Neural stem cell isolation from the whole mouse brain using the novel FABP7-binding fluorescent dye, CDr3

Pathophysiology of Spinal Cord Injury and Tissue Engineering Approach for Its Neuronal Regeneration: Current Status and Future Prospects

A spinal cord injury (SCI) is a very debilitating condition causing loss of sensory and motor function as well as multiple organ failures. Current therapeutic options like surgery and pharmacotherapy show positive results but are incapable of providing a complete cure for chronic SCI symptoms. Tissue engineering, including neuroprotective or growth factors, stem cells, and biomaterial scaffolds, grabs attention because of their potential for regeneration and ability to bridge the gap in the injured spinal cord (SC). Preclinical studies with tissue engineering showed functional recovery and neurorestorative effects. Few clinical trials show the safety and efficacy of the tissue engineering approach. However, more studies should be carried out for potential treatment modalities. In this review, we summarize the pathophysiology of SCI and its current treatment modalities, including surgical, pharmacological, and tissue engineering approaches following SCI in preclinical and clinical phases.

A Bone Morphogenetic Protein Signaling Inhibitor, LDN193189, Converts Ischemia-Induced Multipotent Stem Cells into Neural Stem/Progenitor Cell-Like Cells

Stem cell therapy is used to restore neurological function in stroke patients. We have previously reported that ischemia-induced multipotent stem cells (iSCs), which are likely derived from brain pericytes, develop in poststroke human and mouse brains. Although we have demonstrated that iSCs can differentiate into neural lineage cells, the factors responsible for inducing this differentiation remain unclear. In this study, we found that LDN193189, a bone morphogenetic protein (BMP) inhibitor, caused irreversible changes in the shape of iSCs. In addition, compared with iSCs incubated without LDN193189, the iSCs incubated with LDN193189 (LDN-iSCs) showed upregulated expression of neural lineage-related genes and proteins, including those expressed in neural stem/progenitor cells (NSPCs), and downregulated expression of mesenchymal and pericytic-related genes and proteins. Moreover, microarray analysis revealed that LDN-iSCs and NSPCs had similar gene expression profiles. Furthermore, LDN-iSCs differentiated into electrophysiologically functional neurons. These results indicate that LDN193189 induces NSPC-like cells from iSCs, suggesting that bioactive molecules regulating BMP signaling are potential targets for promoting neurogenesis from iSCs in the pathological brain, such as during ischemic stroke. We believe that our findings will bring us one step closer to the clinical application of iSCs.

Multilayer and MATR3-dependent regulation of mRNAs maintains pluripotency in human induced pluripotent stem cells

Matrin3 (MATR3) is a nuclear RNA/DNA-binding protein that plays pleiotropic roles in gene expression regulation by directly stabilizing target RNAs and supporting the activity of transcription factors by modulating chromatin architecture. MATR3 is involved in the differentiation of neural cells, and, here, we elucidate its critical functions in regulating pluripotent circuits in human induced pluripotent stem cells (hiPSCs). MATR3 downregulation affects hiPSCs' differentiation potential by altering key pluripotency regulators' expression levels, including OCT4, NANOG, and LIN28A by pleiotropic mechanisms. MATR3 binds to the OCT4 and YTHDF1 promoters favoring their expression. YTHDF1, in turn, binds the m6A-modified OCT4 mRNA. Furthermore, MATR3 is recruited on ribosomes and controls pluripotency regulating the translation of specific transcripts, including NANOG and LIN28A, by direct binding and favoring their stabilization. These results show that MATR3 orchestrates the pluripotency circuitry by regulating the transcription, translational efficiency, and epitranscriptome of specific transcripts.

Sonic Hedgehog and Triiodothyronine Pathway Interact in Mouse Embryonic Neural Stem Cells

Neural stem cells are fundamental to development of the central nervous system (CNS)-as well as its plasticity and regeneration-and represent a potential tool for neuro transplantation therapy and research. This study is focused on examination of the proliferation dynamic and fate of embryonic neural stem cells (eNSCs) under differentiating conditions. In this work, we analyzed eNSCs differentiating alone and in the presence of sonic hedgehog (SHH) or triiodothyronine (T3) which play an important role in the development of the CNS. We found that inhibition of the SHH pathway and activation of the T3 pathway increased cellular health and survival of differentiating eNSCs. In addition, T3 was able to increase the expression of the gene for the receptor smoothened (Smo), which is part of the SHH signaling cascade, while SHH increased the expression of the T3 receptor beta gene (Thrb). This might be the reason why the combination of SHH and T3 increased the expression of the thyroxine 5-deiodinase type III gene (Dio3), which inhibits T3 activity, which in turn affects cellular health and proliferation activity of eNSCs.

The distinct difference in azido sugar metabolic rate between neural stem cells and fibroblasts and its application for decontamination of chemically induced neural stem cells

In our report, we found a distinct difference in azido sugar metabolic rate between neural stem cells and fibroblasts, which can be used for selective removal of fibroblasts from neural stem cell mixtures. Chemically induced neural stem cells (ciNSCs) serve as a highly valuable source of NSCs. Incompletely induced fibroblasts could interfere with ciNSC differentiation and become tumorigenic. Herein, we applied our method for the decontamination of ciNSCs and it exhibited excellent selectivity for ciNSCs. The results demonstrate that the ciNSC population can be efficiently purified to 98.1%. As far as we know, this is the highest purity obtained so far. We envision that, in the future, our method could be used as a safe, effective, and chemically-defined tool for decontaminating ciNSCs in both fundamental research and clinical stem cell therapy.

Neurogenic Niche Conversion Strategy Induces Migration and Functional Neuronal Differentiation of Neural Precursor Cells Following Brain Injury

Glial scars formed after brain injuries provide permissive cues for endogenous neural precursor/stem cells (eNP/SCs) to undergo astrogenesis rather than neurogenesis. Following brain injury, eNP/SCs from the subventricular zone leave their niche, migrate to the injured cortex, and differentiate into reactive astrocytes that contribute to glial scar formation. In vivo neuronal reprogramming, directly converting non-neuronal cells such as reactive astrocytes or NG2 glia into neurons, has greatly improved brain injury repair strategies. However, reprogramming carries a high risk of future clinical applications such as tumorigenicity, involving virus. In this study, we constructed a neural matrix to alter the adverse niche at the injured cortex, enabling eNP/SCs to differentiate into functional neurons. We found that the neural matrix functioned as a "glial trap" that largely concentrated and limited reactive astrocytes to the core of the lesion area, thus altering the adverse niche. The eNP/SCs migrated toward the injured cortex and differentiated into functional neurons. In addition, regenerated neurites extended across the boundary of the injured cortex. Mice treated with the neural matrix demonstrated significant behavioral recovery. For the first time, we induced eNP/SC-derived functional neurons in the cortex after brain injury without the use of viruses, microRNAs, or small molecules. Our novel strategy of applying this "glial trap" to obtain functional neurons in the injured cortex may provide a safer and more natural therapeutic alternative to reprogramming in future clinical applications.

Fatty Acid Signaling Mechanisms in Neural Cells: Fatty Acid Receptors

Fatty acids (FAs) are typically associated with structural and metabolic roles, as they can be stored as triglycerides, degraded by β-oxidation or used in phospholipids’ synthesis, the main components of biological membranes. It has been shown that these lipids exhibit also regulatory functions in different cell types. FAs can serve as secondary messengers, as well as modulators of enzymatic activities and substrates for cytokines synthesis. More recently, it has been documented a direct activity of free FAs as ligands of membrane, cytosolic, and nuclear receptors, and cumulative evidence has emerged, demonstrating its participation in a wide range of physiological and pathological conditions. It has been long known that the central nervous system is enriched with poly-unsaturated FAs, such as arachidonic (C20:4ω-6) or docosohexaenoic (C22:6ω-3) acids. These lipids participate in the regulation of membrane fluidity, axonal growth, development, memory, and inflammatory response. Furthermore, a whole family of low molecular weight compounds derived from FAs has also gained special attention as the natural ligands for cannabinoid receptors or key cytokines involved in inflammation, largely expanding the role of FAs as precursors of signaling molecules. Nutritional deficiencies, and alterations in lipid metabolism and lipid signaling have been associated with developmental and cognitive problems, as well as with neurodegenerative diseases. The molecular mechanism behind these effects still remains elusive. But in the last two decades, different families of proteins have been characterized as receptors mediating FAs signaling. This review focuses on different receptors sensing and transducing free FAs signals in neural cells: (1) membrane receptors of the family of G Protein Coupled Receptors known as Free Fatty Acid Receptors (FFARs); (2) cytosolic transport Fatty Acid-Binding Proteins (FABPs); and (3) transcription factors Peroxisome Proliferator-Activated Receptors (PPARs). We discuss how these proteins modulate and mediate direct regulatory functions of free FAs in neural cells. Finally, we briefly discuss the advantages of evaluating them as potential targets for drug design in order to manipulate lipid signaling. A thorough characterization of lipid receptors of the nervous system could provide a framework for a better understanding of their roles in neurophysiology and, potentially, help for the development of novel drugs against aging and neurodegenerative processes.

Antenatal taurine supplementation in fetal rats with growth restriction improves neural stem cell proliferation by inhibiting the activities of Rho family factors

OBJECTIVE

To investigate whether antenatal taurine supplementation improves neural stem cell proliferation in rats with fetal growth restriction (FGR) through regulating the activity of Rho family factors.

METHODS

FGR models were established via food restriction throughout pregnancy. Pregnant rats were randomly divided into the control group, the FGR group (given 40% of the normal daily feeding in the control group), and the Taurine group (FGR model treated with 300 mg/kg·d taurine from gestational day seven). Expression of fatty acid binding protein-7 (FABP-7), Rho-associated coiled coil-forming protein kinase (ROCK2), Ras homolog gene family member A (RhoA), and rac in the brains of newborn rats was detected by reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry (IHC), and Western blotting (WB).

RESULTS

Relative FABP7 mRNA levels, the optical density (OD) values of FABP7-positive cells and the expression levels of the tested proteins all demonstrated that the number of neural stem cells (NSCs) in brain tissue was lower in the FGR group than in the control group but was significantly increased after antenatal taurine supplementation (p < .05). Compared with the control group, the mRNA and protein levels of RhoA and ROCK2 were higher in the FGR group but lower in the Taurine group (p < .05). In contrast, the rac mRNA level was lower in the FGR group than in the control group but was higher in the Taurine group (p < .05).

CONCLUSIONS

Taurine prenatal supplementation improved neural stem cell proliferation in rats with FGR by inhibiting the activity of Rho family factors.

Advances in the design of cell-permeable fluorescent probes for applications in live cell imaging

Advances in the design strategy of cell-permeable small fluorescent probes are discussed. Their applications in imaging specific cell types and intracellular bioanalytes, as well as the cellular environment in live conditions, are presented.

Building a central nervous system: The neural stem cell lineage revealed

Neural stem cells (NSCs) are a multipotent, self-renewing source of undifferentiated cells in the periventricular region of the mammalian central nervous system (CNS). Since their original discovery 25 years ago, much has been learned about their development, persistence, localization, properties and potential. Herein we discuss the current state of knowledge pertaining to neural stem cells with a focus on the lineage relationship between two NSC populations along the neuraxis and their regionally distinct niches in the CNS.

Expression Profiling of Clinical Specimens Supports the Existence of Neural Progenitor-Like Stem Cells in Basal Breast Cancers

BACKGROUND

We previously characterized in salivary adenoid cystic carcinoma (ACC) a novel population of cancer stem cells (CSCs) marked by coexpression of 2 stemness genes, sex-determining region Y (SRY)-related HMG box-containing factor 10 (SOX10) and CD133. We also reported that in ACC and basal-like breast carcinoma (BBC), a triple-negative breast cancer subtype, expression of SOX10 similarly demarcates a highly conserved gene signature enriched with neural stem cell genes. On the basis of these findings, we hypothesized that BBC might be likewise driven by SOX10-positive (SOX10⁺)/CD133⁺ cells with neural stem cell properties.

MATERIALS AND METHODS

To validate our hypothesis on clinical data, we used a novel approach to meta-analysis that merges gene expression data from independent breast cancer studies and ranks genes according to statistical significance of their coexpression with the gene of interest. Genes that showed strong association with CD133/PROM1 as well as SOX10 were validated across different platforms and data sets and analyzed for enrichment with genes involved in neurogenesis.

RESULTS

We identified in clinical breast cancer data sets a highly conserved SOX10/PROM1 gene signature that contains neural stem cell markers common for Schwann cells, ACC, BBC, and melanoma. Identification of tripartite motif-containing 2 (TRIM2), TRIM29, MPZL2, potassium calcium-activated channel subfamily N member 4 (KCNN4), and V-set domain containing T cell activation inhibitor 1 (VTCN1)/B7 homolog 4 (B7H4) within this signature provides insight into molecular mechanisms of CSC maintenance.

CONCLUSION

Our results suggest that BBC is driven by SOX10⁺/CD133⁺ cells that express neural stem cell-specific markers and share molecular similarities with CSCs of neural crest origin. Our study provides clinically relevant information on possible drivers of these cells that might facilitate development of CSC-targeting therapies against this cancer distinguished with poor prognosis and resistance to conventional therapies.

Functional hyaluronate collagen scaffolds induce NSCs differentiation into functional neurons in repairing the traumatic brain injury

The traumatic brain injury (TBI) usually causes brain tissue defects, including neuronal death or loss, which ultimately results in dysfunction in some degree. The cell replacement therapy is now one of the most promising methods for such injury. There are currently various methods to induce the differentiation of stem cells into neurons, but all extremely complex, slow and unstable. Here we report that the sodium hyaluronate collagen scaffold loaded with bFGF (bFGF-controlled releasing system, bFGF-CRS) can induce neural stem cells (NSCs) to differentiate into multi-type and mature functional neurons at a high percentage of 82±1.528% in two weeks. The quantitative real-time (QRT) PCR results reveal that a long-term activation of bFGF receptors could up-regulate ERK/MAPK signal pathways, thus facilitating the formation of presynaptic and postsynaptic structure among the induced neuronal cells (iN cells). The functional synaptic connections established among iN cells were detected by the planar multielectrode dish system. When jointly transplanting the bFGF-CRS and NSCs into the CA1 zone of the rat TBI area, the results suggested that bFGF-CRS provided an optimal microenvironment, which promoted survival, neuronal differentiation of transplanted NSCs and functional synapse formation not only among iN cells but also between iN cells and the host brain tissue in TBI rats, consequently leading to the cognitive function recovery of TBI rats. These findings in vitro and in vivo may lay a foundation for the application of bFGF-CRS and shed light on the delivery of exogenous cells or nutrients to the CNS injury or disease area.

STATEMENT OF SIGNIFICANCE

A sodium hyaluronate collagen scaffold was specifically functionalized with nutrient-bFGF which can induce the differentiation of neural stem cells (NSCs) into multi-type and mature functional neurons at a high percentage in two week. When jointly transplanting the bFGF-CRS and NSCs into the CA1 zone of the traumatic brain injured area of adult rats, the bFGF-CRS could provide an optimal microenvironment, which promoted survival, migration and neuronal differentiation of transplanted NSCs and functional synapse formation among iN cells, as well as between iN cells and host brain tissue in TBI rats, consequently leading to the cognitive function recovery of TBI rats.

Diversity oriented fluorescence library approach (DOFLA) for live cell imaging probe development

A cell is the smallest functional unit of life. All forms of life rely on cellular processes to maintain normal functions, and changes in cell function induced by metabolic disturbances, physicochemical damage, infection, or abnormal gene expression may cause disease. To understand basic biology and to develop therapeutics for diseases, researchers need to study live cells. Along with advances in fluorescence microscopy and in vitro cell culture, live-cell imaging has become an essential tool in modern biology for the study of molecular and cellular events. Although researchers have often used fluorescent proteins to visualize cell-type-specific markers, this method requires genetic manipulations, which may not be appropriate in nontransgenic cells. Immunodetection of cellular markers requires the use of xenogenic antibodies, which may not detect intracellular markers in live cells. One option for overcoming these problems is the use of fluorescent small molecules targeted to specific cell types, which can enter live cells and interact with molecules of interest. We have used combinatorial chemistry to develop a large number of fluorescent small molecules as new imaging probes even without prior information about the probes' binding targets and mechanism, a strategy that we call the diversity oriented fluorescence library approach (DOFLA). We have used DOFLA to produce novel sensors and probes that detect a variety of biological and chemical molecules in vivo as well as in vitro. In this Account, we describe a series of fluorescent small molecules developed using DOFLA that bind specifically to particular cell types. These molecules provide new ways to detect and isolate these cells. The fluorescent probes CDy1, CDg4, and CDb8 tag embryonic stem cells and induced pluripotent stem cells but not fibroblasts or germ-line cells. CDr3 binds to an intracellular neural stem cell marker, fatty acid binding protein 7, which allows researchers to separate neural stem cells from embryonic stems cells and more differentiated cells such as neurons and glia. In addition, we have developed CDr10, which distinguishes microglia from neurons and glia. CDy2 stains myocytes much more brightly than myoblasts because of the increase in mitochondrial membrane potential during myogenesis. GY and PiY selectively stain α and β cells of pancreatic islets, respectively. Histamine Blue binds directly to histamine and stains basophils and macrophages containing high quantities of histamine. Glutathione Green allows researchers to measure the level of glutathione in cells and tissues by binding to glutathione and then triggering a hypsochromic shift. We have also developed a set of compounds that bind to cancer cells based on the cell type of origin and biocompatible surface-enhanced Raman spectroscopy (SERS) nanotags for cancer detection. In addition to discussing these new probes and their cell-type specificity, we also describe their applications in new assays, cell characterization, and pathology studies.