Microglia-containing cerebral organoids derived from induced pluripotent stem cells for the study of neurological diseases

A microglia-containing cerebral organoid model to study early life immune challenges

Prenatal infections and activation of the maternal immune system have been proposed to contribute to causing neurodevelopmental disorders (NDDs), chronic conditions often linked to brain abnormalities. Microglia are the resident immune cells of the brain and play a key role in neurodevelopment. Disruption of microglial functions can lead to brain abnormalities and increase the risk of developing NDDs. How the maternal as well as the fetal immune system affect human neurodevelopment and contribute to NDDs remains unclear. An important reason for this knowledge gap is the fact that the impact of exposure to prenatal risk factors has been challenging to study in the human context. Here, we characterized a model of cerebral organoids (CO) with integrated microglia (COiMg). These organoids express typical microglial markers and respond to inflammatory stimuli. The presence of microglia influences cerebral organoid development, including cell density and neural differentiation, and regulates the expression of several ciliated and mesenchymal cell markers. Moreover, COiMg and organoids without microglia show similar but also distinct responses to inflammatory stimuli. Additionally, IFN-γ induced significant transcriptional and structural changes in the cerebral organoids, that appear to be regulated by the presence of microglia. Specifically, interferon-gamma (IFN-γ) was found to alter the expression of genes linked to autism. This model provides a valuable tool to study how inflammatory perturbations and microglial presence affect neurodevelopmental processes.

hPSCs-derived brain organoids for disease modeling, toxicity testing and drug evaluation

Due to the differences and variances in genetic background, in vitro and animal models cannot meet the modern medical exploration of real human brain structure and function. Recently, brain organoids generated by human pluripotent stem cells (hPSCs) can mimic the structure and physiological function of human brain, being widely used in medical research. Brain organoids generated from normal hPSCs or patient-derived induced pluripotent stem cells offer a more promising approach for the study of diverse human brain diseases. More importantly, the use of the established brain organoid model for drug evaluation is conducive to shorten the clinical transformation period. Herein, we summarize methods for the identification of brain organoids from cellular diversity, morphology and neuronal activity, brain disease modeling, toxicity testing, and drug evaluation. Based on this, it is hoped that this review will provide new insights into the pathogenesis of brain diseases and drug research and development, promoting the rapid development of brain science.

Advances in human cellular mechanistic understanding and drug discovery of brain organoids for neurodegenerative diseases

The prevalence of neurodegenerative diseases (NDs) is increasing rapidly as the aging population accelerates, and there are still no treatments to halt or reverse the progression of these diseases. While traditional 2D cultures and animal models fail to translate into effective therapies benefit patients, 3D cultured human brain organoids (hBOs) facilitate the use of non-invasive methods to capture patient data. The purpose of this study was to review the research and application of hBO in disease models and drug screening in NDs. The pluripotent stem cells are induced in multiple stages to form cerebral organoids, brain region-specific organoids and their derived brain cells, which exhibit complex brain-like structures and perform electrophysiological activities. The brain region-specific organoids and their derived neurons or glial cells contribute to the understanding of the pathogenesis of NDs and the efficient development of drugs, including Alzheimer's disease, Parkinson's disease, Huntington's disease and Amyotrophic lateral sclerosis. Glial-rich brain organoids facilitate the study of glial function and neuroinflammation, including astrocytes, microglia, and oligodendrocytes. Further research on the maturation enhancement, vascularization and multi-organoid assembly of hBO will help to enhance the research and application of NDs cellular models.

The organoid modeling approach to understanding the mechanisms underlying neurodegeneration: A comprehensive review

Neurodegenerative diseases (NDs) are severe disorders of the nervous system, and their causes are still not completely understood. Modeling the complex pathological mechanisms underlying NDs has long posed a significant challenge, as traditional in vitro and animal models often fail to accurately recapitulate the disease phenotypes observed in humans; however, the rise of organoid technology has opened new approaches for developing innovative disease models that can better capture the nuances of the human nervous system. Organoid platforms hold promise for contributing to the design of future clinical trials and advancing our understanding of these devastating neurological conditions and accelerate the discovery of effective, personalized therapies. This comprehensive review discusses the recent advancements in neural organoid technology and explores the potential of patient-derived organoids for modeling NDs conditions and presents findings related to the mechanisms of their development or progress.

Generating iAstrocytes From Human Induced Pluripotent Stem Cells by Combining Low-Density Passaging of Neural Progenitor Cells and Transcription Factor NFIA Transdifferentiation

Astrocytes are key regulators of central nervous system (CNS) homeostasis, and their dysfunction is implicated in neurological and neurodegenerative disorders. Here, we describe a two-step protocol to generate astrocytes from human induced pluripotent stem cells (hiPSCs) using a bankable neural progenitor cell (NPC) intermediate, followed by low-density passaging and overexpression of the gliogenic transcription factor NFIA. A bankable NPC intermediate allows for facile differentiation into both purified neuronal and astrocyte cell types in parallel from the same genetic background, depending on the experimental needs. This article presents a protocol to generate NPCs from hiPSCs, which are then differentiated into hiPSC-derived astrocytes, termed iAstrocytes. The resulting iAstrocytes express key markers of astrocyte identity at transcript and protein levels by bulk RNA-Seq and immunocytochemistry, respectively. Additionally, they respond to the inflammatory stimuli poly(I:C) and generate waves of calcium activity in response to either physical activity or the addition of ATP. Our approach offers a simple and robust method to generate and characterize human astrocytes, which can be used to model human disease affecting this cell type. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Differentiation of hiPSCs to NPCs Basic Protocol 2: Differentiation of NPCs into iAstrocytes Support Protocol 1: Molecular validation of iAstrocytes Support Protocol 2: Calcium imaging-based validation of iAstrocyte function Support Protocol 3: Differentiation of NPCs into neurons.

Induced pluripotent stem cell-derived macrophages as a platform for modelling human disease

Macrophages are innate immune cells that are present in essentially all tissues, where they have vital roles in tissue development, homeostasis and pathogenesis. The importance of macrophages in tissue function is reflected by their association with various human diseases, and studying macrophage functions in both homeostasis and pathological tissue settings is a promising avenue for new targeted therapies that will improve human health. The ability to generate macrophages from induced pluripotent stem (iPS) cells has revolutionized macrophage biology, with the generation of iPS cell-derived macrophages (iMacs) providing unlimited access to genotype-specific cells that can be used to model various human diseases involving macrophage dysregulation. Such disease modelling is achieved by generating iPS cells from patient-derived cells carrying disease-related mutations or by introducing mutations into iPS cells from healthy donors using CRISPR-Cas9 technology. These iMacs that carry disease-related mutations can be used to study the aetiology of the particular disease in vitro. To achieve more physiological relevance, iMacs can be co-cultured in 2D systems with iPS cell-derived cells or in 3D systems with iPS cell-derived organoids. Here, we discuss the studies that have attempted to model various human diseases using iMacs, highlighting how these have advanced our knowledge about the role of macrophages in health and disease.

Human brain organoids containing microglia that have arisen innately adapt to a β-amyloid challenge better than those in which microglia are integrated by co-culture

BACKGROUND

Alzheimer disease (AD) is a heterogenous and multifactorial disease, and its pathology is partly driven by microglia and their activated phenotype. Brain organoids (BOs) are gaining prominence as a relevant model of the human brain for the study of AD; however, BOs are commonly devoid of microglia. To overcome this limitation, current protocols incorporate microglia through either (1) co-culture (BO co-culture), or (2) molecular manipulation at critical windows of BO development to have microglia arise innately (BO innate cultures). It is currently unclear whether the microglia incorporated into BOs by either of these two protocols differ in function.

METHODS

At in vitro day 90, BO innate cultures and BO-co-cultures were challenged with the AD-related β-amyloid peptide (Aβ) for up to 72 h. After Aβ challenge, BOs were collected for immunoblotting. Immunoblots compared immunodensity and protein banding of Aβ and ionized calcium-binding adapter molecule 1 (IBA1, a marker of microglial activation) in BOs. The translational potential of these observations was supported using 56 human cortical samples from neurocognitively normal donors and patients with early-onset AD and late-onset AD. Statistical analyses were conducted using the Kruskal-Wallis test, a two-way ANOVA, or a simple linear regression, and where applicable, followed by Dunn's or Sidak's test.

RESULTS

We show that BO co-cultures promote Aβ oligomerization as early as 24 h and this coincides with a significant increase in IBA1 levels. In contrast, the Aβs do not oligomerize in BO innate cultures and the IBA1 response was modest and only emerged after 48 h. In human cortical samples, we found IBA1 levels correlated with age at onset, age at death, and the putative diagnostic Aβ(1-42)/Aβ(1-40) ratio (particularly in their oligomeric forms) in a sex-dependent manner.

CONCLUSIONS

Our unique observations suggest that BOs with innate microglia model the response of a healthy brain to Aβ, and by extension the initial stages of Aβ challenge. It would be impossible to model these early stages of pathogenesis in BOs where microglia are already compromised, such as those with microglia incorporated by co-culture.

Limitations of human brain organoids to study neurodegenerative diseases: a manual to survive

In 2013, M. Lancaster described the first protocol to obtain human brain organoids. These organoids, usually generated from human-induced pluripotent stem cells, can mimic the three-dimensional structure of the human brain. While they recapitulate the salient developmental stages of the human brain, their use to investigate the onset and mechanisms of neurodegenerative diseases still faces crucial limitations. In this review, we aim to highlight these limitations, which hinder brain organoids from becoming reliable models to study neurodegenerative diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS). Specifically, we will describe structural and biological impediments, including the lack of an aging footprint, angiogenesis, myelination, and the inclusion of functional and immunocompetent microglia—all important factors in the onset of neurodegeneration in AD, PD, and ALS. Additionally, we will discuss technical limitations for monitoring the microanatomy and electrophysiology of these organoids. In parallel, we will propose solutions to overcome the current limitations, thereby making human brain organoids a more reliable tool to model neurodegeneration.

Neuroprotective effect of Withania somnifera leaves extract nanoemulsion against penconazole-induced neurotoxicity in albino rats via modulating TGF-β1/Smad2 signaling pathway

Penconazole (PEN) is a systemic triazole fungicide used to control various fungal diseases on grapes, stone fruits, cucurbits, and strawberries. Still, it leaves residues on treated crops after collection with many hazardous effects on population including neurotoxicity. Withania somnifera leaves extract (WSLE) is known for its memory and brain function enhancing ability. To evoke such action efficiently, WSLE bioactive metabolites are needed to cross the blood-brain barrier, that could limit the availability of such compounds to be localized within the brain. Therefore, in the present study, the association between PEN exposure and neurotoxicity was evaluated, and formulated WSLE nanoemulsion was investigated for improving the permeability of the plant extract across the blood-brain barrier. The rats were divided into five groups (n = 6). The control group was administered distilled water, group II was treated with W. somnifera leaves extract nanoemulsion (WSLE NE), group III received PEN, group IV received PEN and WSLE, and group V received PEN and WSLE NE. All rats were gavaged daily for 6 weeks. Characterization of compounds in WSLE using LC-MS/MS analysis was estimated. Neurobehavioral disorders were evaluated in all groups. Oxidative stress biomarkers, antioxidant enzyme activities, and inflammatory cytokines were measured in brain tissue. Furthermore, the gene expression patterns of GFAP, APP, vimentin, TGF-β1, Smad2 and Bax were measured. Histopathological changes and immunohistochemical expression in the peripheral sciatic nerve and cerebral cortex were evaluated. A total of 91 compounds of different chemo-types were detected and identified in WSLE in both ionization modes. Our data showed behavioral impairment in the PEN-treated group, with significant elevation of oxidative stress biomarkers, proinflammatory cytokines, neuronal damage, and apoptosis. In contrast, the PEN-treated group with WSLE NE showed marked improvement in behavioral performance and histopathological alteration with a significant increase in antioxidant enzyme activity and anti-inflammatory cytokines compared to the group administered WSLE alone. The PEN-treated group with WSLE NE in turn significantly downregulated the expression levels of GFAP, APP, vimentin, TGF-β1, Smad2 and Bax in brain tissue. In conclusion, WSLE NE markedly enhanced the permeability of plant extract constituents through the blood brain barrier to boost its neuroprotective effect against PEN-induced neurotoxicity.

Human pluripotent stem cell (hPSC)-derived microglia for the study of brain disorders. A comprehensive review of existing protocols

Microglia, resident immune cells of the brain that originate from the yolk sac, play a critical role in maintaining brain homeostasis by monitoring and phagocytosing pathogens and cellular debris in the central nervous system (CNS). While they share characteristics with myeloid cells, they are distinct from macrophages. In response to injury, microglia release pro-inflammatory factors and contribute to brain homeostasis through activities such as synapse pruning and neurogenesis. To better understand their role in neurological disorders, the generation of in vitro models of human microglia has become essential. These models, derived from patient-specific induced pluripotent stem cells (iPSCs), provide a controlled environment to study the molecular and cellular mechanisms underlying microglia-mediated neuroinflammation and neurodegeneration. The incorporation or generation of microglia into three-dimensional (3D) organoid cultures provides a more physiologically relevant environment that offers further opportunities to study microglial dynamics and disease modeling. This review describes several protocols that have been recently developed for the generation of human-induced microglia. Importantly, it highlights the promise of these in vitro models in advancing our understanding of brain disorders and facilitating personalized drug screening.

A microglia-containing cerebral organoid model to study early life immune challenges

Prenatal infections and activation of the maternal immune system have been proposed to contribute to causing neurodevelopmental disorders (NDDs), chronic conditions often linked to brain abnormalities. Microglia are the resident immune cells of the brain and play a key role in neurodevelopment. Disruption of microglial functions can lead to brain abnormalities and increase the risk of developing NDDs. How the maternal as well as the fetal immune system affect human neurodevelopment and contribute to NDDs remains unclear. An important reason for this knowledge gap is the fact that the impact of exposure to prenatal risk factors has been challenging to study in the human context. Here, we characterized a model of cerebral organoids (CO) with integrated microglia (COiMg). These organoids express typical microglial markers and respond to inflammatory stimuli. The presence of microglia influences cerebral organoid development, including cell density and neural differentiation, and regulates the expression of several ciliated mesenchymal cell markers. Moreover, COiMg and organoids without microglia show similar but also distinct responses to inflammatory stimuli. Additionally, IFN-γ induced significant transcriptional and structural changes in the cerebral organoids, that appear to be regulated by the presence of microglia. Specifically, interferon-gamma (IFN-γ) was found to alter the expression of genes linked to autism. This model provides a valuable tool to study how inflammatory perturbations and microglial presence affect neurodevelopmental processes.

Investigating the neurobiology of maternal opioid use disorder and prenatal opioid exposure using brain organoid technology

Over the past two decades, Opioid Use Disorder (OUD) among pregnant women has become a major global public health concern. OUD has been characterized as a problematic pattern of opioid use despite adverse physical, psychological, behavioral, and or social consequences. Due to the relapsing-remitting nature of this disorder, pregnant mothers are chronically exposed to exogenous opioids, resulting in adverse neurological and neuropsychiatric outcomes. Collateral fetal exposure to opioids also precipitates severe neurodevelopmental and neurocognitive sequelae. At present, much of what is known regarding the neurobiological consequences of OUD and prenatal opioid exposure (POE) has been derived from preclinical studies in animal models and postnatal or postmortem investigations in humans. However, species-specific differences in brain development, variations in subject age/health/background, and disparities in sample collection or storage have complicated the interpretation of findings produced by these explorations. The ethical or logistical inaccessibility of human fetal brain tissue has also limited direct examinations of prenatal drug effects. To circumvent these confounding factors, recent groups have begun employing induced pluripotent stem cell (iPSC)-derived brain organoid technology, which provides access to key aspects of cellular and molecular brain development, structure, and function in vitro. In this review, we endeavor to encapsulate the advancements in brain organoid culture that have enabled scientists to model and dissect the neural underpinnings and effects of OUD and POE. We hope not only to emphasize the utility of brain organoids for investigating these conditions, but also to highlight opportunities for further technical and conceptual progress. Although the application of brain organoids to this critical field of research is still in its nascent stages, understanding the neurobiology of OUD and POE via this modality will provide critical insights for improving maternal and fetal outcomes.

Primary microglia cell cultures in translational research: Strengths and limitations

Microglia are the resident macrophages in the central nervous system, accounting for 10-15% of the cell mass in the brain. Next to their physiological role in development, monitoring neuronal function and the maintenance of homeostasis, microglia are crucial in the brain's immune defense. Brain injury and chronic neurological disorders are associated with neuroinflammation, in which microglia activation is a central element. Microglia acquire a wide spectrum of activation states in the diseased or injured brain, some of which are neurotoxic. The investigation of microglia (patho)physiology and therapeutic interventions targeting neuroinflammation is a substantial challenge. In addition to in vivo approaches, the application of in vitro model systems has gained significant ground and is essential to complement in vivo work. Primary microglia cultures have proved to be a useful tool. Microglia cultures have offered the opportunity to explore the mechanistic, molecular elements of microglia activation, the microglia secretome, and the efficacy of therapeutic treatments against neuroinflammation. As all model systems, primary microglia cultures have distinct strengths and limitations to be weighed when experiments are designed and when data are interpreted. Here, we set out to provide a succinct overview of the advantages and pitfalls of the use of microglia cultures, which instructs the refinement and further development of this technique to remain useful in the toolbox of microglia researchers. Since there is no conclusive therapy to combat neurotoxicity linked to neuroinflammation in acute brain injury or neurodegenerative disorders, these research tools remain essential to explore therapeutic opportunities.

Revealing the clinical potential of high-resolution organoids

The symbiotic interplay of organoid technology and advanced imaging strategies yields innovative breakthroughs in research and clinical applications. Organoids, intricate three-dimensional cell cultures derived from pluripotent or adult stem/progenitor cells, have emerged as potent tools for in vitro modeling, reflecting in vivo organs and advancing our grasp of tissue physiology and disease. Concurrently, advanced imaging technologies such as confocal, light-sheet, and two-photon microscopy ignite fresh explorations, uncovering rich organoid information. Combined with advanced imaging technologies and the power of artificial intelligence, organoids provide new insights that bridge experimental models and real-world clinical scenarios. This review explores exemplary research that embodies this technological synergy and how organoids reshape personalized medicine and therapeutics.

Organoids as preclinical models of human disease: progress and applications

In the field of biomedical research, organoids represent a remarkable advancement that has the potential to revolutionize our approach to studying human diseases even before clinical trials. Organoids are essentially miniature 3D models of specific organs or tissues, enabling scientists to investigate the causes of diseases, test new drugs, and explore personalized medicine within a controlled laboratory setting. Over the past decade, organoid technology has made substantial progress, allowing researchers to create highly detailed environments that closely mimic the human body. These organoids can be generated from various sources, including pluripotent stem cells, specialized tissue cells, and tumor tissue cells. This versatility enables scientists to replicate a wide range of diseases affecting different organ systems, effectively creating disease replicas in a laboratory dish. This exciting capability has provided us with unprecedented insights into the progression of diseases and how we can develop improved treatments. In this paper, we will provide an overview of the progress made in utilizing organoids as preclinical models, aiding our understanding and providing a more effective approach to addressing various human diseases.

Humanized brain organoids-on-chip integrated with sensors for screening neuronal activity and neurotoxicity

The complex structure and function of the human central nervous system that develops from the neural tube made in vitro modeling quite challenging until the discovery of brain organoids. Human-induced pluripotent stem cells-derived brain organoids offer recapitulation of the features of early human neurodevelopment in vitro, including the generation, proliferation, and differentiation into mature neurons and micro-macroglial cells, as well as the complex interactions among these diverse cell types of the developing brain. Recent advancements in brain organoids, microfluidic systems, real-time sensing technologies, and their cutting-edge integrated use provide excellent models and tools for emulation of fundamental neurodevelopmental processes, the pathology of neurological disorders, personalized transplantation therapy, and high-throughput neurotoxicity testing by bridging the gap between two-dimensional models and the complex three-dimensional environment in vivo. In this review, we summarize how bioengineering approaches are applied to mitigate the limitations of brain organoids for biomedical and clinical research. We further provide an extensive overview and future perspectives of the humanized brain organoids-on-chip platforms with integrated sensors toward brain organoid intelligence and biocomputing studies. Such approaches might pave the way for increasing approvable clinical applications by solving their current limitations.

Human Pluripotent Stem Cell-Derived Alveolar Organoids: Cellular Heterogeneity and Maturity

Chronic respiratory diseases such as idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, and respiratory infections injure the alveoli; the damage evoked is mostly irreversible and occasionally leads to death. Achieving a detailed understanding of the pathogenesis of these fatal respiratory diseases has been hampered by limited access to human alveolar tissue and the differences between mice and humans. Thus, the development of human alveolar organoid (AO) models that mimic in vivo physiology and pathophysiology has gained tremendous attention over the last decade. In recent years, human pluripotent stem cells (hPSCs) have been successfully employed to generate several types of organoids representing different respiratory compartments, including alveolar regions. However, despite continued advances in three-dimensional culture techniques and single-cell genomics, there is still a profound need to improve the cellular heterogeneity and maturity of AOs to recapitulate the key histological and functional features of in vivo alveolar tissue. In particular, the incorporation of immune cells such as macrophages into hPSC-AO systems is crucial for disease modeling and subsequent drug screening. In this review, we summarize current methods for differentiating alveolar epithelial cells from hPSCs followed by AO generation and their applications in disease modeling, drug testing, and toxicity evaluation. In addition, we review how current hPSC-AOs closely resemble in vivo alveoli in terms of phenotype, cellular heterogeneity, and maturity.

Leptomeningeal Neural Organoid (LMNO) Fusions as Models to Study Meninges-Brain Signaling

Neural organoids derived from human induced pluripotent stem cells (iPSCs) provide a model to study the earliest stages of human brain development, including neurogenesis, neural differentiation, and synaptogenesis. However, neural organoids lack supportive tissues and some non-neural cell types that are key regulators of brain development. Neural organoids have instead been co-cultured with non-neural structures and cell types to promote their maturation and model interactions with neuronal cells. One structure that does not form de novo with neural organoids is the meninges, a tri-layered structure that surrounds the CNS and secretes key signaling molecules required for mammalian brain development. Most studies of meninges-brain signaling have been performed in mice or using two-dimensional (2D) cultures of human cells, the latter not recapitulating the architecture and cellular diversity of the tissue. To overcome this, we developed a co-culture system of neural organoids generated from human iPSCs fused with fetal leptomeninges from mice with fluorescently labeled meninges (Col1a1-GFP). These proof-of-concept studies test the stability of the different cell types in the leptomeninges (fibroblast and macrophage) and the fused brain organoid (progenitor and neuron), as well as the interface between the organoid and meningeal tissue. We test the longevity of the fusion pieces after 30 days and 60 days in culture, describe best practices for preparing the meninges sample prior to fusion, and examine the feasibility of single or multiple meninges pieces fused to a single organoid. We discuss potential uses of the current version of the LMNO fusion model and opportunities to improve the system.

Leptomeningeal Neural Organoid (LMNO) Fusions as Models to Study Meninges-Brain Signaling

Neural organoids derived from human induced pluripotent stem cells (iPSCs) provide a model to study the earliest stages of human brain development, including neurogenesis, neural differentiation, and synaptogenesis. However, neural organoids lack supportive tissues and some non-neural cell types that are key regulators of brain development. Neural organoids have instead been co-cultured with non-neural structures and cell types to promote their maturation and model interactions with neuronal cells. One structure that does not form de novo with neural organoids is the meninges, a tri-layered structure that surrounds the CNS and secretes key signaling molecules required for mammalian brain development. Most studies of meninges-brain signaling have been performed in mice or using two-dimensional (2D) cultures of human cells, the latter not recapitulating the architecture and cellular diversity of the tissue. To overcome this, we developed a co-culture system of neural organoids generated from human iPSCs fused with fetal leptomeninges from mice with fluorescently labeled meninges (Col1a1-GFP). These proof-of-concept studies test the stability of the different cell types in the leptomeninges (fibroblast and macrophage) and the fused brain organoid (progenitor and neuron), as well as the interface between the organoid and meningeal tissue. We test the longevity of the fusion pieces after 30 days and 60 days in culture, describe best practices for preparing the meninges sample prior to fusion, and examine the feasibility of single or multiple meninges pieces fused to a single organoid. We discuss potential uses of the current version of the LMNO fusion model and opportunities to improve the system.

Expression and Functional Analysis of core stemness factors OSKM (OCT4, SOX2, KLF4, and MYC) in Pan-cancer

The dedifferentiation process of tumorigenesis and somatic cell reprogramming has some commonness and differences, which is the key question to cancer therapeutic strategy and stem cell applications. To further explore the commonalities and variance between carcinogenesis and induced pluripotent stem cell reprogramming, we investigated the role of stemness factors OSKM (OCT4, SOX2, KLF4, and MYC) in the pan-cancer process using public clinical data. Expression of OSKM in human pan-cancer was analyzed via the Genotype Tissue Expression (GTEx) and The Cancer Genome Atlas (TCGA) database based on the RNA-seq data of tissues. The correlation of expression between OSKM genes was analyzed via the Tumor Immune Evaluation Resource (TIMER) database, while the STRING tool was used to construct the protein-protein interaction network for OSKM. Prognostic impact of OSKM in pan-cancer was analyzed by Cox proportional hazards regression model. The relationships between OSKM and tumor stemness, tumor microenvironment and immune checkpoint and were performed by Sangerbox platform using Pearson correlation analysis. Our results showed that OSKM were universally expressed and significantly altered in tumors compared with adjacent normal tissues in most tumor types. In addition, correlation analysis revealed the relevance of OSKM genes to patient prognosis, cancer cell stemness, tumor microenvironment or immune checkpoint. However, there is little similarity between these genes in terms of how they function in each cancer type. This study elucidates the different roles of core stemness factors OSKM in pan-cancer, offering potential therapeutic targets for novel anti-cancer strategies and knowledge to minimize the potential carcinogenic effects during stem cell transplantation.

Cell Replacement Therapy for Brain Repair: Recent Progress and Remaining Challenges for Treating Parkinson's Disease and Cortical Injury

Neural transplantation represents a promising approach to repairing damaged brain circuitry. Cellular grafts have been shown to promote functional recovery through "bystander effects" and other indirect mechanisms. However, extensive brain lesions may require direct neuronal replacement to achieve meaningful restoration of function. While fetal cortical grafts have been shown to integrate with the host brain and appear to develop appropriate functional attributes, the significant ethical concerns and limited availability of this tissue severely hamper clinical translation. Induced pluripotent stem cell-derived cells and tissues represent a more readily scalable alternative. Significant progress has recently been made in developing protocols for generating a wide range of neural cell types in vitro. Here, we discuss recent progress in neural transplantation approaches for two conditions with distinct design needs: Parkinson's disease and cortical injury. We discuss the current status and future application of injections of dopaminergic cells for the treatment of Parkinson's disease as well as the use of structured grafts such as brain organoids for cortical repair.

Treating Parkinson's Disease with Human Bone Marrow Mesenchymal Stem Cell Secretome: A Translational Investigation Using Human Brain Organoids and Different Routes of In Vivo Administration

Parkinson's disease (PD) is the most common movement disorder, characterized by the progressive loss of dopaminergic neurons from the nigrostriatal system. Currently, there is no treatment that retards disease progression or reverses damage prior to the time of clinical diagnosis. Mesenchymal stem cells (MSCs) are one of the most extensively studied cell sources for regenerative medicine applications, particularly due to the release of soluble factors and vesicles, known as secretome. The main goal of this work was to address the therapeutic potential of the secretome collected from bone-marrow-derived MSCs (BM-MSCs) using different models of the disease. Firstly, we took advantage of an optimized human midbrain-specific organoid system to model PD in vitro using a neurotoxin-induced model through 6-hydroxydopamine (6-OHDA) exposure. In vivo, we evaluated the effects of BM-MSC secretome comparing two different routes of secretome administration: intracerebral injections (a two-site single administration) against multiple systemic administration. The secretome of BM-MSCs was able to protect from dopaminergic neuronal loss, these effects being more evident in vivo. The BM-MSC secretome led to motor function recovery and dopaminergic loss protection; however, multiple systemic administrations resulted in larger therapeutic effects, making this result extremely relevant for potential future clinical applications.

Human iPSC-derived glia models for the study of neuroinflammation

Neuroinflammation is a complex biological process that plays a significant role in various brain disorders. Microglia and astrocytes are the key cell types involved in inflammatory responses in the central nervous system. Neuroinflammation results in increased levels of secreted inflammatory factors, such as cytokines, chemokines, and reactive oxygen species. To model neuroinflammation in vitro, various human induced pluripotent stem cell (iPSC)-based models have been utilized, including monocultures, transfer of conditioned media between cell types, co-culturing multiple cell types, neural organoids, and xenotransplantation of cells into the mouse brain. To induce neuroinflammatory responses in vitro, several stimuli have been established that can induce responses in either microglia, astrocytes, or both. Here, we describe and critically evaluate the different types of iPSC models that can be used to study neuroinflammation and highlight how neuroinflammation has been induced and measured in these cultures.