Brain organoids are new tool for drug screening of neurological diseases

At the level of in vitro drug screening,the development of a phenotypic analysis system with highcontent screening at the core provides a strong platform to support high-throughput drug screening.There are few systematic reports on brain organoids,as a new three-dimensional in vitro model,in terms of model stability,key phenotypic fingerprint,and drug screening schemes,and particula rly rega rding the development of screening strategies for massive numbers of traditional Chinese medicine monomers.This paper reviews the development of brain organoids and the advantages of brain organoids over induced neurons or cells in simulated diseases.The paper also highlights the prospects from model stability,induction criteria of brain organoids,and the screening schemes of brain organoids based on the characteristics of brain organoids and the application and development of a high-content screening system.

Human brain organoid:trends,evolution,and remaining challenges

Advanced brain organoids provide promising platforms for deciphering the cellular and molecular processes of human neural development and diseases.Although various studies and reviews have described developments and advancements in brain organoids,few studies have comprehensively summarized and analyzed the global trends in this area of neuroscience.To identify and further facilitate the development of cerebral organoids,we utilized bibliometrics and visualization methods to analyze the global trends and evolution of brain organoids in the last 10 years.First,annual publications,countries/regions,organizations,journals,authors,co-citations,and keywords relating to brain organoids were identified.The hotspots in this field were also systematically identified.Subsequently,current applications for brain organoids in neuroscience,including human neural development,neural disorders,infectious diseases,regenerative medicine,drug discovery,and toxicity assessment studies,are comprehensively discussed.Towards that end,several considerations regarding the current challenges in brain organoid research and future strategies to advance neuroscience will be presented to further promote their application in neurological research.

Advances and Applications of Brain Organoids

Understanding the fundamental processes of human brain development and diseases is of great importance for our health.However,existing research models such as non-human primate and mouse models remain limited due to their developmental discrepancies compared with humans.Over the past years,an emerging model,the“brain organoid”integrated from human pluripotent stem cells,has been developed to mimic developmental processes of the human brain and disease-associated phenotypes to some extent,making it possible to better understand the complex structures and functions of the human brain.In this review,we summarize recent advances in brain organoid technologies and their applications in brain development and diseases,including neurodevelopmental,neurodegenerative,psychiatric diseases,and brain tumors.Finally,we also discuss current limitations and the potential of brain organoids.

Modeling human neurodevelopmental diseases with brain organoids

Studying the etiology of human neurodevelopmental diseases has long been a challenging task due to the brain’s complexity and its limited accessibility.Human pluripotent stem cells(hPSCs)-derived brain organoids are capable of recapitulating various features and functionalities of the human brain,allowing the investigation of intricate patho-genesis of developmental abnormalities.Over the past years,brain organoids have facilitated identifying disease-associated phenotypes and underlying mechanisms for human neurodevelopmental diseases.Integrating with more cutting-edge technologies,particularly gene editing,brain organoids further empower human disease modeling.Here,we review the latest progress in modeling human neurodevelopmental disorders with brain organoids.

The generation and properties of human cortical organoids as a disease model for malformations of cortical development

As three-dimensional“organ-like”aggregates,human cortical organoids have emerged as powerful models for studying human brain evolution and brain disorders with unique advantages of humanspecificity,fidelity and manipulation.Human cortical organoids derived from human pluripotent stem cells can elaborately replicate many of the key properties of human cortical development at the molecular,cellular,structural,and functional levels,including the anatomy,functional neural network,and interaction among different brain regions,thus facilitating the discovery of brain development and evolution.In addition to studying the neuro-electrophysiological features of brain cortex development,human cortical organoids have been widely used to mimic the pathophysiological features of cortical-related disease,especially in mimicking malformations of cortical development,thus revealing pathological mechanism and identifying effective drugs.In this review,we provide an overview of the generation of human cortical organoids and the properties of recapitulated cortical development and further outline their applications in modeling malformations of cortical development including pathological phenotype,underlying mechanisms and rescue strategies.

Engineering human pluripotent stem cell-derived 3D brain tissues for drug discovery

The quest to find novel therapeutics for mental and neurological disorders has been hindered by the lack of access to l ive human brain samples and relevant experimental models. Conventional 2D human pluripotent stem cell-derived neuronal cultures and animal models do not ful ly recapitulate many endogenous human biochemical processes and disease phenotypes. Currently, the majority of candidate drugs obtained from preclinical testing in conventional systems does not usually translate into success and have a high failure rate in clinical trials. Recent advancements in bioengineering and stem cell technologies have resulted in three-dimensional brain-like tissues, such as oragnoids, which better resemble endogenous tissue and are more physiologically relevant than monolayer cultures. These brain-like tissues can bridge the gap between existing models and the patient, and may revolutionize the field of translational neuroscience. Here, we discuss utilities and challenges of using stem cell-derived human brain tissues in basic research and pharmacotherapy.

Neural lineage differentiation of human pluripotent stem cells:Advances in disease modeling

Brain diseases affect 1 in 6 people worldwide.These diseases range from acute neurological conditions such as stroke to chronic neurodegenerative disorders such as Alzheimer’s disease.Recent advancements in tissue-engineered brain disease models have overcome many of the different shortcomings associated with the various animal models,tissue culture models,and epidemiologic patient data that are commonly used to study brain disease.One innovative method by which to model human neurological disease is via the directed differentiation of human pluripotent stem cells(hPSCs)to neural lineages including neurons,astrocytes,and oligodendrocytes.Three-dimensional models such as brain organoids have also been derived from hPSCs,offering more physiological relevance due to their incorporation of various cell types.As such,brain organoids can better model the pathophysiology of neural diseases observed in patients.In this review,we will emphasize recent developments in hPSC-based tissue culture models of neurological disorders and how they are being used to create neural disease models.

Brain physiome:A concept bridging in vitro 3D brain models and in silico models for predicting drug toxicity in the brain

In the last few decades,adverse reactions to pharmaceuticals have been evaluated using 2D in vitro models and animal models.However,with increasing computational power,and as the key drivers of cellular behavior have been identified,in silico models have emerged.These models are time-efficient and cost-effective,but the prediction of adverse reactions to unknown drugs using these models requires relevant experimental input.Accordingly,the physiome concept has emerged to bridge experimental datasets with in silico models.The brain physiome describes the systemic interactions of its components,which are organized into a multilevel hierarchy.Because of the limitations in obtaining experimental data corresponding to each physiome component from 2D in vitro models and animal models,3D in vitro brain models,including brain organoids and brain-on-a-chip,have been developed.In this review,we present the concept of the brain physiome and its hierarchical organization,including cell-and tissue-level organizations.We also summarize recently developed 3D in vitro brain models and link them with the elements of the brain physiome as a guideline for dataset collection.The connection between in vitro 3D brain models and in silico modeling will lead to the establishment of cost-effective and time-efficient in silico models for the prediction of the safety of unknown drugs.

Brain organoid-on-chip system to study the effects of breast cancer derived exosomes on the neurodevelopment of brain

Early human brain development can be affected by multiple prenatal factors that involve chemical exposures in utero,maternal health characteristics such as psychiatric disorders,and cancer.Breast cancer is one of the most common cancers worldwide arising pregnancy.However,it is not clear whether the breast cancer might influence the brain development of fetus.Exosomes secreted by breast cancer cells play a critical role in mediating intercellular communication and interplay between different organs.In this work,we engineered human induced pluripotent stem cells(hiPSCs)-derived brain organoids in an array of micropillar chip and probed the influences of breast cancer cell(MCF-7)derived-exosomes on the early neurodevelopment of brain.The formed brain organoids can recapitulate essential features of embryonic human brain at early stages,in terms of neurogenesis,forebrain regionalization,and cortical organization.Treatment with breast cancer cell derived-exosomes,brain organoids exhibited enhanced expression of stemness-related marker OCT4 and forebrain marker PAX6.RNA-seq analysis reflected several activated signaling pathways associated with breast cancer,medulloblastoma and neurogenesis in brain organoids induced by tumor-derived exosomes.These results suggested that breast cancer cell-derived exosomes might lead to the impaired neurodevelopment in the brain organoids and the carcinogenesis of brain organoids.It potentially implies the fetus of pregnant women with breast cancer has the risk of impaired neurodevelopmental disorder after birth.

Human stem cell modeling of neuropsychiatric disorders:from polygenicity to convergence

Neuropsychiatric disorders(NPD)are prevalent and devastating,posing an enormous socioeconomic burden to modern society.Recent genetic studies of NPD have identified a plethora of common genetic risk variants with small effect sizes and rare risk variants of high penetrance.While exciting,there is a pressing need to translate these genetic discoveries into better understanding of disease biology and more tailored clinical interventions.Human induced pluripotent stem cell(hiPSC)-derived 2D and 3D neural cultures are becoming a promising cellular model for bridging the gap between genetic findings and disease biology for NPD.Leveraging the accessibility of patient biospecimen to convert into stem cells and the power of genome editing technology to engineer disease risk variants,hiPSC model holds the promise to disentangle the disease polygenicity,model genetic interaction with environmental factors,and uncover convergent gene pathways that may be targeted for more tailored clinical intervention.