Mol. Cells 2022; 45(2): 53-64
Published online February 16, 2022
https://doi.org/10.14348/molcells.2022.2019
© The Korean Society for Molecular and Cellular Biology
Correspondence to : woongsun@korea.ac.kr
This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/.
Three-dimensional cultures of human neural tissue/organlike structures in vitro can be achieved by mimicking the developmental processes occurring in vivo. Rapid progress in the field of neural organoids has fueled the hope (and hype) for improved understanding of brain development and functions, modeling of neural diseases, discovery of new drugs, and supply of surrogate sources of transplantation. In this short review, we summarize the state-of-the-art applications of this fascinating tool in various research fields and discuss the reality of the technique hoping that the current limitations will soon be overcome by the efforts of ingenious researchers.
Keywords central nervous system, human pluripotent stem cells, in vitro modeling, neurodevelopment, neurological disorders, organoid
The advent of new techniques often drives new discoveries that can change our concepts in science. It is likely that three-dimensional (3D) culture of brain-like organoids is one such technique. After the first report on the 3D culture of neural cell aggregates that exhibit some aspects of brain histoarchitecture (Eiraku et al., 2008), there has been an explosion of technical improvements in culture methods, and new discoveries have been made using these techniques (Kadoshima et al., 2013; Lancaster et al., 2013; Nakano et al., 2012; Qian et al., 2016; Warmflash et al., 2014). These 3D cultures of neural cell aggregates, collectively called neural organoids (NOs), are formed by recapitulating the developmental processes and organization of the developing human brain
NOs are produced by mimicking developmental processes, and our knowledge about neural development is the most important resource for the establishment of protocols for the region-specific NO production. Typically, protocols for NO generation consist of 3-4 steps, each mimicking the continuous but conceptually segregated
During the maturation period, NO exhibits many features of histogenesis including migration, neurogenesis, and laminar formation. Studies on cerebral organoids have demonstrated the formation of human-specific outer subventricular zone neurogenic niches, highlighting that hPSC-derived NOs recapitulate the human-specific features of brain development (Bershteyn et al., 2017; Kadoshima et al., 2013; Lancaster et al., 2013; Qian et al., 2016). An extended NO culture can reproduce gliogenesis and myelination, which mainly occur during the postnatal stages (Bershteyn et al., 2017; James et al., 2021; Madhavan et al., 2018; Shaker et al., 2021). However, the occurrence of these postnatal events does not directly indicate that the NO reaches mature stages resembling the postnatal brain. Transcriptome or epigenome analyses suggest that an approximately 10-month culture is required to obtain perinatal features, even though gliogenesis is evident by 2-4 months of culture (Amiri et al., 2018; Gordon et al., 2021; Yoon et al., 2019). These discrepancies might be caused by the protocols for NO production, asynchronized developmental progress in NOs, and different experimental sensitivities/methodologies. Considering that later brain development is more influenced by nearby structures and cell migration across embryonic brain regions, and that neural circuit formation with other brain regions is essential for later brain development (Tau and Peterson, 2010; Valiente and Marín, 2010), regionally isolated NOs cannot replicate this interaction-based neural development. Further, non-neural lineage cell populations, such as blood vessels and microglia (Adams and Eichmann, 2010; Lenz and Nelson, 2018), also play important roles in brain development, which cannot be generated by simple NO induction. Accordingly, many approaches to include multiple components in NO have successfully demonstrated that some aspects of these insufficiencies can be overcome by complex technologies such as fusion, assembly, connection, and polarization (Fig. 2).
Cumulative results have demonstrated that NOs faithfully replicate many aspects of the developmental progress of the human brain. Thus, NOs provide a great opportunity to glimpse human brain development
Modeling human brain diseases using NO technology is one of the major goals that researchers pursue. Considering that NOs are produced via a developmental program for organogenesis, modeling developmental defects were immediately addressed upon the advent of the NO technique. Observation of known developmental defects with specific genetic mutations in NO cultures is considered
Defects in later developmental programs often do not exhibit overt morphological changes; therefore, more precise analyses with physiological tools are required. Methods for detecting the physiological responses of NOs have been widely used only recently (Osaki and Ikeuchi, 2021; Trujillo et al., 2019; Zafeiriou et al., 2020), and the physiological defects in these models are only beginning to be reported (Andersen et al., 2020; Birey et al., 2017; Mariani et al., 2015; Samarasinghe et al., 2021; Ye et al., 2017). For instance, epileptic episodes can be recognized by altered neuronal burst activity and local field potentials. Accordingly, using these physiological tools, Rett’s syndrome and Schizophrenia were successfully modeled using NOs derived from patient iPS cells (Samarasinghe et al., 2021; Ye et al., 2017). The use of NOs for psychiatric diseases is more challenging because these pathologies are known to be associated with neural circuit formation, synaptic plasticity, and other sophisticated abnormalities without gross signs of structural changes (Das et al., 2020; McTeague et al., 2017; Van Spronsen and Hoogenraad, 2010). Many brain regions are involved in the pathogenesis of psychiatric diseases, and region-specific NOs may have limited potential to exhibit these circuit-dependent pathologies. Furthermore, psychiatric diseases are often modeled in experimental animals exhibiting similar behavioral defects. However, the current NO models have limited complexity compared to multiregional neural circuits
NOs have also been successfully used to model neurodegenerative diseases. NOs produced from iPSCs of patients with Alzheimer’s disease (AD)-related mutations exhibit AD-like symptoms, such as amyloid-beta deposits (Jack et al., 2010; Murphy and LeVine, 2010). The NO-based Parkinson’s disease model has also been reported to exhibit Lewy body-like inclusions and alpha-synuclein aggregations (Jo et al., 2021). It is unclear why these late-onset symptoms in aged human patients were observed in the NOs, which replicate a much younger aged brain. It is plausible that the current ‘standard’ cultures of NO may be pro-degenerative owing to non-humanized media and the lack of sufficient signals/factors for healthy growth, which is presumably supplied from the blood or other parts of the body
In terms of disease modeling, there have been many significant attempts to upgrade NO culture systems suitable for high-throughput screening (HTS). At least two important features have been addressed and improved to achieve this goal. First, the variability of NOs in different batches and within batches should be precisely controlled. Notably, the NO induction response is highly dependent on batches. It is unclear what causes these differences, but it is predictable that the quality and/or condition of hPSCs may greatly affect the consequences of treatment. Further, the format of cell culture may affect the homogeneity of cellular responses regardless of batches. For instance, because cultured hPSCs in 3D appear to exhibit more variable responses to induction reagents depending on their relative position in the cluster, there have been attempts to induce hPSCs into neural-lineage cells in 2D (Lee et al., 2020; Renner et al., 2020). The resultant 'primed' neural-fate cells can then be dissociated and reaggregated into 3D spheroids with a precisely controlled number of cells. These 3D spheroids can also form a brain histoarchitecture as seen in 3D-initiated NOs. These approaches have obvious benefits in terms of quantifiability because better control of the initial cell number and conditions strongly contributes to the reduction of variations. Considering that this approach may sacrifice some aspects of the histoarchitectures in conventional NOs, it is especially suitable for producing NOs for brain regions where the histoarchitecture is less obvious or ignorable. Second, culture formation should become large-scale and suitable for automation. To achieve this goal, several culture platforms have been proposed using micro- or macro-fluidic designs. These include micro-spin culture systems and microcavity arrays (Brandenberg et al., 2020; Cho et al., 2021; Qian et al., 2016). With the combination of robotics, large-scale cultures and HTS can be achieved, and NOs can be used for drug screening or toxicology testing at the industrial front.
The NO model provides unique opportunities that cannot be addressed by other experimental models. These irreplaceable features are mainly derived from the maximal flexibility of the
Morphogenesis is controlled by multiple biochemical and physical factors such as cellular polarity, cell adhesion, and viscoelasticity (Von Dassow and Davidson, 2011; Zallen, 2007). Genetic mutation or treatment of small molecules that regulate biochemical pathways have been successfully used to elucidate the role of these multiple factors. However, these changes in
Owing to ethical and technical constraints on human research and the absence of an appropriate model, human evolution research has been almost impossible. Advances in biotechnology, including whole-genome sequencing, comparative genomic analysis, and the NO models, provide new opportunities to investigate human evolutionary studies (Mora-Bermúdez et al., 2016). At least two strategies have been reported for NOs as a model to explore human evolution, and comparison of NOs from human and other non-human primates has revealed that the emergence of human-specific cortical lamina features can be reproduced
Since the cellular composition in NOs can be customized as desired
NOs cannot replicate the brain accurately, and there are many limitations to be addressed. Some of these limitations might be overcome in the future, whereas others are too fundamental problems to solve them. By improving culture conditions and utilizing bioengineering techniques, NOs can be generated more similar to the human brain. Although most information on NO production has been borrowed from developmental studies, knowledge derived from NO-based studies will soon provide valuable insights into human brain development. Considering ethical principles, such as the risk-benefit ratio, it is very difficult to obtain normal human brain specimens. In this respect, even for disease modeling, the potential ability of NOs to replicate the normal human brain is valuable.
The flexibility of the experimental modulation of NO development may open up the so-called field of synthetic embryology. In combination with gene editing, synthetic embryology may serve as a tool for evolutionary biology, as synthetic biology utilizes the fundamental evolutionary concepts. This also means that synthetic neural networks can be produced based on artificial design, similar to the design and production of electrical circuits. These issues have never been addressed using either animal models or human studies; thus, such synthetic approaches will provide answers (and questions) about how neural circuits work and how they produce sophisticated brain functions.
Finally, the importance of an industrial infrastructure for NOs cannot be emphasized. Considering the value of NOs as a disease model for basic research and drug development, enhancing the accessibility of NOs to the equivalent level of experimental animals will be key to maximizing the impact of NO techniques; for example, a biobank of organoids will facilitate NO-based research and development.
This work was supported by the Brain Research Program through the National Research Foundation (NRF), which is funded by the Korean Ministry of Science, ICT & Future Planning (NRF-2021M3E5D9021368).
W.S. conceived the project. W.S. and J.H.L. wrote the manuscript.
The authors have no potential conflicts of interest to disclose.
Summary of the region-specific NO generation procedures
NO type | Neural induction | Regional specification | Neural differentiation/maturation | Reference |
---|---|---|---|---|
Cerebral organoid | - (N2 medium) | - | - | Lancaster et al., 2013 |
Cortical organoid DKK-1 (Wnt inhibitor) LeftyA (TGFβ inhibitor) | BMPRIA-Fc | - | - | Eiraku et al., 2008 |
Cortical organoid | IWP1e (Wnt inhibitor) SB431542 (TGFβ inhibitor) | 40% O2 FBS 10% Matrigel (1% in medium) | Matrigel (2% in medium) | Kadoshima et al., 2013 |
Forebrain organoid | Dorsomorphin (BMP inhibitor) A83-01 (TGFβ inhibitor) | WNT3A CHIR99021 (GSK3 inhibitor) SB431542 (TGFβ inhibitor) | BDNF, GDNF (neurotrophic factors) TGFβ Ascorbic acid (vitamin C) cAMP | Qian et al., 2016 |
Forebrain organoid | Dorsomorphin (BMP inhibitor) SB431542 (TGFβ inhibitor) | FGF2 EGF | BDNF, NT3 (neurotrophic factors) | Paşca et al., 2015 |
Ventral forebrain organoid | - | IWP2 (Wnt inhibitor) SAG (SHH agonist) | Matrigel (1% in medium) | Bagley et al., 2017 |
Subpallium spheroid (ventral forebrain) | Dorsomorphin (BMP inhibitor) SB431542 (TGFβ inhibitor) | FGF2 EGF IWP2 (Wnt inhibitor) SAG (SHH agonist) | BDNF, NT3 (neurotrophic factors) | Birey et al., 2017 |
Choroid plexus organoid | - | CHIR99021 (GSK3 inhibitor) BMP4 | Matrigel (2% in medium) | Pellegrini et al., 2020 |
Hippocampus organoid | IWP1e (Wnt inhibitor) SB431542 (TGFβ inhibitor) | CHIR99021 (GSK3 inhibitor) BMP4 | 40% O2 | Sakaguchi et al., 2015 |
Optic cup organoid | IWP1e (Wnt inhibitor) | CHIR99021 (GSK3 inhibitor) SAG (SHH agonist) FBS | - | Nakano et al., 2012 |
Thalamus organoid | SB431542 (TGFβ inhibitor) LDN193189 (BMP Inhibitor) | BMP7 PD325901 (MEK-ERK inhibitor) | BDNF (neurotrophic factors) Ascorbic acid (vitamin C) | Xiang et al., 2019 |
Hypothalamus organoid | SB431542 (TGFβ inhibitor) LDN193189 (BMP Inhibitor) Thioglycerol | WNT3A Purmorphamine (SHH agonist) | FGF2 CNTF | Qian et al., 2016 |
Midbrain organoid | SB431542 (TGFβ inhibitor) Noggin (BMP inhibitor) CHIR99021 (GSK3 inhibitor) | FGF8 SHH | BDNF, GDNF (neurotrophic factors) Ascorbic acid (vitamin C) cAMP | Jo et al., 2016 |
Midbrain organoid | SB431542 (TGFβ inhibitor) LDN193189 (BMP Inhibitor) SHH, purmorphamine (SHH agonist) FGF8 | LDN193189 (BMP Inhibitor) CHIR99021 (GSK3 inhibitor) SHH, purmorphamine (SHH agonist) FGF8 | BDNF, GDNF (neurotrophic factors) TGFβ Ascorbic acid (vitamin C) cAMP | Qian et al., 2016 |
Midbrain organoid | Dorsomorphin (BMP inhibitor) A83-01 (TGFβ inhibitor) IWP2 (Wnt inhibitor) CHIR99021 (GSK3 inhibitor) | FGF8 SAG (SHH agonist) Laminin | BDNF, GDNF (neurotrophic factors) Ascorbic acid (vitamin C) cAMP | Kwak et al., 2020 |
Cerebellum organoid | SB431542 (TGFβ inhibitor) | FGF2 FGF19 SDF1 | SDF1 | Muguruma et al., 2015 |
Brainstem organoid | Dorsomorphin (BMP inhibitor) SB431542 (TGFβ inhibitor) | Transferrin Insulin Progesterone | BDNF, GDNF, NT-3 (neurotrophic factors) Ascorbic acid (vitamin C) cAMP | Eura et al., 2020 |
Spinal cord organoid | CHIR99021 (GSK3 inhibitor) LDN193189 (BMP Inhibitor) | Retinoic acid Purmorphamine (SHH agonist) | BDNF, GDNF (neurotrophic factors) Ascorbic acid (vitamin C) | Hor et al., 2018 |
Spinal cord organoid | CHIR99021 (GSK3 inhibitor) SB431542 (TGFβ inhibitor) FGF2 | Retinoic acid +/- SAG (SHH agonist) +/- BMP4 | BDNF, GDNF (neurotrophic factors) | Ogura et al., 2018 |
Spinal cord organoid | CHIR99021 (GSK3 inhibitor) SB431542 (TGFβ inhibitor) | FGF2 | Retinoic acid | Lee et al., 2020 |
BDNF, brain-derived neurotrophic factor; BMP, bone morphogenetic protein; CNTF, ciliary neurotrophic factor; cAMP, cyclic adenosine monophosphate; EGF, epidermal growth factor; FBS, fetal bovine serum; FGF, fibroblast growth factor; GDNF, glial cell-derived neurotrophic factor; GSK3, glycogen synthase kinase-3; NT3, neurotrophin-3; SAG, smoothened agonist; SDF1, stromal cell-derived factor 1; SHH, sonic hedgehog; TGFβ, transforming growth factor-beta.
Studies on neurological disease using NOs
Disease | NO type | Causes or risk factors | Major associated disease phenotype in NOs | Potential therapeutic approaches | Reference | |
---|---|---|---|---|---|---|
Neurodevelopmental diseases (morphological defects) | Microcephaly | Cerebral organoid | CDK5RAP2 mutation | Overall smaller organoids Premature neural differentiation (decreased radial glial cells and increased neurons) | Overexpression of CDK5RAP2 | Lancaster et al., 2013 |
Zika virus-induced microcephaly | Forebrain organoid | Zika virus infection | Overall smaller organoids Reduced ventricular zone thickness and increased ventricular lumen size Increased cell apoptosis and suppressed proliferation of neural progenitors | - | Qian et al., 2016 | |
Miller-Dieker syndrome (lissencephaly) | Cerebral organoid | Deletions of chromosome 17 (17p13.3) | Mitotic defect in outer radial glial cells Increased apoptosis of neuroepithelial stem cells Defective neuronal migration of cortical neurons | Compensatory duplication of wild-type chromosome 17 | Bershteyn et al., 2017 | |
Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS syndrome) | Cerebral organoid | NR2F1 haploinsufficiency | Delayed neurogenesis (increased progenitors and reduced neuronal differentiation) | - | Bertacchi et al., 2020 | |
Neural tube defect | Spinal cord organoid | Antiepileptic drug | Delayed progression of neural tube morphogenesis Abnormal morphology of neural tube | - | Lee et al., 2020 | |
Neurodevelopmental diseases (physiological defects) | Autism spectrum disorder | Telencephalic organoid | Idiopathic ASD patient-derived hiPSC | Accelerated cell cycle and decreased cell cycle length during early stages Increased neuronal differentiation and synaptic formation Overproduction of ventral neural progenitors and GABAergic neurons Imbalance between Glutamatergic and GABAergic neurons | FOXG1 Knockdown | Mariani et al., 2015 |
Timothy syndrome | Fused organoid (dorsal forebrain and ventral forebrain) | CACNA1C mutation | Defects in the saltatory movement of GABAergic interneurons | Nimodipine (LTCC blocker) Roscovitine (cyclin-dependent kinase inhibitor) | Birey et al., 2017 | |
Rett syndrome | Fused organoid (cerebral cortex and ganglionic eminence) | MECP2 mutation | Hyperexcitability and hypersynchrony Defects in the balance of excitatory and inhibitory synapses Aberrant neural oscillation | Pifithrin-a (TP53 target inhibitor) | Samarasinghe et al., 2021 | |
Schizophrenia | Forebrain organoid | DISC1 mutation | Delayed cell-cycle progression of radial glial cells Formation of the DISC1/Ndel1 complex | - | Ye et al., 2017 | |
Neurodegenerative disease | Alzheimer’s disease | Cortical organoid | APP duplication PSEN1 mutation | Increased Aβ aggregation Hyperphosphorylation of tau protein Abnormal endosome morphology and recycling | Compound E (γ-secretase inhibitor BACE-1 (β-secretase inhibitor) | Raja et al., 2016 |
Alzheimer’s disease | Cerebral organoid | APOE ε4 | Enhanced cell apoptosis and decreased synaptic integrity Increased Aβ accumulation and phosphorylation of tau | Isogenic conversion of APOE4 to APOE3 | Zhao et al., 2020 | |
Alzheimer’s disease | Cerebral organoid | Sporadic AD patient-derived hiPSC APOE ε4 | Increased Aβ and tau protein Localization of the Aβ plaques in extracellular space Hyperphosphorylation of tau in neurons | 6 FDA-approved candidate drugs | Park et al., 2021 | |
Parkinson’s disease | Midbrain organoid | LRRK2 mutation MPTP-induced neurotoxicity | Reduced dopaminergic differentiation and decreased neurite length Abnormal localization of α-synuclein Increased mitophagy and autophagy | GSK2578215A (LRRK2 kinase inhibitor) TXNIP knockdown | Kim et al., 2019 | |
Parkinson’s disease | Midbrain organoid | GBA1 knockout + SNCA overexpression (dual perturbation) | Reduced dopaminergic differentiation Generation of Lewy body-like inclusions Accumulation of α-synuclein aggregates | - | Jo et al., 2021 | |
Parkinson’s disease | Midbrain organoid | DNAJC6 mutation | Reduced dopaminergic differentiation and neuron degeneration Increased neuronal firing frequency (stressful pacemaking) Aggregation of α-synuclein Mitochondrial and autolysosomal dysfunctions | Forced expression of DNAJC6 and LMX1A | Wulansari et al., 2021 |
AD, Alzheimer’s disease; ASD, autism spectrum disorder; LTCC, L-type calcium channel.
Mol. Cells 2022; 45(2): 53-64
Published online February 28, 2022 https://doi.org/10.14348/molcells.2022.2019
Copyright © The Korean Society for Molecular and Cellular Biology.
Department of Anatomy, Brain Korea 21 Plus Program for Biomedical Science, Korea University College of Medicine, Seoul 02841, Korea
Correspondence to:woongsun@korea.ac.kr
This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/.
Three-dimensional cultures of human neural tissue/organlike structures in vitro can be achieved by mimicking the developmental processes occurring in vivo. Rapid progress in the field of neural organoids has fueled the hope (and hype) for improved understanding of brain development and functions, modeling of neural diseases, discovery of new drugs, and supply of surrogate sources of transplantation. In this short review, we summarize the state-of-the-art applications of this fascinating tool in various research fields and discuss the reality of the technique hoping that the current limitations will soon be overcome by the efforts of ingenious researchers.
Keywords: central nervous system, human pluripotent stem cells, in vitro modeling, neurodevelopment, neurological disorders, organoid
The advent of new techniques often drives new discoveries that can change our concepts in science. It is likely that three-dimensional (3D) culture of brain-like organoids is one such technique. After the first report on the 3D culture of neural cell aggregates that exhibit some aspects of brain histoarchitecture (Eiraku et al., 2008), there has been an explosion of technical improvements in culture methods, and new discoveries have been made using these techniques (Kadoshima et al., 2013; Lancaster et al., 2013; Nakano et al., 2012; Qian et al., 2016; Warmflash et al., 2014). These 3D cultures of neural cell aggregates, collectively called neural organoids (NOs), are formed by recapitulating the developmental processes and organization of the developing human brain
NOs are produced by mimicking developmental processes, and our knowledge about neural development is the most important resource for the establishment of protocols for the region-specific NO production. Typically, protocols for NO generation consist of 3-4 steps, each mimicking the continuous but conceptually segregated
During the maturation period, NO exhibits many features of histogenesis including migration, neurogenesis, and laminar formation. Studies on cerebral organoids have demonstrated the formation of human-specific outer subventricular zone neurogenic niches, highlighting that hPSC-derived NOs recapitulate the human-specific features of brain development (Bershteyn et al., 2017; Kadoshima et al., 2013; Lancaster et al., 2013; Qian et al., 2016). An extended NO culture can reproduce gliogenesis and myelination, which mainly occur during the postnatal stages (Bershteyn et al., 2017; James et al., 2021; Madhavan et al., 2018; Shaker et al., 2021). However, the occurrence of these postnatal events does not directly indicate that the NO reaches mature stages resembling the postnatal brain. Transcriptome or epigenome analyses suggest that an approximately 10-month culture is required to obtain perinatal features, even though gliogenesis is evident by 2-4 months of culture (Amiri et al., 2018; Gordon et al., 2021; Yoon et al., 2019). These discrepancies might be caused by the protocols for NO production, asynchronized developmental progress in NOs, and different experimental sensitivities/methodologies. Considering that later brain development is more influenced by nearby structures and cell migration across embryonic brain regions, and that neural circuit formation with other brain regions is essential for later brain development (Tau and Peterson, 2010; Valiente and Marín, 2010), regionally isolated NOs cannot replicate this interaction-based neural development. Further, non-neural lineage cell populations, such as blood vessels and microglia (Adams and Eichmann, 2010; Lenz and Nelson, 2018), also play important roles in brain development, which cannot be generated by simple NO induction. Accordingly, many approaches to include multiple components in NO have successfully demonstrated that some aspects of these insufficiencies can be overcome by complex technologies such as fusion, assembly, connection, and polarization (Fig. 2).
Cumulative results have demonstrated that NOs faithfully replicate many aspects of the developmental progress of the human brain. Thus, NOs provide a great opportunity to glimpse human brain development
Modeling human brain diseases using NO technology is one of the major goals that researchers pursue. Considering that NOs are produced via a developmental program for organogenesis, modeling developmental defects were immediately addressed upon the advent of the NO technique. Observation of known developmental defects with specific genetic mutations in NO cultures is considered
Defects in later developmental programs often do not exhibit overt morphological changes; therefore, more precise analyses with physiological tools are required. Methods for detecting the physiological responses of NOs have been widely used only recently (Osaki and Ikeuchi, 2021; Trujillo et al., 2019; Zafeiriou et al., 2020), and the physiological defects in these models are only beginning to be reported (Andersen et al., 2020; Birey et al., 2017; Mariani et al., 2015; Samarasinghe et al., 2021; Ye et al., 2017). For instance, epileptic episodes can be recognized by altered neuronal burst activity and local field potentials. Accordingly, using these physiological tools, Rett’s syndrome and Schizophrenia were successfully modeled using NOs derived from patient iPS cells (Samarasinghe et al., 2021; Ye et al., 2017). The use of NOs for psychiatric diseases is more challenging because these pathologies are known to be associated with neural circuit formation, synaptic plasticity, and other sophisticated abnormalities without gross signs of structural changes (Das et al., 2020; McTeague et al., 2017; Van Spronsen and Hoogenraad, 2010). Many brain regions are involved in the pathogenesis of psychiatric diseases, and region-specific NOs may have limited potential to exhibit these circuit-dependent pathologies. Furthermore, psychiatric diseases are often modeled in experimental animals exhibiting similar behavioral defects. However, the current NO models have limited complexity compared to multiregional neural circuits
NOs have also been successfully used to model neurodegenerative diseases. NOs produced from iPSCs of patients with Alzheimer’s disease (AD)-related mutations exhibit AD-like symptoms, such as amyloid-beta deposits (Jack et al., 2010; Murphy and LeVine, 2010). The NO-based Parkinson’s disease model has also been reported to exhibit Lewy body-like inclusions and alpha-synuclein aggregations (Jo et al., 2021). It is unclear why these late-onset symptoms in aged human patients were observed in the NOs, which replicate a much younger aged brain. It is plausible that the current ‘standard’ cultures of NO may be pro-degenerative owing to non-humanized media and the lack of sufficient signals/factors for healthy growth, which is presumably supplied from the blood or other parts of the body
In terms of disease modeling, there have been many significant attempts to upgrade NO culture systems suitable for high-throughput screening (HTS). At least two important features have been addressed and improved to achieve this goal. First, the variability of NOs in different batches and within batches should be precisely controlled. Notably, the NO induction response is highly dependent on batches. It is unclear what causes these differences, but it is predictable that the quality and/or condition of hPSCs may greatly affect the consequences of treatment. Further, the format of cell culture may affect the homogeneity of cellular responses regardless of batches. For instance, because cultured hPSCs in 3D appear to exhibit more variable responses to induction reagents depending on their relative position in the cluster, there have been attempts to induce hPSCs into neural-lineage cells in 2D (Lee et al., 2020; Renner et al., 2020). The resultant 'primed' neural-fate cells can then be dissociated and reaggregated into 3D spheroids with a precisely controlled number of cells. These 3D spheroids can also form a brain histoarchitecture as seen in 3D-initiated NOs. These approaches have obvious benefits in terms of quantifiability because better control of the initial cell number and conditions strongly contributes to the reduction of variations. Considering that this approach may sacrifice some aspects of the histoarchitectures in conventional NOs, it is especially suitable for producing NOs for brain regions where the histoarchitecture is less obvious or ignorable. Second, culture formation should become large-scale and suitable for automation. To achieve this goal, several culture platforms have been proposed using micro- or macro-fluidic designs. These include micro-spin culture systems and microcavity arrays (Brandenberg et al., 2020; Cho et al., 2021; Qian et al., 2016). With the combination of robotics, large-scale cultures and HTS can be achieved, and NOs can be used for drug screening or toxicology testing at the industrial front.
The NO model provides unique opportunities that cannot be addressed by other experimental models. These irreplaceable features are mainly derived from the maximal flexibility of the
Morphogenesis is controlled by multiple biochemical and physical factors such as cellular polarity, cell adhesion, and viscoelasticity (Von Dassow and Davidson, 2011; Zallen, 2007). Genetic mutation or treatment of small molecules that regulate biochemical pathways have been successfully used to elucidate the role of these multiple factors. However, these changes in
Owing to ethical and technical constraints on human research and the absence of an appropriate model, human evolution research has been almost impossible. Advances in biotechnology, including whole-genome sequencing, comparative genomic analysis, and the NO models, provide new opportunities to investigate human evolutionary studies (Mora-Bermúdez et al., 2016). At least two strategies have been reported for NOs as a model to explore human evolution, and comparison of NOs from human and other non-human primates has revealed that the emergence of human-specific cortical lamina features can be reproduced
Since the cellular composition in NOs can be customized as desired
NOs cannot replicate the brain accurately, and there are many limitations to be addressed. Some of these limitations might be overcome in the future, whereas others are too fundamental problems to solve them. By improving culture conditions and utilizing bioengineering techniques, NOs can be generated more similar to the human brain. Although most information on NO production has been borrowed from developmental studies, knowledge derived from NO-based studies will soon provide valuable insights into human brain development. Considering ethical principles, such as the risk-benefit ratio, it is very difficult to obtain normal human brain specimens. In this respect, even for disease modeling, the potential ability of NOs to replicate the normal human brain is valuable.
The flexibility of the experimental modulation of NO development may open up the so-called field of synthetic embryology. In combination with gene editing, synthetic embryology may serve as a tool for evolutionary biology, as synthetic biology utilizes the fundamental evolutionary concepts. This also means that synthetic neural networks can be produced based on artificial design, similar to the design and production of electrical circuits. These issues have never been addressed using either animal models or human studies; thus, such synthetic approaches will provide answers (and questions) about how neural circuits work and how they produce sophisticated brain functions.
Finally, the importance of an industrial infrastructure for NOs cannot be emphasized. Considering the value of NOs as a disease model for basic research and drug development, enhancing the accessibility of NOs to the equivalent level of experimental animals will be key to maximizing the impact of NO techniques; for example, a biobank of organoids will facilitate NO-based research and development.
This work was supported by the Brain Research Program through the National Research Foundation (NRF), which is funded by the Korean Ministry of Science, ICT & Future Planning (NRF-2021M3E5D9021368).
W.S. conceived the project. W.S. and J.H.L. wrote the manuscript.
The authors have no potential conflicts of interest to disclose.
Summary of the region-specific NO generation procedures
NO type | Neural induction | Regional specification | Neural differentiation/maturation | Reference |
---|---|---|---|---|
Cerebral organoid | - (N2 medium) | - | - | Lancaster et al., 2013 |
Cortical organoid DKK-1 (Wnt inhibitor) LeftyA (TGFβ inhibitor) |
BMPRIA-Fc | - | - | Eiraku et al., 2008 |
Cortical organoid | IWP1e (Wnt inhibitor) SB431542 (TGFβ inhibitor) |
40% O2 FBS 10% Matrigel (1% in medium) |
Matrigel (2% in medium) | Kadoshima et al., 2013 |
Forebrain organoid | Dorsomorphin (BMP inhibitor) A83-01 (TGFβ inhibitor) |
WNT3A CHIR99021 (GSK3 inhibitor) SB431542 (TGFβ inhibitor) |
BDNF, GDNF (neurotrophic factors) TGFβ Ascorbic acid (vitamin C) cAMP |
Qian et al., 2016 |
Forebrain organoid | Dorsomorphin (BMP inhibitor) SB431542 (TGFβ inhibitor) |
FGF2 EGF |
BDNF, NT3 (neurotrophic factors) | Paşca et al., 2015 |
Ventral forebrain organoid | - | IWP2 (Wnt inhibitor) SAG (SHH agonist) |
Matrigel (1% in medium) | Bagley et al., 2017 |
Subpallium spheroid (ventral forebrain) |
Dorsomorphin (BMP inhibitor) SB431542 (TGFβ inhibitor) |
FGF2 EGF IWP2 (Wnt inhibitor) SAG (SHH agonist) |
BDNF, NT3 (neurotrophic factors) | Birey et al., 2017 |
Choroid plexus organoid | - | CHIR99021 (GSK3 inhibitor) BMP4 |
Matrigel (2% in medium) | Pellegrini et al., 2020 |
Hippocampus organoid | IWP1e (Wnt inhibitor) SB431542 (TGFβ inhibitor) |
CHIR99021 (GSK3 inhibitor) BMP4 |
40% O2 | Sakaguchi et al., 2015 |
Optic cup organoid | IWP1e (Wnt inhibitor) | CHIR99021 (GSK3 inhibitor) SAG (SHH agonist) FBS |
- | Nakano et al., 2012 |
Thalamus organoid | SB431542 (TGFβ inhibitor) LDN193189 (BMP Inhibitor) |
BMP7 PD325901 (MEK-ERK inhibitor) |
BDNF (neurotrophic factors) Ascorbic acid (vitamin C) |
Xiang et al., 2019 |
Hypothalamus organoid | SB431542 (TGFβ inhibitor) LDN193189 (BMP Inhibitor) Thioglycerol |
WNT3A Purmorphamine (SHH agonist) |
FGF2 CNTF |
Qian et al., 2016 |
Midbrain organoid | SB431542 (TGFβ inhibitor) Noggin (BMP inhibitor) CHIR99021 (GSK3 inhibitor) |
FGF8 SHH |
BDNF, GDNF (neurotrophic factors) Ascorbic acid (vitamin C) cAMP |
Jo et al., 2016 |
Midbrain organoid | SB431542 (TGFβ inhibitor) LDN193189 (BMP Inhibitor) SHH, purmorphamine (SHH agonist) FGF8 |
LDN193189 (BMP Inhibitor) CHIR99021 (GSK3 inhibitor) SHH, purmorphamine (SHH agonist) FGF8 |
BDNF, GDNF (neurotrophic factors) TGFβ Ascorbic acid (vitamin C) cAMP |
Qian et al., 2016 |
Midbrain organoid | Dorsomorphin (BMP inhibitor) A83-01 (TGFβ inhibitor) IWP2 (Wnt inhibitor) CHIR99021 (GSK3 inhibitor) |
FGF8 SAG (SHH agonist) Laminin |
BDNF, GDNF (neurotrophic factors) Ascorbic acid (vitamin C) cAMP |
Kwak et al., 2020 |
Cerebellum organoid | SB431542 (TGFβ inhibitor) | FGF2 FGF19 SDF1 |
SDF1 | Muguruma et al., 2015 |
Brainstem organoid | Dorsomorphin (BMP inhibitor) SB431542 (TGFβ inhibitor) |
Transferrin Insulin Progesterone |
BDNF, GDNF, NT-3 (neurotrophic factors) Ascorbic acid (vitamin C) cAMP |
Eura et al., 2020 |
Spinal cord organoid | CHIR99021 (GSK3 inhibitor) LDN193189 (BMP Inhibitor) |
Retinoic acid Purmorphamine (SHH agonist) |
BDNF, GDNF (neurotrophic factors) Ascorbic acid (vitamin C) |
Hor et al., 2018 |
Spinal cord organoid | CHIR99021 (GSK3 inhibitor) SB431542 (TGFβ inhibitor) FGF2 |
Retinoic acid +/- SAG (SHH agonist) +/- BMP4 |
BDNF, GDNF (neurotrophic factors) | Ogura et al., 2018 |
Spinal cord organoid | CHIR99021 (GSK3 inhibitor) SB431542 (TGFβ inhibitor) |
FGF2 | Retinoic acid | Lee et al., 2020 |
BDNF, brain-derived neurotrophic factor; BMP, bone morphogenetic protein; CNTF, ciliary neurotrophic factor; cAMP, cyclic adenosine monophosphate; EGF, epidermal growth factor; FBS, fetal bovine serum; FGF, fibroblast growth factor; GDNF, glial cell-derived neurotrophic factor; GSK3, glycogen synthase kinase-3; NT3, neurotrophin-3; SAG, smoothened agonist; SDF1, stromal cell-derived factor 1; SHH, sonic hedgehog; TGFβ, transforming growth factor-beta.
Studies on neurological disease using NOs
Disease | NO type | Causes or risk factors | Major associated disease phenotype in NOs | Potential therapeutic approaches | Reference | |
---|---|---|---|---|---|---|
Neurodevelopmental diseases (morphological defects) | Microcephaly | Cerebral organoid | CDK5RAP2 mutation | Overall smaller organoids Premature neural differentiation (decreased radial glial cells and increased neurons) |
Overexpression of CDK5RAP2 | Lancaster et al., 2013 |
Zika virus-induced microcephaly | Forebrain organoid | Zika virus infection | Overall smaller organoids Reduced ventricular zone thickness and increased ventricular lumen size Increased cell apoptosis and suppressed proliferation of neural progenitors |
- | Qian et al., 2016 | |
Miller-Dieker syndrome (lissencephaly) | Cerebral organoid | Deletions of chromosome 17 (17p13.3) | Mitotic defect in outer radial glial cells Increased apoptosis of neuroepithelial stem cells Defective neuronal migration of cortical neurons |
Compensatory duplication of wild-type chromosome 17 | Bershteyn et al., 2017 | |
Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS syndrome) | Cerebral organoid | NR2F1 haploinsufficiency | Delayed neurogenesis (increased progenitors and reduced neuronal differentiation) | - | Bertacchi et al., 2020 | |
Neural tube defect | Spinal cord organoid | Antiepileptic drug | Delayed progression of neural tube morphogenesis Abnormal morphology of neural tube |
- | Lee et al., 2020 | |
Neurodevelopmental diseases (physiological defects) | Autism spectrum disorder | Telencephalic organoid | Idiopathic ASD patient-derived hiPSC | Accelerated cell cycle and decreased cell cycle length during early stages Increased neuronal differentiation and synaptic formation Overproduction of ventral neural progenitors and GABAergic neurons Imbalance between Glutamatergic and GABAergic neurons |
FOXG1 Knockdown | Mariani et al., 2015 |
Timothy syndrome | Fused organoid (dorsal forebrain and ventral forebrain) | CACNA1C mutation | Defects in the saltatory movement of GABAergic interneurons | Nimodipine (LTCC blocker) Roscovitine (cyclin-dependent kinase inhibitor) |
Birey et al., 2017 | |
Rett syndrome | Fused organoid (cerebral cortex and ganglionic eminence) | MECP2 mutation | Hyperexcitability and hypersynchrony Defects in the balance of excitatory and inhibitory synapses Aberrant neural oscillation |
Pifithrin-a (TP53 target inhibitor) | Samarasinghe et al., 2021 | |
Schizophrenia | Forebrain organoid | DISC1 mutation | Delayed cell-cycle progression of radial glial cells Formation of the DISC1/Ndel1 complex |
- | Ye et al., 2017 | |
Neurodegenerative disease | Alzheimer’s disease | Cortical organoid | APP duplication PSEN1 mutation |
Increased Aβ aggregation Hyperphosphorylation of tau protein Abnormal endosome morphology and recycling |
Compound E (γ-secretase inhibitor BACE-1 (β-secretase inhibitor) |
Raja et al., 2016 |
Alzheimer’s disease | Cerebral organoid | APOE ε4 | Enhanced cell apoptosis and decreased synaptic integrity Increased Aβ accumulation and phosphorylation of tau |
Isogenic conversion of APOE4 to APOE3 | Zhao et al., 2020 | |
Alzheimer’s disease | Cerebral organoid | Sporadic AD patient-derived hiPSC APOE ε4 |
Increased Aβ and tau protein Localization of the Aβ plaques in extracellular space Hyperphosphorylation of tau in neurons |
6 FDA-approved candidate drugs | Park et al., 2021 | |
Parkinson’s disease | Midbrain organoid | LRRK2 mutation MPTP-induced neurotoxicity |
Reduced dopaminergic differentiation and decreased neurite length Abnormal localization of α-synuclein Increased mitophagy and autophagy |
GSK2578215A (LRRK2 kinase inhibitor) TXNIP knockdown |
Kim et al., 2019 | |
Parkinson’s disease | Midbrain organoid | GBA1 knockout + SNCA overexpression (dual perturbation) | Reduced dopaminergic differentiation Generation of Lewy body-like inclusions Accumulation of α-synuclein aggregates |
- | Jo et al., 2021 | |
Parkinson’s disease | Midbrain organoid | DNAJC6 mutation | Reduced dopaminergic differentiation and neuron degeneration Increased neuronal firing frequency (stressful pacemaking) Aggregation of α-synuclein Mitochondrial and autolysosomal dysfunctions |
Forced expression of DNAJC6 and LMX1A | Wulansari et al., 2021 |
AD, Alzheimer’s disease; ASD, autism spectrum disorder; LTCC, L-type calcium channel.
. Summary of the region-specific NO generation procedures.
NO type | Neural induction | Regional specification | Neural differentiation/maturation | Reference |
---|---|---|---|---|
Cerebral organoid | - (N2 medium) | - | - | Lancaster et al., 2013 |
Cortical organoid DKK-1 (Wnt inhibitor) LeftyA (TGFβ inhibitor) | BMPRIA-Fc | - | - | Eiraku et al., 2008 |
Cortical organoid | IWP1e (Wnt inhibitor) SB431542 (TGFβ inhibitor) | 40% O2 FBS 10% Matrigel (1% in medium) | Matrigel (2% in medium) | Kadoshima et al., 2013 |
Forebrain organoid | Dorsomorphin (BMP inhibitor) A83-01 (TGFβ inhibitor) | WNT3A CHIR99021 (GSK3 inhibitor) SB431542 (TGFβ inhibitor) | BDNF, GDNF (neurotrophic factors) TGFβ Ascorbic acid (vitamin C) cAMP | Qian et al., 2016 |
Forebrain organoid | Dorsomorphin (BMP inhibitor) SB431542 (TGFβ inhibitor) | FGF2 EGF | BDNF, NT3 (neurotrophic factors) | Paşca et al., 2015 |
Ventral forebrain organoid | - | IWP2 (Wnt inhibitor) SAG (SHH agonist) | Matrigel (1% in medium) | Bagley et al., 2017 |
Subpallium spheroid (ventral forebrain) | Dorsomorphin (BMP inhibitor) SB431542 (TGFβ inhibitor) | FGF2 EGF IWP2 (Wnt inhibitor) SAG (SHH agonist) | BDNF, NT3 (neurotrophic factors) | Birey et al., 2017 |
Choroid plexus organoid | - | CHIR99021 (GSK3 inhibitor) BMP4 | Matrigel (2% in medium) | Pellegrini et al., 2020 |
Hippocampus organoid | IWP1e (Wnt inhibitor) SB431542 (TGFβ inhibitor) | CHIR99021 (GSK3 inhibitor) BMP4 | 40% O2 | Sakaguchi et al., 2015 |
Optic cup organoid | IWP1e (Wnt inhibitor) | CHIR99021 (GSK3 inhibitor) SAG (SHH agonist) FBS | - | Nakano et al., 2012 |
Thalamus organoid | SB431542 (TGFβ inhibitor) LDN193189 (BMP Inhibitor) | BMP7 PD325901 (MEK-ERK inhibitor) | BDNF (neurotrophic factors) Ascorbic acid (vitamin C) | Xiang et al., 2019 |
Hypothalamus organoid | SB431542 (TGFβ inhibitor) LDN193189 (BMP Inhibitor) Thioglycerol | WNT3A Purmorphamine (SHH agonist) | FGF2 CNTF | Qian et al., 2016 |
Midbrain organoid | SB431542 (TGFβ inhibitor) Noggin (BMP inhibitor) CHIR99021 (GSK3 inhibitor) | FGF8 SHH | BDNF, GDNF (neurotrophic factors) Ascorbic acid (vitamin C) cAMP | Jo et al., 2016 |
Midbrain organoid | SB431542 (TGFβ inhibitor) LDN193189 (BMP Inhibitor) SHH, purmorphamine (SHH agonist) FGF8 | LDN193189 (BMP Inhibitor) CHIR99021 (GSK3 inhibitor) SHH, purmorphamine (SHH agonist) FGF8 | BDNF, GDNF (neurotrophic factors) TGFβ Ascorbic acid (vitamin C) cAMP | Qian et al., 2016 |
Midbrain organoid | Dorsomorphin (BMP inhibitor) A83-01 (TGFβ inhibitor) IWP2 (Wnt inhibitor) CHIR99021 (GSK3 inhibitor) | FGF8 SAG (SHH agonist) Laminin | BDNF, GDNF (neurotrophic factors) Ascorbic acid (vitamin C) cAMP | Kwak et al., 2020 |
Cerebellum organoid | SB431542 (TGFβ inhibitor) | FGF2 FGF19 SDF1 | SDF1 | Muguruma et al., 2015 |
Brainstem organoid | Dorsomorphin (BMP inhibitor) SB431542 (TGFβ inhibitor) | Transferrin Insulin Progesterone | BDNF, GDNF, NT-3 (neurotrophic factors) Ascorbic acid (vitamin C) cAMP | Eura et al., 2020 |
Spinal cord organoid | CHIR99021 (GSK3 inhibitor) LDN193189 (BMP Inhibitor) | Retinoic acid Purmorphamine (SHH agonist) | BDNF, GDNF (neurotrophic factors) Ascorbic acid (vitamin C) | Hor et al., 2018 |
Spinal cord organoid | CHIR99021 (GSK3 inhibitor) SB431542 (TGFβ inhibitor) FGF2 | Retinoic acid +/- SAG (SHH agonist) +/- BMP4 | BDNF, GDNF (neurotrophic factors) | Ogura et al., 2018 |
Spinal cord organoid | CHIR99021 (GSK3 inhibitor) SB431542 (TGFβ inhibitor) | FGF2 | Retinoic acid | Lee et al., 2020 |
BDNF, brain-derived neurotrophic factor; BMP, bone morphogenetic protein; CNTF, ciliary neurotrophic factor; cAMP, cyclic adenosine monophosphate; EGF, epidermal growth factor; FBS, fetal bovine serum; FGF, fibroblast growth factor; GDNF, glial cell-derived neurotrophic factor; GSK3, glycogen synthase kinase-3; NT3, neurotrophin-3; SAG, smoothened agonist; SDF1, stromal cell-derived factor 1; SHH, sonic hedgehog; TGFβ, transforming growth factor-beta..
. Studies on neurological disease using NOs.
Disease | NO type | Causes or risk factors | Major associated disease phenotype in NOs | Potential therapeutic approaches | Reference | |
---|---|---|---|---|---|---|
Neurodevelopmental diseases (morphological defects) | Microcephaly | Cerebral organoid | CDK5RAP2 mutation | Overall smaller organoids Premature neural differentiation (decreased radial glial cells and increased neurons) | Overexpression of CDK5RAP2 | Lancaster et al., 2013 |
Zika virus-induced microcephaly | Forebrain organoid | Zika virus infection | Overall smaller organoids Reduced ventricular zone thickness and increased ventricular lumen size Increased cell apoptosis and suppressed proliferation of neural progenitors | - | Qian et al., 2016 | |
Miller-Dieker syndrome (lissencephaly) | Cerebral organoid | Deletions of chromosome 17 (17p13.3) | Mitotic defect in outer radial glial cells Increased apoptosis of neuroepithelial stem cells Defective neuronal migration of cortical neurons | Compensatory duplication of wild-type chromosome 17 | Bershteyn et al., 2017 | |
Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS syndrome) | Cerebral organoid | NR2F1 haploinsufficiency | Delayed neurogenesis (increased progenitors and reduced neuronal differentiation) | - | Bertacchi et al., 2020 | |
Neural tube defect | Spinal cord organoid | Antiepileptic drug | Delayed progression of neural tube morphogenesis Abnormal morphology of neural tube | - | Lee et al., 2020 | |
Neurodevelopmental diseases (physiological defects) | Autism spectrum disorder | Telencephalic organoid | Idiopathic ASD patient-derived hiPSC | Accelerated cell cycle and decreased cell cycle length during early stages Increased neuronal differentiation and synaptic formation Overproduction of ventral neural progenitors and GABAergic neurons Imbalance between Glutamatergic and GABAergic neurons | FOXG1 Knockdown | Mariani et al., 2015 |
Timothy syndrome | Fused organoid (dorsal forebrain and ventral forebrain) | CACNA1C mutation | Defects in the saltatory movement of GABAergic interneurons | Nimodipine (LTCC blocker) Roscovitine (cyclin-dependent kinase inhibitor) | Birey et al., 2017 | |
Rett syndrome | Fused organoid (cerebral cortex and ganglionic eminence) | MECP2 mutation | Hyperexcitability and hypersynchrony Defects in the balance of excitatory and inhibitory synapses Aberrant neural oscillation | Pifithrin-a (TP53 target inhibitor) | Samarasinghe et al., 2021 | |
Schizophrenia | Forebrain organoid | DISC1 mutation | Delayed cell-cycle progression of radial glial cells Formation of the DISC1/Ndel1 complex | - | Ye et al., 2017 | |
Neurodegenerative disease | Alzheimer’s disease | Cortical organoid | APP duplication PSEN1 mutation | Increased Aβ aggregation Hyperphosphorylation of tau protein Abnormal endosome morphology and recycling | Compound E (γ-secretase inhibitor BACE-1 (β-secretase inhibitor) | Raja et al., 2016 |
Alzheimer’s disease | Cerebral organoid | APOE ε4 | Enhanced cell apoptosis and decreased synaptic integrity Increased Aβ accumulation and phosphorylation of tau | Isogenic conversion of APOE4 to APOE3 | Zhao et al., 2020 | |
Alzheimer’s disease | Cerebral organoid | Sporadic AD patient-derived hiPSC APOE ε4 | Increased Aβ and tau protein Localization of the Aβ plaques in extracellular space Hyperphosphorylation of tau in neurons | 6 FDA-approved candidate drugs | Park et al., 2021 | |
Parkinson’s disease | Midbrain organoid | LRRK2 mutation MPTP-induced neurotoxicity | Reduced dopaminergic differentiation and decreased neurite length Abnormal localization of α-synuclein Increased mitophagy and autophagy | GSK2578215A (LRRK2 kinase inhibitor) TXNIP knockdown | Kim et al., 2019 | |
Parkinson’s disease | Midbrain organoid | GBA1 knockout + SNCA overexpression (dual perturbation) | Reduced dopaminergic differentiation Generation of Lewy body-like inclusions Accumulation of α-synuclein aggregates | - | Jo et al., 2021 | |
Parkinson’s disease | Midbrain organoid | DNAJC6 mutation | Reduced dopaminergic differentiation and neuron degeneration Increased neuronal firing frequency (stressful pacemaking) Aggregation of α-synuclein Mitochondrial and autolysosomal dysfunctions | Forced expression of DNAJC6 and LMX1A | Wulansari et al., 2021 |
AD, Alzheimer’s disease; ASD, autism spectrum disorder; LTCC, L-type calcium channel..
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