Identification and dynamic regulation of tight junction protein expression in human neural stem cells

The Role of TIM-1 and CD300a in Zika Virus Infection Investigated with Cell-Based Electrical Impedance

Orthoflaviviruses cause a major threat to global public health, and no antiviral treatment is available yet. Zika virus (ZIKV) entry, together with many other viruses, is known to be enhanced by phosphatidylserine (PS) receptors such as T-cell immunoglobulin mucin domain protein 1 (TIM-1). In this study, we demonstrate for the first time, using cell-based electrical impedance (CEI) biosensing, that ZIKV entry is also enhanced by expression of CD300a, another PS receptor. Furthermore, inhibiting CD300a in immature monocyte-derived dendritic cells partially but significantly inhibits ZIKV replication. As we have previously demonstrated that CEI is a useful tool to study Orthoflavivirus infection in real time, we now use this technology to determine how these PS receptors influence the kinetics of in vitro ZIKV infection. Results show that ZIKV entry is highly sensitive to minor changes in TIM-1 expression, both after overexpression of TIM-1 in infection-resistant HEK293T cells, as well as after partial knockout of TIM-1 in susceptible A549 cells. These results are confirmed by quantification of viral copy number and viral infectivity, demonstrating that CEI is highly suited to study and compare virus-host interactions. Overall, the results presented here demonstrate the potential of targeting this universal viral entry pathway.

Identity and nature of neural stem cells in the adult human subventricular zone

The existence of neural stem cells (NSCs) in adult human brain neurogenic regions remains unresolved. To address this, we created a cell atlas of the adult human subventricular zone (SVZ) derived from fresh neurosurgical samples using single-cell transcriptomics. We discovered 2 adult radial glia (RG)-like populations, aRG1 and aRG2. aRG1 shared features with fetal early RG (eRG) and aRG2 were transcriptomically similar to fetal outer RG (oRG). We also captured early neuronal and oligodendrocytic NSC states. We found that the biological programs driven by their transcriptomes support their roles as early lineage NSCs. Finally, we show that these NSCs have the potential to transition between states and along lineage trajectories. These data reveal that multipotent NSCs reside in the adult human SVZ.

Occludin: a gatekeeper of brain Infection by HIV-1

Compromised structure and function of the blood-brain barrier (BBB) is one of the pathological hallmarks of brain infection by HIV-1. BBB damage during HIV-1 infection has been associated with modified expression of tight junction (TJ) proteins, including occludin. Recent evidence indicated occludin as a redox-sensitive, multifunctional protein that can act as both an NADH oxidase and influence cellular metabolism through AMPK kinase. One of the newly identified functions of occludin is its involvement in regulating HIV-1 infection. Studies suggest that occludin expression levels and the rate of HIV-1 infection share a reverse, bidirectional relationship; however, the mechanisms of this relationship are unclear. In this review, we describe the pathways involved in the regulation of HIV-1 infection by occludin. We propose that occludin may serve as a potential therapeutic target to control HIV-1 infection and to improve the lives of people living with HIV-1.

Mechanotransduction through adhesion molecules: Emerging roles in regulating the stem cell niche

Stem cells have been shown to play an important role in regenerative medicine due to their proliferative and differentiation potential. The challenge, however, lies in regulating and controlling their potential for this purpose. Stem cells are regulated by growth factors as well as an array of biochemical and mechanical signals. While the role of biochemical signals and growth factors in regulating stem cell homeostasis is well explored, the role of mechanical signals has only just started to be investigated. Stem cells interact with their niche or to other stem cells via adhesion molecules that eventually transduce mechanical cues to maintain their homeostatic function. Here, we present a comprehensive review on our current understanding of the influence of the forces perceived by cell adhesion molecules on the regulation of stem cells. Additionally, we provide insights on how this deeper understanding of mechanobiology of stem cells has translated toward therapeutics.

Expression and localization of tight junction-related proteins in adult rat pituitary stem/progenitor cell niches

Pituitary endocrine cells are supplied by Sox2-expressing stem/progenitor cells in the anterior lobe of the adult pituitary gland. These SOX2-positive cells are maintained in two types of microenvironments (niches): the marginal cell layer (MCL)-niche and the parenchymal-niche. Recently, we isolated dense SOX2-positive cell clusters from the parenchymal-niche by taking advantage of their resistance to protease treatment as parenchymal stem/progenitor cell (PS)-clusters. In the present study, by analyzing these isolated PS-clusters, we attempted to identify novel structural characteristics of pituitary stem/progenitor cell niches. Quantitative real-time PCR showed that tight junction-related genes were distinctly expressed in the isolated PS-clusters. Immunocytostaining showed that the tight junction molecules, ZO-1 and occludin, were localized in the apical membrane facing the pseudo-follicle-like structure of the isolated PS-clusters regardless of the expression of S100β, which distinguishes the sub-population of SOX2-positive cells. Furthermore, immunohistochemistry of the pituitary glands of adult rats clearly demonstrated that ZO-1 and occludin were densely present in the parenchymal-niche encircling the pseudo-follicle, while they were observed in the apical membrane in the MCL-niche facing the residual lumen. Collectively, these tight junction-related proteins might be involved in the architecture and maintenance of the plasticity of pituitary stem/progenitor cell niches.

The role of the mucin-glycan foraging Ruminococcus gnavus in the communication between the gut and the brain

Ruminococcus gnavus is a prevalent member of the human gut microbiota, which is over-represented in inflammatory bowel disease and neurological disorders. We previously showed that the ability of R. gnavus to forage on mucins is strain-dependent and associated with sialic acid metabolism. Here, we showed that mice monocolonized with R. gnavus ATCC 29149 (Rg-mice) display changes in major sialic acid derivatives in their cecum content, blood, and brain, which is accompanied by a significant decrease in the percentage of sialylated residues in intestinal mucins relative to germ-free (GF) mice. Changes in metabolites associated with brain function such as tryptamine, indolacetate, and trimethylamine N-oxide were also detected in the cecal content of Rg-mice when compared to GF mice. Next, we investigated the effect of R. gnavus monocolonization on hippocampus cell proliferation and behavior. We observed a significant decrease of PSA-NCAM immunoreactive granule cells in the dentate gyrus (DG) of Rg-mice as compared to GF mice and recruitment of phagocytic microglia in the vicinity. Behavioral assessments suggested an improvement of the spatial working memory in Rg-mice but no change in other cognitive functions. These results were also supported by a significant upregulation of genes involved in proliferation and neuroplasticity. Collectively, these data provide first insights into how R. gnavus metabolites may influence brain regulation and function through modulation of granule cell development and synaptic plasticity in the adult hippocampus. This work has implications for further understanding the mechanisms underpinning the role of R. gnavus in neurological disorders.

Hybrid SMART spheroids to enhance stem cell therapy for CNS injuries

Although stem cell therapy holds enormous potential for treating debilitating injuries and diseases in the central nervous system, low survival and inefficient differentiation have restricted its clinical applications. Recently, 3D cell culture methods, such as stem cell–based spheroids and organoids, have demonstrated advantages by incorporating tissue-mimetic 3D cell-cell interactions. However, a lack of drug and nutrient diffusion, insufficient cell-matrix interactions, and tedious fabrication procedures have compromised their therapeutic effects in vivo. To address these issues, we developed a biodegradable nanomaterial-templated 3D cell assembly method that enables the formation of hybrid stem cell spheroids with deep drug delivery capabilities and homogeneous incorporation of 3D cell-matrix interactions. Hence, high survival rates, controlled differentiation, and functional recovery were demonstrated in a spinal cord injury animal model. Overall, our hybrid stem cell spheroids represent a substantial development of material-facilitated 3D cell culture systems and can pave the way for stem cell–based treatment of CNS injuries.

High SPIN4 Expression Is Linked to Advanced Nodal Status and Inferior Prognosis in Nasopharyngeal Carcinoma Patients

Nasopharyngeal carcinoma (NPC), characterized by the infiltration of lymphocytes, is a malignancy derived from the epithelium of the nasopharynx. Despite its sensitivity to radiation and chemotherapy, NPC has a high propensity for recurrence and metastasis. Although lymph node levels have been indicated as an independent prognostic factor for NPC, there has been no precise prognostic biomarker to predict clinical outcomes for NPC before advanced disease. In the present study, we surveyed differentially expressed genes in NPC via the next-generation sequencing (NGS)-based Oncomine database and identified the spindlin family member 4 (SPIN4) gene as the most relevant to advanced nodal status. We collected 124 tumor samples from NPC patients receiving biopsy, and the expression level of SPIN4 was evaluated by immunohistochemistry. The results showed that tumors with high SPIN4 expression were significantly correlated with advanced nodal status (p < 0.001) and advanced AJCC stages (p < 0.001). High SPIN4 expression in tumor samples was an unfavorable prognostic factor for all three endpoints at the univariate level: disease-specific survival (DSS), distal metastasis-free survival (DMeFS), and local recurrence-free survival (LRFS) (all p < 0.05). High SPIN4 expression remained independently prognostic of worse DMeFS (p = 0.049) at the multivariate level. Using bioinformatics analysis, we further found that high SPIN4 level may link tight junctions to cancer cell survival. Collectively, these results imply that high SPIN4 expression is linked to an aggressive clinical course, including advanced nodal status and poor survival in NPC patients, emphasizing the promising prognostic utility of SPIN4 expression.

MSC spheroids-loaded collagen hydrogels simultaneously promote neuronal differentiation and suppress inflammatory reaction through PI3K-Akt signaling pathway

It is critical for the clinical success to take the anti-inflammatory function into consideration when integrating the neurogenesis into the nerve repair materials. To this aim, we prepared mesenchymal stem cell (MSC) spheroids-loaded collagen (Col) hydrogels with combined superior anti-inflammatory efficacy and neurogenic activity. The size of the MSC spheroids showed a strong modulation effect on both functions, and the MSC spheroids-100 sample exhibited the best neuronal and anti-inflammatory potentials. The observed dual functions were likely based on the elevated intrinsic cell-cell contacts and cell-extracellular matrix interactions from the MSC spheroids. MSC self-assembly as spheroids expedited the secretions of endogenous trophic factors and extracellular matrix (ECM), which was beneficial to drive neural stem cell differentiation into the neuronal lineage. In addition, the formation of the MSC spheroids secreted more amounts and types of cytokines as well as immunomodulatory paracrine factors to suppress LPS-induced inflammatory reaction. LC-MS/MS analysis further demonstrated that MSC spheroids contributed to the activation of neuroactive ligand-receptor interaction, thereby triggering downstream PI3K-Akt signal pathway, which was likely due to the acceleration of ECM-receptor interaction, gap junction and tight junction. Importantly, inhibiting Akt pathway significantly suppressed the neuronal differentiation, indicating that PI3K-Akt signal pathway was critically involved in the Col-MSC spheroid hydrogel mediated neuroprotection and neurogenesis. Such findings not only provided a simple approach for improving MSC-based therapies for neuron-related diseases, but also shed insight on understanding the underlying mechanisms of MSC-mediated neuronal differentiation.

Selection of an Efficient AAV Vector for Robust CNS Transgene Expression

Adeno-associated virus (AAV) capsid libraries have generated improved transgene delivery vectors. We designed an AAV library construct, iTransduce, that combines a peptide library on the AAV9 capsid with a Cre cassette to enable sensitive detection of transgene expression. After only two selection rounds of the library delivered intravenously in transgenic mice carrying a Cre-inducible fluorescent protein, we flow sorted fluorescent cells from brain, and DNA sequencing revealed two dominant capsids. One of the capsids, termed AAV-F, mediated transgene expression in the brain cortex more than 65-fold (astrocytes) and 171-fold (neurons) higher than the parental AAV9. High transduction efficiency was sex-independent and sustained in two mouse strains (C57BL/6 and BALB/c), making it a highly useful capsid for CNS transduction of mice. Future work in large animal models will test the translation potential of AAV-F.

Ineffective esophageal motility: Concepts, future directions, and conclusions from the Stanford 2018 symposium

BACKGROUND

Ineffective esophageal motility (IEM) is a heterogenous minor motility disorder diagnosed when ≥50% ineffective peristaltic sequences (distal contractile integral <450 mm Hg cm s) coexist with normal lower esophageal sphincter relaxation (integrated relaxation pressure < upper limit of normal) on esophageal high-resolution manometry (HRM). Ineffective esophageal motility is not consistently related to disease states or symptoms and may be seen in asymptomatic healthy individuals.

PURPOSE

A 1-day symposium of esophageal experts reviewed existing literature on IEM, and this review represents the conclusions from the symposium. Severe IEM (>70% ineffective sequences) is associated with higher esophageal reflux burden, particularly while supine, but milder variants do not progress over time or consistently impact quality of life. Ineffective esophageal motility can be further characterized using provocative maneuvers during HRM, especially multiple rapid swallows, where augmentation of smooth muscle contraction defines contraction reserve. The presence of contraction reserve may predict better prognosis, lesser reflux burden and confidence in a standard fundoplication for surgical management of reflux. Other provocative maneuvers (solid swallows, standardized test meal, rapid drink challenge) are useful to characterize bolus transit in IEM. No effective pharmacotherapy exists, and current managements target symptoms and concurrent reflux. Novel testing modalities (baseline and mucosal impedance, functional lumen imaging probe) show promise in elucidating pathophysiology and stratifying IEM phenotypes. Specific prokinetic agents targeting esophageal smooth muscle need to be developed for precision management.

In the line-up: deleted genes associated with DiGeorge/22q11.2 deletion syndrome: are they all suspects?

BACKGROUND

22q11.2 deletion syndrome (22q11DS), a copy number variation (CNV) disorder, occurs in approximately 1:4000 live births due to a heterozygous microdeletion at position 11.2 (proximal) on the q arm of human chromosome 22 (hChr22) (McDonald-McGinn and Sullivan, Medicine 90:1-18, 2011). This disorder was known as DiGeorge syndrome, Velo-cardio-facial syndrome (VCFS) or conotruncal anomaly face syndrome (CTAF) based upon diagnostic cardiovascular, pharyngeal, and craniofacial anomalies (McDonald-McGinn and Sullivan, Medicine 90:1-18, 2011; Burn et al., J Med Genet 30:822-4, 1993) before this phenotypic spectrum was associated with 22q11.2 CNVs. Subsequently, 22q11.2 deletion emerged as a major genomic lesion associated with vulnerability for several clinically defined behavioral deficits common to a number of neurodevelopmental disorders (Fernandez et al., Principles of Developmental Genetics, 2015; Robin and Shprintzen, J Pediatr 147:90-6, 2005; Schneider et al., Am J Psychiatry 171:627-39, 2014).

RESULTS

The mechanistic relationships between heterozygously deleted 22q11.2 genes and 22q11DS phenotypes are still unknown. We assembled a comprehensive "line-up" of the 36 protein coding loci in the 1.5 Mb minimal critical deleted region on hChr22q11.2, plus 20 protein coding loci in the distal 1.5 Mb that defines the 3 Mb typical 22q11DS deletion. We categorized candidates based upon apparent primary cell biological functions. We analyzed 41 of these genes that encode known proteins to determine whether haploinsufficiency of any single 22q11.2 gene-a one gene to one phenotype correspondence due to heterozygous deletion restricted to that locus-versus complex multigenic interactions can account for single or multiple 22q11DS phenotypes.

CONCLUSIONS

Our 22q11.2 functional genomic assessment does not support current theories of single gene haploinsufficiency for one or all 22q11DS phenotypes. Shared molecular functions, convergence on fundamental cell biological processes, and related consequences of individual 22q11.2 genes point to a matrix of multigenic interactions due to diminished 22q11.2 gene dosage. These interactions target fundamental cellular mechanisms essential for development, maturation, or homeostasis at subsets of 22q11DS phenotypic sites.

Blood-brain barrier-supported neurogenesis in healthy and diseased brain

Adult neurogenesis is one of the most important mechanisms contributing to brain development, learning, and memory. Alterations in neurogenesis underlie a wide spectrum of brain diseases. Neurogenesis takes place in highly specialized neurogenic niches. The concept of neurogenic niches is becoming widely accepted due to growing evidence of the important role of the microenvironment established in the close vicinity to stem cells in order to provide adequate control of cell proliferation, differentiation, and apoptosis. Neurogenic niches represent the platform for tight integration of neurogenesis and angiogenesis supported by specific properties of cerebral microvessel endothelial cells contributing to establishment of partially compromised blood-brain barrier (BBB) for the adjustment of local conditions to the current metabolic needs of stem and progenitor cells. Here, we review up-to-date data on microvascular dynamics in activity-dependent neurogenesis, specific properties of BBB in neurogenic niches, endothelial-driven mechanisms of clonogenic activity, and future perspectives for reconstructing the neurogenic niches in vitro.

Gene Expression Changes in Long-Term In Vitro Human Blood-Brain Barrier Models and Their Dependence on a Transwell Scaffold Material

Disruption of the blood-brain barrier (BBB) is the hallmark of many neurovascular disorders, making it a critically important focus for therapeutic options. However, testing the effects of either drugs or pathological agents is difficult due to the potentially damaging consequences of altering the normal brain microenvironment. Recently, in vitro coculture tissue models have been developed as an alternative to animal testing. Despite low cost, these platforms use synthetic scaffolds which prevent normal barrier architecture, cellular crosstalk, and tissue remodeling. We created a biodegradable electrospun gelatin mat "biopaper" (BP) as a scaffold material for an endothelial/astrocyte coculture model allowing cell-cell contact and crosstalk. To compare the BP and traditional models, we investigated the expression of 27 genes involved in BBB permeability, cellular function, and endothelial junctions at different time points. Gene expression levels demonstrated higher expression of transcripts involved in endothelial junction formation, including TJP2 and CDH5, in the BP model. The traditional model had higher expression of genes associated with extracellular matrix-associated proteins, including SPARC and COL4A1. Overall, the results demonstrate that the BP coculture model is more representative of a healthy BBB state, though both models have advantages that may be useful in disease modeling.

The blood brain barrier: Insights from development and ageing

The blood brain barrier is a necessity for cerebral homeostasis and response to environmental insult, thus loss in functionality with age creates opportunities for disease to arise in the aged brain. Understanding how the barrier is developed and maintained throughout the earlier years of adult life can identify key processes that may have beneficial applications in the restoration of the aged brain. With an unprecedented increasing global aged population, the prevention and treatment of age-associated disorders has become a rising healthcare priority demanding novel approaches for the development of therapeutic strategies. The aging cardiovascular system has long been recognised to be a major factor in age-associated diseases such as stroke, atherosclerosis and cardiac arrest. Changes in the highly specialised cerebral vasculature may similarly drive neurodegenerative and neuropsychiatric disease.

DT-13 Ameliorates TNF-α-Induced Vascular Endothelial Hyperpermeability via Non-Muscle Myosin IIA and the Src/PI3K/Akt Signaling Pathway

DT-13(25(R,S)-ruscogenin-1-O-[β-d-glucopyranosyl-(1→2)][β-d-xylopyranosyl-(1→3)]-β-d-fucopyranoside) has been identified as an important factor in TNF-α-induced vascular inflammation. However, the effect of DT-13 on TNF-α-induced endothelial permeability and the potential molecular mechanisms remain unclear. Hence, this study was undertaken to elucidate the protective effect of DT-13 on TNF-α-induced endothelial permeability and the underlying mechanisms in vivo and in vitro. The in vivo results showed that DT-13 could ameliorate endothelial permeability in mustard oil-induced plasma leakage in the skin and modulate ZO-1 organization. In addition, the in vitro results showed that pretreatment with DT-13 could increase the transendothelial electrical resistance value and decrease the sodium fluorescein permeability coefficient. Moreover, DT-13 altered the mRNA and protein levels of ZO-1 as determined by real-time PCR, Western blotting, and immunofluorescence analyses. DT-13 treatment decreased the phosphorylations of Src, PI3K, and Akt in TNF-α-treated human umbilical vein endothelial cells (HUVECs). Further analyses with PP2 (10 µM, inhibitor of Src) indicated that DT-13 modulated endothelial permeability in TNF-α-induced HUVECs in an Src-dependent manner. LY294002 (10 µM, PI3K inhibitor) also had the same effect on DT-13 but did not affect phosphorylation of Src. Following decreased expression of non-muscle myosin IIA (NMIIA), the effect of DT-13 on the phosphorylations of Src, PI3K, and Akt was abolished. This study provides pharmacological evidence showing that DT-13 significantly ameliorated the TNF-α-induced vascular endothelial hyperpermeability through modulation of the Src/PI3K/Akt pathway and NMIIA, which play an important role in this process.

Human neural stem cell-induced endothelial morphogenesis requires autocrine/paracrine and juxtacrine signaling

Transplanted neural stem cells (NSC) interact with the host brain microenvironment. A neovascularization is commonly observed in the vicinity of the cell deposit, which is correlated with behavioral improvements. To elucidate the signaling mechanisms between human NSCs and endothelial cells (ECs), these were cocultured in an in vitro model in which NSC-induced endothelial morphogenesis produced a neurovascular environment. Soluble (autocrine/paracrine) and contact–mediated (juxtacrine) signaling molecules were evaluated for two conditionally immortalized fetal NSC lines derived from the cortical anlage (CTXOE03) and ganglionic eminence (STROC05), as well as an adult EC line (D3) derived from the cerebral microvasculature of a hippocampal biopsy. STROC05 were 4 times as efficient to induce endothelial morphogenesis compared to CTXOE03. The cascade of reciprocal interactions between NSCs and ECs in this process was determined by quantifying soluble factors, receptor mapping, and immunocytochemistry for extracellular matrix molecules. The mechanistic significance of these was further evaluated by pharmacological blockade. The sequential cell-specific regulation of autocrine/paracrine and juxtacrine signaling accounted for the differential efficiency of NSCs to induce endothelial morphogenesis. These in vitro studies shed new light on the reciprocal interactions between NSCs and ECs, which are pivotal for our mechanistic understanding of the efficacy of NSC transplantation.

Potential of Neural Stem Cell-Based Therapy for Parkinson's Disease

Neural stem cell (NSC) transplantation is an emerging strategy for restoring neuronal function in neurological disorders, such as Parkinson's disease (PD), which is characterized by a profound and selective loss of nigrostriatal dopaminergic (DA) neurons. Adult neurogenesis generates newborn neurons that can be observed at specialized niches where endothelial cells (ECs) play a significant role in regulating the behavior of NSCs, including self-renewal and differentiating into all neural lineage cells. In this minireview, we highlight the importance of establishing an appropriate microenvironment at the target site of NSC transplantation, where grafted cells integrate into the surroundings in order to enhance DA neurotransmission. Using a novel model of NSC-EC coculture, it is possible to combine ECs with NSCs, to generate such a neurovascular microenvironment. With appropriate NSCs selected, the composition of the transplant can be investigated through paracrine and juxtacrine signaling within the neurovascular unit (NVU). With target site cellular and acellular compartments of the microenvironment recognized, guided DA differentiation of NSCs can be achieved. As differentiated DA neurons integrate into the existing nigrostriatal DA pathway, the symptoms of PD can potentially be alleviated by reversing characteristic neurodegeneration.