Collagen type IV promotes the differentiation of neuronal progenitors and inhibits astroglial differentiation in cortical cell cultures

Molecular and functional profiling of cell diversity and identity in the lateral superior olive, an auditory brainstem center with ascending and descending projections

The lateral superior olive (LSO), a prominent integration center in the auditory brainstem, contains a remarkably heterogeneous population of neurons. Ascending neurons, predominantly principal neurons (pLSOs), process interaural level differences for sound localization. Descending neurons (lateral olivocochlear neurons, LOCs) provide feedback into the cochlea and are thought to protect against acoustic overload. The molecular determinants of the neuronal diversity in the LSO are largely unknown. Here, we used patch-seq analysis in mice at postnatal days P10-12 to classify developing LSO neurons according to their functional and molecular profiles. Across the entire sample (n = 86 neurons), genes involved in ATP synthesis were particularly highly expressed, confirming the energy expenditure of auditory neurons. Two clusters were identified, pLSOs and LOCs. They were distinguished by 353 differentially expressed genes (DEGs), most of which were novel for the LSO. Electrophysiological analysis confirmed the transcriptomic clustering. We focused on genes affecting neuronal input-output properties and validated some of them by immunohistochemistry, electrophysiology, and pharmacology. These genes encode proteins such as osteopontin, Kv11.3, and Kvβ3 (pLSO-specific), calcitonin-gene-related peptide (LOC-specific), or Kv7.2 and Kv7.3 (no DEGs). We identified 12 "Super DEGs" and 12 genes showing "Cluster similarity." Collectively, we provide fundamental and comprehensive insights into the molecular composition of individual ascending and descending neurons in the juvenile auditory brainstem and how this may relate to their specific functions, including developmental aspects.

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.

Development of Brain-Derived Bioscaffolds for Neural Progenitor Cell Culture

Biomaterials derived from brain extracellular matrix (ECM) have the potential to promote neural tissue regeneration by providing instructive cues that can direct cell survival, proliferation, and differentiation. This study focused on the development and characterization of microcarriers derived from decellularized brain tissue (DBT) as a platform for neural progenitor cell culture. First, a novel detergent-free decellularization protocol was established that effectively reduced the cellular content of porcine and rat brains, with a >97% decrease in the dsDNA content, while preserving collagens (COLs) and glycosaminoglycans (GAGs). Next, electrospraying methods were applied to generate ECM-derived microcarriers incorporating the porcine DBT that were stable without chemical cross-linking, along with control microcarriers fabricated from commercially sourced bovine tendon COL. The DBT microcarriers were structurally and biomechanically similar to the COL microcarriers, but compositionally distinct, containing a broader range of COL types and higher sulfated GAG content. Finally, we compared the growth, phenotype, and neurotrophic factor gene expression levels of rat brain-derived progenitor cells (BDPCs) cultured on the DBT or COL microcarriers within spinner flask bioreactors over 2 weeks. Both microcarrier types supported BDPC attachment and expansion, with immunofluorescence staining results suggesting that the culture conditions promoted BDPC differentiation toward the oligodendrocyte lineage, which may be favorable for cell therapies targeting remyelination. Overall, our findings support the further investigation of the ECM-derived microcarriers as a platform for neural cell derivation for applications in regenerative medicine.

Enhancing Stem Cell-Based Therapeutic Potential by Combining Various Bioengineering Technologies

Stem cell-based therapeutics have gained tremendous attention in recent years due to their wide range of applications in various degenerative diseases, injuries, and other health-related conditions. Therapeutically effective bone marrow stem cells, cord blood- or adipose tissue-derived mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and more recently, induced pluripotent stem cells (iPSCs) have been widely reported in many preclinical and clinical studies with some promising results. However, these stem cell-only transplantation strategies are hindered by the harsh microenvironment, limited cell viability, and poor retention of transplanted cells at the sites of injury. In fact, a number of studies have reported that less than 5% of the transplanted cells are retained at the site of injury on the first day after transplantation, suggesting extremely low (<1%) viability of transplanted cells. In this context, 3D porous or fibrous national polymers (collagen, fibrin, hyaluronic acid, and chitosan)-based scaffold with appropriate mechanical features and biocompatibility can be used to overcome various limitations of stem cell-only transplantation by supporting their adhesion, survival, proliferation, and differentiation as well as providing elegant 3-dimensional (3D) tissue microenvironment. Therefore, stem cell-based tissue engineering using natural or synthetic biomimetics provides novel clinical and therapeutic opportunities for a number of degenerative diseases or tissue injury. Here, we summarized recent studies involving various types of stem cell-based tissue-engineering strategies for different degenerative diseases. We also reviewed recent studies for preclinical and clinical use of stem cell-based scaffolds and various optimization strategies.

Comparison of Microglial Morphology and Function in Primary Cerebellar Cell Cultures on Collagen and Collagen-Mimetic Hydrogels

Neuronal-glial cell cultures are usually grown attached to or encapsulated in an adhesive environment as evenly distributed networks lacking tissue-like cell density, organization and morphology. In such cultures, microglia have activated amoeboid morphology and do not display extended and intensively branched processes characteristic of the ramified tissue microglia. We have recently described self-assembling functional cerebellar organoids promoted by hydrogels containing collagen-like peptides (CLPs) conjugated to a polyethylene glycol (PEG) core. Spontaneous neuronal activity was accompanied by changes in the microglial morphology and behavior, suggesting the cells might play an essential role in forming the functional neuronal networks in response to the peptide signalling. The present study examines microglial cell morphology and function in cerebellar cell organoid cultures on CLP-PEG hydrogels and compares them to the cultures on crosslinked collagen hydrogels of similar elastomechanical properties. Material characterization suggested more expressed fibril orientation and denser packaging in crosslinked collagen than CLP-PEG. However, CLP-PEG promoted a significantly higher microglial motility (determined by time-lapse imaging) accompanied by highly diverse morphology including the ramified (brightfield and confocal microscopy), more active Ca2+ signalling (intracellular Ca2+ fluorescence recordings), and moderate inflammatory cytokine level (ELISA). On the contrary, on the collagen hydrogels, microglial cells were significantly less active and mostly round-shaped. In addition, the latter hydrogels did not support the neuron synaptic activity. Our findings indicate that the synthetic CLP-PEG hydrogels ensure more tissue-like microglial morphology, motility, and function than the crosslinked collagen substrates.

Impact of Reck expression and promoter activity in neuronal in vitro differentiation

Reck (REversion-inducing Cysteine-rich protein with Kazal motifs) tumor suppressor gene encodes a multifunctional glycoprotein which inhibits the activity of several matrix metalloproteinases (MMPs), and has the ability to modulate the Notch and canonical Wnt pathways. Reck-deficient neuro-progenitor cells undergo precocious differentiation; however, modulation of Reck expression during progression of the neuronal differentiation process is yet to be characterized. In the present study, we demonstrate that Reck expression levels are increased during in vitro neuronal differentiation of PC12 pheochromocytoma cells and P19 murine teratocarcinoma cells and characterize mouse Reck promoter activity during this process. Increased Reck promoter activity was found upon induction of differentiation in PC12 cells, in accordance with its increased mRNA expression levels in mouse in vitro models. Interestingly, Reck overexpression, prior to the beginning of the differentiation protocol, led to diminished efficiency of the neuronal differentiation process. Taken together, our findings suggest that increased Reck expression at early stages of differentiation diminishes the number of neuron-like cells, which are positive for the beta-3 tubulin marker. Our data highlight the importance of Reck expression evaluation to optimize in vitro neuronal differentiation protocols.

Neurothreads: Development of supportive carriers for mature dopaminergic neuron differentiation and implantation

In this study we present the use of elastic macroporous cryogels for differentiation and transplantation of mature neurons. We develop a coating suitable for long-term neuronal culture, including stem cell differentiation, by covalent immobilization of neural adhesion proteins. In the context of cell therapy for Parkinson's disease, we show compatibility with established dopaminergic differentiation of both immortalized mesencephalic progenitors - LUHMES - and human embryonic stem cells (hESCs). We adjust structural properties of the biomaterial to create carriers - Neurothreads - favourable for cell viability during transplantation. Finally, we show feasibility of preservation of mature neurons, supported by Neurothreads, one month after in-vivo transplantation. Preliminary data suggests that the Neurothread approach could provide more mature and less proliferative cells in vivo.

Aberrant Expression of Collagen Gene Family in the Brain Regions of Male Mice with Behavioral Psychopathologies Induced by Chronic Agonistic Interactions

Chronic agonistic interactions promote the development of experimental psychopathologies in animals: a depression-like state in chronically defeated mice and the pathology of aggressive behavior in the mice with repeated wins. The abundant research data indicate that such psychopathological states are associated with significant molecular and cellular changes in the brain. This paper aims to study the influence of a 20-day period of agonistic interactions on the expression patterns of collagen family genes encoding the proteins which are basic components of extracellular matrix (ECM) in different brain regions of mice using the RNA-Seq database. Most of differentially expressed collagen genes were shown to be upregulated in the hypothalamus and striatum of chronically aggressive and defeated mice and in the hippocampus of defeated mice, whereas downregulation of collagen genes was demonstrated in the ventral tegmental areas in both experimental groups. Aberrant expression of collagen genes induced by chronic agonistic interactions may be indicative of specific ECM defects in the brain regions of mice with alternative social experience. This is the first study demonstrating remodeling of ECM under the development of experimental disorders.

Microfabricated intracortical extracellular matrix-microelectrodes for improving neural interfaces

Intracortical neural microelectrodes, which can directly interface with local neural microcircuits with high spatial and temporal resolution, are critical for neuroscience research, emerging clinical applications, and brain computer interfaces (BCI). However, clinical applications of these devices remain limited mostly by their inability to mitigate inflammatory reactions and support dense neuronal survival at their interfaces. Herein we report the development of microelectrodes primarily composed of extracellular matrix (ECM) proteins, which act as a bio-compatible and an electrochemical interface between the microelectrodes and physiological solution. These ECM-microelectrodes are batch fabricated using a novel combination of micro-transfer-molding and excimer laser micromachining to exhibit final dimensions comparable to those of commercial silicon-based microelectrodes. These are further integrated with a removable insertion stent which aids in intracortical implantation. Results from electrochemical models and in vivo recordings from the rat's cortex indicate that ECM encapsulations have no significant effect on the electrochemical impedance characteristics of ECM-microelectrodes at neurologically relevant frequencies. ECM-microelectrodes are found to support a dense layer of neuronal somata and neurites on the electrode surface with high neuronal viability and exhibited markedly diminished neuroinflammation and glial scarring in early chronic experiments in rats.

Ndr2 Kinase Controls Neurite Outgrowth and Dendritic Branching Through α1 Integrin Expression

The serine/threonine kinase Ndr2 has been shown to control the inside-out activation of the β₁subunit of integrins and the formation of neurites in both primary neurons and neurally differentiated pheochromacytoma (PC12) cells. In this study, we demonstrate that Ndr2 kinase furthermore determines the substrate specificity of neurite extension in PC12 cells via expression of α₁β₁ integrins. We show that stable overexpression of Ndr2 in PC12 cells increases neurite growth and extension on poly-D-lysine substrate, likely involving an increased expression of active β₁ integrin in the growth tips of these cells. By contrast, the Ndr2 overexpressing cells do not show the α₁β₁ integrin-mediated enhancement of neurite growth on collagen IV substrate that can be seen in control cells. Moreover, they entirely fail to increase in response to activation of α₁β₁ integrins via a soluble KTS ligand and show a diminished accumulation of α₁ integrin in neurite tips, although the expression of this subunit is induced during differentiation to comparable levels as in control cells. Finally, we demonstrate that Ndr2 overexpression similarly inhibits the α₁β₁ integrin-dependent dendritic growth of primary hippocampal neurons on laminin 111 substrate. By contrast, lack of Ndr2 impairs the dendritic growth regardless of the substrate. Together, these results suggest that Ndr2 regulates α₁ integrin trafficking in addition to β₁ integrin subunit activation and thereby controls the neurite growth on different extracellular matrix (ECM) substrates.

Decellularized Matrix Derived from Neural Differentiation of Embryonic Stem Cells Enhances the Neurogenic Potential of Dental Follicle Stem Cells

INTRODUCTION

Dental follicle stem cells (DFSCs) possess neurogenic potential because they originate from the embryonic neural crest. This study investigated whether neural differentiation of DFSCs can be enhanced by culture on decellularized matrix substrata (NSC-DECM) derived from neurogenesis of human embryonic stem cells (hESCs).

METHODS

The hESCs were differentiated into neural stem cells (NSCs), and NSC-DECM was extracted from confluent monolayers of NSCs through treatment with deionized water. DFSCs seeded on NSC-DECM, Geltrex, and tissue culture polystyrene (TCPS) were subjected to neural induction during a period of 21 days. Expression of early/intermediate (Musashi1, PAX6, NSE, and βIII-tubulin) and mature/late (NGN2, NeuN, NFM, and MASH1) neural markers by DFSCs was analyzed at the 7-, 14-, and 21-day time points with quantitative real-time polymerase chain reaction. Immunocytochemistry for detection of βIII-tubulin, PAX6, and NGN2 expression by DFSCs on day 7 of neural induction was also carried out.

RESULTS

Quantitative RT-PCR showed that expression of PAX6, Musashi1, βIII-tubulin, NSE, NGN2, and NFM by DFSCs was enhanced on NSC-DECM versus either the Geltrex or TCPS groups. Immunocytochemistry showed that DFSCs in the NSC-DECM group displayed more intense staining for βIII-tubulin, PAX6, and NGN2 expression, together with more neurite outgrowths and elongated morphology, as compared with either Geltrex or TCPS.

CONCLUSIONS

DECM derived from neurogenesis of hESCs can enhance the neurogenic potential of DFSCs.

Promotion and guidance of neural network formation on SU-8 photoresist microchannels adjusted with multilayer films

Induction of neural stem/progenitor cells (NSPCs) and establishment of neural network are important issues on neural engineering. In this work, a platform was designed to control and evaluate the differentiation of NSPCs, neurite direction, and to promote the neurite outgrowth. Polyelectrolyte multilayer (PEM) films provide surface properties by and have been used to regulate NSPCs differentiation in our previous study. Herein, a culture platform composed of SU-8 microchannel and PEM films was designed to achieve the goal of promoting NSPCs differentiation and to evaluate the effect of PEM films on the guidance of neural network formation. In this culture platform, NSPCs were induced into functional neurons, and neural network formation was accomplished on ITO glass-PEM films successfully.

Keratin mediated attachment of stem cells to augment cardiomyogenic lineage commitment

The objective of this work was to develop a simple surface modification technique using keratin derived from human hair for efficient cardiomyogenic lineage commitment of human mesenchymal stem cells (hMSCs). Keratin was extracted from discarded human hair containing both the acidic and basic components along with the heterodimers. The extracted keratin was adsorbed to conventional tissue culture polystyrene surfaces at different concentration. Keratin solution of 500μg/ml yielded a well coated layer of 12±1nm thickness with minimal agglomeration. The keratin coated surfaces promoted cell attachment and proliferation. Large increases in the mRNA expression of known cardiomyocyte genes such as cardiac actinin, cardiac troponin and β-myosin heavy chain were observed. Immunostaining revealed increased expression of sarcomeric α-actinin and tropomyosin whereas Western blots confirmed higher expression of tropomyosin and myocyte enhancer factor 2C in cells on the keratin coated surface than on the non-coated surface. Keratin promoted DNA demethylation of the Atp2a2 and Nkx2.5 genes thereby elucidating the importance of epigenetic changes as a possible molecular mechanism underlying the increased differentiation. A global gene expression analysis revealed a significant alteration in the expression of genes involved in pathways associated in cardiomyogenic commitment including cytokine and chemokine signaling, cell-cell and cell-matrix interactions, Wnt signaling, MAPK signaling, TGF-β signaling and FGF signaling pathways among others. Thus, adsorption of keratin offers a facile and affordable yet potent route for inducing cardiomyogenic lineage commitment of stem cells with important implications in developing xeno-free strategies in cardiovascular regenerative medicine.

Mimicking Neural Stem Cell Niche by Biocompatible Substrates

Neural stem cells (NSCs) participate in the maintenance, repair, and regeneration of the central nervous system. During development, the primary NSCs are distributed along the ventricular zone of the neural tube, while, in adults, NSCs are mainly restricted to the subependymal layer of the subventricular zone of the lateral ventricles and the subgranular zone of the dentate gyrus in the hippocampus. The circumscribed areas where the NSCs are located contain the secreted proteins and extracellular matrix components that conform their niche. The interplay among the niche elements and NSCs determines the balance between stemness and differentiation, quiescence, and proliferation. The understanding of niche characteristics and how they regulate NSCs activity is critical to building in vitro models that include the relevant components of the in vivo niche and to developing neuroregenerative approaches that consider the extracellular environment of NSCs. This review aims to examine both the current knowledge on neurogenic niche and how it is being used to develop biocompatible substrates for the in vitro and in vivo mimicking of extracellular NSCs conditions.

The effect of hypoxia and laminin-rich substrates on the proliferative behavior of human neural stem cells

Human neural stem cells cultured on laminin and Matrigel under hypoxia significantly increase both the stem cell density and the percentage of activity proliferating cells.

Enhanced In Vitro Biocompatibility of Chemically Modified Poly(dimethylsiloxane) Surfaces for Stable Adhesion and Long-term Investigation of Brain Cerebral Cortex Cells

Studies on the mammalian brain cerebral cortex have gained increasing importance due to the relevance of the region in controlling critical higher brain functions. Interactions between the cortical cells and surface extracellular matrix (ECM) proteins play a pivotal role in promoting stable cell adhesion, growth, and function. Poly(dimethylsiloxane) (PDMS) based platforms have been increasingly used for on-chip in vitro cellular system analysis. However, the inherent hydrophobicity of the PDMS surface has been unfavorable for any long-term cell system investigations due to transitory physical adsorption of ECM proteins on PDMS surfaces followed by eventual cell dislodgement due to poor anchorage and viability. To address this critical issue, we employed the (3-aminopropyl)triethoxysilane (APTES) based cross-linking strategy to stabilize ECM protein immobilization on PDMS. The efficiency of surface modification in supporting adhesion and long-term viability of neuronal and glial cells was analyzed. The chemically modified surfaces showed a relatively higher cell survival with an increased neurite length and neurite branching. These changes were understood in terms of an increase in surface hydrophilicity, protein stability, and cell-ECM protein interactions. The modification strategy could be successfully applied for stable cortical cell culture on the PDMS microchip for up to 3 weeks in vitro.

A non-tight junction function of claudin-7-Interaction with integrin signaling in suppressing lung cancer cell proliferation and detachment

Background

Claudins are a family of tight junction (TJ) membrane proteins involved in a broad spectrum of human diseases including cancer. Claudin-7 is a unique TJ membrane protein in that it has a strong basolateral membrane distribution in epithelial cells and in tissues. Therefore, this study aims to investigate the functional significance of this non-TJ localization of claudin-7 in human lung cancer cells.

Methods

Claudin-7 expression was suppressed or deleted by lentivirus shRNA or by targeted-gene deletion. Cell cycle analysis and antibody blocking methods were employed to assay cell proliferation and cell attachment, respectively. Electron microscopy and transepthelial electrical resistance measurement were performed to examine the TJ ultrastructure and barrier function. Co-immunolocalization and co-immunoprecipitation was used to study claudin-7 interaction with integrin β1. Tumor growth in vivo were analyzed using athymic nude mice.

Results

Claudin-7 co-localizes and forms a stable complex with integrin β1. Both suppressing claudin-7 expression by lentivirus shRNA in human lung cancer cells (KD cells) and deletion of claudin-7 in mouse lungs lead to the reduction in integrin β1 and phospho-FAK levels. Suppressing claudin-7 expression increases cell growth and cell cycle progression. More significantly, claudin-7 KD cells have severe defects in cell-matrix interactions and adhere poorly to culture plates with a remarkably reduced integrin β1 expression. When cultured on uncoated glass coverslips, claudin-7 KD cells grow on top of each other and form spheroids while the control cells adhere well and grow as a monolayer. Reintroducing claudin-7 reduces cell proliferation, upregulates integrin β1 expression and increases cell-matrix adhesion. Integrin β1 transfection partially rescues the cell attachment defect. When inoculated into nude mice, claudin-7 KD cells produced significantly larger tumors than control cells.

Conclusion

In this study, we identified a previously unrecognized function of claudin-7 in regulating cell proliferation and maintaining epithelial cell attachment through engaging integrin β1.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0387-0) contains supplementary material, which is available to authorized users.

Extracellular matrix-regulated neural differentiation of human multipotent marrow progenitor cells enhances functional recovery after spinal cord injury

BACKGROUND CONTEXT

Recent advanced studies have demonstrated that cytokines and extracellular matrix (ECM) could trigger various types of neural differentiation. However, the efficacy of differentiation and in vivo transplantation has not yet thoroughly been investigated.

PURPOSE

To highlight the current understanding of the effects of ECM on neural differentiation of human bone marrow-derived multipotent progenitor cells (MPCs), regarding state-of-art cure for the animal with acute spinal cord injury (SCI), and explore future treatments aimed at neural repair.

STUDY DESIGN

A selective overview of the literature pertaining to the neural differentiation of the MSCs and experimental animals aimed at improved repair of SCI.

METHODS

Extracellular matrix proteins, tenascin-cytotactin (TN-C), tenascin-restrictin (TN-R), and chondroitin sulfate (CS), with the cytokines, nerve growth factor (NGF)/brain-derived neurotrophic factor (BDNF)/retinoic acid (RA) (NBR), were incorporated to induce transdifferentiation of human MPCs. Cells were treated with NBR for 7 days, and then TN-C, TN-R, or CS was added for 2 days. The medium was changed every 2 days. Twenty-four animals were randomly assigned to four groups with six animals in each group: one experimental and three controls. Animals received two (bilateral) injections of vehicle, MPCs, NBR-induced MPCs, or NBR/TN-C-induced MPCs into the lesion sites after SCI. Functional assessment was measured using the Basso, Beattie, and Bresnahan locomotor rating score. Data were analyzed using analysis of variance followed by Student-Newman-Keuls (SNK) post hoc tests.

RESULTS

Results showed that MPCs with the transdifferentiation of human MPCs to neurons were associated with increased messenger-RNA (mRNA) expression of neuronal markers including nestin, microtubule-associated protein (MAP) 2, glial fibrillary acidic protein, βIII tubulin, and NGF. Greater amounts of neuronal morphology appeared in cultures incorporated with TN-C and TN-R than those with CS. The addition of TN-C enhanced mRNA expressions of MAP2, βIII tubulin, and NGF, whereas TN-R did not significantly change. Conversely, CS exposure decreased MAP2, βIII tubulin, and NGF expressions. The TN-C-treated MSCs significantly and functionally repaired SCI-induced rats at Day 42. Present results indicate that ECM components, such as tenascins and CS in addition to cytokines, may play functional roles in regulating neurogenesis by human MPCs.

CONCLUSIONS

These findings suggest that the combined use of TN-C, NBR, and human MPCs offers a new feasible method for nerve repair.

The influence of extracellular matrix composition on the differentiation of neuronal subtypes in tissue engineered innervated intestinal smooth muscle sheets

Differentiation of enteric neural stem cells into several appropriate neural phenotypes is crucial while considering transplantation as a cellular therapy to treat enteric neuropathies. We describe the formation of tissue engineered innervated sheets, where intestinal smooth muscle and enteric neuronal progenitor cells are brought into close association in extracellular matrix (ECM) based microenvironments. Uniaxial alignment of constituent smooth muscle cells was achieved by substrate microtopography. The smooth muscle component of the tissue engineered sheets maintained a contractile phenotype irrespective of the ECM composition, and generated equivalent contractions in response to potassium chloride stimulation, similar to native intestinal tissue. We provided enteric neuronal progenitor cells with permissive ECM-based compositional and viscoelastic cues to generate excitatory and inhibitory neuronal subtypes. In the presence of the smooth muscle cells, the enteric neuronal progenitor cells differentiated to functionally innervate the smooth muscle. The differentiation of specific neuronal subtypes was influenced by the ECM microenvironment, namely combinations of collagen I, collagen IV, laminin and/or heparan sulfate. The physiology of differentiated neurons within tissue engineered sheets was evaluated. Sheets with composite collagen and laminin had the most similar patterns of Acetylcholine-induced contraction to native intestinal tissue, corresponding to an increased protein expression of choline acetyltransferase. An enriched nitrergic neuronal population, evidenced by an increased expression of neuronal nitric oxide synthase, was obtained in tissue engineered sheets that included collagen IV. These sheets had a significantly increased magnitude of electrical field stimulated relaxation, sensitive maximally to nitric oxide synthase inhibition. Tissue engineered sheets containing laminin and/or heparan sulfate had a balanced expression of contractile and relaxant motor neurons. Our studies demonstrated that neuronal subtype was modulated by varying ECM composition. This observation could be utilized to derive enriched populations of specific enteric neurons in vitro prior to transplantation.

Mass production of early-stage bone-marrow-derived mesenchymal stem cells of rat using gelatin-coated matrix

Although preparation of early-stage bone-marrow-derived mesenchymal stem cells (BM-MSCs) is critical for successful cell transplantation therapy, no culture system offers a sufficient number of early-stage BM-MSCs for cell transplantation. Accordingly, we developed a culture system capable of producing a large number of early-stage BM-MSCs by using gelatin-coated matrix. The greatest retrieval and proliferation rates of the earliest-stage rat BM-MSCs were detected in bone-marrow-derived cells cultured on 1% (wt/v) gelatin-coated matrix, which showed significantly greater colony forming unit-fibroblast number, diameter, and total cell number. Moreover, continuous culture of the earliest-stage BM-MSCs on 1% (wt/v) gelatin-coated matrix resulted in a maximum of 21.2 ± 2.7 fold increase in the cumulative total number of early-stage BM-MSCs at passage 5. BM-MSCs generated in large quantities due to a reduced doubling time and an increased yield of cell population in S/G2/M phase showed typical fibroblast-like morphology and no significant differences in BM-MSC-related surface marker expression and differentiation potential, except for an increased ratio of differentiation into a neurogenic lineage. The use of gelatin-coated matrix in the retrieval and culture of BM-MSCs contributes greatly to the effective isolation and mass production of early-stage BM-MSCs.

Collagen XVII: a shared antigen in neurodermatological interactions?

Collagen XVII is a nonfibril-forming transmembrane collagen, which functions as both a matrix protein and a cell-surface receptor. It is particularly copious in the skin, where it is known to be a structural component of hemidesmosomes. In addition, collagen XVII has been found to be present in the central nervous system, thus offering an explanation for the statistical association between bullous pemphigoid, in which autoimmunity is directed against dermal collagen XVII, and neurological diseases. In support of the hypothesis that collagen XVII serves as a shared antigen mediating an immune response between skin and brain, research on animal and human tissue, as well as numerous epidemiological and case studies, is presented.

Extracellular matrix and the neural stem cell niche

Basal lamina is present in many stem cell niches, but we still have a poor understanding of the role of this and other extracellular matrix (ECM) components. Here, we review current knowledge regarding ECM expression and function in the neural stem cell niche, focusing on the subependymal zone of the adult CNS. An increasing complexity of ECM molecules has been described, and a number of receptors expressed on the stem cells identified. Experiments perturbing the niche using genetics or cytotoxic ablation of the rapidly dividing precursors, or using explant culture models to examine specific growth factors, have been influential in showing how changes in these ECM receptors might regulate neural stem cell behavior. However the role of changes in the matrix itself remains to be determined. The answers will be important, as they will point to the molecules required to engineer niches ex-vivo so as to provide tools for regenerative neuroscience.

A multipotent clonal human periodontal ligament cell line with neural crest cell phenotypes promotes neurocytic differentiation, migration, and survival

Repair of injured peripheral nerve is thought to play important roles in tissue homeostasis and regeneration. Recent experiments have demonstrated enhanced functional recovery of damaged neurons by some types of somatic stem cells. It remains unclear, however, if periodontal ligament (PDL) stem cells possess such functions. We recently developed a multipotent clonal human PDL cell line, termed cell line 1-17. Here, we investigated the effects of this cell line on neurocytic differentiation, migration, and survival. This cell line expressed the neural crest cell marker genes Slug, SOX10, Nestin, p75NTR, and CD49d and mesenchymal stem cell-related markers CD13, CD29, CD44, CD71, CD90, CD105, and CD166. Rat adrenal pheochromocytoma cells (PC12 cells) underwent neurocytic differentiation when co-cultured with cell line 1-17 or in conditioned medium from cell line 1-17 (1-17CM). ELISA analysis revealed that 1-17CM contained approximately 50 pg/ml nerve growth factor (NGF). Cell line 1-17-induced migration of PC12 cells, which was inhibited by a neutralizing antibody against NGF. Furthermore, 1-17CM exerted antiapoptotic effects on differentiated PC12 cells as evidenced by inhibition of neurite retraction, reduction in annexin V and caspase-3/7 staining, and induction of Bcl-2 and Bcl-xL mRNA expression. Thus, cell line 1-17 promoted neurocytic differentiation, migration, and survival through secretion of NGF and possibly synergistic factors. PDL stem cells may play a role in peripheral nerve reinnervation during PDL regeneration.

All-trans-retinoid acid induces the differentiation of encapsulated mouse embryonic stem cells into GABAergic neurons

Embryonic stem (ES) cells are pluripotent cells that can differentiate into all three main germ layers: endoderm, mesoderm, and ectoderm. Although a number of methods have been developed to differentiate ES cells into neuronal phenotypes such as sensory and motor neurons, the efficient generation of GABAergic interneurons from ES cells still presents an ongoing challenge. Because the main output of inhibitory GABAergic interneurons is the gamma-aminobutyric-acid (GABA), a neurotransmitter whose controlled homeostasis is required for normal brain function, the efficient generation in culture of functional interneurons may have future implications on the treatment of neurological disorders such as epilepsy, autism, and schizophrenia. The goal of this work was to examine the generation of GABAergic neurons from mouse ES cells by comparing an embryoid body-based methodology versus a hydrogel-based encapsulation protocol that involves the use of all-trans-retinoid acid (RA). We observed that (1) there was a 2-fold increase in neuronal differentiation in encapsulated versus non-encapsulated cells and (2) there was an increase in the specificity for interneuronal differentiation in encapsulated cells, as assessed by mRNA expression and electrophysiology approaches. Furthermore, our results indicate that most of the neurons obtained from encapsulated mouse ES cells are GABA-positive (∼87%). Thus, these results suggest that combining encapsulation of ES cells and RA treatment provide a more efficient and scalable differentiation strategy for the generation in culture of functional GABAergic interneurons. This technology may have implications for future cell replacement therapies and the treatment of CNS disorders.

Control of neural cell composition in poly(ethylene glycol) hydrogel culture with soluble factors

Poly(ethylene glycol) (PEG) hydrogels are being developed as cell delivery vehicles that have great potential to improve neuronal replacement therapies. Current research priorities include (1) characterizing neural cell growth within PEG hydrogels relative to standard culture systems and (2) generating neuronal-enriched populations within the PEG hydrogel environment. This study compares the percentage of neural precursor cells (NPCs), neurons, and glia present when dissociated neural cells are seeded within PEG hydrogels relative to standard monolayer culture. Results demonstrate that PEG hydrogels enriched the initial cell population for NPCs, which subsequently gave rise to neurons, then to glia. Relative to monolayer culture, PEG hydrogels maintained an increased percentage of NPCs and a decreased percentage of glia. This neurogenic advantage of PEG hydrogels is accentuated in the presence of basic fibroblast growth factor and epidermal growth factor, which more potently increase NPC and neuronal expression markers when applied to cells cultured within PEG hydrogels. Finally, this work demonstrates that glial differentiation can be selectively eliminated upon supplementation with a γ-secretase inhibitor. Together, this study furthers our understanding of how the PEG hydrogel environment influences neural cell composition and also describes select soluble factors that are useful in generating neuronal-enriched populations within the PEG hydrogel environment.

Neural differentiation regulated by biomimetic surfaces presenting motifs of extracellular matrix proteins

The interaction between cells and the extracellular matrix (ECM) is essential during development. To elucidate the function of ECM proteins on cell differentiation, we developed biomimetic surfaces that display specific ECM peptide motifs in a controlled manner. Presentation of ECM domains for collagen, fibronectin, and laminin influenced the formation of neurites by differentiating PC12 cells. The effect of these peptide sequences was also tested on the development of adult neural stem/progenitor cells. In this system, collagen I and fibronectin induced the formation of beta-III-tubulin positive cells, whereas collagen IV reduced such differentiation. Biomimetic surfaces composed of multiple peptide types enabled the combinatorial effects of various ECM motifs to be studied. Surfaces displaying combined motifs were often predictable as a result of the synergistic effects of ECM peptides studied in isolation. For example, the additive effects of fibronectin and laminin resulted in greater expression of beta-III-tubulin positive cells, whereas the negative effect of the collagen IV domain was canceled out by coexpression of collagen I. However, simultaneous expression of certain ECM domains was less predictable. These data highlight the complexity of the cellular response to combined ECM signals and the need to study the function of ECM domains individually and in combination.

Diverse roles of the vasculature within the neural stem cell niche

An interdependent relationship between the vascular and nervous systems begins during the earliest stages of development and persists through the mammalian lifespan. Accordingly, the process of adult neurogenesis involves the coordinated response of both systems to maintain a specialized microenvironment (niche) that tips the scale towards maintenance or regeneration, as needed. Understanding the nature and regulation of this balance will provide a foundation on which the potential for molecular- and stem cell-based therapies can be developed to treat prevalent CNS diseases and disorders. The vasculature is cited as a prominent feature within the adult subventricular zone and subgranular zone, known adult neural stem cell niches, helping to retain neural stem and progenitor cell potential. The vascular compartment within the neural stem cell niche has the unique opportunity to not only regulate neural stem and progenitor cells through direct contact with, and paracrine signaling from, endothelial and mural cells that make up blood vessels, but also integrates systemic signals into the local microenvironment via distribution of soluble factors from blood circulation to regulate stem cell niche behavior. Understanding the intricate role that the vasculature plays to influence neural stem cells in the context of niche regulation will help to bridge the gap from bench to bedside for the development of regeneration-based therapies for the CNS.

Heterogeneous differentiation of human mesenchymal stem cells in response to extended culture in extracellular matrices

Extracellular matrix proteins (ECMs) guide differentiation of adult stem cells, but the temporal distribution of differentiation (i.e., heterogeneity) in a given population has not been investigated. We tested the effect of individual ECM proteins on lineage commitment of human bone marrow-derived mesenchymal stem cells (MSCs) over time. We exposed stem cell populations to ECM proteins representing the primary tissue structures of the body (i.e., collagens type I, III, IV; laminin; and fibronectin) and determined the lineage commitment of the stem cells at 1, 7, and 14 days. We found that collagens that can participate in the formation of fibrils guide differentiation of cardiomyocytes, adipocytes, and osteoblasts. ECMs of the basement membrane initiate differentiation of cardiomyocytes and osteoblasts but not adipocytes, and small facilitator ECMs (e.g., fibronectin) do not significantly affect stem cell differentiation. Differentiation was ECM-dependent because culture on tissue culture polystyrene, with consistent cell morphology, proliferation, and death, initiated differentiation of osteoblasts only. Thus, we show that ECMs independently trigger differentiation of human adult MSCs and that differentiation in this context can be guided down multiple lineages using the same ECM stimulus. This work highlights the importance of more clearly defining progenitor populations, especially those cultured in the presence of ECMs before transplantation.

Interactions of primary neuroepithelial progenitor and brain endothelial cells: distinct effect on neural progenitor maintenance and differentiation by soluble factors and direct contact

Neurovascular interactions are crucial for the normal development of the central nervous system. To study such interactions in primary cultures, we developed a procedure to simultaneously isolate neural progenitor and endothelial cell fractions from embryonic mouse brains. Depending on the culture conditions endothelial cells were found to favor maintenance of the neuroprogenitor phenotype through the production of soluble factors, or to promote neuronal differentiation of neural progenitors through direct contact. These apparently opposing effects could reflect differential cellular interactions needed for the proper development of the brain.

Neural differentiation of embryonic stem cells is induced by signalling from non-neural niche cells

BACKGROUND/AIMS

Embryonic stem cell (ESC) transplantation offers new therapeutic strategies for neurodegenerative diseases and injury. However, the mechanisms underlying integration and differentiation of engrafted ESCs are poorly understood. This study elucidates the influence of exogenous signals on ESC differentiation using in vitro modelling of non-stem/stem cell interactions.

METHODS

Murine ESCs were co-cultured with endothelial cells and astrocytes or conditioned medium obtained from endothelial or astrocyte cultures. After 7 days of co-culture isolated RNA was analysed using RT-PCR for the expression of pluripotency marker oct-4, neural progenitor marker nestin, and neurofilament (NFL), an early marker of neuronal lineage commitment. The presence of the glial cell surface marker A2B5 was determined in ESCs by flow cytometry.

RESULTS

Neuronal differentiation was inhibited in ESCs when grown in close vicinity to cerebral endothelial or glial cells. Under these conditions, ESC differentiation was predominantly directed towards a glial fate. However, treatment of ESCs with endothelial cell- or astrocyte-conditioned medium promoted neuronal as well as glial differentiation.

CONCLUSION

Our results indicate that ESC fate is determined by endothelial and glial cells that comprise the environmental niche of these stem cells in vivo. The direction of differentiation processes appears to be dependent on humoral factors secreted by adjacent cell lines.

Tissue inhibitor of metalloproteinase-2 (TIMP-2) expression is regulated by multiple neural differentiation signals

Neuronal differentiation requires exquisitely timed cell cycle arrest for progenitors to acquire an appropriate neuronal cell fate and is achieved by communication between soluble signals, such as growth factors and extracellular matrix molecules. Here we report that the expression of TIMP-2, a matrix metalloproteinase inhibitor, is up-regulated by signals that control proliferation (bFGF and EGF) and differentiation (retinoic acid and NGF) in neural progenitor and neuroblastoma cell lines. TIMP-2 expression coincides with the appearance of neurofilament-positive neurons, indicating that TIMP-2 may play a role in neurogenesis. The up-regulation of TIMP-2 expression by proliferate signals suggests a role in the transition from proliferation to neuronal differentiation. Live labeling experiments demonstrate TIMP-2 expression only on alpha(3) integrin-positive cells. Thus, TIMP-2 function may be mediated via interaction with integrin receptor(s). We propose that TIMP-2 represents a component of the neurogenic signaling cascade induced by mitogenic stimuli that may withdraw progenitor cells from the cell cycle permitting their terminal neuronal differentiation.

Collagen matrix in spinal cord injury

The fibrous scar that develops after central nervous system (CNS) injury is considered a major impediment for axonal regeneration. It consists of a dense collagen IV meshwork, which serves as a binding matrix for numerous other extracellular matrix components and inhibitory molecules like proteoglycans and semaphorins, but also growth-promoting factors. Inhibition of collagen matrix formation in brain and spinal cord lesions leads to axonal regeneration and functional recovery, although collagen IV per se is not inhibitory for axonal outgrowth. This review focuses on the molecular properties of the collagen IV matrix and its interactions with various molecules that are expressed after CNS lesion. Moreover, studies on collagen expression and matrix formation after injury of regenerating versus non-regenerating nervous systems are reviewed. Major differences in collagen deposition in the CNS and the peripheral nervous system (PNS) and differences in specific cell responses to extracellular matrix deposition in the lesion area are discussed. Therapeutic treatments aiming at suppression of fibrous scarring have been shown to promote axon regeneration in various lesion paradigms of the mammalian CNS.

Engineering microenvironment for expansion of sensitive anchorage-dependent mammalian cells

Tissue engineering involves ex vivo seeding of anchorage-dependent mammalian cells onto scaffolds, or transplanting cells in vivo. The cell expansion currently requires repeated cell detachment from solid substrata by enzymatic, chemical or mechanical means. The report here presents a high yield three-dimensional culture and harvest system circumventing the conventional detachment requirements. Cells mixed with dilute cationic collagen were microencapsulated within an ultra-thin shell of synthetic polymers. The cationic collagen could rapidly form a conformal layer of collagen fibers around cells to support cell proliferation and functions. The collagen could be readily removed from cells with a buffer rinse after harvesting from the fragile microcapsules. The cells harvested from this system demonstrate improved attachment, morphology and functions over conventionally cultured cells, upon binding to ligand-conjugated polymer surfaces. The harvested cells can be re-encapsulated and allowed to proliferate again, or used immediately in applications.

Temporal expression changes during differentiation of neural stem cells derived from mouse embryonic stem cell

Temporal analysis in gene expression during differentiation of neural stem cells (NSCs) was performed by using in-house microarrays composed of 10,368 genes. The changes in mRNA level were measured during differentiation day 1, 2, 3, 6, 12, and 15. Out of 10,368 genes analyzed, 259 genes were up-regulated or down-regulated by 2-fold or more at least at one time-point during differentiation, and were classified into six clusters based on their expression patterns by K-means clustering. Clusters characterized by gradual increase have large numbers of genes involved in transport and cell adhesion; those which showed gradual decrease have much of genes in nucleic acid metabolism, cell cycle, transcription factor, and RNA processing. In situ hybridization (ISH) validated microarray data and it also showed that Fox M1, cyclin D2, and CDK4 were highly expressed in CNS germinal zones and ectonucleotide pyrophosphatase/phosphodiesterase 2 (Enpp2) was highly expressed in choroid plexus where stem/progenitor cells are possibly located. Together, this clustering analysis of expression patterns of functionally classified genes may give insight into understanding of CNS development and mechanisms of NSCs proliferation and differentiation.

Integrin dependent protein tyrosine phosphorylation is a key regulatory event in collagen IV mediated adhesion and proliferation of human lung tumor cell line, Calu-1

BACKGROUND

The clinical phenomenon of lung cancer metastasis to specific target organs is believed to be a direct interaction between tumor cells and extracellular matrix components. During invasion, tumor cells attach to the basement membrane protein, collagen type IV, degrade it, migrate through blood vessels, and adhere to extracellular matrix proteins.

METHODS

Four nonsmall-cell lung cancer cells were tested for adhesion, proliferation, migration and morphologic alterations on collagen type IV matrix by immunoprecipitation, Western blotting, phase contrast and time lapse video microscopy.

RESULTS

Collagen type IV promoted Calu-1 cell adhesion (< 15 minutes) and motility (< 6 hours) without any significant effect on proliferation. beta(1)-integrin is essential for collagen type IV adhesion and 8 to 10 fold higher expression of beta1-integrin on the surface of Calu-1 cells was identified. A protein tyrosine phosphatase inhibitor, peroxyvanadate, caused 50% inhibition in the adhesion process within 5 minutes but exposure to 60 micromol/L genistein for 72 hours, a protein tyrosine kinase inhibitor, drastically inhibits Calu-1 cell proliferation (> 70%). We examined the influence of beta1-integrin, peroxyvanadate and genistein on the spreading morphogenesis of Calu-1 cells on Collagen type IV. Use of either 1 microg of anti beta1-integrin inhibitory antibody (P5D2), 100 micromol/L peroxyvanadate or 60 micromol/L genistein had dramatic influence on the spreading of Calu-1 cells. Finally, Focal adhesion kinase was identified as a phosphoprotein target.

CONCLUSIONS

We have characterized an in vitro model of matrix-specific binding of a lung cancer cell line, Calu-1 to Coll IV. Calu-1 cells use primarily a beta1-integrin mediated intracellular tyrosine phosphorylation phenomenon as the key regulatory mechanism for its binding advantage to Coll IV matrix.

Comprehensive transcriptome analysis of differentiation of embryonic stem cells into midbrain and hindbrain neurons

Neurogenesis is one of the most complex events in embryonic development. However, little information is available regarding the molecular events that occur during neurogenesis. To identify regulatory genes and underlying mechanisms involved in the differentiation of embryonic stem (ES) cells to neurons, gene expression profiling was performed using cDNA microarrays. In mouse ES cells, we compared the gene expression of each differentiated cell stage using a five-stage lineage selection method. Of 10,368 genes, 1633 (16%) known regulatory genes were differentially expressed at least 2-fold or greater at one or more stages. At stage 3, during which ES cells differentiate into neural stem cells, modulation of nearly 1000 genes was observed. Most of transcription factors (Otx2, Ebf-3, Ptx3, Sox4, 13, 18, engrailed, Irx2, Pax8, and Lim3), signaling molecules (Wnt, TGF, and Shh family members), and extracellular matrix/adhesion molecules (collagens, MAPs, and NCAM) were up-regulated. However, some genes which may play important roles in maintaining the pluripotency of ES cells (Kruppel-like factor 2, 4, 5, 9, myeloblast oncogene like2, ZFP 57, and Esg-1) were down-regulated. The many genes identified with this approach that are modulated during neurogenesis will facilitate studies of the mechanisms underlying ES cell differentiation, neural induction, and neurogenesis.

Astrocytes in culture express fibrillar collagen

The use of monoclonal antibodies has led to much progress in the characterization of extracellular matrix components of the CNS. F1C3 is a monoclonal antibody raised against the astrocytic cell line, Neu7. Analysis by immunoprecipitation and Western blots of the F1C3 antigen in Neu7 cell lysates and conditioned medium reveals a recognition of several protein bands around 140-230 kD. Internal peptide sequence data from these bands indicate that they are highly homologous to fibrillar collagens, and the F1C3 antigen is specifically digested by the collagenase I protease. Other glial cell lines show F1C3 antigen expression including A7, C6, and U373. Cultures of neonatal primary astrocytes also express F1C3 antigen, and Western blot analysis of rat brain extracts from different ages and parts of the brain confirm an in vivo expression of F1C3 protein. The significance of the expression of fibrillar collagen-like proteins by astrocytes is discussed together with its possible implication during developmental processes and in the context of CNS lesions and regeneration.

Enhanced metabolic activity coincides with survival and differentiation of cultured rat retinal ganglion cells exposed to glutamate

Neurotransmitters are prominent candidates for trans-cellular signals that influence the development of the CNS. The present study has examined the effect of glutamate on survival, differentiation and metabolic activity of cultured rat retinal ganglion cells at 3 days in vitro. Retinal cultures from neonatal Wistar rats were treated with glutamate for 48 h. The metabolic activity was markedly increased in the retinal ganglion cells exposed to 20 microM glutamate. This was accompanied by an enhanced survival of these neurons. The number of differentiated retinal ganglion cells as determined by microtubule-associated protein-2 labeling was significantly increased following exposure to low but not higher doses of glutamate. The effect of glutamate on the metabolic activity and differentiation was blocked by tetrodotoxin. The results of the present study shows that glutamate has a significant effect on survival, differentiation and metabolic activity. An increase in the metabolic activity indicates an enhancement in the electrical activity. Thus, our results are consistent with the hypothesis that glutamate is critically involved in the regulation of electrical activity in developing rat retinal ganglion cells.

Neural stem cells and regulation of cell number

Normal CNS development involves the sequential differentiation of multipotent stem cells. Alteration of the numbers of stem cells, their self-renewal ability, or their proliferative capacity will have major effects on the appropriate development of the nervous system. In this review, we discuss different mechanisms that regulate neural stem cell differentiation. Proliferation signals and cell cycle regulators may regulate cell kinetics or total number of cell divisions. Loss of trophic support and cytokine receptor activation may differentially contribute to the induction of cell death at specific stages of development. Signaling from differentiated progeny or asymmetric distribution of specific molecules may alter the self-renewal characteristics of stem cells. We conclude that the final decision of a cell to self-renew, differentiate or remain quiescent is dependent on an integration of multiple signaling pathways and at each instant will depend on cell density, metabolic state, ligand availability, type and levels of receptor expression, and downstream cross-talk between distinct signaling pathways.