The Role of the Extracellular Matrix in Neural Progenitor Cell Proliferation and Cortical Folding During Human Neocortex Development

Altered extracellular matrix structure and elevated stiffness in a brain organoid model for disease

The viscoelastic properties of tissues influence their morphology and cellular behavior, yet little is known about changes in these properties during brain malformations. Lissencephaly, a severe cortical malformation caused by LIS1 mutations, results in a smooth cortex. Here, we show that human-derived brain organoids with LIS1 mutation exhibit increased stiffness compared to controls at multiple developmental stages. This stiffening correlates with abnormal extracellular matrix (ECM) expression and organization, as well as elevated water content, measured by diffusion-weighted MRI. Short-term MMP9 treatment reduces both stiffness and water diffusion levels to control values. Additionally, a computational microstructure mechanical model predicts mechanical changes based on ECM organization. These findings suggest that LIS1 plays a critical role in ECM regulation during brain development and that its mutation leads to significant viscoelastic alterations.

Dysregulation of REST and its target genes impacts the fate of neural progenitor cells in down syndrome

Increasing shreds of evidence suggest that neurogenic-to-gliogenic shift may be critical to the abnormal neurodevelopment observed in individuals with Down syndrome (DS). REST, the Repressor Element-1 Silencing Transcription factor, regulates the differentiation and development of neural cells. Downregulation of REST may lead to defects in post-differentiation neuronal morphology in the brain of the DS fetal. This study aims to elucidate the role of REST in DS-derived NPCs using bioinformatics analyses and laboratory validations. We identified and validated vital REST-targeted DEGs: CD44, TGFB1, FN1, ITGB1, and COL1A1. Interestingly, these genes are involved in neurogenesis and gliogenesis in DS-derived NPCs. Furthermore, we identified nuclear REST loss and the neuroblast marker, DCX, was downregulated in DS human trisomic induced pluripotent stem cells (hiPSCs)-derived NPCs, whereas the glioblast marker, NFIA, was upregulated. Our findings indicate that the loss of REST is critical in the neurogenic-to-gliogenic shift observed in DS-derived NPCs. REST and its target genes may collectively regulate the NPC phenotype.

Hyaluronidase-induced matrix remodeling contributes to long-term synaptic changes

Extracellular brain space contains water, dissolved ions, and multiple other signaling molecules. The neural extracellular matrix (ECM) is also a significant component of the extracellular space. The ECM is synthesized by neurons, astrocytes, and other types of cells. Hyaluronan, a hyaluronic acid polymer, is a key component of the ECM. The functions of hyaluronan include barrier functions and signaling. In this article, we investigate physiological processes during the acute phase of enzymatic ECM removal. We found that hyaluronidase, an ECM removal agent, triggers simultaneous membrane depolarization and sharp calcium influx into neurons. Spontaneous action potential firing frequency increased rapidly after ECM destruction in interneurons, but not pyramidal neurons. Hyaluronidase-dependent calcium entry can be blocked by a selective antagonist of N-methyl-D-aspartate (NMDA) receptors, revealing these receptors as the main player in the observed phenomenon. Additionally, we demonstrate increased NMDA-dependent long-term potentiation at CA3-to-CA1 synapses during the acute phase of ECM removal. These findings suggest that hyaluronan is a significant synaptic player.

Manufacturing Uniform Cerebral Organoids for Neurological Disease Modeling and Drug Evaluation

Human cerebral organoids are promising tools for investigating brain development and the pathogenesis underlying neurological disorders. To use organoids for drug effectiveness and safety screening, the organoids dispensed into each well must be prepared under precisely the same conditions as the cells. Despite decades of extensive research on approaches to improve organoid generation, various challenges remain, such as low yields and heterogeneity in size and differentiation both within and between batches. Here, we newly established uniform cerebral organoids (UCOs) derived from induced pluripotent stem cells by optimizing organoid size and performing real-time monitoring of telencephalic differentiation marker expression. These organoids exhibited morphological uniformity and consistent expression of FOXG1 during telencephalic differentiation, with high productivity. Moreover, UCOs faithfully recapitulated early corticogenesis, concomitant with the establishment of neuroepithelial populations, cortical plate neurons, and glial cells. Furthermore, UCOs systematically developed neural networks and exhibited both excitatory and inhibitory electrophysiological signals when exposed to neurotransmission blockers. Neurodevelopmental disease models derived from UCOs manifested neurite outgrowth defects, which could be ameliorated with targeted drug treatment. We propose UCOs as an advanced platform with low organoid variations and high reproducibility for modeling both brain development and neurological diseases.

Using different zebrafish models to explore liver regeneration

The liver possesses an impressive capability to regenerate following various injuries. Given its profound implications for the treatment of liver diseases, which afflict millions globally, liver regeneration stands as a pivotal area of digestive organ research. Zebrafish (Danio rerio) has emerged as an ideal model organism in regenerative medicine, attributed to their remarkable ability to regenerate tissues and organs, including the liver. Many fantastic studies have been performed to explore the process of liver regeneration using zebrafish, especially the extreme hepatocyte injury model. Biliary-mediated liver regeneration was first discovered in the zebrafish model and then validated in mammalian models and human patients. Considering the notable expansion of biliary epithelial cells in many end-stage liver diseases, the promotion of biliary-mediated liver regeneration might be another way to treat these refractory liver diseases. To date, a comprehensive review discussing the current advancements in zebrafish liver regeneration models is lacking. Therefore, this review aims to investigate the utility of different zebrafish models in exploring liver regeneration, highlighting the genetic and cellular insights gained and discussing the potential translational impact on human health.

A Hybrid 2D-to-3D in vitro Differentiation Platform Improves Outcomes of Cerebral Cortical Organoid Generation in hiPSCs

Three-dimensional (3D) cerebral cortical organoids are popular in vitro cellular model systems widely used to study human brain development and disease, compared to traditional stem cell-derived methods that use two-dimensional (2D) monolayer cultures. Despite the advancements made in protocol development for cerebral cortical organoid derivation over the past decade, limitations due to biological, mechanistic, and technical variables remain in generating these complex 3D cellular systems. Building from our previously established differentiation system, we have made modifications to our existing 3D cerebral cortical organoid protocol that resolve several of these technical and biological challenges when working with diverse groups of human induced pluripotent stem cell (hiPSC) lines. This improved protocol blends a 2D monolayer culture format for the specification of neural stem cells and expansion of neuroepithelial progenitor cells with a 3D system for improved self-aggregation and subsequent organoid development. Furthermore, this "hybrid" approach is amenable to both an accelerated cerebral cortical organoid protocol as well as an alternative long-term differentiation protocol. In addition to establishing a hybrid technical format, this protocol also offers phenotypic and morphological characterization of stage-specific cellular profiles using antibodies and fluorescent-based dyes for live cell imaging. © 2024 Wiley Periodicals LLC. Basic Protocol 1: hiPSC-based 2D monolayer specification into neural stem cells (NSCs) Basic Protocol 2: Serial passaging and 2D monolayer expansion of neuroepithelial progenitor cells (NPCs) Support Protocol 1: Direct cryopreservation and rapid thawing of NSCs and NPCs Basic Protocol 3: Bulk aggregation of 3D neurospheres and accelerated cerebral cortical organoid differentiation Alternate Protocol 1: Bulk aggregation of 3D neurospheres and long-term cerebral cortical organoid differentiation Support Protocol 2: High-throughput 3D neurosphere formation and 2D neurosphere migration assay Support Protocol 3: LIVE/DEAD stain cell imaging assay of 3D neurospheres Support Protocol 4: NeuroFluor NeuO live cell dye for 3D cerebral cortical organoids.

A 3D Bioprinted Cortical Organoid Platform for Modeling Human Brain Development

The ability to promote three-dimensional (3D) self-organization of induced pluripotent stem cells into complex tissue structures called organoids presents new opportunities for the field of developmental biology. Brain organoids have been used to investigate principles of neurodevelopment and neuropsychiatric disorders and serve as a drug screening and discovery platform. However, brain organoid cultures are currently limited by a lacking ability to precisely control their extracellular environment. Here, this work employs 3D bioprinting to generate a high-throughput, tunable, and reproducible scaffold for controlling organoid development and patterning. Additionally, this approach supports the coculture of organoids and vascular cells in a custom architecture containing interconnected endothelialized channels. Printing fidelity and mechanical assessments confirm that fabricated scaffolds closely match intended design features and exhibit stiffness values reflective of the developing human brain. Using organoid growth, viability, cytoarchitecture, proliferation, and transcriptomic benchmarks, this work finds that organoids cultured within the bioprinted scaffold long-term are healthy and have expected neuroectodermal differentiation. Lastly, this work confirms that the endothelial cells (ECs) in printed channel structures can migrate toward and infiltrate into the embedded organoids. This work demonstrates a tunable 3D culturing platform that can be used to create more complex and accurate models of human brain development and underlying diseases.

Sil1-deficient fibroblasts generate an aberrant extracellular matrix leading to tendon disorganisation in Marinesco-Sjögren syndrome

BACKGROUND

Marinesco-Sjögren syndrome (MSS) is an autosomal recessive neuromuscular disorder that arises in early childhood and is characterized by congenital cataracts, myopathy associated with muscle weakness, and degeneration of Purkinje neurons leading to ataxia. About 60% of MSS patients have loss-of-function mutations in the SIL1 gene. Sil1 is an endoplasmic reticulum (ER) protein required for the release of ADP from the master chaperone Bip, which in turn will release the folded proteins. The expression of non-functional Sil1 leads to the accumulation of unfolded proteins in the ER and this triggers the unfolded protein response (UPR). A dysfunctional UPR could be a key element in the pathogenesis of MSS, although our knowledge of the molecular pathology of MSS is still incomplete.

METHODS

RNA-Seq transcriptomics was analysed using the String database and the Ingenuity Pathway Analysis platform. Fluorescence confocal microscopy was used to study the remodelling of the extracellular matrix (ECM). Transmission electron microscopy (TEM) was used to reveal the morphology of the ECM in vitro and in mouse tendon.

RESULTS

Our transcriptomic analysis, performed on patient-derived fibroblasts, revealed 664 differentially expressed (DE) transcripts. Enrichment analysis of DE genes confirmed that the patient fibroblasts have a membrane trafficking issue. Furthermore, this analysis indicated that the extracellular space/ECM and the cell adhesion machinery, which together account for around 300 transcripts, could be affected in MSS. Functional assays showed that patient fibroblasts have a reduced capacity of ECM remodelling, reduced motility, and slower spreading during adhesion to Petri dishes. TEM micrographs of negative-stained ECM samples from these fibroblasts show differences of filaments in terms of morphology and size. Finally, structural analysis of the myotendinous junction of the soleus muscle and surrounding regions of the Achilles tendon revealed a disorganization of collagen fibres in the mouse model of MSS (woozy).

CONCLUSIONS

ECM alterations can affect the proper functioning of several organs, including those damaged in MSS such as the central nervous system, skeletal muscle, bone and lens. On this basis, we propose that aberrant ECM is a key pathological feature of MSS and may help explain most of its clinical manifestations.

Multiscale engineering of brain organoids for disease modeling

Brain organoids hold great potential for modeling human brain development and pathogenesis. They recapitulate certain aspects of the transcriptional trajectory, cellular diversity, tissue architecture and functions of the developing brain. In this review, we explore the engineering strategies to control the molecular-, cellular- and tissue-level inputs to achieve high-fidelity brain organoids. We review the application of brain organoids in neural disorder modeling and emerging bioengineering methods to improve data collection and feature extraction at multiscale. The integration of multiscale engineering strategies and analytical methods has significant potential to advance insight into neurological disorders and accelerate drug development.

Exploring the properties and potential of the neural extracellular matrix for next-generation regenerative therapies

The extracellular matrix (ECM) is a dynamic and complex network of proteins and molecules that surrounds cells and tissues in the nervous system and orchestrates a myriad of biological functions. This review carefully examines the diverse interactions between cells and the ECM, as well as the transformative chemical and physical changes that the ECM undergoes during neural development, aging, and disease. These transformations play a pivotal role in shaping tissue morphogenesis and neural activity, thereby influencing the functionality of the central nervous system (CNS). In our comprehensive review, we describe the diverse behaviors of the CNS ECM in different physiological and pathological scenarios and explore the unique properties that make ECM-based strategies attractive for CNS repair and regeneration. Addressing the challenges of scalability, variability, and integration with host tissues, we review how advanced natural, synthetic, and combinatorial matrix approaches enhance biocompatibility, mechanical properties, and functional recovery. Overall, this review highlights the potential of decellularized ECM as a powerful tool for CNS modeling and regenerative purposes and sets the stage for future research in this exciting field. This article is categorized under: Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

Neuronal Stem Cells from Late-Onset Alzheimer Patients Show Altered Regulation of Sirtuin 1 Depending on Apolipoprotein E Indicating Disturbed Stem Cell Plasticity

Late-onset Alzheimer's disease (AD) is a complex multifactorial disease. The greatest known risk factor for late-onset AD is the E4 allele of the apolipoprotein E (APOE), while increasing age is the greatest known non-genetic risk factor. The cell type-specific functions of neural stem cells (NSCs), in particular their stem cell plasticity, remain poorly explored in the context of AD pathology. Here, we describe a new model that employs late-onset AD patient-derived induced pluripotent stem cells (iPSCs) to generate NSCs and to examine the role played by APOE4 in the expression of aging markers such as sirtuin 1 (SIRT1) in comparison to healthy subjects carrying APOE3. The effect of aging was investigated by using iPSC-derived NSCs from old age subjects as healthy matched controls. Transcript and protein analysis revealed that genes were expressed differently in NSCs from late-onset AD patients, e.g., exhibiting reduced autophagy-related protein 7 (ATG7), phosphatase and tensin homolog (PTEN), and fibroblast growth factor 2 (FGF2). Since SIRT1 expression differed between APOE3 and APOE4 NSCs, the suppression of APOE function in NSCs also repressed the expression of SIRT1. However, the forced expression of APOE3 by plasmids did not recover differently expressed genes. The altered aging markers indicate decreased plasticity of NSCs. Our study provides a suitable in vitro model to investigate changes in human NSCs associated with aging, APOE4, and late-onset AD.

Transcriptional consequences of trisomy 21 on neural induction

Introduction

Down syndrome, caused by trisomy 21, is a complex developmental disorder associated with intellectual disability and reduced growth of multiple organs. Structural pathologies are present at birth, reflecting embryonic origins. A fundamental unanswered question is how an extra copy of human chromosome 21 contributes to organ-specific pathologies that characterize individuals with Down syndrome, and, relevant to the hallmark intellectual disability in Down syndrome, how trisomy 21 affects neural development. We tested the hypothesis that trisomy 21 exerts effects on human neural development as early as neural induction.

Methods

Bulk RNA sequencing was performed on isogenic trisomy 21 and euploid human induced pluripotent stem cells (iPSCs) at successive stages of neural induction: embryoid bodies at Day 6, early neuroectoderm at Day 10, and differentiated neuroectoderm at Day 17.

Results

Gene expression analysis revealed over 1,300 differentially expressed genes in trisomy 21 cells along the differentiation pathway compared to euploid controls. Less than 5% of the gene expression changes included upregulated chromosome 21 encoded genes at every timepoint. Genes involved in specific growth factor signaling pathways (WNT and Notch), metabolism (including oxidative stress), and extracellular matrix were altered in trisomy 21 cells. Further analysis uncovered heterochronic expression of genes.

Conclusion

Trisomy 21 impacts discrete developmental pathways at the earliest stages of neural development. The results suggest that metabolic dysfunction arises early in embryogenesis in trisomy 21 and may affect development and function more broadly.

Human neuronal maturation comes of age: cellular mechanisms and species differences

The delayed and prolonged postmitotic maturation of human neurons, compared with neurons from other species, may contribute to human-specific cognitive abilities and neurological disorders. Here we review the mechanisms of neuronal maturation, applying lessons from model systems to understand the specific features of protracted human cortical maturation and species differences. We cover cell-intrinsic features of neuronal maturation, including transcriptional, epigenetic and metabolic mechanisms, as well as cell-extrinsic features, including the roles of activity and synapses, the actions of glial cells and the contribution of the extracellular matrix. We discuss evidence for species differences in biochemical reaction rates, the proposed existence of an epigenetic maturation clock and the contributions of both general and modular mechanisms to species-specific maturation timing. Finally, we suggest approaches to measure, improve and accelerate the maturation of human neurons in culture, examine crosstalk and interactions among these different aspects of maturation and propose conceptual models to guide future studies.

The SVZ stem cell niche-components, functions, and in vitro modelling

Neocortical development depends on the intrinsic ability of neural stem and progenitor cells to proliferate and differentiate to generate the different kinds of neurons in the adult brain. These progenitor cells can be distinguished into apical progenitors, which occupy a stem cell niche in the ventricular zone and basal progenitors, which occupy a stem cell niche in the subventricular zone (SVZ). During development, the stem cell niche provided in the subventricular zone enables the increased proliferation and self-renewal of basal progenitors, which likely underlie the expansion of the human neocortex. However, the components forming the SVZ stem cell niche in the developing neocortex have not yet been fully understood. In this review, we will discuss potential components of the SVZ stem cell niche, i.e., extracellular matrix composition and brain vasculature, and their possible key role in establishing and maintaining this niche during fetal neocortical development. We will also emphasize the potential role of basal progenitor morphology in maintaining their proliferative capacity within the stem cell niche of the SVZ. Finally, we will focus on the use of brain organoids to i) understand the unique features of basal progenitors, notably basal radial glia; ii) study components of the SVZ stem cell niche; and iii) provide future directions on how to improve brain organoids, notably the organoid SVZ, and make them more reliable models of human neocortical development and evolution studies.

Intracellular traffic and polarity in brain development

Neurons forming the human brain are generated during embryonic development by neural stem and progenitor cells via a process called neurogenesis. A crucial feature contributing to neural stem cell morphological and functional heterogeneity is cell polarity, defined as asymmetric distribution of cellular components. Cell polarity is built and maintained thanks to the interplay between polarity proteins and polarity-generating organelles, such as the endoplasmic reticulum (ER) and the Golgi apparatus (GA). ER and GA affect the distribution of membrane components and work as a hub where glycans are added to nascent proteins and lipids. In the last decades our knowledge on the role of polarity in neural stem and progenitor cells have increased tremendously. However, the role of traffic and associated glycosylation in neural stem and progenitor cells is still relatively underexplored. In this review, we discuss the link between cell polarity, architecture, identity and intracellular traffic, and highlight how studies on neurons have shaped our knowledge and conceptual framework on traffic and polarity. We will then conclude by discussing how a group of rare diseases, called congenital disorders of glycosylation (CDG) offers the unique opportunity to study the contribution of traffic and glycosylation in the context of neurodevelopment.

A controllable perfusion microfluidic chip for facilitating the development of retinal ganglion cells in human retinal organoids

Retinal organoids (ROs) derived from human pluripotent stem cells (hPSCs) have become a promising model in vitro to recapitulate human retinal development, which can be further employed to explore the mechanisms of retinal diseases. However, the current culture systems for ROs lack physiologically relevant microenvironments, such as controllable mechano-physiological cues and dynamic feedback between cells and the extracellular matrix (ECM), which limits the accurate control of RO development. Therefore, we designed a controllable perfusion microfluidic chip (CPMC) with the advantages of precisely controlling fluidic shear stress (FSS) and oxygen concentration distribution in a human embryonic stem cell (hESC)-derived RO culture system. We found that ROs cultured under this system allow for expanding the retinal progenitor cell (RPC) pool, orchestrating the retinal ganglion cell (RGC) specification, and axon growth without disturbing the spatial and temporal patterning events at the early stage of RO development. Furthermore, RNA sequencing data revealed that the activation of voltage-gated ion channels and the increased expression of ECM components synergistically improve the growth of ROs and facilitate the differentiation of RGCs. This study elaborates on the advantages of the designed CPMC to promote RO growth and provide a controllable and reliable platform for the efficient maturity of RGCs in the ROs, promising applications in modeling RGC-related disorders, drug screening, and cell transplantation.

MeCP2 dysfunction prevents proper BMP signaling and neural progenitor expansion in brain organoid

OBJECTIVES

Sporadic mutations in MeCP2 are a hallmark of Rett syndrome (RTT). Many RTT brain organoid models have exhibited pathogenic phenotypes such as decreased spine density and small size of soma with altered electrophysiological signals. However, previous models are mainly focused on the phenotypes observed in the late phase and rarely provide clues for the defect of neural progenitors which generate different types of neurons and glial cells.

METHODS

We newly established the RTT brain organoid model derived from MeCP2-truncated iPS cells which were genetically engineered by CRISPR/Cas9 technology. By immunofluorescence imaging, we studied the development of NPC pool and its fate specification into glutamatergic neurons or astrocytes in RTT organoids. By total RNA sequencing, we investigated which signaling pathways were altered during the early brain development in RTT organoids.

RESULTS

Dysfunction of MeCP2 caused the defect of neural rosette formation in the early phase of cortical development. In total transcriptome analysis, BMP pathway-related genes are highly associated with MeCP2 depletion. Moreover, levels of pSMAD1/5 and BMP target genes are excessively increased, and treatment of BMP inhibitors partially rescues the cell cycle progression of neural progenitors. Subsequently, MeCP2 dysfunction reduced the glutamatergic neurogenesis and induced overproduction of astrocytes. Nevertheless, early inhibition of BMP pathway rescued VGLUT1 expression and suppressed astrocyte maturation.

INTERPRETATION

Our results demonstrate that MeCP2 is required for the expansion of neural progenitor cells by modulating BMP pathway at early stages of development, and this influence persists during neurogenesis and gliogenesis at later stages of brain organoid development.

The Human Extracellular Matrix Diseasome Reveals Genotype-Phenotype Associations with Clinical Implications for Age-Related Diseases

The extracellular matrix (ECM) is earning an increasingly relevant role in many disease states and aging. The analysis of these disease states is possible with the GWAS and PheWAS methodologies, and through our analysis, we aimed to explore the relationships between polymorphisms in the compendium of ECM genes (i.e., matrisome genes) in various disease states. A significant contribution on the part of ECM polymorphisms is evident in various types of disease, particularly those in the core-matrisome genes. Our results confirm previous links to connective-tissue disorders but also unearth new and underexplored relationships with neurological, psychiatric, and age-related disease states. Through our analysis of the drug indications for gene-disease relationships, we identify numerous targets that may be repurposed for age-related pathologies. The identification of ECM polymorphisms and their contributions to disease will play an integral role in future therapeutic developments, drug repurposing, precision medicine, and personalized care.

Tumor Microenvironment in Glioma Invasion

A major malignant trait of gliomas is their remarkable infiltration capacity. When glioma develops, the tumor cells have already reached the distant part. Therefore, complete removal of the glioma is impossible. Recently, research on the involvement of the tumor microenvironment in glioma invasion has advanced. Local hypoxia triggers cell migration as an environmental factor. The transcription factor hypoxia-inducible factor (HIF) -1α, produced in tumor cells under hypoxia, promotes the transcription of various invasion related molecules. The extracellular matrix surrounding tumors is degraded by proteases secreted by tumor cells and simultaneously replaced by an extracellular matrix that promotes infiltration. Astrocytes and microglia become tumor-associated astrocytes and glioma-associated macrophages/microglia, respectively, in relation to tumor cells. These cells also promote glioma invasion. Interactions between glioma cells actively promote infiltration of each other. Surgery, chemotherapy, and radiation therapy transform the microenvironment, allowing glioma cells to invade. These findings indicate that the tumor microenvironment may be a target for glioma invasion. On the other hand, because the living body actively promotes tumor infiltration in response to the tumor, it is necessary to reconsider whether the invasion itself is friend or foe to the brain.