Laminin enhances the growth of human neural stem cells in defined culture media

Protocol for evaluating mitochondrial respiration in iPSC-derived neurons by the Seahorse XF analyzer

Here, we present a protocol describing the quantification of oxygen consumption rate (OCR) and maximal respiration rate (MRR) in living induced pluripotent stem cell (iPSC)-derived neurons using the Seahorse analyzer. We guide you through the whole process: culture amplification and seeding of neural progenitor cells (NPCs), their differentiation into neurons, and normalization of the results to cell number in the analytical phase. The assessment of cellular mitochondrial function, by analyzing mitochondrial respiration, could be useful in various diseases as well as in drug screening. For complete details on the use and execution of this protocol, please refer to Aleo et al.1.

The Placenta as a Source of Human Material for Neuronal Repair

Stem cell therapy has the potential to meet unsolved problems in tissue repair and regeneration, particularly in the neural tissues. However, an optimal source has not yet been found. Growing evidence indicates that positive effects produced in vivo by mesenchymal stem cells (MSCs) can be due not only to their plasticity but also to secreted molecules including extracellular vesicles (EVs) and the extracellular matrix (ECM). Trophic effects produced by MSCs may reveal the key to developing effective tissue-repair strategies, including approaches based on brain implants or other implantable neural electrodes. In this sense, MSCs will become increasingly valuable and needed in the future. The placenta is a temporary organ devoted to protecting and supporting the fetus. At the same time, the placenta represents an abundant and extremely convenient source of MSCs. Nonetheless, placenta-derived MSCs (P-MSCs) remain understudied as compared to MSCs isolated from other sources. This review outlines the limited literature describing the neuroregenerative effects of P-MSC-derived biomaterials and advocates for exploiting the potential of this untapped source for human regenerative therapies.

Progress in the development of piezoelectric biomaterials for tissue remodeling

Piezoelectric biomaterials have demonstrated significant potential in the past few decades to heal damaged tissue and restore cellular functionalities. Herein, we discuss the role of bioelectricity in tissue remodeling and explore ways to mimic such tissue-like properties in synthetic biomaterials. In the past decade, biomedical engineers have adopted emerging functional biomaterials-based tissue engineering approaches using innovative bioelectronic stimulation protocols based on dynamic stimuli to direct cellular activation, proliferation, and differentiation on engineered biomaterial constructs. The primary focus of this review is to discuss the concepts of piezoelectric energy harvesting, piezoelectric materials, and their application in soft (skin and neural) and hard (dental and bone) tissue regeneration. While discussing the prospective applications as an engineered tissue, an important distinction has been made between piezoceramics, piezopolymers, and their composites. The superiority of piezopolymers over piezoceramics to circumvent issues such as stiffness mismatch, biocompatibility, and biodegradability are highlighted. We aim to provide a comprehensive review of the field and identify opportunities for the future to develop clinically relevant and state-of-the-art biomaterials for personalized and remote health care.

Laminin-associated integrins mediate Diffuse Intrinsic Pontine Glioma infiltration and therapy response within a neural assembloid model

Diffuse Intrinsic Pontine Glioma (DIPG) is a highly aggressive and fatal pediatric brain cancer. One pre-requisite for tumor cells to infiltrate is adhesion to extracellular matrix (ECM) components. However, it remains largely unknown which ECM proteins are critical in enabling DIPG adhesion and migration and which integrin receptors mediate these processes. Here, we identify laminin as a key ECM protein that supports robust DIPG cell adhesion and migration. To study DIPG infiltration, we developed a DIPG-neural assembloid model, which is composed of a DIPG spheroid fused to a human induced pluripotent stem cell-derived neural organoid. Using this assembloid model, we demonstrate that knockdown of laminin-associated integrins significantly impedes DIPG infiltration. Moreover, laminin-associated integrin knockdown improves DIPG response to radiation and HDAC inhibitor treatment within the DIPG-neural assembloids. These findings reveal the critical role of laminin-associated integrins in mediating DIPG progression and drug response. The results also provide evidence that disrupting integrin receptors may offer a novel therapeutic strategy to enhance DIPG treatment outcomes. Finally, these results establish DIPG-neural assembloid models as a powerful tool to study DIPG disease progression and enable drug discovery.

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.

Nanoscale surface coatings and topographies for neural interfaces

With the lack of minimally invasive tools for probing neuronal systems across spatiotemporal scales, understanding the working mechanism of the nervous system and limited assessments available are imperative to prevent or treat neurological disorders. In particular, nanoengineered neural interfaces can provide a solution to this technological barrier. This review covers recent surface engineering approaches, including nanoscale surface coatings, and a range of topographies from the microscale to the nanoscale, primarily focusing on neural-interfaced biosystems. Specifically, the immobilization of bioactive molecules to fertilize the neural cell lineage, topographical engineering to induce mechanotransduction in neural cells, and enhanced cell-chip coupling using three-dimensional structured surfaces are highlighted. Advances in neural interface design will help us understand the nervous system, thereby achieving the effective treatments for neurological disorders. STATEMENT OF SIGNIFICANCE: • This review focuses on designing bioactive neural interface with a nanoscale chemical modification and topographical engineering at multiscale perspective. • Versatile nanoscale surface coatings and topographies for neural interface are summarized. • Recent advances in bioactive materials applicable for neural cell culture, electrophysiological sensing, and neural implants are reviewed.

Assembling Spheroids of Rat Primary Neurons Using a Stress-Free 3D Culture System

Neural injuries disrupt the normal functions of the nervous system, whose complexities limit current treatment options. Because of their enhanced therapeutic effects, neurospheres have the potential to advance the field of regenerative medicine and neural tissue engineering. Methodological steps can pose challenges for implementing neurosphere assemblies; for example, conventional static cultures hinder yield and throughput, while the presence of the necrotic core, time-consuming methodology, and high variability can slow their progression to clinical application. Here we demonstrate the optimization of primary neural cell-derived neurospheres, developed using a high-throughput, stress-free, 3D bioreactor. This process provides a necessary baseline for future studies that could develop co-cultured assemblies of stem cells combined with endothelial cells, and/or biomaterials and nanomaterials for clinical therapeutic use. Neurosphere size and neurite spreading were evaluated under various conditions using Image J software. Primary neural cells obtained from the hippocampi of three-day-old rat pups, when incubated for 24 h in a reactor coated with 2% Pluronic and seeded on Poly-D-Lysine-coated plates establish neurospheres suitable for therapeutic use within five days. Most notably, neurospheres maintained high cell viability of ≥84% and expressed the neural marker MAP2, neural marker β-Tubulin III, and glial marker GFAP at all time points when evaluated over seven days. Establishing these factors reduces the variability in developing neurospheres, while increasing the ease and output of the culture process and maintaining viable cellular constructs.

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.

Human cortical spheroids with a high diversity of innately developing brain cell types

BACKGROUND

Three-dimensional (3D) human brain spheroids are instrumental to study central nervous system (CNS) development and (dys)function. Yet, in current brain spheroid models the limited variety of cell types hampers an integrated exploration of CNS (disease) mechanisms.

METHODS

Here we report a 5-month culture protocol that reproducibly generates H9 embryonic stem cell-derived human cortical spheroids (hCSs) with a large cell-type variety.

RESULTS

We established the presence of not only neuroectoderm-derived neural progenitor populations, mature excitatory and inhibitory neurons, astrocytes and oligodendrocyte (precursor) cells, but also mesoderm-derived microglia and endothelial cell populations in the hCSs via RNA-sequencing, qPCR, immunocytochemistry and transmission electron microscopy. Transcriptomic analysis revealed resemblance between the 5-months-old hCSs and dorsal frontal rather than inferior regions of human fetal brains of 19-26 weeks of gestational age. Pro-inflammatory stimulation of the generated hCSs induced a neuroinflammatory response, offering a proof-of-principle of the applicability of the spheroids.

CONCLUSIONS

Our protocol provides a 3D human brain cell model containing a wide variety of innately developing neuroectoderm- as well as mesoderm-derived cell types, furnishing a versatile platform for comprehensive examination of intercellular CNS communication and neurological disease mechanisms.

Effect of Degree of Deacetylation of Chitosan/Chitin on Human Neural Stem Cell Culture

Stem cell therapy and research for neural diseases depends on reliable reproduction of neural stem cells. Chitosan-based materials have been proposed as a substrate for culturing human neural stem cells (hNSCs) in the pursuit of clinically compatible culture conditions that are chemically defined and compliant with good manufacturing practices. The physical and biochemical properties of chitosan and chitin are strongly regulated by the degree of deacetylation (DD). However, the effect of DD on hNSC behavior has not been systematically investigated. In this study, films with DD ranging from 93% to 14% are fabricated with chitosan and chitin. Under xeno-free conditions, hNSCs proliferate preferentially on films with a higher DD, exhibiting adherent morphology and retaining multipotency. Lowering the DD leads to formation of neural stem cell spheroids due to unsteady adhesion. The neural spheroids present NSC multipotency protein expression reduction and cytoplasmic translocation. This study provides an insight into the influence of the DD on hNSCs behavior and may serve as a guideline for hNSC research using chitosan-based biomaterials. It demonstrates the capability of controlling hNSC fate by simply tailoring the DD of chitosan.

Message in a Scaffold: Natural Biomaterials for Three-Dimensional (3D) Bioprinting of Human Brain Organoids

Brain organoids are invaluable tools for pathophysiological studies or drug screening, but there are still challenges to overcome in making them more reproducible and relevant. Recent advances in three-dimensional (3D) bioprinting of human neural organoids is an emerging approach that may overcome the limitations of self-organized organoids. It requires the development of optimal hydrogels, and a wealth of research has improved our knowledge about biomaterials both in terms of their intrinsic properties and their relevance on 3D culture of brain cells and tissue. Although biomaterials are rarely biologically neutral, few articles have reviewed their roles on neural cells. We here review the current knowledge on unmodified biomaterials amenable to support 3D bioprinting of neural organoids with a particular interest in their impact on cell homeostasis. Alginate is a particularly suitable bioink base for cell encapsulation. Gelatine is a valuable helper agent for 3D bioprinting due to its viscosity. Collagen, fibrin, hyaluronic acid and laminin provide biological support to adhesion, motility, differentiation or synaptogenesis and optimize the 3D culture of neural cells. Optimization of specialized hydrogels to direct differentiation of stem cells together with an increased resolution in phenotype analysis will further extend the spectrum of possible bioprinted brain disease models.

Neural progenitor cell-derived extracellular matrix as a new platform for neural differentiation of human induced pluripotent stem cells

The culture microenvironment has been demonstrated to regulate stem cell fate and to be a crucial aspect for quality-controlled stem cell maintenance and differentiation to a specific lineage. In this context, extracellular matrix (ECM) proteins are particularly important to mediate the interactions between the cells and the culture substrate. Human induced pluripotent stem cells (hiPSCs) are usually cultured as anchorage-dependent cells and require adhesion to an ECM substrate to support their survival and proliferation in vitro. Matrigel, a common substrate for hiPSC culture is a complex and undefined mixture of ECM proteins which are expensive and not well suited to clinical application. Decellularized cell-derived ECM has been shown to be a promising alternative to the common protein coatings used in stem cell culture. However, very few studies have used this approach as a niche for neural differentiation of hiPSCs. Here, we developed a new stem cell culture system based on decellularized cell-derived ECM from neural progenitor cells (NPCs) for expansion and neural differentiation of hiPSCs, as an alternative to Matrigel and poly-l-ornithine/laminin-coated well plates. Interestingly, hiPSCs were able to grow and maintain their pluripotency when cultured on decellularized ECM from NPCs (NPC ECM). Furthermore, NPC ECM enhanced the neural differentiation of hiPSCs compared to poly-l-ornithine/laminin-coated wells, which are used in most neural differentiation protocols, presenting a statistically significant enhancement of neural gene expression markers, such as βIII-Tubulin and MAP2. Taken together, our results demonstrate that NPC ECM provides a functional microenvironment, mimicking the neural niche, which may have interesting future applications for the development of new strategies in neural stem cell research.

Divergence between Neuronal and Oligodendroglial Cell Fate, in Postnatal Brain Neural Stem Cells, Leads to Divergent Properties in Polymorphic In Vitro Assays

Two main stem cell pools exist in the postnatal mammalian brain that, although they share some “stemness” properties, also exhibit significant differences. Multipotent neural stem cells survive within specialized microenvironments, called niches, and they are vulnerable to ageing. Oligodendroglial lineage-restricted progenitor cells are widely distributed in the brain parenchyma and are more resistant to the effects of ageing. Here, we create polymorphic neural stem cell cultures and allow cells to progress towards the neuronal and the oligodendroglial lineage. We show that the divergence of cell fate is accompanied by a divergence in the properties of progenitors, which reflects their adaptation to life in the niche or the parenchyma. Neurogenesis shows significant spatial restrictions and a dependence on laminin, a major niche component, while oligodendrogenesis shows none of these constraints. Furthermore, the blocking of integrin-β1 leads to opposing effects, reducing neurogenesis and enhancing oligodendrogenesis. Therefore, polymorphic neural stem cell assays can be used to investigate the divergence of postnatal brain stem cells and also to predict the in vivo effects of potential therapeutic molecules targeting stem and progenitor cells, as we do for the microneurotrophin BNN-20.

The extracellular matrix molecule tenascin-C modulates cell cycle progression and motility of adult neural stem/progenitor cells from the subependymal zone

Adult neurogenesis has been described in two canonical regions of the adult central nervous system (CNS) of rodents, the subgranular zone (SGZ) of the hippocampus and the subependymal zone (SEZ) of the lateral ventricles. The stem cell niche of the SEZ provides a privileged environment composed of a specialized extracellular matrix (ECM) that comprises the glycoproteins tenascin-C (Tnc) and laminin-1 (LN1). In the present study, we investigated the function of these ECM glycoproteins in the adult stem cell niche. Adult neural stem/progenitor cells (aNSPCs) of the SEZ were prepared from wild type (Tnc^+/+) and Tnc knockout (Tnc^−/−) mice and analyzed using molecular and cell biological approaches. A delayed maturation of aNSPCs in Tnc^−/− tissue was reflected by a reduced capacity to form neurospheres in response to epidermal growth factor (EGF). To examine a potential influence of the ECM on cell proliferation, aNSPCs of both genotypes were studied by cell tracking using digital video microscopy. aNSPCs were cultivated on three different substrates, namely, poly-d-lysine (PDL) and PDL replenished with either LN1 or Tnc for up to 6 days in vitro. On each of the three substrates aNSPCs displayed lineage trees that could be investigated with regard to cell cycle length. The latter appeared reduced in Tnc^−/− aNSPCs on PDL and LN1 substrates, less so on Tnc that seemed to compensate the absence of the ECM compound to some extent. Close inspection of the lineage trees revealed a subpopulation of late dividing aNSPCs_late that engaged into cycling after a notable delay. aNSPCs_late exhibited a clearly different morphology, with a larger cell body and conspicuous processes. aNSPCs_late reiterated the reduction in cell cycle length on all substrates tested, which was not rescued on Tnc substrates. When the migratory activity of aNSPC-derived progeny was determined, Tnc^−/− neuroblasts displayed significantly longer migration tracks. This was traced to an increased rate of migration episodes compared to the wild-type cells that rested for longer time periods. We conclude that Tnc intervenes in the proliferation of aNSPCs and modulates the motility of neuroblasts in the niche of the SEZ.

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

Extracellular matrix (ECM) has long been known to regulate many aspects of neural development in many different species. However, the role of the ECM in the development of the human neocortex is not yet fully understood. In this review we discuss the role of the ECM in human neocortex development and the different model systems that can be used to investigate this. In particular, we will focus on how the ECM regulates human neural stem and progenitor cell proliferation and differentiation, how the ECM regulates the architecture of the developing human neocortex and the effect of mutations in ECM and ECM-associated genes in neurodevelopmental disorders.

Laminin-111-Enriched Fibrin Hydrogels Enhance Functional Muscle Regeneration Following Trauma

Volumetric muscle loss (VML) is the surgical or traumatic loss of skeletal muscle, which can cause loss of limb function or permanent disability. VML injuries overwhelms the endogenous regenerative capacity of skeletal muscle and results in poor functional healing outcomes. Currently, there are no approved tissue engineering treatments for VML injuries. In this study, fibrin hydrogels enriched with laminin-111 (LM-111; 50-450 μg/mL) were used for the treatment of VML of the tibialis anterior in a rat model. Treatment with fibrin hydrogel containing 450 μg/mL of LM-111 (FBN450) improved muscle regeneration following VML injury. FBN450 hydrogel treatment increased the relative proportion of contractile to fibrotic tissue as indicated by the myosin: collagen ratio on day 28 post-VML injury. FBN450 hydrogels also enhanced myogenic protein expression and increased the quantity of small to medium size myofibers (500-2000 μm²) as well as innervated myofibers. Improved contractile tissue deposition due to FBN450 hydrogel treatment resulted in a significant improvement (∼60%) in torque production at day 28 postinjury. Taken together, these results suggest that the acellular FBN450 hydrogels provide a promising therapeutic strategy for VML that is worthy of further investigation.

Mechanically robust hybrid hydrogels of photo-crosslinkable gelatin and laminin-mimetic peptide amphiphiles for neural induction

Self-assembling bio-instructive materials that can provide a biomimetic tissue microenvironment with the capability to regulate cellular behaviors represent an attractive platform in regenerative medicine. Herein, we develop a hybrid neuro-instructive hydrogel that combines the properties of a photo-crosslinkable gelatin methacrylate (GelMA) and self-assembling peptide amphiphiles (PAs) bearing a laminin-derived neuro-inductive epitope (PA-GSR). Electrostatic interaction and ultraviolet light crosslinking mechanisms were combined to create dual-crosslinked hybrid hydrogels with tunable stiffness. Spectroscopic, microscopic and theoretical techniques show that the cationic PA-GSR(+) electrostatically co-assembles with the negatively charged GelMA to create weak hydrogels with hierarchically ordered microstructures, which were further photo-crosslinked to create mechanically robust hydrogels. Dynamic oscillatory rheology and micromechanical testing show that photo-crosslinking of the co-assembled GelMA and PA-GSR(+) hydrogel results in robust hydrogels displaying improved stiffness. Gene expression analysis was used to show that GelMA/PA-GSR(+) hydrogels can induce human mesenchymal stem cells (hMSCs) into neural-lineage cells and supports neural-lineage specification of neuroblast-like cells (SH-SY5Y) in a growth-factor-free manner. Also, metabolomics analysis suggests that the hydrogel alters the metabolite profiles in the cells by affecting multiple molecular pathways. This work highlights a new approach for the design of PA-based hybrid hydrogels with robust mechanical properties and biological functionalities for nerve tissue regeneration.

Advancing models of neural development with biomaterials

Human pluripotent stem cells have emerged as a promising in vitro model system for studying the brain. Two-dimensional and three-dimensional cell culture paradigms have provided valuable insights into the pathogenesis of neuropsychiatric disorders, but they remain limited in their capacity to model certain features of human neural development. Specifically, current models do not efficiently incorporate extracellular matrix-derived biochemical and biophysical cues, facilitate multicellular spatio-temporal patterning, or achieve advanced functional maturation. Engineered biomaterials have the capacity to create increasingly biomimetic neural microenvironments, yet further refinement is needed before these approaches are widely implemented. This Review therefore highlights how continued progression and increased integration of engineered biomaterials may be well poised to address intractable challenges in recapitulating human neural development.

Progress in mimicking brain microenvironments to understand and treat neurological disorders

Neurological disorders including traumatic brain injury, stroke, primary and metastatic brain tumors, and neurodegenerative diseases affect millions of people worldwide. Disease progression is accompanied by changes in the brain microenvironment, but how these shifts in biochemical, biophysical, and cellular properties contribute to repair outcomes or continued degeneration is largely unknown. Tissue engineering approaches can be used to develop in vitro models to understand how the brain microenvironment contributes to pathophysiological processes linked to neurological disorders and may also offer constructs that promote healing and regeneration in vivo. In this Perspective, we summarize features of the brain microenvironment in normal and pathophysiological states and highlight strategies to mimic this environment to model disease, investigate neural stem cell biology, and promote regenerative healing. We discuss current limitations and resulting opportunities to develop tissue engineering tools that more faithfully recapitulate the aspects of the brain microenvironment for both in vitro and in vivo applications.

Pentapeptide IKVAV-engineered hydrogels for neural stem cell attachment

Spinal cord injury remains irreversible with current treatment paradigms, due to the inability to rebuild the regenerative environment for neurons after injury. Neural tissue engineering that encapsulates the neural stem/progenitor cells within an artificial scaffold provides a possibility to regenerate neurons for spinal cord injury repair. The attachment and survival of these neural cells usually require similar microenvironments to the extracellular matrix for support. Here, a three-dimensional pentapeptide IKVAV-functionalized poly(lactide ethylene oxide fumarate) (PLEOF) hydrogel is developed. In vitro tests demonstrate that the IKVAV-PLEOF hydrogels are biodegradable and hemo-biocompatible. This IKVAV-PLEOF hydrogel is shown to support neural stem cell attachment, growth, proliferation, and differentiation. Additionally, the neural stem cells could be readily formed as spheroids that subsequently encapsulated, attached, and proliferated within the three-dimensional hydrogel constructs. Additionally, an in vivo test confirms the biodegradability and biocompatibility of the IKVAV-PLEOF hydrogels revealing that the hydrogels biodegrade, new blood vessels form, and few inflammatory responses are observed after 4-week implantation. The neural stem cell spheroid-laden hydrogels may have further implications in spinal cord injury regenerative and brain repair in neural tissue engineering.

Cell-to-Cell Adhesion and Neurogenesis in Human Cortical Development: A Study Comparing 2D Monolayers with 3D Organoid Cultures

Organoids (ORGs) are increasingly used as models of cerebral cortical development. Here, we compared transcriptome and cellular phenotypes between telencephalic ORGs and monolayers (MONs) generated in parallel from three biologically distinct induced pluripotent stem cell (iPSC) lines. Multiple readouts revealed increased proliferation in MONs, which was caused by increased integrin signaling. MONs also exhibited altered radial glia (RG) polarity and suppression of Notch signaling, as well as impaired generation of intermediate progenitors, outer RG, and cortical neurons, which were all partially reversed by reaggregation of dissociated cells. Network analyses revealed co-clustering of cell adhesion, Notch-related transcripts and their transcriptional regulators in a module strongly downregulated in MONs. The data suggest that ORGs, with respect to MONs, initiate more efficient Notch signaling in ventricular RG owing to preserved cell adhesion, resulting in subsequent generation of intermediate progenitors and outer RG, in a sequence that recapitulates the cortical ontogenetic process.

•

Organoid’s radial glia cells engage efficient Notch signaling

•

Monolayer hyperproliferation is due to increased integrin signaling

•

Neurogenesis' arrest by cell dissociation is partially reversed with reaggregation

Nylon mesh-based 3D scaffolds for the adherent culture of neural stem/progenitor cells

We developed novel scaffolds for the adherent culture of neural stem/progenitor cells on the woven mesh. Nylon mesh (NM) is an inert material for cell adhesion. We prepared polyacrylic acid-grafted nylon mesh (PAA-NM) by graft polymerization method using gamma-irradiation. Matrigel was covalently immobilized to the carboxyl groups in PAA-NM by chemical conjugation using 1-ethyl-3-(3-dimethylamino propyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) to prepare the Matrigel-immobilized PAA-grafted nylon mesh (M-PAA-NM). Cell adhesion property of mouse neural stem/progenitor cells (NSPCs) between the NM, PAA-NM, and M-PAA-NM was different from each other. The neurosphere-like clusters of NSPCs were weakly bound to NM and PAA-NM without spreading. The NSPCs were firmly adhered to, spread, and covered the surface of M-PAA-NM. We evaluated the state of differentiation by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immnocytochemistry. A neuronal marker β III tubulin, a glial marker glial fibrillary acidic protein (GFAP) and a mature glial marker S100β were expressed at a low level in the cultured cells while immature NSPCs marker Nestin and Sox2 were slightly lower without significant statistical difference. We concluded that the M-PAA-NM is a good substrate for adherent culture of NSPCs without triggering their cell differentiation, and also provides the maintenance of their growth with fewer passages in comparison with the conventional suspension culture of NSPCs in neurospheres.

Modulatory properties of extracellular matrix glycosaminoglycans and proteoglycans on neural stem cells behavior: Highlights on regenerative potential and bioactivity

Despite the poor regenerative capacity of the adult central nervous system (CNS) in mammals, two distinct regions, subventricular zone (SVZ) and the subgranular zone (SGZ), continue to generate new functional neurons throughout life which integrate into the pre-existing neuronal circuitry. This process is not fixed but highly modulated, revealing many intrinsic and extrinsic mechanisms by which this performance can be optimized for a given environment. The capacity for self-renewal, proliferation, migration, and multi-lineage potency of neural stem cells (NSCs) underlines the necessity of controlling stem cell fate. In this context, the native and local microenvironment plays a critical role, and the application of this highly organized architecture in the CNS has been considered as a fundamental concept in the generation of new effective therapeutic strategies in tissue engineering approaches. The brain extracellular matrix (ECM) is composed of biomacromolecules, including glycosaminoglycans, proteoglycans, and glycoproteins that provide various biological actions through biophysical and biochemical signaling pathways. Herein, we review predominantly the structure and function of the mentioned ECM composition and their regulatory impact on multiple and diversity of biological functions, including neural regeneration, survival, migration, differentiation, and final destiny of NSCs.

The Extracellular Matrix in the Evolution of Cortical Development and Folding

The evolution of the mammalian cerebral cortex leading to humans involved a remarkable sophistication of developmental mechanisms. Specific adaptations of progenitor cell proliferation and neuronal migration mechanisms have been proposed to play major roles in this evolution of neocortical development. One of the central elements influencing neocortex development is the extracellular matrix (ECM). The ECM provides both a structural framework during tissue formation and to present signaling molecules to cells, which directly influences cell behavior and movement. Here we review recent advances in the understanding of the role of ECM molecules on progenitor cell proliferation and neuronal migration, and how these contribute to cerebral cortex expansion and folding. We discuss how transcriptomic studies in human, ferret and mouse identify components of ECM as being candidate key players in cortex expansion during development and evolution. Then we focus on recent functional studies showing that ECM components regulate cortical progenitor cell proliferation, neuron migration and the mechanical properties of the developing cortex. Finally, we discuss how these features differ between lissencephalic and gyrencephalic species, and how the molecular evolution of ECM components and their expression profiles may have been fundamental in the emergence and evolution of cortex folding across mammalian phylogeny.

Functionalization of Electrospun Nanofibers and Fiber Alignment Enhance Neural Stem Cell Proliferation and Neuronal Differentiation

Neural stem cells (NSCs) have the potential to generate the cells of the nervous system and, when cultured on nanofiber scaffolds, constitute a promising approach for neural tissue engineering. In this work, the impact of combining nanofiber alignment with functionalization of the electrospun poly-ε-caprolactone (PCL) nanofibers with biological adhesion motifs on the culture of an NSC line (CGR8-NS) is evaluated. A five-rank scale for fiber density was introduced, and a 4.5 level, corresponding to 70–80% fiber density, was selected for NSC in vitro culture. Aligned nanofibers directed NSC distribution and, especially in the presence of laminin (PCL-LN) and the RGD-containing peptide GRGDSP (PCL-RGD), promoted higher cell elongation, quantified by the eccentricity and axis ratio. In situ differentiation resulted in relatively higher percentage of cells expressing Tuj1 in PCL-LN, as well as significantly longer neurite development (41.1 ± 1.0 μm) than PCL-RGD (32.0 ± 1.0 μm), pristine PCL (25.1 ± 1.2 μm), or PCL-RGD randomly oriented fibers (26.5 ± 1.4 μm), suggesting that the presence of LN enhances neuronal differentiation. This study demonstrates that aligned nanofibers, functionalized with RGD, perform as well as PCL-LN fibers in terms of cell adhesion and proliferation. The presence of the full LN protein improves neuronal differentiation outcomes, which may be important for the use of this system in tissue engineering applications.

Exploiting the Complexities of Glioblastoma Stem Cells: Insights for Cancer Initiation and Therapeutic Targeting

The discovery of glioblastoma stem cells (GSCs) in the 2000s revolutionized the cancer research field, raising new questions regarding the putative cell(s) of origin of this tumor type, and partly explaining the highly heterogeneous nature of glioblastoma (GBM). Increasing evidence has suggested that GSCs play critical roles in tumor initiation, progression, and resistance to conventional therapies. The remarkable oncogenic features of GSCs have generated significant interest in better defining and characterizing these cells and determining novel pathways driving GBM that could constitute attractive key therapeutic targets. While exciting breakthroughs have been achieved in the field, the characterization of GSCs is a challenge and the cell of origin of GBM remains controversial. For example, the use of several cell-surface molecular markers to identify and isolate GSCs has been a challenge. It is now widely accepted that none of these markers is, per se, sufficiently robust to distinguish GSCs from normal stem cells. Finding new strategies that are able to more efficiently and specifically target these niches could also prove invaluable against this devastating and therapy-insensitive tumor. In this review paper, we summarize the most relevant findings and discuss emerging concepts and open questions in the field of GSCs, some of which are, to some extent, pertinent to other cancer stem cells.

Transcriptional Regulators and Human-Specific/Primate-Specific Genes in Neocortical Neurogenesis

During development, starting from a pool of pluripotent stem cells, tissue-specific genetic programs help to shape and develop functional organs. To understand the development of an organ and its disorders, it is important to understand the spatio-temporal dynamics of the gene expression profiles that occur during its development. Modifications in existing genes, the de-novo appearance of new genes, or, occasionally, even the loss of genes, can greatly affect the gene expression profile of any given tissue and contribute to the evolution of organs or of parts of organs. The neocortex is evolutionarily the most recent part of the brain, it is unique to mammals, and is the seat of our higher cognitive abilities. Progenitors that give rise to this tissue undergo sequential waves of differentiation to produce the complete sets of neurons and glial cells that make up a functional neocortex. We will review herein our understanding of the transcriptional regulators that control the neural precursor cells (NPCs) during the generation of the most abundant class of neocortical neurons, the glutametergic neurons. In addition, we will discuss the roles of recently-identified human- and primate-specific genes in promoting neurogenesis, leading to neocortical expansion.

Hydrogels Derivatized With Cationic Moieties or Functional Peptides as Efficient Supports for Neural Stem Cells

The increasing incidence of neurodegenerative diseases such as Alzheimer's or Parkinson's disease represents a significant burden for patients and national health systems. The conditions are primarily caused by the death of neurons and other neural cell types. One important aim of current stem cell research is to find a way to replace the lost cells. In this perspective, neural stem cells (NSCs) have been considered as a promising tool in the field of regenerative medicine. The behavior of NSCs is modulated by environmental influences, for example hormones, growth factors, cytokines, and extracellular matrix molecules or biomechanics. These factors can be studied by using well-defined hydrogels, which are polymeric networks of synthetic or natural origin with the ability to swell in water. These gels can be modified with a variety of molecules and optimized with regard to their mechanical properties to mimic the natural extracellular environment. In particular modifications applying distinct units such as functional domains and peptides can modulate the development of NSCs with regard to proliferation, differentiation and migration. One well-known peptide sequence that affects the behavior of NSCs is the integrin recognition sequence RGD that has originally been derived from fibronectin. In the present review we provide an overview concerning the applications of modified hydrogels with an emphasis on synthetic hydrogels based on poly(acrylamides), as modified with either cationic moieties or the peptide sequence RGD. This knowledge might be used in tissue engineering and regenerative medicine for the therapy of spinal cord injuries, neurodegenerative diseases and traumata.

Coating Materials for Neural Stem/Progenitor Cell Culture and Differentiation

Neural stem/progenitor cells (NSPCs) have a potential to treat various neurological diseases, such as Parkinson's Disease, Alzheimer's Disease, and Spinal Cord Injury. However, the limitation of NSPC sources and the difficulty to maintain their stemness or to differentiate them into specific therapeutic cells are the main hurdles for clinical research and application. Thus, for obtaining a therapeutically relevant number of NSPCs in vitro, it is important to understand factors regulating their behaviors and to establish a protocol for stable NSPC proliferation and differentiation. Coating materials for cell culture, such as Matrigel, laminin, collagen, and other coating materials, can significantly affect NSPC characteristics. This article provides a review of coating materials for NSPC culturing in both two dimensions and three dimensions, and their functions in NSPC proliferation and differentiation, and presents a useful guide to select coating materials for researchers.

Extracellular matrix-inducing Sox9 promotes both basal progenitor proliferation and gliogenesis in developing neocortex

Neocortex expansion is largely based on the proliferative capacity of basal progenitors (BPs), which is increased by extracellular matrix (ECM) components via integrin signaling. Here we show that the transcription factor Sox9 drives expression of ECM components and that laminin 211 increases BP proliferation in embryonic mouse neocortex. We show that Sox9 is expressed in human and ferret BPs and is required for BP proliferation in embryonic ferret neocortex. Conditional Sox9 expression in the mouse BP lineage, where it normally is not expressed, increases BP proliferation, reduces Tbr2 levels and induces Olig2 expression, indicative of premature gliogenesis. Conditional Sox9 expression also results in cell-non-autonomous stimulation of BP proliferation followed by increased upper-layer neuron production. Our findings demonstrate that Sox9 exerts concerted effects on transcription, BP proliferation, neuron production, and neurogenic vs. gliogenic BP cell fate, suggesting that Sox9 may have contributed to promote neocortical expansion.

The effect of Matrigel as scaffold material for neural stem cell transplantation for treating spinal cord injury

Traumatic injury to the spinal cord causes permanent loss of function and major personal, social, and economic problems. Cell-based delivery strategies is a promising approach for treating spinal cord injury (SCI). However, the inhospitable microenvironment in the injured spinal cord results in poor cell survival and uncontrolled differentiation of the transplanted stem cells. The combination of a scaffold with cells has been developed with a tendency for achieving greater survival and integration with the host tissue. We investigated the effect of Matrigel combined with neural stem cells (NSCs) in vitro and in vivo. We compared the effect of different types of scaffold on the survival and differentiation of brain-derived NSCs in an in vitro culture. Subsequently, NSCs were transplanted subcutaneously into nude mice to detect graft survival and differentiation in vivo. Finally, phosphate-buffered saline (PBS), Matrigel alone, or Matrigel seeded with NSCs was injected into 48 subacute, clinically relevant rat models of SCI (16 rats per group). Matrigel supported cell survival and differentiation efficiently in vitro and in vivo. SCI rats transplanted with NSCs in Matrigel showed improved behavioral recovery and neuronal and reactive astrocyte marker expression levels compared to PBS- or Matrigel-transplanted rats. Functional repair and neuronal and reactive astrocyte marker expression was slightly improved in the Matrigel-alone group relative to the PBS group, but not statistically significantly. These data suggest that Matrigel is a promising scaffold material for cell transplantation to the injured spinal cord.

Regulation of Cell Cycle Entry and Exit: A Single Cell Perspective

The transition between proliferating and quiescent states must be carefully regulated to ensure that cells divide to create the cells an organism needs only at the appropriate time and place. Cyclin-dependent kinases (CDKs) are critical for both transitioning cells from one cell cycle state to the next, and for regulating whether cells are proliferating or quiescent. CDKs are regulated by association with cognate cyclins, activating and inhibitory phosphorylation events, and proteins that bind to them and inhibit their activity. The substrates of these kinases, including the retinoblastoma protein, enforce the changes in cell cycle status. Single cell analysis has clarified that competition among factors that activate and inhibit CDK activity leads to the cell's decision to enter the cell cycle, a decision the cell makes before S phase. Signaling pathways that control the activity of CDKs regulate the transition between quiescence and proliferation in stem cells, including stem cells that generate muscle and neurons. © 2020 American Physiological Society. Compr Physiol 10:317-344, 2020.

Laminin-Inspired Cell-Instructive Microenvironments for Neural Stem Cells

Laminin is a heterotrimeric glycoprotein with a key role in the formation and maintenance of the basement membrane architecture and properties, as well as on the modulation of several biological functions, including cell adhesion, migration, differentiation and matrix-mediated signaling. In the central nervous system (CNS), laminin is differentially expressed during development and homeostasis, with an impact on the modulation of cell function and fate. Within neurogenic niches, laminin is one of the most important and well described extracellular matrix (ECM) proteins. Specifically, efforts have been made to understand laminin assembly, domain architecture, and interaction of its different bioactive domains with cell surface receptors, soluble signaling molecules, and ECM proteins, to gain insight into the role of this ECM protein and its receptors on the modulation of neurogenesis, both in homeostasis and during repair. This is also expected to provide a rational basis for the design of biomaterial-based matrices mirroring the biological properties of the basement membrane of neural stem cell niches, for application in neural tissue repair and cell transplantation. This review provides a general overview of laminin structure and domain architecture, as well as the main biological functions mediated by this heterotrimeric glycoprotein. The expression and distribution of laminin in the CNS and, more specifically, its role within adult neural stem cell niches is summarized. Additionally, a detailed overview on the use of full-length laminin and laminin derived peptide/recombinant laminin fragments for the development of hydrogels for mimicking the neurogenic niche microenvironment is given. Finally, the main challenges associated with the development of laminin-inspired hydrogels and the hurdles to overcome for these to progress from bench to bedside are discussed.

Evaluation of Stemness Maintenance Properties of the Recombinant Human Laminin α2 LG1-3 Domains in Human Mesenchymal Stem Cells

BACKGROUND

Laminin, a member of the Extracellular Matrix (ECM), is a glycoprotein that is used as a factor that affects cell adhesion, proliferation, survival, and differentiation. Of these, five globular domains (LG domains) of the alpha chain play an important role in influencing the cell by binding to the integrin.

OBJECTIVE

This study aimed to evaluate the ability of globular domains 1-3 of laminin alpha2 (rhLAMA2LG1-3) in maintaining the pluripotency of human Mesenchymal Stem Cells (hMSCs), which are widely used in regenerative medicine.

METHODS

hMSCs were grown in the medium supplemented with rhLAMA2LG1-3, then the effect of the protein on hMSCs were confirmed through cell adhesion assay, proliferation assay and RTPCR.

RESULTS

rhLAMA2LG1-3 expressed in Escherichia coli has a molecular weight of 70 kDa, at 1 µg/ml concentration of rhLAMA2LG1-3, the attachment and proliferation of hMSCs were approximately 3.18-fold and 1.67-fold, respectively, more efficient than those of untreated controls. In addition, the undifferentiated state and degree of stemness of hMSCs were measured, on the basis of CD90 and CD105 levels. In the rhLAMA2LG1-3-treated hMSCs, the expression levels of CD90 and CD105 increased by 2.83-fold and 1.62-fold, respectively, compared to those in untreated controls.

CONCLUSIONS

rhLAMA2LG1-3 can be potentially used in stem cell therapy to improve the viability and maintain the undifferentiated state of hMSCs.

Cost-Effective Cosmetic-Grade Hyaluronan Hydrogels for ReNcell VM Human Neural Stem Cell Culture

Hyaluronic acid (HA) is a polysaccharide polymer frequently used as a starting material to fabricate hydrogels, especially for recapitulating the brain's extracellular matrix (ECM) for in vitro neural stem cell (NSC) cultures. Here, we report the successful synthesis of a methacrylated HA (MeHA) polymer from an inexpensive cosmetic-grade hyaluronan starting material. The MeHA polymers synthesized from cosmetic-grade HA yielded similar chemical purity to those from pharmaceutical/research-grade HA reported in the literature. Crosslinked MeHA (x-MeHA) hydrogels were formed using radical polymerization which resulted in mechanical properties matching previously reported mechanical property ranges for enhanced neuronal differentiation of NSCs. We assessed cellular adhesion, spreading, proliferation, and stiffness-dependent neuronal differentiation properties of ReNcell VM human neural stem cells (hNSCs) and compared our results to studies reported in the literature (that utilized non-human and human pluripotent cell-derived NSCs).

How the extracellular matrix shapes neural development

During development, both cells and tissues must acquire the correct shape to allow their proper function. This is especially relevant in the nervous system, where the shape of individual cell processes, such as the axons and dendrites, and the shape of entire tissues, such as the folding of the neocortex, are highly specialized. While many aspects of neural development have been uncovered, there are still several open questions concerning the mechanisms governing cell and tissue shape. In this review, we discuss the role of the extracellular matrix (ECM) in these processes. In particular, we consider how the ECM regulates cell shape, proliferation, differentiation and migration, and more recent work highlighting a key role of ECM in the morphogenesis of neural tissues.

Organs to Cells and Cells to Organoids: The Evolution of in vitro Central Nervous System Modelling

With 100 billion neurons and 100 trillion synapses, the human brain is not just the most complex organ in the human body, but has also been described as "the most complex thing in the universe." The limited availability of human living brain tissue for the study of neurogenesis, neural processes and neurological disorders has resulted in more than a century-long strive from researchers worldwide to model the central nervous system (CNS) and dissect both its striking physiology and enigmatic pathophysiology. The invaluable knowledge gained with the use of animal models and post mortem human tissue remains limited to cross-species similarities and structural features, respectively. The advent of human induced pluripotent stem cell (hiPSC) and 3-D organoid technologies has revolutionised the approach to the study of human brain and CNS in vitro, presenting great potential for disease modelling and translational adoption in drug screening and regenerative medicine, also contributing beneficially to clinical research. We have surveyed more than 100 years of research in CNS modelling and provide in this review an historical excursus of its evolution, from early neural tissue explants and organotypic cultures, to 2-D patient-derived cell monolayers, to the latest development of 3-D cerebral organoids. We have generated a comprehensive summary of CNS modelling techniques and approaches, protocol refinements throughout the course of decades and developments in the study of specific neuropathologies. Current limitations and caveats such as clonal variation, developmental stage, validation of pluripotency and chromosomal stability, functional assessment, reproducibility, accuracy and scalability of these models are also discussed.

The hypoxic peri-arteriolar glioma stem cell niche, an integrated concept of five types of niches in human glioblastoma

Glioblastoma is the most lethal primary brain tumor and poor survival of glioblastoma patients is attributed to the presence of glioma stem cells (GSCs). These therapy-resistant, quiescent and pluripotent cells reside in GSC niches, which are specific microenvironments that protect GSCs against radiotherapy and chemotherapy. We previously showed the existence of hypoxic peri-arteriolar GSC niches in glioblastoma tumor samples. However, other studies have described peri-vascular niches, peri-hypoxic niches, peri-immune niches and extracellular matrix niches of GSCs. The aim of this review was to critically evaluate the literature on these five different types of GSC niches. In the present review, we describe that the five niche types are not distinct from one another, but should be considered to be parts of one integral GSC niche model, the hypoxic peri-arteriolar GSC niche. Moreover, hypoxic peri-arteriolar GSC niches are structural and functional look-alikes of hematopoietic stem cell (HSC) niches in the bone marrow. GSCs are maintained in peri-arteriolar niches by the same receptor-ligand interactions as HSCs in bone marrow. Our concept should be rigidly tested in the near future and applied to develop therapies to expel and keep GSCs out of their protective niches to render them more vulnerable to standard therapies.

Looking into the Future: Toward Advanced 3D Biomaterials for Stem-Cell-Based Regenerative Medicine

Stem-cell-based therapies have the potential to provide novel solutions for the treatment of a variety of diseases, but the main obstacles to such therapies lie in the uncontrolled differentiation and functional engraftment of implanted tissues. The physicochemical microenvironment controls the self-renewal and differentiation of stem cells, and the key step in mimicking the stem cell microenvironment is to construct a more physiologically relevant 3D culture system. Material-based 3D assemblies of stem cells facilitate the cellular interactions that promote morphogenesis and tissue organization in a similar manner to that which occurs during embryogenesis. Both natural and artificial materials can be used to create 3D scaffolds, and synthetic organic and inorganic porous materials are the two main kinds of artificial materials. Nanotechnology provides new opportunities to design novel advanced materials with special physicochemical properties for 3D stem cell culture and transplantation. Herein, the advances and advantages of 3D scaffold materials, especially with respect to stem-cell-based therapies, are first outlined. Second, the stem cell biology in 3D scaffold materials is reviewed. Third, the progress and basic principles of developing 3D scaffold materials for clinical applications in tissue engineering and regenerative medicine are reviewed.

Defining standard enzymatic dissociation methods for individual brains and spinal cords in EAE

Objective

To determine the capacity, effectiveness, efficiency, and reliability of select tissue dissociation methods to isolate mononuclear cells from the CNS of mice with experimental autoimmune encephalomyelitis (EAE).

Methods

As part of an assay qualification, we tested the isolation method Percoll PLUS vs a commercially available enzymatic Neural Tissue Dissociation Kit (Kit), and the enzymes accutase and papain in C57BL/6 mice with active EAE. In a stepwise approach, we applied the following 4 criteria to each dissociation method: (1) mononuclear cell viability post-processing was required to be ≥80% per brain or spinal cord sample, (2) absolute live mononuclear cell numbers was required to be ≥5 × 10⁵ per brain or spinal cord sample of mice with clinical EAE, (3) test-retest reliability had to be verified, and (4) the absolute mononuclear cell numbers in brain and spinal cord had to correlate with the EAE disease course.

Results

Enzymatic dissociations allowed for greatly increased cell yield and specifically allowed for downstream assays from individual brains and spinal cords in C57BL/6 mice with EAE. All enzymatic dissociations provided a more efficient and effective method for isolating mononuclear cells from brains and spinal cord. Only the Kit assay provided a significant correlation between absolute mononuclear cell numbers in the spinal cord and EAE disease severity.

Conclusions

Enzymatic dissociation of CNS tissue of C57BL/6 mice with active EAE with the Kit should be the standard method. The identification of optimized CNS dissociation methods in EAE has the potential to identify cellular events that are pertinent to MS pathogenesis.

Laminin and Platelet-Derived Growth Factor-BB Promote Neuronal Differentiation of Human Urine-Derived Stem Cells

Urine-derived stem cells (USCs) are considered as a promising cell source capable of neuronal differentiation. In addition, specific growth factors and extracellular matrix are essential for enhancing their neuronal differentiation efficiency. In this study, we investigated the possibility of neuronal differentiation of USCs and the role of laminin and platelet-derived growth factor BB (PDGF-BB) as promoting factors. USCs were isolated from fresh urine of healthy donors. Cultured USCs were adherent to the plate and their morphology was similar to the cobblestone. In addition, they showed chromosome stability, rapid proliferation rate, colony forming capacity, and mesenchymal stem cell characteristics. For inducing the neuronal differentiation, USCs were cultured for 14 days in neuronal differentiation media supplemented with/without laminin and/or PDGF-BB. To identify the expression of neuronal markers, RT-PCR, flow cytometry analysis and immunocytochemistry were used. After neuronal induction, the cells showed neuron-like morphological change and high expression level of neuronal markers. In addition, laminin and PDGF-BB respectively promoted the neuronal differentiation of USCs and the combination of laminin and PDGF-BB showed a synergistic effect for the neuronal differentiation of USCs. In conclusion, USCs are noteworthy cell source in the field of neuronal regeneration and laminin and PDGF-BB promote their neuronal differentiation efficiency.

Integration of neurogenesis and angiogenesis models for constructing a neurovascular tissue

Neurovascular unit (NVU) is a basic unit in the brain, including neurons, glial cells, blood vessels and extracellular matrix. This concept implies the importance of a three-dimensional (3D) culture model including these cell types for investigating brain functions. However, little is known about the construction of an in vitro 3D NVU model. In the present study, we aimed at constructing 3D neurovascular tissues by combining in vitro neurogenesis and angiogenesis models using a microfluidic platform, which is a critical step toward the NVU construction in vitro. Three gel conditions, which were fibrin gel, fibrin-Matrigel mixed gel and fibrin-hyaluronan mixed gel, were investigated to optimize the gel components in terms of neurogenesis and angiogenesis. First, fibrin-Matrigel mixed gel was found to promote neural stem cell (NSC) differentiation into neurons and neurite extension. In particular, 3D neural networks were constructed in 2-8 mg/ml fibrin-Matrigel mixed gel. Second, we found that capillary-like structures were also formed in the fibrin-Matrigel mixed gel by coculturing brain microvascular endothelial cells (BMECs) and human mesenchymal stem cells (MSCs). Finally, we combined both neural and vascular culture models and succeeded in constructing 3D neurovascular tissues with an optimized seeding condition of NSCs, BMECs and MSCs.

Microenvironments to study migration and somal translocation in cortical neurons

Migrating post-mitotic neurons of the developing cerebral cortex undergo terminal somal translocation (ST) when they reach their final destination in the cortical plate. This process is crucial for proper cortical layering and its perturbation can lead to brain dysfunction. Here we present a reductionist biomaterials platform that faithfully supports and controls the distinct phases of terminal ST in vitro. We developed microenvironments with different adhesive molecules to support neuronal attachment, neurite extension, and migration in distinct manners. Efficient ST occurred when the leading process of migratory neurons crossed from low-to high-adhesive areas on a substrate, promoting spreading of the leading growth cone. Our results indicate that elementary adhesive cell-substrate interactions strongly influence migratory behavior and the final positioning of neurons during their developmental journey. This in vitro model allows advanced experimentation to reveal the microenvironmental requirements underlying cortical layer development and disorders.

Surface functionalisation of nanodiamonds for human neural stem cell adhesion and proliferation

Biological systems interact with nanostructured materials on a sub-cellular level. These interactions may govern cell behaviour and the precise control of a nanomaterial's structure and surface chemistry allow for a high degree of tunability to be achieved. Cells are surrounded by an extra-cellular matrix with nano-topographical properties. Diamond based materials, and specifically nanostructured diamond has attracted much attention due to its extreme electrical and mechanical properties, chemical inertness and biocompatibility. Here the interaction of nanodiamond monolayers with human Neural Stem Cells (hNSCs) has been investigated. The effect of altering surface functionalisation of nanodiamonds on hNSC adhesion and proliferation has shown that confluent cellular attachment occurs on oxygen terminated nanodiamonds (O-NDs), but not on hydrogen terminated nanodiamonds (H-NDs). Analysis of H and O-NDs by Atomic Force Microscopy, contact angle measurements and protein adsorption suggests that differences in topography, wettability, surface charge and protein adsorption of these surfaces may underlie the difference in cellular adhesion of hNSCs reported here.

The role of laminins in cartilaginous tissues: from development to regeneration

As a key molecule of the extracellular matrix, laminin provides a delicate microenvironment for cell functions. Recent findings suggest that laminins expressed by cartilage-forming cells (chondrocytes, progenitor cells and stem cells) could promote chondrogenesis. However, few papers outline the effect of laminins on providing a favorable matrix microenvironment for cartilage regeneration. In this review, we delineated the expression of laminins in hyaline cartilage, fibrocartilage and cartilage-like tissue (nucleus pulposus) throughout several developmental stages. We also examined the effect of laminins on the biological activities of chondrocytes, including adhesion, migration and survival. Furthermore, we scrutinized the potential influence of various laminin isoforms on cartilage-forming cells' proliferation and chondrogenic differentiation. With this information, we hope to facilitate the understanding of the spatial and temporal interactions between cartilage-forming cells and laminin microenvironment to eventually advance cell-based cartilage engineering and regeneration.

Scaffolds for 3D in vitro culture of neural lineage cells

Understanding how neurodegenerative disorders develop is not only a key challenge for researchers but also for the wider society, given the rapidly aging populations in developed countries. Advances in this field require new tools with which to recreate neural tissue in vitro and produce realistic disease models. This in turn requires robust and reliable systems for performing 3D in vitro culture of neural lineage cells. This review provides a state of the art update on three-dimensional culture systems for in vitro development of neural tissue, employing a wide range of scaffold types including hydrogels, solid porous polymers, fibrous materials and decellularised tissues as well as microfluidic devices and lab-on-a-chip systems. To provide some context with in vivo development of the central nervous system (CNS), we also provide a brief overview of the neural stem cell niche, neural development and neural differentiation in vitro. We conclude with a discussion of future directions for this exciting and important field of biomaterials research.

STATEMENT OF SIGNIFICANCE

Neurodegenerative diseases, including dementia, Parkinson's and Alzheimer's diseases and motor neuron diseases, are a major societal challenge for aging populations. Understanding these conditions and developing therapies against them will require the development of new physical models of healthy and diseased neural tissue. Cellular models resembling neural tissue can be cultured in the laboratory with the help of 3D scaffolds - materials that allow the organization of neural cells into tissue-like structures. This review presents recent work on the development of different types of scaffolds for the 3D culture of neural lineage cells and the generation of functioning neural-like tissue. These in vitro culture systems are enabling the development of new approaches for modelling and tackling diseases of the brain and CNS.