. The in vitro hepatotoxic potencies of the drugs acetaminophen and flupirtine maleate were found to be very similar between TAMH spheroidal and the monolayer cultures. Both the advantages and disadvantages of TAMH spheroids as an in vitro hepatotoxicity model compared to monolayer model are discussed.

Are the BPA analogues an alternative to classical BPA? Comparison between 2D and alternative 3D in vitro neuron model to assess cytotoxic and genotoxic effects

BPA is used in a wide range of consumer products with very concern toxicological properties. The European Union has restricted its use to protect human health. Industry has substituted BPA by BPA analogues. However, there is a lack of knowledge about their impacts. In this work, BPA and 5 BPA analogues (BPS, BPAP, BPAF, BPFL and BPC) have been studied in classical SH-SY5Y and the alternative 3D in vitro models after 24 and 96 h of exposure. Cell viability, percentage of ROS, cell cycle phases as well as the morphology of the spheroids were measured. The 2D model was more sensitive than the 3D models with differences in cell viability higher than 60% after 24 h of exposure, and different mechanisms of ROS production. After chronic exposure, both models were more affected in comparison to the 24 h exposure. After a recovery time (96 h), the spheroids exposed to 2.5-40 µM were able to recover cell viability and the morphology. Among the BPs tested, BPFL>BPAF>BPAP and >BPC revealed higher toxicological effects, while BPS was the only one with lower effects than BPA. To conclude, the SH-SY5Y 3D model is a suitable candidate to perform more reliable in vitro neurotoxicity tests.

High-Voltage Electrostatic Field Hydrogel Microsphere 3D Culture System Improves Viability and Liver-like Properties of HepG2 Cells

Three-dimensional (3D) hepatocyte models have become a research hotspot for evaluating drug metabolism and hepatotoxicity. Compared to two-dimensional (2D) cultures, 3D cultures are better at mimicking the morphology and microenvironment of hepatocytes in vivo. However, commonly used 3D culture techniques are not suitable for high-throughput drug screening (HTS) due to their high cost, complex handling, and inability to simulate cell-extracellular matrix (ECM) interactions. This article describes a method for rapid and reproducible 3D cell cultures with ECM-cell interactions based on 3D culture instrumentation to provide more efficient HTS. We developed a microsphere preparation based on a high-voltage electrostatic (HVE) field and used sodium alginate- and collagen-based hydrogels as scaffolds for 3D cultures of HepG2 cells. The microsphere-generating device enables the rapid and reproducible preparation of bioactive hydrogel microspheres. This 3D culture system exhibited better cell viability, heterogeneity, and drug-metabolizing activity than 2D and other 3D culture models, and the long-term culture characteristics of this system make it suitable for predicting long-term liver toxicity. This system improves the overall applicability of HepG2 spheroids in safety assessment studies, and this simple and controllable high-throughput-compatible method shows potential for use in drug toxicity screening assays and mechanistic studies.

HER-2-Targeted Boron Neutron Capture Therapy with Carborane-integrated Immunoliposomes Prepared via an Exchanging Reaction

Boron neutron capture therapy (BNCT) is a promising modality for cancer treatment because of its minimal invasiveness. To maximize the therapeutic benefits of BNCT, the development of efficient platforms for the delivery of boron agents is indispensable. Here, carborane-integrated immunoliposomes were prepared via an exchanging reaction to achieve HER-2-targeted BNCT. The conjugation of an anti-HER-2 antibody to carborane-integrated liposomes successfully endowed these liposomes with targeting properties toward HER-2-overexpressing human ovarian cancer cells (SK-OV3); the resulting BNCT activity toward SK-OV3 cells obtained using the current immunoliposomal system was 14-fold that of the l-BPA/fructose complex, which is a clinically available boron agent. Moreover, the growth of spheroids treated with this system followed by thermal neutron irradiation was significantly suppressed compared with treatment with the l-BPA/fructose complex.

3D tumor spheroids: morphological alterations a yardstick to anti-cancer drug response

Tumor spheroids are one of the well-characterized 3D culture systems bearing close resemblance to the physiological tissue organization and complexity of avascular solid tumor stage with hypoxic core. They hold a wide-spread application in the field of pharmaceutical science and anti-cancer drug research. However, the difficulty in determining optimal technique for the generation of spheroids with uniform size and shape, evaluation of experimental outputs, or mass production often limits their usage in anti-cancer research and in high-throughput drug screening. In recent times, several studies have demonstrated various simple techniques for generating uniform-size 3D spheroids, including the hanging drop (HD), liquid overlay technique (LOT), and microfluidic approaches. Morphological alterations apart from biochemical assays, and staining techniques are suitably employed for the evaluation of experimental outcomes within 3D spheroid models. Morphological alterations in response to effective anti-cancer drug treatment in 3D tumor spheroids such as reduced spheroid size, loss of spheroid compactness and integrity or smooth surface, are highly reliable. These alterations can significantly reduce the need for biochemical assays and staining techniques, resulting in both time and cost savings. The present article specifically covers a variety of available procedures in spheroid generation. For practical applicability, we have supplemented our review study with the generation of glioblastoma U87 spheroids using HD and LOT methods. Additionally, we have also incorporated the outcome of U87 spheroid treatment with doxorubicin on spheroid morphology.

SLC31A1 Identifying a Novel Biomarker with Potential Prognostic and Immunotherapeutic Potential in Pan-Cancer

Solute carrier family 31 member 1 (SLC31A1) encodes a protein that functions as a homotrimer for the uptake of dietary copper. As a vital member of the cuproptosis gene family, it plays an essential role in both normal tissues and tumors. In this study, we analyzed SLC31A1 across human cancer types to gain a better understanding of SLC31A1's role in cancer development. We searched for information using online databases to analyze, systematically and comprehensively, the role of SLC31A1 in tumors. Amongst nine cancer types, the expression of SLC31A1 was significantly different between tumors and normal tissues. According to further analysis, pancreatic cancer had the highest mutation rate of the SLC31A1 gene, and the methylation levels of the gene were significantly reduced in seven tumors. The expression of SLC31A1 is also linked to the infiltration of tumors by immune cells, the expression of immune checkpoint genes, and immunotherapy markers (TMB and MSI), suggesting that SLC31A1 may be of particular relevance in immunotherapy. This thorough analysis of SLC31A1 across different types of cancer gives us a clear and comprehensive insight into its role in causing cancer on a systemic level.

Amyloid fibril-based thixotropic hydrogels for modeling of tumor spheroids in vitro

Biomaterials mimicking extracellular matrices (ECM) for three-dimensional (3D) cultures have gained immense interest in tumor modeling and in vitro organ development. Here, we introduce a new class of amyloid fibril-based peptide hydrogels as a versatile biomimetic ECM scaffold for 3D cell culture and homogenous tumor spheroid modeling. We show that these amyloid fibril-based hydrogels are thixotropic and allow cancer cell adhesion, proliferation, and migration. All seven designed hydrogels support 3D cell culture with five different cancer cell lines forming spheroid with necrotic core and upregulation of the cancer biomarkers. We further developed the homogenous, single spheroid using the drop cast method and the data suggest that all hydrogels support the tumor spheroid formation but with different necrotic core diameters. The detailed gene expression analysis of MCF7 spheroid by microarray suggested the involvement of pro-oncogenes and significant regulatory pathways responsible for tumor spheroid formation. Further, using breast tumor tissue from a mouse xenograft model, we show that selected amyloid hydrogels support the formation of tumor spheroids with a well-defined necrotic core, cancer-associated gene expression, higher drug resistance, and tumor heterogeneity reminiscent of the original tumor. Altogether, we have developed an easy-to-use, rapid, cost-effective, and scalable platform for generating in vitro cancer models for the screening of anti-cancer therapeutics and developing personalized medicine.

Replacement, Reduction, and Refinement of Animal Experiments in Anticancer Drug Development: The Contribution of 3D In Vitro Cancer Models in the Drug Efficacy Assessment

In the last decades three-dimensional (3D) in vitro cancer models have been proposed as a bridge between bidimensional (2D) cell cultures and in vivo animal models, the gold standards in the preclinical assessment of anticancer drug efficacy. 3D in vitro cancer models can be generated through a multitude of techniques, from both immortalized cancer cell lines and primary patient-derived tumor tissue. Among them, spheroids and organoids represent the most versatile and promising models, as they faithfully recapitulate the complexity and heterogeneity of human cancers. Although their recent applications include drug screening programs and personalized medicine, 3D in vitro cancer models have not yet been established as preclinical tools for studying anticancer drug efficacy and supporting preclinical-to-clinical translation, which remains mainly based on animal experimentation. In this review, we describe the state-of-the-art of 3D in vitro cancer models for the efficacy evaluation of anticancer agents, focusing on their potential contribution to replace, reduce and refine animal experimentations, highlighting their strength and weakness, and discussing possible perspectives to overcome current challenges.

Combined Toxic Effects of BPA and Its Two Analogues BPAP and BPC in a 3D HepG2 Cell Model

Bisphenol A (BPA) is one of the most commonly used substances in the manufacture of various everyday products. Growing concerns about its hazardous properties, including endocrine disruption and genotoxicity, have led to its gradual replacement by presumably safer analogues in manufacturing plastics. The widespread use of BPA and, more recently, its analogues has increased their residues in the environment. However, our knowledge of their toxicological profiles is limited and their combined effects are unknown. In the present study, we investigated the toxic effects caused by single bisphenols and by the combined exposure of BPA and its two analogues, BPAP and BPC, after short (24-h) and prolonged (96-h) exposure in HepG2 spheroids. The results showed that BPA did not reduce cell viability in HepG2 spheroids after 24-h exposure. In contrast, BPAP and BPC affected cell viability in HepG2 spheroids. Both binary mixtures (BPA/BPAP and BPA/BPC) decreased cell viability in a dose-dependent manner, but the significant difference was only observed for the combination of BPA/BPC (both at 40 µM). After 96-h exposure, none of the BPs studied affected cell viability in HepG2 spheroids. Only the combination of BPA/BPAP decreased cell viability in a dose-dependent manner that was significant for the combination of 4 µM BPA and 4 µM BPAP. None of the BPs and their binary mixtures studied affected the surface area and growth of spheroids as measured by planimetry. In addition, all BPs and their binary mixtures studied triggered oxidative stress, as measured by the production of reactive oxygen species and malondialdehyde, at both exposure times. Overall, the results suggest that it is important to study the effects of BPs as single compounds. It is even more important to study the effects of combined exposures, as the combined effects may differ from those induced by single compounds.

Adverse (geno)toxic effects of bisphenol A and its analogues in hepatic 3D cell model

Bisphenol A (BPA) is one of the most widely used and versatile chemical compounds in polymer additives and epoxy resins for manufacturing a range of products for human applications. It is known as endocrine disruptor, however, there is growing evidence that it is genotoxic. Because of its adverse effects, the European Union has restricted its use to protect human health and the environment. As a result, the industry has begun developing BPA analogues, but there are not yet sufficient toxicity data to claim that they are safe. We investigated the adverse toxic effects of BPA and its analogues (BPS, BPAP, BPAF, BPFL, and BPC) with emphasis on their cytotoxic and genotoxic activities after short (24-h) and prolonged (96-h) exposure in in vitro hepatic three-dimensional cell model developed from HepG2 cells. The results showed that BPFL and BPC (formed by an additional ring system) were the most cytotoxic analogues that affected cell viability, spheroid surface area and morphology, cell proliferation, and apoptotic cell death. BPA, BPAP, and BPAF induced DNA double-strand break formation (γH2AX assay), whereas BPAF and BPC increased the percentage of p-H3-positive cells, indicating their aneugenic activity. All BPs induced DNA single-strand break formation (comet assay), with BPAP (≥0.1 μM) being the most effective and BPA and BPC the least effective (≥1 μM) under conditions applied. The results indicate that not all of the analogues studied are safer alternatives to BPA and thus more in-depth research is urgently needed to adequately evaluate the risks of BPA analogues and assess their safety for humans.

Cell Dome as an Evaluation Platform for Organized HepG2 Cells

Human-hepatoblastoma-derived cell line, HepG2, has been widely used in liver and liver cancer studies. HepG2 spheroids produced in a three-dimensional (3D) culture system provide a better biological model than cells cultured in a two-dimensional (2D) culture system. Since cells at the center of spheroids exhibit specific behaviors attributed to hypoxic conditions, a 3D cell culture system that allows the observation of such cells using conventional optical or fluorescence microscopes would be useful. In this study, HepG2 cells were cultured in "Cell Dome", a micro-dome in which cells are enclosed in a cavity consisting of a hemispherical hydrogel shell. HepG2 cells formed hemispherical cell aggregates which filled the cavity of Cell Domes on 18 days of culture and the cells could continue to be cultured for 29 days. The cells at the center of hemispherical cell aggregates were observed using a fluorescence microscope. The cells grew in Cell Domes for 18 days exhibited higher Pi-class Glutathione S-Transferase enzymatic activity, hypoxia inducible factor-1α gene expression, and higher tolerance to mitomycin C than those cultured in 2D on tissue culture dishes (* p < 0.05). These results indicate that the center of the glass adhesive surface of hemispherical cell aggregates which is expected to have the similar environment as the center of the spheroids can be directly observed through glass plates. In conclusion, Cell Dome would be useful as an evaluation platform for organized HepG2 cells.

Ultrastructural Characterization of Human Gingival Fibroblasts in 3D Culture

Cell spheroids are applied in various fields of research, such as the fabrication of three-dimensional artificial tissues in vitro, disease modeling, stem cell research, regenerative therapy, and biotechnology. A preclinical 3D culture model of primary human gingival fibroblasts free of external factors and/or chemical inducers is presented herein. The ultrastructure of the spheroids was characterized to establish a cellular model for the study of periodontal tissue regeneration. The liquid overlay technique was used with agarose to generate spheroids. Fibroblasts in 2D culture and cell spheroids were characterized by immunofluorescence, and cell spheroids were characterized by optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy, backscattered electrons, and Fourier transform infrared spectroscopy. Ostegenic related genes were analyzed by RT-qPCR. Gingival fibroblasts formed spheroids spontaneously and showed amorphous calcium phosphate nanoparticle deposits on their surface. The results suggest that human gingival fibroblasts have an intrinsic potential to generate a mineralized niche in 3D culture.

Culture of cancer spheroids and evaluation of anti-cancer drugs in 3D-printed miniaturized continuous stirred tank reactors (mCSTR)

Cancer continues to be a leading cause of mortality in modern societies; therefore, improved and more reliable in vitro cancer models are needed to expedite fundamental research and anti-cancer drug development. Here, we describe the use of a miniaturized continuous stirred tank reactor (mCSTR) to first fabricate and mature cancer spheroids (i.e, derived from MCF7 cells, DU145 cells, and a mix of MCF7 cells and fibroblasts), and then to conduct anti-cancer drug assays under continuous perfusion. This 3 mL mCSTR features an off-center agitation system that enables homogeneous chaotic laminar mixing at low speeds to support cell aggregation. We incubated cell suspensions for 3 days in ultra-low-adherence (ULA) plates to allow formation of discoid cell aggregates (~600 µm in diameter). These cell aggregates were then transferred into mCSTRs and continuously fed with culture medium. We characterized the spheroid morphology and the expression of relevant tumor biomarkers at different maturation times for up to 4 weeks. The spheroids progressively increased in size during the first 5 to 6 days of culture to reach a steady diameter between 600 and 800 µm. In proof-of-principle experiments, we demonstrated the use of this mCSTR in anti-cancer drug testing. Three drugs commonly used in breast cancer treatment (doxorubicin, docetaxel, and paclitaxel) were probed at different concentrations in MCF7 derived spheroids. In these experiments, we evaluated cell viability, glucose consumption, spheroid morphology, lactate dehydrogenase activity, and the expression of genes associated with drug resistance (ABCB1 and ABCC1) and anti-apoptosis (Bcl2). We envision the use of this agitated system as a tumor-on-a-chip platform to expedite efficacy and safety testing of novel anti-cancer drugs and possibly in personalized medicine applications.

HepG2 spheroids as a biosensor-like cell-based system for (geno)toxicity assessment

3D spheroids developed from HepG2 cells were used as a biosensor-like system for the detection of (geno)toxic effects induced by chemicals. Benzo(a)pyrene (B(a)P) and amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) with well-known mechanisms of action were used for system validation. HepG2 spheroids grown for 3 days were exposed to BaP and PhIP for 24 and 72 h. The growth and viability of spheroids were monitored by planimetry and Live/Dead staining of cells. Multi-parametric flow cytometric analysis was applied for simultaneous detection of specific end-effects including cell cycle analysis (Hoechst staining), cell proliferation (KI67 marker), and DNA double-strand breaks (ℽH2AX) induced by genotoxic compounds. Depending on the exposure concentration/time, BaP reduced spheroid growth, affected cell proliferation by arresting cells in S and G2 phase and induced DNA double-strand breaks (DSB). Simultaneous staining of ℽH2AX formation and cell cycle analysis revealed that after BaP (10 μM; 24 h) exposure 60% of cells in G0/G1 phase had DNA DSB, while after 72 h only 20% of cells contained DSB indicating efficient repair of DNA lesions. PhIP did not influence the spheroid size whereas accumulation of cells in the G2 phase occurred after both treatment times. The evaluation of DNA damage revealed that at 200 μM PhIP 50% of cells in G0/G1 phase had DNA DSB, which after 72-h exposure dropped to 40%, showing lower repair capacity of PhIP-induced DSB compared to BaP-induced. The developed approach using simultaneous detection of several parameters provides mechanistic data and thus contributes to more reliable genotoxicity assessment of chemicals as a high-content screening tool.

Treatment of cylindrospermopsin by hydroxyl and sulfate radicals: Does degradation equal detoxification?

Drinking water treatment ultimately aims to provide safe and harmless drinking water. Therefore, the suitability of a treatment process should not only be assessed based on reducing the concentration os a pollutant concentration but, more importantly, on reducing its toxicity. Hence, the main objective of this study was to answer whether the degradation of a highly toxic compound of global concern for drinking water equals its detoxification. We, therefore, investigated the treatment of cylindrospermopsin (CYN) by •OH and SO₄^-• produced in Fenton and Fenton-like reactions. Although SO₄^-• radicals removed the toxin more effectively, both radical species substantially degraded CYN. The underlying degradation mechanisms were similar for both radical species and involved hydroxylation, dehydrogenation, decarboxylation, sulfate group removal, ring cleavage, and further fragmentation. The hydroxymethyl uracil and tricyclic guanidine moieties were the primary targets. Furthermore, the residual toxicity, assessed by a 3-dimensional human in vitro liver model, was substantially reduced during the treatment by both radical species. Although the results indicated that some of the formed degradation products might still be toxic, the overall reduction of the toxicity together with the proposed degradation pathways allowed us to conclude: "Yes, degradation of CYN equals its detoxification!".

Generation of Oxygenating Fluorinated Methacrylamide Chitosan Microparticles to Increase Cell Survival and Function in Large Liver Spheroids

Despite advances in the development of complex culture technologies, the utility, survival, and function of large 3D cell aggregates, or spheroids, are impeded by mass transport limitations. The incorporation of engineered microparticles into these cell aggregates offers a promising approach to increase spheroid integrity through the creation of extracellular spaces to improve mass transport. In this study, we describe the formation of uniform oxygenating fluorinated methacrylamide chitosan (MACF) microparticles via a T-shaped microfluidic device, which when incorporated into spheroids increased extracellular spacing and enhanced oxygen transport via perfluorocarbon substitutions. The addition of MACF microparticles into large liver cell spheroids supported the formation of stable and large spheroids (>500 μm in diameter) made of a heterogeneous population of immortalized human hepatoma (HepG2) and hepatic stellate cells (HSCs) (4 HepG2/1 HSC), especially at a 150:1 ratio of cells to microparticles. Further, as confirmed by the albumin, urea, and CYP3A4 secretion amounts into the culture media, biological functionality was maintained over 10 days due to the incorporation of MACF microparticles as compared to controls without microparticles. Importantly, we demonstrated the utility of fluorinated microparticles in reducing the number of hypoxic cells within the core regions of spheroids, while also promoting the diffusion of other small molecules in and out of these 3D in vitro models.

Metabolomics analysis of the 3D L-02 cell cultures revealing the key role of metabolism of amino acids in ameliorating hepatotoxicity of perfluorooctanoic acid

To simulate the real cell status and morphology in the living systems is substantial for using cell models to address the detrimental effects of toxic contaminants. In this study, the comparative profiles of metabolites in three-dimensional (3D) human normal liver (L-02) cell spheroids with perfluorooctanoic acid (PFOA) treatment were analyzed using a metabolomic approach. The uniform 3D cell spheroids were well formed in 3 days (e.g., sphericity index >0.9) and stably maintained over the subsequent 11 days. The cytotoxicity of PFOA to the 3D L-02 cell spheroids was highly dependent on both exposure concentration and duration. Comparative analysis of metabolomes showed that the number of differential metabolites in the 3D cell spheroids treated with 300 μM PFOA for 10 days (n = 59) was greater than those with a 4-day exposure to 300 μM PFOA (n = 17). Six metabolic pathways related to amino acids metabolism were only found in the 3D cell spheroids with a 10-day treatment of 300 μM PFOA, which could not be found in the 2D monolayer cells and those 3D cell spheroids with a 4-day exposure. The suppression of PFOA on glutamine metabolism substantially decreased glutathione (GSH) production and accordingly increased the level of reactive oxygen species in the 3D cell spheroids. On the contrary, the supplementation of glutamine increased GSH production and the viability of cell spheroids, indicating that glutamine metabolism played a critical role in the chronic toxic effects of PFOA. Our study strongly suggested that comprehensive toxicological methodologies based on the 3D cell models could currently be robust and suitable for addressing the chronic adverse effects of toxic contaminants.

Fingerprinting Metabolic Activity and Tissue Integrity of 3D Lung Cancer Spheroids under Gold Nanowire Treatment

Inadequacy of most animal models for drug efficacy assessments has led to the development of improved in vitro models capable of mimicking in vivo exposure scenarios. Among others, 3D multicellular spheroid technology is considered to be one of the promising alternatives in the pharmaceutical drug discovery process. In addition to its physiological relevance, this method fulfills high-throughput and low-cost requirements for preclinical cell-based assays. Despite the increasing applications of spheroid technology in pharmaceutical screening, its application, in nanotoxicity testing is still in its infancy due to the limited penetration and uptake rates into 3D-cell assemblies. To gain a better understanding of gold nanowires (AuNWs) interactions with 3D spheroids, a comparative study of 2D monolayer cultures and 3D multicellular spheroids was conducted using two lung cancer cell lines (A549 and PC9). Cell apoptosis (live/dead assay), metabolic activity, and spheroid integrity were evaluated following exposure to AuNWs at different dose-time manners. Results revealed a distinct different cellular response between 2D and 3D cell cultures during AuNWs treatment including metabolic rates, cell viability, dose-response curves and, uptake rates. Our data also highlighted further need for more physiologically relevant tissue models to investigate in depth nanomaterial-biology interactions. It is important to note that higher concentrations of AuNWs with lower exposure times and lower concentrations of AuNWs with higher exposure times of 3 days resulted in the loss of spheroid integrity by disrupting cell-cell contacts. These findings could help to increase the understanding of AuNWs-induced toxicity on tissue levels and also contribute to the establishment of new analytical approaches for toxicological and drug screening studies.

Fabrication of Size-Controllable and Arrangement-Orderly HepG2 Spheroids for Drug Screening via Decellularized Liver Matrix-Derived Micropattern Array Chips

Three-dimensional (3D) culture via micropattern arrays to generate cellular spheroids seems a promising in vitro biomimetic system for liver tissue engineering applications, such as drug screening. Recently, organ-derived decellularized extracellular matrix emerges as arguably the most biomimetic bioink. Herein, decellularized liver matrix (DLM)-derived micropattern array chips were developed to fabricate size-controllable and arrangement-orderly HepG2 spheroids for drug screening. The porcine DLM was obtained by the removal of cellular components and then ground into powder, followed by enzymolysis. DLM as a coating substrate was compared with collagen type I (Col I) and Matrigel in terms of biological performance for enhancing cell adhesion, proliferation, and functions. Subsequently, we used poly(dimethylsiloxane) (PDMS) to adsorb DLM as the bioink to fabricate micropattern array chips. The optimal shape and size of micropattern were determined by evaluating the morphology, viability, and functions of HepG2 3D cellular aggregates. In addition, drug-susceptibility testing (paclitaxel, doxorubicin HCl, and disulfiram) was performed on this novel platform. The DLM provided the tissue-specific microenvironment that provided suitable supports for HepG2 cells, compared to Col I and Matrigel. A circular micropattern with a diameter of 100 μm was the optimal processing parameter to rapidly fabricate large-scale, size-controllable, and arrangement-orderly HepG2 cellular aggregates with 3D spheroid’s shape and high cell viability. Drug screening testing showed that the effect of a drug could be directly demonstrated on-chip by confocal microscopy measuring the viability of spheroids. We provide a novel platform for the large-scale generation of HepG2 spheroids with uniform size and arrangement, thus bringing convenience, reducing error, and increasing reproducibility for a rapid drug discovery by fluorescence quantitative analysis. This methodology may be possible to apply in advancing personalized medicine and drug discovery.

In Vivo and In Vitro Models of Hepatocellular Carcinoma: Current Strategies for Translational Modeling

Hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide and the third leading cause of cancer-related death globally. HCC is a complex multistep disease and usually emerges in the setting of chronic liver diseases. The molecular pathogenesis of HCC varies according to the etiology, mainly caused by chronic hepatitis B and C virus infections, chronic alcohol consumption, aflatoxin-contaminated food, and non-alcoholic fatty liver disease associated with metabolic syndrome or diabetes mellitus. The establishment of HCC models has become essential for both basic and translational research to improve our understanding of the pathophysiology and unravel new molecular drivers of this disease. The ideal model should recapitulate key events observed during hepatocarcinogenesis and HCC progression in view of establishing effective diagnostic and therapeutic strategies to be translated into clinical practice. Despite considerable efforts currently devoted to liver cancer research, only a few anti-HCC drugs are available, and patient prognosis and survival are still poor. The present paper provides a state-of-the-art overview of in vivo and in vitro models used for translational modeling of HCC with a specific focus on their key molecular hallmarks.

Establishment of a human three-dimensional chip-based chondro-synovial coculture joint model for reciprocal cross talk studies in arthritis research

Rheumatoid arthritis is characterised by a progressive, intermittent inflammation at the synovial membrane, which ultimately leads to the destruction of the synovial joint. The synovial membrane as the joint capsule's inner layer is lined with fibroblast-like synoviocytes that are the key player supporting persistent arthritis leading to bone erosion and cartilage destruction. While microfluidic models that model molecular aspects of bone erosion between bone-derived cells and synoviocytes have been established, RA's synovial-chondral axis has not yet been realised using a microfluidic 3D model based on human patient in vitro cultures. Consequently, we established a chip-based three-dimensional tissue coculture model that simulates the reciprocal cross talk between individual synovial and chondral organoids. When co-cultivated with synovial organoids, we could demonstrate that chondral organoids induce a higher degree of cartilage physiology and architecture and show differential cytokine response compared to their respective monocultures highlighting the importance of reciprocal tissue-level cross talk in the modelling of arthritic diseases.

Angiogenic Sprouting Dynamics Mediated by Endothelial-Fibroblast Interactions in Microfluidic Systems

Angiogenesis, the development of new blood vessels from existing vasculature, is a key process in normal development and pathophysiology. In vitro models are necessary for investigating mechanisms of angiogenesis and developing antiangiogenic therapies. Microfluidic cell culture models of angiogenesis are favored for their ability to recapitulate 3D tissue structures and control spatiotemporal aspects of the microenvironments. To capture the angiogenesis process, microfluidic models often include endothelial cells and a fibroblast component. However, the influence of fibroblast organization on resulting angiogenic behavior remains unclear. Here a comparative study of angiogenic sprouting on a microfluidic chip induced by fibroblasts in 2D monolayer, 3D dispersed, and 3D spheroid culture formats, is conducted. Vessel morphology and sprout distribution for each configuration are measured, and these observations are correlated with measurements of secreted factors and numerical simulations of diffusion gradients. The results demonstrate that angiogenic sprouting varies in response to fibroblast organization with correlating variations in secretory profile and secreted factor gradients across the microfluidic device. This study is anticipated to shed light on how sprouting dynamics are mediated by fibroblast configuration such that the microfluidic cell culture design process includes the selection of a fibroblast component where the effects are known and leveraged.

Bioengineering a humanized 3D tri-culture osteosarcoma model to assess tumor invasiveness and therapy response

To date, anticancer therapies with evidenced efficacy in preclinical models fail during clinical trials. The shortage of robust drug screening platforms that accurately predict patient's response underlie these misleading results. To provide a reliable platform for tumor drug discovery, we herein propose a relevant humanized 3D osteosarcoma (OS) model exploring the potential of methacryloyl platelet lysates (PLMA)-based hydrogels to sustain spheroid growth and invasion. The architecture and synergistic cell-microenvironment interaction of an invading tumor was recapitulated encapsulating spheroids in PLMA hydrogels, alone or co-cultured with osteoblasts and mesenchymal stem cells. The stem cells alignment toward OS spheroid suggested that tumor cells chemotactically attracted the surrounding stromal cells, which supported tumor growth and invasion into the hydrogels. The exposure of established models to doxorubicin revealed an improved drug resistance of PLMA-based models, comparing with scaffold-free spheroids. The proposed OS models highlighted the feasibility of PLMA hydrogels to support tumor invasion and recapitulate tumor-stromal cell crosstalk, demonstrating the potential of this 3D platform for complex tumor modelling. STATEMENT OF SIGNIFICANCE: Cell invasion mechanisms involved in tumor progression have been recapitulated in the field of 3D in vitro modeling, leveraging the great advance in biomimetic materials. In line with the growing interest in human-derived biomaterials, the aim of this study is to explore for the first time the potential of methacryloyl platelet lysates (PLMA)-based hydrogels to develop a humanized 3D osteosarcoma model to assess tumor invasiveness and drug sensitivity. By co-culturing tumor spheroids with human osteoblasts and human mesenchymal stem cells, this study demonstrated the importance of the synergistic tumor cell-microenvironment interaction in tumor growth, invasion and drug resistance. The established 3D osteosarcoma model highlighted the feasibility of PLMA hydrogels as a relevant 3D platform for complex tumor modelling.

Biobanked Glioblastoma Patient-Derived Organoids as a Precision Medicine Model to Study Inhibition of Invasion

Glioblastoma (GBM) is highly resistant to treatment and invasion into the surrounding brain is a cancer hallmark that leads to recurrence despite surgical resection. With the emergence of precision medicine, patient-derived 3D systems are considered potentially robust GBM preclinical models. In this study, we screened a library of 22 anti-invasive compounds (i.e., NF-kB, GSK-3-B, COX-2, and tubulin inhibitors) using glioblastoma U-251 MG cell spheroids. We evaluated toxicity and invasion inhibition using a 3D Matrigel invasion assay. We next selected three compounds that inhibited invasion and screened them in patient-derived glioblastoma organoids (GBOs). We developed a platform using available macros for FIJI/ImageJ to quantify invasion from the outer margin of organoids. Our data demonstrated that a high-throughput invasion screening can be done using both an established cell line and patient-derived 3D model systems. Tubulin inhibitor compounds had the best efficacy with U-251 MG cells, however, in ex vivo patient organoids the results were highly variable. Our results indicate that the efficacy of compounds is highly related to patient intra and inter-tumor heterogeneity. These results indicate that such models can be used to evaluate personal oncology therapeutic strategies.

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.

A 3D cell printing-fabricated HepG2 liver spheroid model for high-content in situ quantification of drug-induced liver toxicity

3D spheroid cultures are attractive candidates for application in in vitro drug-induced hepatotoxicity testing models to improve the reliability of biological information obtainable from a simple 2D culture model. Various 3D spheroid culture models exist for hepatotoxicity screening, but quantitative assays of spheroid response in situ are still challenging to achieve with the current 3D liver toxicity platforms. In this study, we developed a 3D printing-based HepG2 liver spheroid culture model for in situ quantitative evaluation and high-content monitoring of drug-induced hepatotoxicity. HepG2 liver spheroids grown in mini-fabricated hydrogel constructs using a 3D bioprinter were used to obtain the EC₅₀ values and to measure the multi-parametric hepatotoxic effects, including mitochondrial permeability transition (MPT), cytosolic calcium levels, and apoptosis. Interestingly, the average fluorescence intensities of apoptotic and cell death markers, calculated for out-of-focus and in-focus spheroids, increased proportionally as a function of the drug concentration, allowing for the determination of the EC₅₀ values. In addition, 3D HepG2 spheroids were more resistant to nefazodone-induced MPT than 2D HepG2 cells, indicating that the gelatin/alginate hydrogel culture system provides enhanced resistance to hepatotoxic drugs. The drug response of HepG2 liver spheroids was also found to be unrelated to the spheroid size. These results demonstrate that the present 3D cell-printing-based embedded HepG2 liver spheroid platform is a promising approach for screening and characterizing drug-induced hepatotoxicity.

Sorafenib for hepatocellular carcinoma: potential molecular targets and resistance mechanisms

Hepatocellular carcinoma (HCC) is the most widespread typical therapy-resistant, unresectable type of malignant solid tumour with a high death rate constituting huge medical concern. Sorafenib is a small molecule oral multi-target kinase potent inhibitor that acts by suppressing/blocking the multiplication of the tumour cells, angiogenesis, and encouraging apoptosis of the tumour cells. Though, the precise mechanism of tumour cell death induction by sorafenib is yet under exploration. Furthermore, genetic heterogeneity plays a critical role in developing sorafenib resistance, which leads the way to identify the need for predictive biomarkers responsible for drug resistance. Therefore, it is essential to find out the fundamental resistance mechanisms to expand therapeutic plans. The authors summarize the molecular concepts of resistance, progression, potential molecular targets, HCC management therapies, and discussion on the advancements expected in the coming future, inclusive of biomarker-driven treatment strategies, which may provide the prospects to design innovative therapeutically targeted strategies for the HCC treatment and the clinical implementation of emerging targeted agents.

Development of a 3D spheroid cell culture system from fish cell lines for in vitro infection studies: Evaluation with Saprolegnia parasitica

Understanding the ways in which pathogens infect host cells is essential to improve and develop new treatment strategies. This study aimed to generate a novel in vitro infection model by establishing a reproducible 3D spheroid cell culture system that may lead to a reduced need for animals in fish disease research. 2D models (commonly cell lines) cannot replicate many key conditions of in vivo infections, but 3D spheroids have the potential to provide bridging technology between in vivo and in vitro systems. 3D spheroids were generated using cells from rainbow trout (Oncorhynchus mykiss) cell lines, RTG-2 and RTS-11. The RTG-2 spheroids were tested for their potential to be infected upon exposure to Saprolegnia parasitica spores. Positive infiltration of mycelia into the spheroids was verified by confocal microscopy. As a closer analogue of in vivo conditions encountered during infection, the straightforward model developed in this study shows promise as an additional tool that can be used to further our understanding of host-pathogen interactions for Saprolegnia and possibly a variety of other fish pathogens.

A Microfluidic Multisize Spheroid Array for Multiparametric Screening of Anticancer Drugs and Blood-Brain Barrier Transport Properties

Physiological-relevant in vitro tissue models with their promise of better predictability have the potential to improve drug screening outcomes in preclinical studies. Despite the advances of spheroid models in pharmaceutical screening applications, variations in spheroid size and consequential altered cell responses often lead to nonreproducible and unpredictable results. Here, a microfluidic multisize spheroid array is established and characterized using liver, lung, colon, and skin cells as well as a triple-culture model of the blood-brain barrier (BBB) to assess the effects of spheroid size on (a) anticancer drug toxicity and (b) compound penetration across an advanced BBB model. The reproducible on-chip generation of 360 spheroids of five dimensions on a well-plate format using an integrated microlens technology is demonstrated. While spheroid size-related IC50 values vary up to 160% using the anticancer drugs cisplatin (CIS) or doxorubicin (DOX), reduced CIS:DOX drug dose combinations eliminate all lung microtumors independent of their sizes. A further application includes optimizing cell seeding ratios and size-dependent compound uptake studies in a perfused BBB model. Generally, smaller BBB-spheroids reveal an 80% higher compound penetration than larger spheroids while verifying the BBB opening effect of mannitol and a spheroid size-related modulation on paracellular transport properties.

Fabrication of PNIPAm-based thermoresponsive hydrogel microwell arrays for tumor spheroid formation

Complex three-dimensional (3D) cell cultures are being increasingly implemented in biomedical research as they provide important insights into complex cancer biology, and cell-cell and cell-matrix interactions in the tumor microenvironment. However, most methods used today for 3D cell culture are limited by high cost, the need for specialized skills, low throughput and the use of unnatural culture environments. We report the development of a unique biomimetic hydrogel microwell array platform for the generation and stress-free isolation of cancer spheroids. The poly N-isopropylacrylamide-based hydrogel microwell array (PHMA) has thermoresponsive properties allowing for the attachment and growth of cell aggregates/ spheroids at 37 °C, and their easy isolation at room temperature (RT). The reversible phase transition of the microwell arrays at 35 °C was confirmed visually and by differential scanning calorimetry. Swelling/ shrinking studies and EVOS imaging established that the microwell arrays are hydrophilic and swollen at temperatures <35 °C, while they shrink and are hydrophobic at temperatures >35 °C. Spheroid development within the PHMA was optimized for seeding density, incubation time and cell viability. Spheroids of A549, HeLa and MG-63 cancer cell lines, and human lung fibroblast (HLF) cell line generated within the PHMAs had relatively spherical morphology with hypoxic cores. Finally, using MG-63 cell spheroids as representative models, a proof-of-concept drug response study using doxorubicin hydrochloride was conducted. Overall, we demonstrate that the PHMAs are an innovative alternative to currently used 3D cell culture techniques, for the high-throughput generation of cell spheroids for disease modeling and drug screening applications.

A Decade of Organs-on-a-Chip Emulating Human Physiology at the Microscale: A Critical Status Report on Progress in Toxicology and Pharmacology

Organ-on-a-chip technology has the potential to accelerate pharmaceutical drug development, improve the clinical translation of basic research, and provide personalized intervention strategies. In the last decade, big pharma has engaged in many academic research cooperations to develop organ-on-a-chip systems for future drug discoveries. Although most organ-on-a-chip systems present proof-of-concept studies, miniaturized organ systems still need to demonstrate translational relevance and predictive power in clinical and pharmaceutical settings. This review explores whether microfluidic technology succeeded in paving the way for developing physiologically relevant human in vitro models for pharmacology and toxicology in biomedical research within the last decade. Individual organ-on-a-chip systems are discussed, focusing on relevant applications and highlighting their ability to tackle current challenges in pharmacological research.

Application of HepG2/C3A liver spheroids as a model system for genotoxicity studies

HepG2 cells continue to be a valuable tool in early drug discovery and pharmaceutical development. In the current study we develop a 3D in vitro liver model, using HepG2/C3A cells that is predictive of human genotoxic exposure. HepG2/C3A cells cultured for 7-days in agarose-coated microplates formed spheroids which were uniform in shape and had well defined outer perimeters and no evidence of a hypoxic core. Quantitative real-time-PCR analysis showed statistically significant transcriptional upregulation of xenobiotic metabolising genes (CYP1A1, CYP1A2, UG1A1, UGT1A3, UGT1A6, EPHX, NAT2) and genes linked to liver function (ALB, CAR) in 3D cultures. In response to three model pro-genotoxicants: benzo[a]pyrene, amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-aminoanthracene (2-AA), we observed further transcriptional upregulation of xenobiotic metabolising genes (CYP1A1, CYP1A2, NAT1/2, SULT1A2, UGT1A1, UGT1A3) compared to untreated spheroids. Consistent with this, spheroids were more sensitive than 2D monolayers to compound induced single- and double- stranded DNA-damage as assessed by the comet assay and γH2AX phosphorylation respectively. In contrast, levels of DNA-damage induced by the direct acting mutagen 4-nitroquinoline N-oxide (4NQO) was the same in spheroids and monolayers. In support of the enhanced genotoxic response in spheroids we also observed transcriptional upregulation of genes relating to DNA-damage and cellular stress response (e.g. GADD45A and CDKN1A) in spheroids. In conclusion, HepG2/C3A 3D spheroids are a sensitive model for in vitro genotoxicity assessment with potential applications in early stage drug development.

Do Patient-derived Spheroid Culture Models Have Relevance in Chondrosarcoma Research?

BACKGROUND

In high-grade chondrosarcoma, 5-year survival is lower than 50%. Therefore, it is important that preclinical models that mimic the disease with the greatest possible fidelity are used to potentially develop new treatments. Accumulating evidence suggests that two-dimensional (2-D) cell culture may not accurately represent the tumor's biology. It has been demonstrated in other cancers that three-dimensional (3-D) cancer cell spheroids may recapitulate tumor biology and response to treatment with greater fidelity than traditional 2-D techniques. To our knowledge, the formation of patient-derived chondrosarcoma spheroids has not been described.

QUESTIONS/PURPOSES

(1) Can patient-derived chondrosarcoma spheroids be produced? (2) Do spheroids recapitulate human chondrosarcoma better than 2-D cultures, both morphologically and molecularly? (3) Can chondrosarcoma spheroids provide an accurate model to test novel treatments?

METHODS

Experiments to test the feasibility of spheroid formation of chondrosarcoma cells were performed using HT-1080, an established chondrosarcoma cell line, and two patient-derived populations, TP19-S26 and TP19-S115. Cells were cultured in flasks, trypsinized, and seeded into 96-well ultra-low attachment plates with culture media. After spheroids formed, they were monitored daily by bright-field microscopy. Spheroids were fixed using paraformaldehyde and embedded in agarose. After dehydration with isopropanol, paraffin-embedded spheroids were sectioned, and slides were stained with hematoxylin and eosin. To compare differences and similarities in gene expression between 2-D and 3-D chondrosarcoma cultures and primary tumors, and to determine whether these spheroids recapitulated the biology of chondrosarcoma, RNA was extracted from 2-D cultures, spheroids, and tumors. Quantitative polymerase chain reaction was performed to detect chondrosarcoma markers of interest, including vascular endothelial growth factor alpha, hypoxia-inducible factor 1α, COL2A1, and COL10A1. To determine whether 2-D and 3-D cultures responded differently to novel chondrosarcoma treatments, we compared their sensitivities to disulfiram and copper chloride treatment. To test their sensitivity to disulfiram and copper chloride treatment, 10,000 cells were seeded into 96-well plates for 2-D culturing and 3000 cells in each well for 3-D culturing. After treating the cells with disulfiram and copper for 48 hours, we detected cell viability using quantitative presto-blue staining and measured via plate reader.

RESULTS

Cell-line and patient-derived spheroids were cultured and monitored over 12 days. Qualitatively, we observed that HT-1080 demonstrated unlimited growth, while TP19-S26 and TP19-S115 contracted during culturing relative to their initial size. Hematoxylin and eosin staining of HT-1080 spheroids revealed that cell-cell attachments were more pronounced at the periphery of the spheroid structure than at the core, while the core was less dense. Spheroids derived from the intermediate-grade chondrosarcoma TP19-S26 were abundant in extracellular matrix, and spheroids derived from the dedifferentiated chondrosarcoma TP19-S115 had a higher cellularity and heterogeneity with spindle cells at the periphery. In the HT-1080 cells, differences in gene expression were appreciated with spheroids demonstrating greater expressions of VEGF-α (1.01 ± 0.16 versus 6.48 ± 0.55; p = 0.003), COL2A1 (1.00 ± 0.10 versus 7.46 ± 2.52; p < 0.001), and COL10A1 (1.01 ± 0.19 versus 22.53 ± 4.91; p < 0.001). Differences in gene expressions were also noted between primary tumors, spheroids, and 2-D cultures in the patient-derived samples TP19-S26 and TP19-S115. TP19-S26 is an intermediate-grade chondrosarcoma. With the numbers we had, we could not detect a difference in VEGF-α and HIF1α gene expression compared with the primary tumor. COL2A1 (1.00 ± 0.14 versus 1.76 ± 0.10 versus 335.66 ± 31.13) and COL10A1 (1.06 ± 0.378 versus 5.98 ± 0.45 versus 138.82 ± 23.4) expressions were both greater in the tumor (p (COL2A1) < 0.001; p (COL10A1) < 0.0001) and 3-D cultures (p (COL2A1) = 0.004; p (COL10A1) < 0.0001) compared with 2-D cultures. We could not demonstrate a difference in VEGF-α and HIF1α expressions in TP19-S115, a dedifferentiated chondrosarcoma, in the tumor compared with 2-D and 3-D cultures. COL2A1 (1.00 ± 0.02 versus 1.86 ± 0.18 versus 2.95 ± 0.56) and COL10A1 (1.00 ± 0.03 versus 5.52 ± 0.66 versus 3.79 ± 0.36) expressions were both greater in spheroids (p (COL2A1) = 0.003; p (COL10A1) < 0.0001) and tumors (p (COL2A1) < 0.001; p (COL10A1) < 0.0001) compared with 2-D cultures. Disulfiram-copper chloride treatment demonstrated high cytotoxicity in HT-1080 and SW-1353 chondrosarcoma cells grown in the 2-D monolayer, but 3-D spheroids were highly resistant to this treatment.

CONCLUSION

We provide preliminary findings that it is possible to generate 3-D spheroids from chondrosarcoma cell lines and two human chondrosarcomas (one dedifferentiated chondrosarcoma and one intermediate-grade chondrosarcoma). Chondrosarcoma spheroids derived from human tumors demonstrated morphology more reminiscent of primary tumors than cells grown in 2-D culture. Spheroids displayed similar expressions of cartilage markers as the primary tumor, and we observed a higher expression of collagen markers in the spheroids compared with cells grown in monolayer. Spheroids also demonstrated greater chemotherapy resistance than monolayer cells, but more patient-derived spheroids are needed to further conclude that 3-D cultures may mimic the chemoresistance that chondrosarcomas demonstrate clinically. Additional studies on patient-derived chondrosarcoma spheroids are warranted.

CLINICAL RELEVANCE

Chondrosarcomas demonstrate resistance to chemotherapy and radiation, and we believe that if they can be replicated, models such as 3-D spheroids may provide a method to test novel treatments for human chondrosarcoma. Additional comprehensive genomic studies are required to compare 2-D and 3-D models with the primary tumor to determine the most effective way to study this disease in vitro.

Modeling the photodynamic effect in 2D versus 3D cell culture under normoxic and hypoxic conditions

BACKGROUND

Photodynamic therapy (PDT), mainly as a combined therapy, can still be considered a promising technology for targeted cancer treatment. Besides the several and essential benefits of PDT, there are some concerns and limitations, such as complex dosimetry, tumor hypoxia, and other mechanisms of resistance. In this study, we present how the cell culture model and cell culture conditions may affect the response to PDT treatment. It was studied by applying two different 3D cell culture, non-scaffold, and hydrogel-based models under normoxic and hypoxic conditions. In parallel, a detailed mechanism of the action of zinc phthalocyanine M2TG3 was presented.

METHODS

Hydrogel-based and tumor spheroids consisting of LNCaP cells, were used as 3D cell culture models in experiments performed under normoxic and hypoxic (1% of oxygen) conditions. Several analyses were performed to compare the activity of M2TG3 under different conditions, such as cytotoxicity, the level of proapoptotic and stress-related proteins, caspase activity, and antioxidant gene expression status. Additionally, we tested bioluminescence and fluorescence assays as a useful approach for a hydrogel-based 3D cell culture.

RESULTS

We found that M2TG3 might lead to apoptotic cancer cell death and is strongly dependent on the model and oxygen availability. Moreover, the expression of the genes modulated in the antioxidative system in 2D and 3D cell culture models were presented. The tested bioluminescence assay revealed several advantages, such as repetitive measurements on the same sample and simultaneous analysis of different parameters due to the non-lysing nature of this assay.

CONCLUSIONS

It was shown that M2TG3 can effectively cause cancer cell death via a different mechanism, depending on cell culture conditions such as the model and oxygen availability.

Physical Characterization of Colorectal Cancer Spheroids and Evaluation of NK Cell Infiltration Through a Flow-Based Analysis

To improve pathogenetic studies in cancer development and reliable preclinical testing of anti-cancer treatments, three-dimensional (3D) cultures, including spheroids, have been widely recognized as more physiologically relevant in vitro models of in vivo tumor behavior. Currently, the generation of uniformly sized spheroids is still challenging: different 3D cell culture methods produce heterogeneous populations in dimensions and morphology, that may strongly influence readouts reliability correlated to tumor growth rate or antitumor natural killer (NK) cell-mediated cytotoxicity. In this context, an increasing consensus claims the integration of microfluidic technologies within 3D cell culture, as the physical characterization of tumor spheroids is unavoidably demanded to standardize protocols and assays for in vitro testing. In this paper, we employed a flow-based method specifically conceived to measure weight, size and focused onto mass density values of tumor spheroids. These measurements are combined with confocal and digital imaging of such samples. We tested the spheroids of four colorectal cancer (CRC) cell lines that exhibit statistically relevant differences in their physical characteristics, even though starting from the same cell seeding density. These variations are seemingly cell line-dependent and associated with the number of growing cells and the degree of spheroid compaction as well, supported by different adenosine-triphosphate contents. We also showed that this technology can estimate the NK cell killing efficacy by measuring the weight loss and diameter shrinkage of tumor spheroids, alongside with the commonly used cell viability in vitro test. As the activity of NK cells relies on their infiltration rate, the in vitro sensitivity of CRC spheroids proved to be exposure time- and cell line-dependent with direct correlation to the cell viability reduction. All these functional aspects can be measured by the system and are documented by digital image analysis. In conclusion, this flow-based method potentially paves the way towards standardization of 3D cell cultures and its early adoption in cancer research to test antitumor immune response and set up new immunotherapy strategies.

Cytotoxicity, Retention, and Anti-inflammatory Effects of a CeO2 Nanoparticle-Based Supramolecular Complex in a 3D Liver Cell Culture Model

Both cerium oxide (CeOx) nanoparticles and mefenamic acid (MFA) are known anti-inflammatory agents with hepatoprotective properties and are therefore prescribed for one of the major diseases in the world, nonalcoholic fatty liver disease (NAFLD). To study the potential cytotoxicity and anti-inflammatory effects as well as drug retention of a potential therapeutic CeOx/MFA supramolecular complex, a well-standardized hepatic (HepG2) spheroid model was used. Results showed that the highest cytotoxicity for the CeOx/MFA supramolecular complex was found at 50 μg/mL, while effective doses of 0.1 and 1 μg/mL yielded a significant decrease of TNF-α and IL-8 secretion. Time-resolved analysis of HepG2 spheroids revealed a spatiotemporal distribution of the supramolecular complex and limited clearance from the internal microtissue over a period of 8 days in cultivation. In summary, our results point at rapid uptake, distribution, and biostability of the supramolecular complex within the HepG2 liver spheroid model as well as a significant anti-inflammatory response at noncytotoxic levels.

Issues with Cancer Spheroid Models in Therapeutic Drug Screening

In vitro screening for anti-cancer agents currently uses mainly cell lines in 2D culture. It is generally assumed that 3D culture, namely spheroids, represents physiologically more relevant models for tumors. Unfortunately, drug testing in spheroids is not as easy and reproducible as in 2D culture because there are factors that limit the universal use of spheroids as screening platforms. Technical problems in the generation of uniform spheroids, cell/tumor-specific differences in the ability to form spheroids, and more complex readout parameters are the main reasons for differences between spheroid data. The review discusses requirements for cancer spheroids to be representative models, suitable methodologies to generate spheroids for the screening and readout parameters for the evaluation of anti-cancer agents.

Characterization of In Vitro 3D Cell Model Developed from Human Hepatocellular Carcinoma (HepG2) Cell Line

In genetic toxicology, there is a trend against the increased use of in vivo models as highlighted by the 3R strategy, thus encouraging the development and implementation of alternative models. Two-dimensional (2D) hepatic cell models, which are generally used for studying the adverse effects of chemicals and consumer products, are prone to giving misleading results. On the other hand, newly developed hepatic three-dimensional (3D) cell models provide an attractive alternative, which, due to improved cell interactions and a higher level of liver-specific functions, including metabolic enzymes, reflect in vivo conditions more accurately. We developed an in vitro 3D cell model from the human hepatocellular carcinoma (HepG2) cell line. The spheroids were cultured under static conditions and characterised by monitoring their growth, morphology, and cell viability during the time of cultivation. A time-dependent suppression of cell division was observed. Cell cycle analysis showed time-dependent accumulation of cells in the G0/G1 phase. Moreover, time-dependent downregulation of proliferation markers was shown at the mRNA level. Genes encoding hepatic markers, metabolic phase I/II enzymes, were time-dependently deregulated compared to monolayers. New knowledge on the characteristics of the 3D cell model is of great importance for its further development and application in the safety assessment of chemicals, food products, and complex mixtures.

Ultrastructural Features of Gold Nanoparticles Interaction with HepG2 and HEK293 Cells in Monolayer and Spheroids

Use of multicellular spheroids in studies of nanoparticles (NPs) has increased in the last decade, however details of NPs interaction with spheroids are poorly known. We synthesized AuNPs (12.0 ± 0.1 nm in diameter, transmission electron microscopy (TEM data) and covered them with bovine serum albumin (BSA) and polyethyleneimine (PEI). Values of hydrodynamic diameter were 17.4 ± 0.4; 35.9 ± 0.5 and ±125.9 ± 2.8 nm for AuNPs, AuBSA-NPs and AuPEI-NPs, and Z-potential (net charge) values were −33.6 ± 2.0; −35.7 ± 1.8 and 39.9 ± 1.3 mV, respectively. Spheroids of human hepatocarcinoma (HepG2) and human embryo kidney (HEK293) cells (Corning ® spheroid microplates CLS4515-5EA), and monolayers of these cell lines were incubated with all NPs for 15 min–4 h, and fixed in 4% paraformaldehyde solution. Samples were examined using transmission and scanning electron microscopy. HepG2 and HEK2893 spheroids showed tissue-specific features and contacted with culture medium by basal plasma membrane of the cells. HepG2 cells both in monolayer and spheroids did not uptake of the AuNPs, while AuBSA-NPs and AuPEI-NPs readily penetrated these cells. All studied NPs penetrated HEK293 cells in both monolayer and spheroids. Thus, two different cell cultures maintained a type of the interaction with NPs in monolayer and spheroid forms, which not depended on NPs Z-potential and size.

Ready to go 3D? A semi-automated protocol for microwell spheroid arrays to increase scalability and throughput of 3D cell culture testing

3-dimensional (3D) cell cultures are being increasingly recognized as physiologically more relevant in vitro models than traditional monolayer cultures, because they better mimic in vivo-like microenvironment, cell-cell and cell-extracellular matrix interactions. Nevertheless, the broader use of 3D models might be limited by requirements for special consumables, equipment, or skills for 3D cell cultures, and by their limited throughput and scalability. In this study, we optimized and adapted a commercially available agarose-micromolding technique to produce scaffold-free spheroid cultures. Brightfield microscopy was used for routine nondestructive and noninvasive evaluation of spheroid formation and growth. The workflow is compatible with manual, as well as high speed automated microscopic image acquisition, and it is supplemented with an in-house developed macro 'Spheroid_Finder' for open source software Fiji to facilitate rapid automated image analysis. This protocol was used to characterize and quantify spheroid formation and growth of two different hepatic cell lines, hTERT immortalized, but non-cancerous, adult human liver stem cell line HL1-hT1, and human hepatocellular carcinoma cell line HepG2, as well as their responses to a model antiproliferative and cytotoxic agent, 5-fluorouracil. The complete protocol provides a simple and ready-to-use solution to initiate scaffold-free spheroid cultures in any laboratory with standard equipment for mammalian in vitro cell culture work. Thus, it allows to increase throughput and scale of spheroid culture experiments, which can be greatly utilized in different areas of biomedical, pharmaceutical and toxicological research.

Simplified low-cost methodology to establish, histologically process and analyze three-dimensional cancer cell spheroid arrays

Differently of two-dimensional cell culture, three-dimensional (3D) multicellular spheroid model allows cells to establish cell-cell/cell-matrix interactions over the entire cell surface, more closely mimicking tumor microenvironments and cellular subpopulations with specific standards of morphology, differentiation and gene expression. Thenceforth several methodologies involving or the 3D cell aggregates generation or its histological processing and analysis have emerged, but in general they are laborious, expensive and complex to set up as a routine technique. Thus, we developed a complete methodology, detailing a simple, accessible and low-cost step by step, including 1) the 3D cell aggregate generation using hanging drop technique; 2) providing a simple way to assess morphological parameters of generated spheroids; followed by 3) a multiple and organized histological processing, keeping several individual spheroids inside an agarose apparatus, maintaining a known order and position of each ones, similar to tissue microarray principle; 4) until the last step, where it is allowed a simultaneous histological composition analysis of several spheroid slices, organized side by side, in a same block section, through conventional stainings or 5) immunostaining against different molecular markers. Therefore, the present methodology aims to popularize 3D cell culture, allowing to make this a regular technique in basic cell biology research, once all steps are performed without using onerous reagents, materials or equipment. In addition to bring the agarose apparatus as a simple low cost novelty, allowing high-throughput analysis of several spheroids simultaneously in an organized manner.

Emerging trends in modeling human liver disease in vitro

The liver executes 500+ functions, such as protein synthesis, xenobiotic metabolism, bile production, and metabolism of carbohydrates/fats/proteins. Such functions can be severely degraded by drug-induced liver injury, nonalcoholic fatty liver disease, hepatitis B and viral infections, and hepatocellular carcinoma. These liver diseases, which represent a significant global health burden, are the subject of novel drug discovery by the pharmaceutical industry via the use of in vitro models of the human liver, given significant species-specific differences in disease profiles and drug outcomes. Isolated primary human hepatocytes (PHHs) are a physiologically relevant cell source to construct such models; however, these cells display a rapid decline in the phenotypic function within conventional 2-dimensional monocultures. To address such a limitation, several engineered platforms have been developed such as high-throughput cellular microarrays, micropatterned cocultures, self-assembled spheroids, bioprinted tissues, and perfusion devices; many of these platforms are being used to coculture PHHs with liver nonparenchymal cells to model complex cell cross talk in liver pathophysiology. In this perspective, we focus on the utility of representative platforms for mimicking key features of liver dysfunction in the context of chronic liver diseases and liver cancer. We further discuss pending issues that will need to be addressed in this field moving forward. Collectively, these in vitro liver disease models are being increasingly applied toward the development of new therapeutics that display an optimal balance of safety and efficacy, with a focus on expediting development, reducing high costs, and preventing harm to patients.

Euphorbia factor L2 inhibits TGF-β-induced cell growth and migration of hepatocellular carcinoma through AKT/STAT3

BACKGROUND

Euphorbia factor L2 has potent effects on ascites, hydropsy and cancers.

PURPOSE

We investigated the pharmacological effects of Euphorbia factor L2 (EFL2) on hepatocellular carcinoma (HCC).

METHODS

MTT assay was conducted to determine the proliferative activity of EFL2 on Hep G2 and SMMC-7721 cells. Wound-healing assay, colony formation assay, western blotting and quantitative PCR were carried out to examine the cell migration, p-AKT and p-STAT3 signaling. Moreover, we used human tumor xenograft BALB/c nude mice to detect the effect of EFL2 on HCC in vivo.

RESULTS

EFL2 inhibited the proliferation of SMMC-7721 and Hep G2 cells in concentration- and time-dependent manners. EFL2 also suppressed the cell migration and colony formation of hepatocellular carcinoma cells. Using a transforming growth factor-β (TGF-β)-induced epithelial-mesenchymal transition (EMT) model, we provided evidences that EFL2 could also inhibit TGF-β induced cell growth, vimentin, N-cadherin expressions, activation of p-AKT and p-STAT3, whereas up-regulate E-cadherin expression. Furthermore, EFL2 inhibited tumor growth and STAT3 phosphorylation in vivo.

CONCLUSION

In conclusion, EFL2 has the potential to be explored as a candidate treatment agent for HCC by inhibiting cell growth and migration both in vitro and in vivo.