Brain organoids: A revolutionary tool for modeling neurological disorders and development of therapeutics.

Brain organoids are self-organized, three-dimensional (3D) aggregates derived from pluripotent stem cells that have cell types and cellular architectures resembling those of the developing human brain. The current understanding of human brain developmental processes and neurological disorders has advanced significantly with the introduction of this in vitro model. Brain organoids serve as a translational link between two-dimensional (2D) cultures and in vivo models which imitate the neural tube formation at the early and late stages and the differentiation of neuroepithelium with whole-brain regionalization. In addition, the generation of region-specific brain organoids made it possible to investigate the pathogenic and etiological aspects of acquired and inherited brain disease along with drug discovery and drug toxicity testing. In this review article, we first summarize an overview of the existing methods and platforms used for generating brain organoids and their limitations and then discuss the recent advancement in brain organoid technology. In addition, we discuss how brain organoids have been used to model aspects of neurodevelopmental and neurodegenerative diseases, including autism spectrum disorder (ASD), Rett syndrome, Zika virus-related microcephaly, Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD).

Effect of paclitaxel priming on doxorubicin penetration in a multicellular layer model of human colorectal cancer cells.

Tumor priming is considered a promising strategy for improving drug distribution in malignant tissues. Multicellular layers (MCLs) of human cancer cells are potentially useful models for evaluating tumor-priming agents. We evaluated the priming effects of paclitaxel (PTX) on doxorubicin (DOX) penetration using MCLs of the human colorectal cancer cell lines including DLD-1, HCT-116, and HT-29. The penetration of DOX treated at 50 µM for 3 h was highly limited in all three MCLs. The penetration of the priming agent PTX into MCLs was determined using rhodamine-labeled PTX and appeared to be cell line-dependent: full penetration was observed in HCT-116 and HT-29 MCLs, whereas only limited penetration occurred in DLD-1 MCLs. PTX pretreatment at 20 µM for 24 or 48 h induced a tumor-priming effect in DOX distribution, with a 3 to 5.6-fold-increase in HCT-116 and HT-29 MCLs but a less than two-fold increase in DLD-1 MCLs. PTX treatment decreased fibronectin expression in HCT-116 and HT-29 MCLs but not in DLD-1, suggesting that the prominent priming effect of PTX in HCT-116 and HT-29 MCLs may be associated with the downregulation of fibronectin expression. Our study demonstrated that MCLs of human cancer cells are a useful model not only for the study of drug penetration into tumor tissues but also for screening and evaluating tumor-priming agents.

Suppression of the antitumoral activity of natural killer cells under indirect coculture with cancer-associated fibroblasts in a pancreatic TIME-on-chip model.

BACKGROUND: Recently, natural killer (NK) cells emerged as a treatment option for various solid tumors. However, the immunosuppressive tumor immune microenvironment (TIME) can reduce the cytotoxic ability of NK cells in pancreatic ductal adenocarcinoma. Cancer-associated fibroblasts within the tumor stroma can suppress immune surveillance by dysregulating factors involved in the cellular activity of NK cells. Herein, the effect of activated pancreatic stellate cells (aPSCs) on NK cell-mediated anticancer efficacy under three-dimensional (3D) coculture conditions was investigated. METHODS: 3D cocultures of PANC-1 tumor spheroids (TSs) with aPSCs and NK-92 cells in a collagen matrix were optimized to identify the occurring cellular interactions and differential cytokine profiles in conditioned media using microchannel chips. PANC-1 TSs and aPSCs were indirectly cocultured, whereas NK-92 cells were allowed to infiltrate the TS channel using convective medium flow. RESULTS: Coculture with aPSCs promoted PANC-1 TSs growth and suppressed the antitumor cytotoxic effects of NK-92 cells. Mutual inhibition of cellular activity without compromising migration ability was observed between aPSCs and NK-92 cells. Moreover, the reduced killing activity of NK-92 cells was found to be related with reduced granzyme B expression in NK cells. CONCLUSIONS: Herein, a novel TIME-on-chip model based on the coculture of PANC-1 TSs, aPSCs, and NK-92 cells was described. This model may be useful for studying the detailed mechanisms underlying NK cells dysregulation and for exploring future therapeutic interventions to restore NK cell activity in the tumor microenvironment.

High-throughput multiplex assays with mouse macrophages on pillar plate platforms.

It is challenging to rapidly identify immune responses that reflect the state and capability of immune cells due to complex heterogeneity of immune cells and their plasticity to pathogens and modulating molecules. Thus, high-throughput and easy-to-use cell culture and analysis platforms are highly desired for characterizing complex immune responses and elucidating their underlying mechanisms as well. In response to this need, we have developed a micropillar chip and a 384-pillar plate, printed mouse macrophage, RAW 264.7 cell line in alginate on the pillar plate platforms, and established multiplex cell-based assays to rapidly measure cell viability, expression of cell surface markers, and secretion of cytokines upon stimulation with model compound, lipopolysaccharide (LPS), as well as synthetic N-glycan polymers that mimic native glycoconjugates and could bind to lectin receptors on RAW 264.7 cells. Interestingly, changes in RAW 264.7 cell viability, expression levels of cell surface makers, and release of cytokines measured from the pillar plate platforms in the presence and absence of LPS were well correlated with those obtained from their counterpart, the 96-well plate with 2D-cultured macrophages. With this approach, we identified that α2,3-linked N-sialyllactose polymer has significant macrophage modulation activity among the N-glycan polymers tested. Therefore, we successfully demonstrated that our pillar plate platforms with 3D-cultured macrophages can streamline immune cell imaging and analysis in high throughput in response to compound stimulation. We envision that the pillar plate platforms could potentially be used for rapid characterization of immune cell responses and for screening immune cell-modulating molecules.

Pediatric glioblastoma cells inhibit neurogenesis and promote astrogenesis, phenotypic transformation and migration of human neural progenitor cells within cocultures.

Neural progenitor cell (NPC) fate is influenced by a variety of biological cues elicited from the surrounding microenvironment and recent studies suggest their possible role in pediatric glioblastoma multiforme (GBM) development. Since a few GBM cells also display NPC characteristics, it is not clear whether NPCs transform to tumor cell phenotype leading to the onset of GBM formation, or NPCs migrate to developing tumor sites in response to paracrine signaling from GBM cells. Elucidating the paracrine interactions between GBM cells and NPCs in vivo is challenging due to the inherent complexity of the CNS. Here, we investigated the interactions between human NPCs (ReNcell) and human pediatric GBM-derived cells (SJ-GBM2) using a Transwell® coculture setup to assess the effects of GBM cells on ReNcells (cytokine and chemokine release, viability, phenotype, differentiation, migration). Standalone ReNcell or GBM cultures served as controls. Qualitative and quantitative results from ELISA®, Live/Dead® and BrdU assays, immunofluorescence labeling, western blot analysis, and scratch test suggests that although ReNcell viability remained unaffected in the presence of pediatric GBM cells, their morphology, phenotype, differentiation patterns, neurite outgrowth, migration patterns (average speed, distance, number of cells) and GSK-3ß expression were significantly influenced. The cumulative distance migrated by the cells in each condition was fit to Furth's formula, derived formally from Ornstein-Uhlenbeck process. ReNcell differentiation into neural lineage was compromised and astrogenesis promoted within cocultures. Such coculture platform could be extended to identify the specific molecules contributing to the observed phenomena, to investigate whether NPCs could be transplanted to replace lesions of excised tumor sites, and to elucidate the underlying molecular pathways involved in GBM-NPC interactions within the tumor microenvironment.

3D-cultured neural stem cell microarrays on a micropillar chip for high-throughput developmental neurotoxicology.

Numerous chemicals including environmental toxicants and drugs have not been fully evaluated for developmental neurotoxicity. A key gap exists in the ability to predict accurately and robustly in vivo outcomes based on in vitro assays. This is particularly the case for predicting the toxicity of chemicals on the developing human brain. A critical need for such in vitro assays is choice of a suitable model cell type. To that end, we have performed high-throughput in vitro assessment of proliferation and differentiation of human neural stem cells (hNSCs). Conventional in vitro assays typically use immunofluorescence staining to quantify changes in cell morphology and expression of neural cell-specific biomarkers, which is often time-consuming and subject to variable specificities of available antibodies. To alleviate these limitations, we developed a miniaturized, three-dimensional (3D) hNSC culture with ReNcell VM on microarray chip platforms and established a high-throughput promoter-reporter assay system using recombinant lentiviruses on hNSC spheroids to assess cell viability, self-renewal, and differentiation. Optimum cell viability and spheroid formation of 3D ReNcell VM culture were observed on a micropillar chip over a period of 9 days in a mixture of 0.75% (w/v) alginate and 1 mg/mL growth factor reduced (GFR) Matrigel with 25 mM CaCl2 as a crosslinker for alginate. In addition, 3D ReNcell VM culture exhibited self-renewal and differentiation on the microarray chip platform, which was efficiently monitored by enhanced green fluorescent protein (EGFP) expression of four NSC-specific biomarkers including sex determining region Y-box 2 (SOX2), glial fibrillary acidic protein (GFAP), synapsin1, and myelin basic protein (MBP) with the promoter-reporter assay system.

Biophysical and biomechanical properties of neural progenitor cells as indicators of developmental neurotoxicity.

Conventional in vitro toxicity studies have focused on identifying IC50 and the underlying mechanisms, but how toxicants influence biophysical and biomechanical changes in human cells, especially during developmental stages, remain understudied. Here, using an atomic force microscope, we characterized changes in biophysical (cell area, actin organization) and biomechanical (Young's modulus, force of adhesion, tether force, membrane tension, tether radius) aspects of human fetal brain-derived neural progenitor cells (NPCs) induced by four classes of widely used toxic compounds, including rotenone, digoxin, N-arachidonoylethanolamide (AEA), and chlorpyrifos, under exposure up to 36 h. The sub-cellular mechanisms (apoptosis, mitochondria membrane potential, DNA damage, glutathione levels) by which these toxicants induced biochemical changes in NPCs were assessed. Results suggest a significant compromise in cell viability with increasing toxicant concentration (p < 0.01), and biophysical and biomechanical characteristics with increasing exposure time (p < 0.01) as well as toxicant concentration (p < 0.01). Impairment of mitochondrial membrane potential appears to be the most sensitive mechanism of neurotoxicity for rotenone, AEA and chlorpyrifos exposure, but compromise in plasma membrane integrity for digoxin exposure. The surviving NPCs remarkably retained stemness (SOX2 expression) even at high toxicant concentrations. A negative linear correlation (R2 = 0.92) exists between the elastic modulus of surviving cells and the number of living cells in that environment. We propose that even subtle compromise in cell mechanics could serve as a crucial marker of developmental neurotoxicity (mechanotoxicology) and therefore should be included as part of toxicology assessment repertoire to characterize as well as predict developmental outcomes.

High-throughput metabolism-induced toxicity assays demonstrated on a 384-pillar plate.

The US Environmental Protection Agency (EPA) launched the Transform Tox Testing Challenge in 2016 with the goal of developing practical methods that can be integrated into conventional high-throughput screening (HTS) assays to better predict the toxicity of parent compounds and their metabolites in vivo. In response to this need and to retrofit existing HTS assays for assessing metabolism-induced toxicity of compounds, we have developed a 384-pillar plate that is complementary to traditional 384-well plates and ideally suited for culturing human cells in three dimensions at a microscale. Briefly, human embryonic kidney (HEK) 293 cells in a mixture of alginate and Matrigel were printed on the 384-pillar plates using a microarray spotter, which were coupled with 384-well plates containing nine model compounds provided by the EPA, five representative Phase I and II drug metabolizing enzymes (DMEs), and one no enzyme control. Viability and membrane integrity of HEK 293 cells were measured with the calcein AM and CellTiter-Glo® kit to determine the IC50 values of the nine parent compounds and DME-generated metabolites. The Z' factors and the coefficient of variation measured were above 0.6 and below 14%, respectively, indicating that the assays established on the 384-pillar plate are robust and reproducible. Out of nine compounds tested, six compounds showed augmented toxicity with DMEs and one compound showed detoxification with a Phase II DME. This result indicates that the 384-pillar plate platform can be used to measure metabolism-induced toxicity of compounds in high-throughput with individual DMEs. As xenobiotics metabolism is a complex process with a variety of DMEs involved, the predictivity of our approach could be further improved with mixtures of DMEs.

Prediction of metabolism-induced hepatotoxicity on three-dimensional hepatic cell culture and enzyme microarrays.

Human liver contains various oxidative and conjugative enzymes that can convert nontoxic parent compounds to toxic metabolites or, conversely, toxic parent compounds to nontoxic metabolites. Unlike primary hepatocytes, which contain myriad drug-metabolizing enzymes (DMEs), but are difficult to culture and maintain physiological levels of DMEs, immortalized hepatic cell lines used in predictive toxicity assays are easy to culture, but lack the ability to metabolize compounds. To address this limitation and predict metabolism-induced hepatotoxicity in high-throughput, we developed an advanced miniaturized three-dimensional (3D) cell culture array (DataChip 2.0) and an advanced metabolizing enzyme microarray (MetaChip 2.0). The DataChip is a functionalized micropillar chip that supports the Hep3B human hepatoma cell line in a 3D microarray format. The MetaChip is a microwell chip containing immobilized DMEs found in the human liver. As a proof of concept for generating compound metabolites in situ on the chip and rapidly assessing their toxicity, 22 model compounds were dispensed into the MetaChip and sandwiched with the DataChip. The IC50 values obtained from the chip platform were correlated with rat LD50 values, human C max values, and drug-induced liver injury categories to predict adverse drug reactions in vivo. As a result, the platform had 100% sensitivity, 86% specificity, and 93% overall predictivity at optimum cutoffs of IC50 and C max values. Therefore, the DataChip/MetaChip platform could be used as a high-throughput, early stage, microscale alternative to conventional in vitro multi-well plate platforms and provide a rapid and inexpensive assessment of metabolism-induced toxicity at early phases of drug development.

High-throughput screening (HTS) of anticancer drug efficacy on a micropillar/microwell chip platform.

Contemporary cancer therapy refers to treatment based on genetic abnormalities found in patient's tumor. However, this approach is faced with numerous challenges, including tumor heterogeneity and molecular evolution, insufficient tumor samples available along with genetic information linking to clinical outcomes, lack of therapeutic drugs containing pharmacogenomic information, and technical limitations of rapid drug efficacy tests with insufficient quantities of primary cancer cells from patients. To address these problems and improve clinical outcomes of current personalized gene-targeted cancer therapy, we have developed a micropillar/microwell chip platform, which is ideally suited for encapsulating primary cancer cells in nanoscale spots of hydrogels on the chip, generating efficacy data with various drugs, eventually allowing for a comparison of the in vitro data obtained from the chip with clinical data as well as gene expression data. As a proof of concept in this study, we have encapsulated a U251 brain cancer cell line and three primary brain cancer cells from patients (448T, 464T, and 775T) in 30 nL droplets of alginate and then tested the therapeutic efficacy of 24 anticancer drugs by measuring their dose responses. As a result, the IC50 values of 24 anticancer drugs obtained from the brain cancer cells clearly showed patient cell-specific efficacy, some of which were well-correlated with their oncogene overexpression (c-Met and FGFR1) as well as the in vivo previous results of the mouse xenograft model with the three primary brain cancer cells.

High-throughput, miniaturized clonogenic analysis of a limiting dilution assay on a micropillar/microwell chip with brain tumor cells.

The limiting dilution assay (LDA) is a clonogenic drug efficacy test designed to determine a value for drug efficacy based on an all-or-none (positive or negative) response within replicates. It also attempts to calculate minimum cell numbers for cells to form colony in each drugged conditions, wherein a large value implies high drug efficacy (as a large number of extant cells are required to start a colony). However, traditional LDAs are time-consuming to set up, often requiring many replicates for statistical analysis, and manual colony identification under a microscope to determine a positive or negative response is tedious and is susceptible to human error. To address these issues, a high-throughput miniaturized LDA assay is developed using a micropillar/microwell chip platform using an automatic colony identification method. Three glioblastoma multiforme (GBM) brain tumor isolates (448T, 464T, and 775T) are used to test this new assay, using the c-Met kinase inhibitors SU11274 and PHA665752 as the target drugs. The results show that the minimum cell number of 775T is larger than that of the other two cell types (SU11274 and PHA665752) in both the sampled drugs, a result that is in good agreement with the results of previous conventional experiments using 96 well plates.

Application of the DataChip/MetaChip technology for the evaluation of ajoene toxicity in vitro.

The DataChip is a universal platform for three-dimensional (3D) cell cultures on a micropillar chip, which can be applicable to a variety of human cells to simulate organ-specific toxicity. In addition, the MetaChip is developed for various combinations of drug metabolizing enzymes that can be spotted into the microwell chip and incubated with 3D human cells to simulate systematic compound metabolism in the human liver on a microscale format. Ajoenes have been known for various therapeutics activities, including anticancer effects, but there was limited information available in regard to their metabolism and cytotoxicity. In the present work, the metabolism-mediated toxicity of ajoenes was evaluated on a DataChip/MetaChip platform. In detail, we tested cytotoxicity of E- and Z-ajoene on 3D cultured Hep3B human hepatoma cells coupled with mixtures of drug metabolizing enzymes. Metabolic profiles of ajoenes were assessed with 23 representative drug metabolizing enzymes on the MetaChip. As a result, cytotoxicity of E-ajoene was significantly augmented in the presence of cytochrome P450 (CYP) isoforms, such as CYP2E1 and CYP3A5. Both E- and Z-ajoene were drastically detoxified in the presence of Phase II enzymes, including major UGTs, SULTs, NATs, and GSTs. Interestingly, All Mix, an artificial human liver microsome containing representative P450 mixture and phase II enzyme mixture, attenuated P450-induced cytotoxicity of ajoenes. Conclusively, we were able to confirm the metabolism-medicated toxicity of ajoenes on the chip.

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.

High-Throughput Assessment of Metabolism-Mediated Neurotoxicity by Co-Culture of Neurospheres and Liver Spheroids.

The liver's role in the biotransformation of chemicals is critical for both augmented toxicity and detoxification. However, there has been a significant lack of effort to integrate biotransformation into in vitro neurotoxicity testing. Traditional in vitro neurotoxicity testing systems are unable to assess the qualitative and quantitative differences between parent chemicals and their metabolites as they would occur in the human body. As a result, traditional in vitro toxicity screening systems cannot incorporate hepatic biotransformation to predict the neurotoxic potential of chemical metabolites. To bridge this gap, a high-throughput, metabolism-mediated neurotoxicity testing system has been developed, which combines metabolically competent HepaRG cell spheroids with a three-dimensional (3D) culture of ReNcell VM human neural progenitor cell line. The article outlines protocols for generating HepaRG cell spheroids using an ultralow attachment (ULA) 384-well plate and for cultivating ReNcell VM in 3D on a 384-pillar plate with sidewalls and slits (384PillarPlate). Metabolically sensitive test compounds are introduced into the ULA 384-well plate containing HepaRG spheroids and then tested with 3D-cultured ReNcell VM on the 384PillarPlate. This configuration permits the in situ generation of metabolites by HepaRG cells and their subsequent testing on neurospheres. By analyzing cell viability data, researchers can determine the IC50 values for each compound, thus evaluating metabolism-mediated neurotoxicity. © 2024 Wiley Periodicals LLC. Basic Protocol 1: HepaRG spheroid culture in an ultralow attachment (ULA) 384-well plate and the assessment of drug-metabolizing enzyme (DME) activities Basic Protocol 2: 3D neural stem cell (NSC) culture on a 384PillarPlate and compound treatment for the assessment of metabolism-mediated neurotoxicity Basic Protocol 3: Image acquisition, processing, and data analysis.

Self-assembling peptides induced by eyes absent enzyme to boost the efficacy of doxorubicin therapy in drug-resistant breast cancer cells.

Enzyme-induced self-assembly (EISA) is a recently developed nanotechnology technique in which small molecules are induced by cellular enzymes self-assembling into nanostructures inside cancer cells. This technique can boost the efficacy of chemotherapy drugs by avoiding drug efflux, inhibiting the cells' DNA repair mechanisms, and targeting the mitochondria. In this work, we study the self-assembly of a short peptide and its fluorescence analogue induced by Eyes absent (EYA) tyrosine phosphatases to boost the efficacy of doxorubicin (DOX) therapy in drug-resistant types of breast cancer cells, MDA-MB-231 and MCF-7. The peptides Fmoc-FF-YP and NBD-FF-YP were synthesized with the solid-phase peptide synthesis (SPPS) method and analyzed with HPLC and MALDI-TOF. Dynamic light scattering was used to determine the size distribution of peptides exposed to the EYA enzyme in vitro. The presence of EYA enzymes in breast cancer cells was confirmed using the western blotting assay. The intracellular location of the peptide self-assembly was studied by imaging fluorescence NBD-tagged peptides. The efficacy of the peptide alone and with DOX was determined against MCF-7 and MDA-MB-231 using MTT and LIVE-DEAD assays. Nucleus and cytoplasm F-actin (Phalloidin) staining was used to determine cell morphology changes in response to the combination therapy of peptides/DOX. At an optimal concentration, the peptides are not toxic to the cells; however, they boost the efficacy of DOX against drug-resistant breast cancer cells. We used state-of-the-art computer-aided techniques to predict the molecular structure of peptides and their interactions with EYA. This study demonstrates an approach for incorporating non-cytotoxic components into DOX combination therapy, thereby avoiding increased systemic burden or adverse effects.

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.

Uniform cerebral organoid culture on a pillar plate by simple and reproducible spheroid transfer from an ultralow attachment well plate.

Human induced pluripotent stem cell (iPSC)-derived brain organoids have potential to recapitulate the earliest stages of brain development, serving as an effectivein vitromodel for studying both normal brain development and disorders. However, current brain organoid culture methods face several challenges, including low throughput, high variability in organoid generation, and time-consuming, multiple transfer and encapsulation of cells in hydrogels throughout the culture. These limitations hinder the widespread application of brain organoids including high-throughput assessment of compounds in clinical and industrial lab settings. In this study, we demonstrate a straightforward approach of generating multiple cerebral organoids from iPSCs on a pillar plate platform, eliminating the need for labor-intensive, multiple transfer and encapsulation steps to ensure the reproducible generation of cerebral organoids. We formed embryoid bodies in an ultra-low attachment 384-well plate and subsequently transferred them to the pillar plate containing Matrigel, using a straightforward sandwiching and inverting method. Each pillar on the pillar plate contains a single spheroid, and the success rate of spheroid transfer was in a range of 95%-100%. Using this approach, we robustly generated cerebral organoids on the pillar plate and demonstrated an intra-batch coefficient of variation below 9%-19% based on ATP-based cell viability and compound treatment. Notably, our spheroid transfer method in combination with the pillar plate allows miniaturized culture of cerebral organoids, alleviates the issue of organoid variability, and has potential to significantly enhance assay throughput by allowingin situorganoid assessment as compared to conventional organoid culture in 6-/24-well plates, petri dishes, and spinner flasks.

Cryopreservation of Neuroectoderm on a Pillar Plate and In Situ Differentiation into Human Brain Organoids.

Cryopreservation in cryovials extends cell storage at low temperatures, and advances in organoid cryopreservation improve reproducibility and reduce generation time. However, cryopreserving human organoids presents challenges due to the limited diffusion of cryoprotective agents (CPAs) into the organoid core and the potential toxicity of these agents. To overcome these obstacles, we developed a cryopreservation technique using a pillar plate platform. To demonstrate cryopreservation application to human brain organoids (HBOs), early stage HBOs were produced by differentiating induced pluripotent stem cells (iPSCs) into neuroectoderm (NE) in an ultralow attachment (ULA) 384-well plate. The NE was transferred and encapsulated in Matrigel on the pillar plate. The NE on the pillar plate was exposed to four commercially available CPAs, including the PSC cryopreservation kit, CryoStor CS10, 3dGRO, and 10% DMSO, before being frozen overnight at -80 °C and subsequently stored in a liquid nitrogen dewar. We examined the impact of the CPA type, organoid size, and CPA exposure duration on cell viability post-thaw. Additionally, the differentiation of NE into HBOs on the pillar plate was assessed using RT-qPCR and immunofluorescence staining. The PSC cryopreservation kit proved to be the least toxic for preserving the early stage HBOs on the pillar plate. Notably, smaller HBOs showed higher cell viability postcryopreservation than larger ones. An incubation period of 80 min with the PSC kit was essential to ensure optimal CPA diffusion into HBOs with a diameter of 400-600 µm. These cryopreserved early stage HBOs successfully matured over 30 days, exhibiting gene expression patterns akin to noncryopreserved HBOs. The cryopreserved early stage HBOs on the pillar plate maintained high viability after thawing and successfully differentiated into mature HBOs. This on-chip cryopreservation method could extend to other small organoids, by integrating cryopreservation, thawing, culturing, staining, rinsing, and imaging processes within a single system, thereby preserving the 3D structure of the organoids.

Dynamic culture of cerebral organoids using a pillar/perfusion plate for the assessment of developmental neurotoxicity.

Despite the potential toxicity of commercial chemicals to the development of the nervous system (known as developmental neurotoxicity or DNT), conventionalin vitrocell models have primarily been employed for the assessment of acute neuronal toxicity. On the other hand, animal models used for the assessment of DNT are not physiologically relevant due to the heterogenic difference between humans and animals. In addition, animal models are low-throughput, time-consuming, expensive, and ethically questionable. Recently, human brain organoids have emerged as a promising alternative to assess the detrimental effects of chemicals on the developing brain. However, conventional organoid culture systems have several technical limitations including low throughput, lack of reproducibility, insufficient maturity of organoids, and the formation of the necrotic core due to limited diffusion of nutrients and oxygen. To address these issues and establish predictive DNT models, cerebral organoids were differentiated in a dynamic condition in a unique pillar/perfusion plate, which were exposed to test compounds to evaluate DNT potential. The pillar/perfusion plate facilitated uniform, dynamic culture of cerebral organoids with improved proliferation and maturity by rapid, bidirectional flow generated on a digital rocker. Day 9 cerebral organoids in the pillar/perfusion plate were exposed to ascorbic acid (DNT negative) and methylmercury (DNT positive) in a dynamic condition for 1 and 3 weeks, and changes in organoid morphology and neural gene expression were measured to determine DNT potential. As expected, ascorbic acid did not induce any changes in organoid morphology and neural gene expression. However, exposure of day 9 cerebral organoids to methylmercury resulted in significant changes in organoid morphology and neural gene expression. Interestingly, methylmercury did not induce adverse changes in cerebral organoids in a static condition, thus highlighting the importance of dynamic organoid culture in DNT assessment.

Enhanced Maturity and Functionality of Vascularized Human Liver Organoids through 3D Bioprinting and Pillar Plate Culture.

Liver tissues, composed of hepatocytes, cholangiocytes, stellate cells, Kupffer cells, and sinusoidal endothelial cells, are differentiated from endodermal and mesodermal germ layers. By mimicking the developmental process of the liver, various differentiation protocols have been published to generate human liver organoids (HLOs) in vitro using induced pluripotent stem cells (iPSCs). However, HLOs derived solely from the endodermal germ layer often encounter technical hurdles, such as insufficient maturity and functionality, limiting their utility for disease modeling and hepatotoxicity assays. To overcome this, we separately differentiated EpCAM+ endodermal progenitor cells (EPCs) and mesoderm-derived vascular progenitor cells (VPCs) from the same human iPSC line. These cells were then mixed in BME-2 matrix and concurrently differentiated into vascular human liver organoids (vHLOs). Remarkably, vHLOs exhibited significantly higher maturity than vasculature-free HLOs, as demonstrated by increased coagulation factor secretion, albumin secretion, drug-metabolizing enzyme (DME) expression, and bile acid transportation. To enhance assay throughput and miniaturize vHLO culture, we 3D bioprinted expandable HLOs (eHLOs) in BME-2 matrix on a pillar plate platform derived from EPCs and VPCs and compared with HLOs derived from endoderm alone. Compared to HLOs cultured in a 50 µL BME-2 matrix dome in a 24-well plate, vHLOs cultured on the pillar plate exhibited superior maturity, likely due to enhanced nutrient and signaling molecule diffusion. The integration of physiologically relevant patterned liver organoids with the unique pillar plate platform enhanced the capabilities for high-throughput screening and disease modeling.