Osteopontin mediates survival, proliferation and migration of neural stem cells through the chemokine receptor CXCR4

Inhibition of BMP-mediated SMAD pathway supports the pluripotency of pig embryonic stem cells in the absence of feeder cells

Here, we examined the effects of the BMP signaling pathway inhibitor LDN-193189 on the pluripotency of porcine embryonic stem cells (ESCs) in the absence of feeder cells using molecular and transcriptomic techniques. Additionally, the effects of some extracellular matrix components on porcine ESC pluripotency were evaluated to develop an optimized and sustainable feeder-free culture system for porcine ESCs. Feeder cells were found to play an important role in supporting the pluripotency of porcine ESCs by blocking trophoblast and mesodermal differentiation through the inhibition of the BMP pathway. Additionally, treatment with LDN-193189, an inhibitor of the BMP pathway, maintained the pluripotency and homogeneity of porcine ESCs for an extended period in the absence of feeder cells by stimulating the secretion of chemokines and suppressing differentiation, based on transcriptome analysis. Conclusively, these results suggest that LDN-193189 could be a suitable replacement for feeder cells in the maintenance of porcine ESC pluripotency during culture. Additionally, these findings contribute to the understanding of pluripotency gene networks and comparative embryogenesis.

Current Status and Progress in Stem Cell Therapy for Intracerebral Hemorrhage

Intracerebral hemorrhage is a highly prevalent and prognostically poor disease, imposing immeasurable harm on human life and health. However, the treatment options for intracerebral hemorrhage are severely limited, particularly in terms of improving the microenvironment of the lesion, promoting neuronal cell survival, and enhancing neural function. This review comprehensively discussed the application of stem cell therapy for intracerebral hemorrhage, providing a systematic summary of its developmental history, types of transplants, transplantation routes, and transplantation timing. Moreover, this review presented the latest research progress in enhancing the efficacy of stem cell transplantation, including pretransplantation preconditioning, genetic modification, combined therapy, and other diverse strategies. Furthermore, this review pioneeringly elaborated on the barriers to clinical translation for stem cell therapy. These discussions were of significant importance for promoting stem cell therapy for intracerebral hemorrhage, facilitating its clinical translation, and improving patient prognosis.

A Dual Role of Osteopontin in Modifying B Cell Responses

The occurrence of B cell aggregates within the central nervous system (CNS) has prompted the investigation of the potential sources of pathogenic B cell and T cell responses in a subgroup of secondary progressive multiple sclerosis (MS) patients. Nevertheless, the expression profile of molecules associated with these aggregates and their role in aggregate development and persistence is poorly described. Here, we focused on the expression pattern of osteopontin (OPN), which is a well-described cytokine, in MS brain tissue. Autopsied brain sections from MS cases with and without B cell pathology were screened for the presence of CD20⁺ B cell aggregates and co-expression of OPN. To demonstrate the effect of OPN on B cells, flow cytometry, ELISA and in vitro aggregation assays were conducted using the peripheral blood of healthy volunteers. Although OPN was expressed in MS brain tissue independent of B cell pathology, it was also highly expressed within B cell aggregates. In vitro studies demonstrated that OPN downregulated the co-stimulatory molecules CD80 and CD86 on B cells. OPN-treated B cells produced significantly lower amounts of IL-6. However, OPN-treated B cells also exhibited a higher tendency to form homotypic cell aggregates in vitro. Taken together, our data indicate a conflicting role of OPN in modulating B cell responses.

Therapeutic Potential of Chinese Medicine for Endogenous Neurogenesis: A Promising Candidate for Stroke Treatment

Strokes are a leading cause of morbidity and mortality in adults worldwide. Extensive preclinical studies have shown that neural-stem-cell-based treatments have great therapeutic potential for stroke. Several studies have confirmed that the effective components of traditional Chinese medicine can protect and maintain the survival, proliferation, and differentiation of endogenous neural stem cells through different targets and mechanisms. Therefore, the use of Chinese medicines to activate and promote endogenous nerve regeneration and repair is a potential treatment option for stroke patients. Here, we summarize the current knowledge regarding neural stem cell strategies for ischemic strokes and the potential effects of these Chinese medicines on neuronal regeneration.

Immunomodulatory and Anti-inflammatory effect of Neural Stem/Progenitor Cells in the Central Nervous System

Neuroinflammation is a critical event that responds to disturbed homeostasis and governs various neurological diseases in the central nervous system (CNS). The excessive inflammatory microenvironment in the CNS can adversely affect endogenous neural stem cells, thereby impeding neural self-repair. Therapies with neural stem/progenitor cells (NSPCs) have shown significant inhibitory effects on inflammation, which is mainly achieved through intercellular contact and paracrine signalings. The intercellular contact between NSPCs and immune cells, the activated CNS- resident microglia, and astrocyte plays a critical role in the therapeutic NSPCs homing and immunomodulatory effects. Moreover, the paracrine effect mainly regulates infiltrating innate and adaptive immune cells, activated microglia, and astrocyte through the secretion of bioactive molecules and extracellular vesicles. However, the molecular mechanism involved in the immunomodulatory effect of NSPCs is not well discussed. This article provides a systematic analysis of the immunomodulatory mechanism of NSPCs, discusses efficient ways to enhance its immunomodulatory ability, and gives suggestions on clinical therapy.

Regulation of Genes Related to Cognition after tDCS in an Intermittent Hypoxic Brain Injury Rat Model

Background: Hypoxic brain injury is a condition caused by restricted oxygen supply to the brain. Several studies have reported cognitive decline, particularly in spatial memory, after exposure to intermittent hypoxia (IH). However, the effect and mechanism of action of IH exposure on cognition have not been evaluated by analyzing gene expression after transcranial direct current stimulation (tDCS). Hence, the purpose of this study was to investigate the effects of tDCS on gene regulation and cognition in a rat model of IH-induced brain injury. Methods: Twenty-four 10-week-old male Sprague−Dawley rats were divided into two groups: IH exposed rats with no stimulation and IH-exposed rats that received tDCS. All rats were exposed to a hypoxic chamber containing 10% oxygen for twelve hours a day for five days. The stimulation group received tDCS at an intensity of 200 µA over the frontal bregma areas for 30 min each day for a week. As a behavior test, the escape latency on the Morris water maze (MWM) test was measured to assess spatial memory before and after stimulation. After seven days of stimulation, gene microarray analysis was conducted with a KEGG mapper tool. Results: Although there were no significant differences between the groups before and after stimulation, there was a significant effect of time and a significant time × group interaction on escape latency. In the microarray analysis, significant fold changes in 12 genes related to neurogenesis were found in the stimulation group after tDCS (p < 0.05, fold change > 2 times, the average of the normalized read count (RC) > 6 times). The highly upregulated genes in the stimulation group after tDCS were SOS, Raf, PI3K, Rac1, IRAK, and Bax. The highly downregulated genes in the stimulation group after tDCS were CHK, Crk, Rap1, p38, Ras, and NF-kB. Conclusion: In this study, we confirmed that SOS, Raf, PI3K, Rac1, IRAK, and Bax were upregulated and that CHK, Crk, Rap1, p38, Ras, and NF-kB were downregulated in a rat model of IH-induced brain injury after application of tDCS.

Osteopontin/secreted phosphoprotein-1 harnesses glial-, immune-, and neuronal cell ligand-receptor interactions to sense and regulate acute and chronic neuroinflammation

Osteopontin (OPN) also known by its official gene designation secreted phosphoprotein-1 (SPP1) is a fascinating, multifunctional protein expressed in a number of cell types that functions not only in intercellular communication, but also in the extracellular matrix (ECM). OPN/SPP1 possesses cytokine, chemokine, and signal transduction functions by virtue of modular structural motifs that provide interaction surfaces for integrins and CD44-variant receptors. In humans, there are three experimentally verified splice variants of OPN/SPP1 and CD44's ten exons are also alternatively spiced in a cell/tissue-specific manner, although very little is known about how this is regulated in the central nervous system (CNS). Post-translational modifications of phosphorylation, glycosylation, and localized cleavage by specific proteases in the cells and tissues where OPN/SPP1 functions, provides additional layers of specificity. However, the former make elucidating the exact molecular mechanisms of OPN/SPP1 function more complex. Flexibility in OPN/SPP1 structure and its engagement with integrins having the ability to transmit signals in inside-out and outside-in direction, is likely why OPN/SPP1 can serve as an early detector of inflammation and ongoing tissue damage in response to cancer, stroke, traumatic brain injury, pathogenic infection, and neurodegeneration, processes that impair tissue homeostasis. This review will focus on what is currently known about OPN/SPP1 function in the brain.

Non-invasive brain stimulation for osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease, the prevalence of OA is increasing, and the elderly are the most common in patients with OA. OA has a severe impact on the daily life of patients, this increases the demand for treatment of OA. In recent years, the application of non-invasive brain stimulation (NIBS) has attracted extensive attention. It has been confirmed that NIBS plays an important role in regulating cortical excitability and oscillatory rhythm in specific brain regions. In this review, we summarized the therapeutic effects and mechanisms of different NIBS techniques in OA, clarified the potential of NIBS as a treatment choice for OA, and provided prospects for further research in the future.

Propofol induces the apoptosis of neural stem cells via microRNA-9-5p / chemokine CXC receptor 4 signaling pathway

Recent studies suggested that propofol, one of the most widely used anesthetics, may cause neurotoxicity in the developing brain, leading to cognitive deficits in adults. However, the underlying mechanisms remain unclear. In this study, we aimed to evaluate the mechanisms of propofol neurotoxicity in the neural stem cells (NSCs). The mRNA and protein expression levels of microRNA-9-5p (miR-9-5p) and chemokine CXC receptor 4 (CXCR4) were determined by quantitative reverse transcription-polymerase chain reaction and Western blotting analyses. Cell viability and apoptosis were evaluated using the cell counting kit-8 and Hoechst staining kits. The levels of apoptosis-related proteins B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein, and caspase-3 were detected by Western blotting analysis. These results confirmed that propofol activated cell apoptosis in a dose-dependent manner. A significant increase in the miR-9-5p and CXCR4 expression was observed in the propofol-treated cells. The overexpression of miR-9-5p induced apoptosis in NSCs, accompanied by elevated apoptosis-related protein activity. Furthermore, mitigated CXCR4 expression reduced propofol-induced cell apoptosis. We conclude that propofol induces cell death in NSCs, and overexpression of miR-9-5p/CXCR4 contributes to propofol-induced cell apoptosis, which might be a target for developing novel strategies to treat propofol neurotoxicity.

Osteopontin regulates proliferation, migration, and survival of astrocytes depending on their activation phenotype

The glycoprotein osteopontin is highly upregulated in central nervous system (CNS) disorders such as ischemic stroke. Osteopontin regulates cell growth, cell adhesion, homeostasis, migration, and survival of various cell types. Accordingly, osteopontin is considered an essential regulator of regeneration and repair in the ischemic milieu. Astrocytes are the most abundant cells in the CNS and play significant roles in health and disease. Astrocytes are involved in homeostasis, promote neuroprotection, and regulate synaptic plasticity. Upon activation, astrocytes may adopt different phenotypes, termed A1 and A2. The direct effects of osteopontin on astrocytes, especially in distinct activation states, are yet unknown. The current study aimed to elucidate the impact of osteopontin on resting and active astrocytes. We established an inflammatory in vitro model of activated (A1) primary astrocytes derived from neonatal wistar rats by exposure to a distinct combination of proinflammatory cytokines. To model ischemic stroke in vitro, astrocytes were subjected to oxygen and glucose deprivation (OGD) in the presence or absence of osteopontin. Osteopontin modulated the activation phenotype by attenuating A1- and restoring A2-marker expression without compromising the active astrocytes' immunocompetence. Osteopontin promoted the proliferation of active and the migration of resting astrocytes. Following transient OGD, osteopontin mitigated the delayed ongoing death of primary astrocytes, promoting their survival. Data suggest that osteopontin differentially regulates essential functions of resting and active astrocytes and confirm a significant regulatory role of osteopontin in an in vitro ischemia model. Furthermore, the data suggest that osteopontin constitutes a promising target for experimental therapies modulating neuroregeneration and repair.

A subpopulation of embryonic microglia respond to maternal stress and influence nearby neural progenitors

The interplay between hypothalamic neurons and microglia as they integrate stressors to regulate homeostasis is of growing interest. We asked if microglia in the embryonic hypothalamus were likewise stress responsive and, if so, whether their precocious activation perturbs nearby neural stem cell (NSC) programs. We performed single-cell transcriptomics to define embryonic hypothalamic microglia heterogeneity and identified four microglial subsets, including a subpopulation adjacent to NSCs that was responsive to gestational cold stress. Stress exposure elevated CCL3 and CCL4 secretion, but only in male brains, and ex vivo CCL4 treatment of hypothalamic NSCs altered proliferation and differentiation. Concomitantly, gestational stress decreased PVN oxytocin neurons only in male embryos, which was reversed by microglia depletion. Adult offspring exposed to gestational stress displayed altered social behaviors, which was likewise microglia dependent, but only in males. Collectively, immature hypothalamic microglia play an unappreciated role in translating maternal stressors to sexually dimorphic perturbation of neurodevelopmental programs.

Potential Mechanisms and Perspectives in Ischemic Stroke Treatment Using Stem Cell Therapies

Ischemic stroke (IS) remains one of the major causes of death and disability due to the limited ability of central nervous system cells to regenerate and differentiate. Although several advances have been made in stroke therapies in the last decades, there are only a few approaches available to improve IS outcome. In the acute phase of IS, mechanical thrombectomy and the administration of tissue plasminogen activator have been widely used, while aspirin or clopidogrel represents the main therapy used in the subacute or chronic phase. However, in most cases, stroke patients fail to achieve satisfactory functional recovery under the treatments mentioned above. Recently, cell therapy, especially stem cell therapy, has been considered as a novel and potential therapeutic strategy to improve stroke outcome through mechanisms, including cell differentiation, cell replacement, immunomodulation, neural circuit reconstruction, and protective factor release. Different stem cell types, such as mesenchymal stem cells, marrow mononuclear cells, and neural stem cells, have also been considered for stroke therapy. In recent years, many clinical and preclinical studies on cell therapy have been carried out, and numerous results have shown that cell therapy has bright prospects in the treatment of stroke. However, some cell therapy issues are not yet fully understood, such as its optimal parameters including cell type choice, cell doses, and injection routes; therefore, a closer relationship between basic and clinical research is needed. In this review, the role of cell therapy in stroke treatment and its mechanisms was summarized, as well as the function of different stem cell types in stroke treatment and the clinical trials using stem cell therapy to cure stroke, to reveal future insights on stroke-related cell therapy, and to guide further studies.

Gynura divaricata Water Extract Presented the Possibility to Enhance Neuronal Regeneration

Gynura divaricata (GD) is an Asian herb widely used as an alternative medicine and functional food for type 2 diabetes. Diabetic neuropathy is considered as an important complication of diabetic patients. This study focused on neuroregenerative effects of GD for use in the prevention of diabetic neuropathy. GD leaves were cut and boiled in water to mimic real-life cooking. The boiled content was filtered through white gauze and lyophilized to preserve as dried powder. Antioxidant assay was performed using DPPH assays. UHPLC-QTOF-MS/MS was employed to test for important compounds in the extract of these herbs. MTT assay was used to test for cell viability. The extracts at concentration of 250 μg/mL were tested with human gingival cell to observe the change of gene expression. The DPPH assay showed that GD water extract at the concentration of 5000 μg/mL could inhibit DPPH radical for 39.2%. The results showed that 5000 µg of GD water extract contained total phenolic content equivalent to 310.9 µg standard gallic acid. UHPLC-QTOF-MS/MS result found phenolic acids and flavonoids as the main components. Human gingival cells treated with 250 μg/mL of GD water extract for 10 days showed upregulation of some neuronal differentiation markers. Staining with Cdr3 dye confirmed the presentation of neuronal progenitors. The extract at the concentration of 250 μg/mL was also tested with apical papilla cells to screen for change of gene expression by RNA sequencing. The result also showed significant upregulation of alpha-internexin (INA). These results indicated that GD water extract might have an inductive effect for neural regeneration and could be used as functional food and supplementation for the prevention or treatment of diabetic neuropathy. This work provided the basic knowledge for further investigations into the benefits of GD for diabetic neuropathy.

Immunohistochemical Detection of Neural Stem Cells and Glioblastoma Stem Cells in the Subventricular Zone of Glioblastoma Patients

Glioblastoma usually recurs after therapy consisting of surgery, radiotherapy, and chemotherapy. Recurrence is at least partly caused by glioblastoma stem cells (GSCs) that are maintained in intratumoral hypoxic peri-arteriolar microenvironments, or niches, in a slowly dividing state that renders GSCs resistant to radiotherapy and chemotherapy. Because the subventricular zone (SVZ) is a major niche for neural stem cells (NSCs) in the brain, we investigated whether GSCs are present in the SVZ at distance from the glioblastoma tumor. We characterized the SVZ of brains of seven glioblastoma patients using fluorescence immunohistochemistry and image analysis. NSCs were identified by CD133 and SOX2 but not CD9 expression, whereas GSCs were positive for all three biomarkers. NSCs were present in all seven samples and GSCs in six out of seven samples. The SVZ in all samples were hypoxic and expressed the same relevant chemokines and their receptors as GSC niches in glioblastoma tumors: stromal-derived factor-1α (SDF-1α), C-X-C receptor type 4 (CXCR4), osteopontin, and CD44. In conclusion, in glioblastoma patients, GSCs are present at distance from the glioblastoma tumor in the SVZ. These findings suggest that GSCs in the SVZ niche are protected against radiotherapy and chemotherapy and protected against surgical resection due to their distant localization and thus may contribute to tumor recurrence after therapy.

Protective Mechanism and Treatment of Neurogenesis in Cerebral Ischemia

Stroke is the fifth leading cause of death worldwide and is a main cause of disability in adults. Neither currently marketed drugs nor commonly used treatments can promote nerve repair and neurogenesis after stroke, and the repair of neurons damaged by ischemia has become a research focus. This article reviews several possible mechanisms of stroke and neurogenesis and introduces novel neurogenic agents (fibroblast growth factors, brain-derived neurotrophic factor, purine nucleosides, resveratrol, S-nitrosoglutathione, osteopontin, etc.) as well as other treatments that have shown neuroprotective or neurogenesis-promoting effects.

Plasma biomarkers of the amyloid pathway are associated with geographic atrophy secondary to age-related macular degeneration

Geographic atrophy (GA) is an advanced form of dry age-related macular degeneration (AMD), in which local inflammation and hyperactivity of the complement pathway have been implicated in its pathophysiology. This study explores whether any surrogate biomarkers are specifically associated with GA. Plasma from subjects with GA, intermediate dry AMD and non-AMD control were evaluated in 2 cohorts. Cohort 1 was assayed in a 320-analyte Luminex library. Statistical analysis was performed using non-parametric and parametric methods (Kruskal-Wallis, principal component analysis, partial least squares and multivariate analysis of variance (MANOVA) and univariate ANCOVAs). Bioinformatic analysis was conducted and identified connections to the amyloid pathway. Statistically significant biomarkers identified in Cohort 1 were then re-evaluated in Cohort 2 using individual ELISA and multiplexing. Of 320 analytes in Cohort 1, 273 were rendered measurable, of which 56 were identified as changing. Among these markers, 40 were identified in univariate ANCOVAs. Serum amyloid precursor protein (sAPP) was analyzed by a separate ELISA and included in further analyses. The 40 biomarkers, sAPP and amyloid-β (Aβ) (1–42) (included for comparison) were evaluated in Cohort 2. This resulted in 11 statistically significant biomarkers, including sAPP and Aβ(1–40), but not Aβ(1–42). Other biomarkers identified included serum proteases- tissue plasminogen activator, tumor-associated trypsinogen inhibitor, matrix metalloproteinases 7 and 9, and non-proteases- insulin-like growth factor binding protein 6, AXL receptor tyrosine kinase, omentin, pentraxin-3 and osteopontin. Findings suggest that there is a preferential processing of APP to Aβ(1–40) over Aβ(1–42), and a potential role for the carboxylase activity of the γ-secretase protein, which preferentially splices sAPPβ to Aβ(1–40). Other markers are associated with the breakdown and remodeling of the extracellular matrix, and loss of homeostasis, possibly within the photoreceptor-retinal pigment epithelium-choriocapillaris complex. These data suggest novel disease pathways associated with GA pathogenesis and could provide potential novel targets for treatment of GA.

Osteopontin as a candidate of therapeutic application for the acute brain injury

Acute brain injury is the leading cause of human death and disability worldwide, which includes intracerebral haemorrhage, subarachnoid haemorrhage, cerebral ischaemia, traumatic brain injury and hypoxia‐ischaemia brain injury. Currently, clinical treatments for neurological dysfunction of acute brain injury have not been satisfactory. Osteopontin (OPN) is a complex adhesion protein and cytokine that interacts with multiple receptors including integrins and CD44 variants, exhibiting mostly neuroprotective roles and showing therapeutic potential for acute brain injury. OPN‐induced tissue remodelling and functional repair mainly rely on its positive roles in the coordination of pro‐inflammatory and anti‐inflammatory responses, blood‐brain barrier maintenance and anti‐apoptotic actions, as well as other mechanisms such as affecting the chemotaxis and proliferation of nerve cells. The blood OPN strongly parallel with the OPN induced in the brain and can be used as a novel biomarker of the susceptibility, severity and outcome of acute brain injury. In the present review, we summarized the molecular signalling mechanisms of OPN as well as its overall role in different kinds of acute brain injury.

Osteopontin and Integrin Mediated Modulation of Post-Synapses in HIV Envelope Glycoprotein Exposed Hippocampal Neurons

The advent of Human Immunodeficiency Virus (HIV) antiretrovirals have reduced the severity of HIV related neurological comorbidities but they nevertheless remain prevalent. Synaptic degeneration due to the action of several viral factors released from infected brain myeloid and glia cells and inflammatory cytokines has been attributed to the manifestation of a range of cognitive and behavioral deficits. The contributions of specific pro-inflammatory factors and their interplay with viral factors in the setting of treatment and persistence are incompletely understood. Exposure of neurons to chemokine receptor-4(CXCR4)-tropic HIV-1 envelope glycoprotein (Env) can lead to post-synaptic degradation of dendritic spines. The contribution of members of the extracellular matrix (ECM) and specifically, of perineuronal nets (PNN) toward synaptic degeneration, is not fully known, even though these structures are found to be disrupted in post-mortem HIV-infected brains. Osteopontin (Opn, gene name SPP1), a cytokine-like protein, is found in abundance in the HIV-infected brain. In this study, we investigated the role of Opn and its ECM integrin receptors, β1- and β3 integrin in modifying neuronal synaptic sculpting. We found that in hippocampal neurons incubated with HIV-1 Env protein and recombinant Opn, post-synaptic-95 (PSD-95) puncta were significantly increased and distributed to dendritic spines when compared to Env-only treated neurons. This effect was mediated through β3 integrin, as silencing of this receptor abrogated the increase in post-synaptic spines. Silencing of β1 integrin, however, did not block the increase of post-synaptic spines in hippocampal cultures treated with Opn. However, a decrease in the PNN to βIII-tubulin ratio was found, indicating an increased capacity to support spine growth. From these results, we conclude that one of the mechanisms by which Opn counters the damaging impact of the HIV Env protein on hippocampal post-synaptic plasticity is through complex interactions between Opn and components of the ECM which activate downstream protective signaling pathways that help maintain the potential for effective post-synaptic plasticity.

The Role of Osteopontin in Amyotrophic Lateral Sclerosis: A Systematic Review

Context: Osteopontin (OPN) is a matrix phosphoprotein expressed by a variety of tissues and cells, including the immune system and the nervous system. Previous studies have shown that OPN may have a role in neurodegenerative diseases, including multiple sclerosis, Parkinson’s disease, and Alzheimer’s disease. Objectives: The present study aimed to systematically review studies investigating the role of OPN in amyotrophic lateral sclerosis (ALS) patients or the disease animal model. Evidence Acquisition: We searched the Cochrane Library, PubMed, Web of Science, and Scopus to find relevant articles published up to January 20, 2019. Both human and animal model studies of ALS were considered. Results: A total of nine articles (four human studies and five animal model studies) were included. Two of the human studies reported that the CSF levels of OPN were higher among ALS patients compared to controls. The other two human studies found that OPN levels in cortical neurons did not differ significantly between ALS cases and the non-neurological control group. One of the studies found that the expression level of OPN in astrocytes was similar between ALS patients and the control group, but the level of microglial OPN significantly increased in ALS cases. Four of the animal model studies reported that the expression of OPN mRNA in spinal cord microglia significantly increased during the disease progression. The remaining animal model study found that OPN was selectively expressed by fast fatigue-resistant and slow motor neurons (MNs), which are resistant to ALS, and that the OPN expression was low among fast-fatigable MNs. Conclusions: Prompt microglial activation is a hallmark pathology of ALS, and OPN is among the most widely expressed proteins by these activated glial cells. Therefore, OPN might have a role in ALS pathogenesis. The existing evidence is not sufficient to justify whether OPN has a neurotoxic or neuroprotective role in ALS. We encourage researchers to investigate the role of OPN in ALS pathogenesis more extensively.

CD44 expression in stem cells and niche microglia/macrophages following ischemic stroke

Background

CD44, an adhesion molecule in the hyaluronate receptor family, plays diverse and important roles in multiple cell types and organs. Increasing evidence is mounting for CD44 expression in various types of stem cells and niche cells surrounding stem cells. However, the precise phenotypes of CD44⁺ cells in the brain under pathologic conditions, such as after ischemic stroke, remain unclear.

Methods

In the present study, using a mouse model for cerebral infarction by middle cerebral artery (MCA) occlusion, we examined the localization and traits of CD44⁺ cells.

Results

In sham-mice operations, CD44 was rarely observed in the cortex of MCA regions. Following ischemic stroke, CD44⁺ cells emerged in ischemic areas of the MCA cortex during the acute phase. Although CD44 at ischemic areas was, in part, expressed in stem cells, it was also expressed in hematopoietic lineages, including activated microglia/macrophages, surrounding the stem cells. CD44 expression in microglia/macrophages persisted through the chronic phase following ischemic stroke.

Conclusions

These data demonstrate that CD44 is expressed in stem cells and cells in the niches surrounding them, including inflammatory cells, suggesting that CD44 may play an important role in reparative processes within ischemic areas under neuroinflammatory conditions; in particular, strokes.

Defining the adult hippocampal neural stem cell secretome: In vivo versus in vitro transcriptomic differences and their correlation to secreted protein levels

Adult hippocampal neural stem and progenitor cells (NSPCs) secrete a variety of proteins that affect tissue function. Though several individual NSPC-derived proteins have been shown to impact key cellular processes, a broad characterization is lacking. Secretome profiling of low abundance stem cell populations is typically achieved via proteomic characterization of in vitro, isolated cells. Here, we identified hundreds of secreted proteins in conditioned media from in vitro adult mouse hippocampal NSPCs using an antibody array and mass spectrometry. Comparison of protein abundance between antibody array and mass spectrometry plus quantification of several key secreted proteins by ELISA revealed notable disconnect between methods in what proteins were identified as being high versus low abundance, suggesting that data from antibody arrays in particular should be approached with caution. We next assessed the NSPC secretome on a transcriptional level with single cell and bulk RNA sequencing (RNAseq) of cultured NSPCs. Comparison of RNAseq transcript levels of highly secreted proteins revealed that quantification of gene expression did not necessarily predict relative protein abundance. Interestingly, comparing our in vitro NSPC gene expression data with similar data from freshly isolated, in vivo hippocampal NSPCs revealed strong correlations in global gene expression between in vitro and in vivo NSPCs. Understanding the components and functions of the NSPC secretome is essential to understanding how these cells may modulate the hippocampal neurogenic niche. Cumulatively, our data emphasize the importance of using proteomics in conjunction with transcriptomics and highlights the need for better methods of unbiased secretome profiling.

Crosstalk between stressed brain cells: direct and indirect effects of ischemia and aglycemia on microglia

Background

In cerebral ischemia, microglia have a dichotomous role in keeping the balance between pro- and anti-inflammatory mediators to avoid deleterious chronic inflammation and to leverage repair processes.

Methods

We examined functional and inflammatory markers in primary rat microglia in vitro after oxygen-glucose deprivation (OGD) or glucose deprivation (aglycemia). We then investigated the preconditioning effect of OGD or aglycemia upon a subsequent strong inflammatory stimulus, here lipopolysaccharides (LPS). Moreover, an “in vitro brain model” of neurons and glia, differentiated from primary rat neural stem cells, was exposed to OGD or aglycemia. Conditioned medium (CM) of this neuronal/glial co-culture was then used to condition microglia, followed by LPS as a “second hit.”

Results

OGD or aglycemia at sublethal doses did not significantly affect microglia function, including the expression of inflammatory markers. However, preconditioning with either OGD or aglycemia led to a decreased pro-inflammatory response to a subsequent stimulus with LPS. Interestingly, the anti-inflammatory markers IGF-1 and IL-10 were additionally reduced after such preconditioning, while expression of CD206 remained unaffected. Treatment with CM from the neuronal/glial co-culture alone did not affect the expression of inflammatory markers in microglia. In contrast, treatment with CM increased the expression of both pro- and anti-inflammatory markers in microglia upon a second hit with LPS. Interestingly, this effect could be attenuated in microglia treated with CM from neuronal/glia co-cultures preconditioned with OGD or aglycemia.

Conclusions

Data suggest specific and distinct microglia signatures in response to metabolic stress. While metabolic stress directly and indirectly applied to microglia did not mitigate their subsequent response to inflammation, preconditioning with metabolic stress factors such as OGD and aglycemia elicited a decreased inflammatory response to a subsequent inflammation stimulus.

Development of an Anisotropically Organized Brain dECM Hydrogel-Based 3D Neuronal Culture Platform for Recapitulating the Brain Microenvironment in Vivo

To mimic the brain tissue microenvironment in vitro, the biological and structural properties of the utilized system must be similar to those of the native brain in the microenvironment in vivo. To promote the bioactive (biological) properties of matrix hydrogels, we used the decellularized extracellular matrix (dECM) of porcine brain, which was found to enhance neuronal differentiation/outgrowth and neuron-to-brain dECM interactions. To implement the desired structural properties, we aligned microfibrils within a composite hydrogel mixed with the brain dECM and collagen I, with or without encapsulated neurons, by the stretching and releasing of a hydrogel-based chip. We then tested the ability of the aligned brain dECM hydrogel-based three-dimensional (3D) culture platform to mimic the in vivo brain microenvironment. We found that dECM-containing gels harbored brain-derived ECM proteins, including collagen I, collagen IV, laminin, and various cytokines, and that neurons incubated in these gels exhibited enhanced neurite outgrowth and development compared to those incubated in collagen gel (dECM 0 mg/mL). We evaluated the surface morphology and mechanical properties of the hydrogel with and without the brain dECM and found that their encapsulated neurons showed similar levels of cell viability. We then used a mechanical process to align the composite dECM hydrogel, conferring the desired structural properties to our system. Together, our results suggest that our newly developed brain dECM-based 3D culture platform could potentially be further developed for use in drug screening.

Transcranial Current Stimulation Alters the Expression of Immune-Mediating Genes

Despite its extensive use in clinical studies, the molecular mechanisms underlying the effects of transcranial direct current stimulation (tDCS) remain to be elucidated. We previously described subacute effects of tDCS on immune- and stem cells in the rat brain. To investigate the more immediate effects of tDCS regulating those cellular responses, we treated rats with a single session of either anodal or cathodal tDCS, and analyzed the gene expression by microarray; sham-stimulated rats served as control. Anodal tDCS increased expression of several genes coding for the major histocompatibility complex I (MHC I), while cathodal tDCS increased the expression of the immunoregulatory protein osteopontin (OPN). We confirmed the effects of gene upregulation by immunohistochemistry at the protein level. Thus, our data show a novel mechanism for the actions of tDCS on immune- and inflammatory processes, providing a target for future therapeutic studies.

The Retina of Osteopontin deficient Mice in Aging

Osteopontin (OPN) is a secreted glycosylated phosphoprotein that influences cell survival, inflammation, migration, and homeostasis after injury. As the role of OPN in the retina remains unclear, this study issue was addressed by aiming to study how the absence of OPN in knock-out mice affects the retina and the influence of age on these effects. The study focused on retinal ganglion cells (RGCs) and glial cells (astrocytes, Müller cells, and resident microglia) in 3- and 20-month-old mice. The number of RGCs in the retina was quantified and the area occupied by astrocytes was measured. In addition, the morphology of Müller cells and microglia was examined in retinal sections. The deficiency in OPN reduces RGC density by 25.09% at 3 months of age and by 60.37% at 20 months of age. The astrocyte area was also reduced by 51.01% in 3-month-old mice and by 57.84% at 20 months of age, although Müller glia and microglia did not seem to be affected by the lack of OPN. This study demonstrates the influence of OPN on astrocytes and RGCs, whereby the absence of OPN in the retina diminishes the area occupied by astrocytes and produces a secondary reduction in the number of RGCs. Accordingly, OPN could be a target to develop therapies to combat neurodegenerative diseases and astrocytes may represent a key mediator of such effects.

Microglia promote the proliferation of neural precursor cells by secreting osteopontin

Microglia are central nervous system-resident immune cells that play a crucial role in brain development by interacting with neural precursor cells (NPCs). It has been reported that microglia regulate the number of NPC by phagocytosis, inducing apoptosis, and promoting proliferation. Microglia surrounding the subventricular zone express osteopontin (OPN) during brain development. The present study investigated the role of microglia in proliferation of NPCs in vitro, and identified the OPN receptor critical for proliferation of NPCs. Microglia co-cultured with NPCs in the presence of an OPN-neutralizing antibody resulted in OPN inhibition and reduced microglia-induced proliferation of NPCs. NPCs express integrin αvβ3, which has been identified as an OPN receptor. Cilengitide, an inhibitor of integrin αvβ3, also inhibited microglia-induced proliferation of NPCs. These results suggest that microglia promote the proliferation of NPCs via OPN-integrin αvβ3 signaling.

Effects of Ascorbic Acid on Osteopontin Expression and Axonal Myelination in the Developing Cerebellum of Lead-Exposed Rat Pups

Osteopontin (OPN) is a multi-functional protein that binds to integrin and calcium-binding phosphoprotein. OPN is required for normal neuronal development and its axonal myelination. We studied the combined effect of lead (Pb) and ascorbic acid treatment on OPN expression in the developing cerebellum. We randomly divided pregnant female rats into three groups: control, Pb (lead acetate, 0.3%, drinking water), and Pb plus ascorbic acid (PA; ascorbic acid, 100 mg/kg, oral intubation) groups. The blood level of Pb was significantly increased, while ascorbic acid reduced Pb levels in the dams and pups. At postnatal day (PND) 21, results from Nissl staining and OPN immunohistochemistry demonstrated that OPN was detected in the Purkinje cell layer in the cerebellum. Ascorbic acid treatment mitigated Pb exposure-induced reduction in the number of intact Purkinje cells and OPN immunoreactive Purkinje cells in the cerebellum of pups. In addition, Pb-induced reduction in the number of oligodendrocytes and myelin-associated glycoprotein is associated with the malformation of the myelin sheath. Ascorbic acid provided protection from Pb-induced impairments. Pb-induced structural deficits in the cerebellum resulted in functional deterioration observed during locomotive tests (bar holding test and wire mesh ascending test), while ascorbic acid ameliorated these harmful effects. Present results suggest that the change of OPN is associated with myelination in the developing cerebellum. The results also demonstrated that exposure to Pb is harmful, while ascorbic acid treatment is beneficial.

Osteopontin counters human immunodeficiency virus type 1-induced impairment of neurite growth through mammalian target of rapamycin and beta-integrin signaling pathways

Despite the fact that human immunodeficiency virus type 1 (HIV-1) does not enter or replicate in neurons, its infection of a subset of resident brain glia cells (microglia and astrocytes) induces via disparate mechanisms, dysregulation of glutamate metabolism, neurotoxicity, and inflammation. Antiretroviral therapies suppress viral load, but cellular activation and release of proinflammatory factors, some of which is likely related to viral reservoirs, continue to promote a microenvironment that is injurious to neurons. However, the molecular mechanisms remain to be identified. Osteopontin (OPN) is a proinflammatory cytokine-like, extracellular matrix protein that is elevated within the brain and CSF in several neurodegenerative disorders, including HIV-associated cognitive disorder. However, the impact of elevated OPN on neuronal integrity and function in HIV-infected individuals who exhibit cognitive dysfunction remains unknown. In this study, using a neuronal cell line and primary cultures of cortical rat neurons, we identify the mammalian target of rapamycin pathway involvement in a signaling interaction between OPN-β1-integrins and the HIV-1 envelope glycoprotein, which stimulates neurite growth. These findings link for the first time HIV X4-envelope receptor engagement and osteopontin-mediated signaling through β1-integrin receptors to the mTOR pathway and alterations in the cytoskeleton of cortical neurons.

Osteopontin Attenuates Secondary Neurodegeneration in the Thalamus after Experimental Stroke

Cortical cerebral ischemia elicits neuroinflammation as well as secondary neuronal degeneration in remote areas. Locally distinct and specific secondary neurodegeneration affecting thalamic nuclei connected to cortical areas highlights such processes. Osteopontin (OPN) is a cytokine-like glycoprotein that is excreted in high amounts after cerebral ischemia and exerts various immunomodulatory functions. We here examined putative protective effects of OPN in secondary thalamic degeneration. We subjected male Wistar rats to photothrombosis and subsequently injected OPN or placebo intracerebroventricularly. Immunohistochemical and fluorescence staining was used to detect the extent of neuronal degeneration and microglia activation. Ex vivo autoradiography with radiotracers available for human in vivo PET studies, i.e., CIS-4-[¹⁸F]Fluor-D-Proline (D-cis-[¹⁸F]FPRO), and [6-³H]thymidine ([³H]thymidine), confirmed degeneration and proliferation, respectively. We found secondary neurodegeneration in the thalamus characterized by microglial activation and neuronal loss. Neuronal loss was restricted to areas of microglial infiltration. Treatment with OPN significantly decreased neurodegeneration, inflammation and microglial proliferation. Microglia displayed morphological signs of activation without expressing markers of M1 or M2 polarization. D-CIS-[¹⁸F]FPRO-uptake mirrored attenuated degeneration in OPN-treated animals. Notably, [³H]thymidine and BrdU-staining revealed increased stem cell proliferation after treatment with OPN. The data suggest that OPN is able to ameliorate secondary neurodegeneration in thalamic nuclei. These effects can be visualized by radiotracers D-CIS-[¹⁸F]FPRO and [³H]thymidine, opening new vistas for translational studies. Graphical Abstract Intracerebroventricular injection of osteopontin attenuates thalamic degeneration after cortical ischemia (pink area). Disruption of thalamocortical connections (blue) and degeneration of thalamic nuclei (encircled) leads to microglia activation. Osteopontin protects from both neurodegeneration and microglia activation as assessed by histological analysis and autoradiograpic studies.

Synergistic effect of extracellularly supplemented osteopontin and osteocalcin on stem cell proliferation, osteogenic differentiation, and angiogenic properties

A high demand for functional bone grafts is being observed worldwide, especially due to the increased life expectancy. Osteoinductive components should be incorporated into functional bone grafts, accelerating cell recruitment, cell proliferation, angiogenesis, and new bone formation at a defect site. Noncollagenous bone matrix proteins, especially osteopontin (OPN) and osteocalcin (OC), have been reported to regulate some physiological process, such as cell migration and bone mineralization. However, the effects of OPN and OC on cell proliferation, osteogenic differentiation, mineralization, and angiogenesis are still undefined. Therefore, we assessed the exogenous effect of OPN and OC supplementation on human bone marrow mesenchymal stem/stromal cells (hBM MSC) proliferation and osteogenic differentiation. OPN dose-dependently increased the proliferation of hBM MSC, as well as improved the angiogenic properties of human umbilical vein endothelial cells (HUVEC) by increasing the capillary-like tube formation in vitro. On the other hand, OC enhanced the differentiation of hBM MSC into osteoblasts and demonstrated an increase in extracellular calcium levels and alkaline phosphatase activity, as well as higher messenger RNA levels of mature osteogenic markers osteopontin and osteocalcin. In vivo assessment of OC/OPN-enhanced scaffolds in a critical-sized defect rabbit long-bone model revealed no infection, while new bone was being formed. Taken together, these results suggest that OC and OPN stimulate bone regeneration by inducing stem cell proliferation, osteogenesis and by enhancing angiogenic properties. The synergistic effect of OC and OPN observed in this study can be applied as an attractive strategy for bone regeneration therapeutics by targeting different vital cellular processes.

Osteopontin levels in plasma, muscles, and bone in patient with non-healing diabetic foot ulcers: A new player in wound healing process?

BACKGROUND

The present study was designed to investigate the impact of osteopontin (OPN) in different tissue (e.g., plasma, muscles and bone) on amputation rate (in-hospital and during one year follow-up) for non-healing diabetic foot ulcers (DFUs).

METHODS

This pilot study consisted of 30 diabetic patients, hospitalized due to non-healing DFUs. Patients were divided into two groups: Group 1 included 14 patients who underwent limb-preserved debridement procedure without amputation; Group 2 included 16 subjects who underwent amputation. Additionally, recurrent amputation rate during 1 year follow-up was investigated.

RESULTS

Plasma OPN was higher and bone OPN was lower in Group 2 compared to Group 1 (p = 0.016 and p = 0.004, respectively). In the logistic regression analysis, bone OPN emerged as a significant independent predictor of amputation (OR = 0.042, 95% CI 0.003-0.699, p = 0.027). Plasma OPN was also associated with amputation such that each unit increase in plasma OPN was associated with an increase in odds of amputation of 17.7% (95% CI 0.997-1.388, p = 0.045). During 1 year follow-up 11 patients underwent recurrent amputation. Plasma OPN were higher and bone osteopontin was lower in patients who underwent amputation compared to patients who did not need amputation at one year follow-up. However, in GLM analysis bone OPN was only marginally associated with one year amputation (OR 0.001, 95% CI 0.000-2.0, p = 0.076).

CONCLUSIONS

Decreased levels of OPN in bone and increased plasma OPN are independently associated with in-hospital amputation. Consequently, plasma OPN may be relevant in the routine assessment of amputation risk in this patient population.

Bioluminescence imaging visualizes osteopontin-induced neurogenesis and neuroblast migration in the mouse brain after stroke

Background

Osteopontin (OPN), an acidic phosphoglycoprotein, is upregulated in the brain after cerebral ischemia. We previously reported that OPN supports migration, survival, and proliferation of neural stem cells (NSC) in primary cell culture, as well as their differentiation into neurons. We here analyzed the effects of OPN on neuroblasts in vivo in the context of cerebral ischemia.

Methods

Transgenic mice expressing luciferase under the control of the neuroblast-specific doublecortin (DCX)-promoter, allowing visualization of neuroblasts in vivo using bioluminescence imaging (BLI), were injected with OPN intracerebroventricularly while control mice were injected with vehicle buffer. To assess the effects of OPN after ischemia, additional mice were subjected to photothrombosis and injected with either OPN or vehicle.

Results

OPN enhanced the migration of neuroblasts both in the healthy brain and after ischemia, as quantified by BLI in vivo. Moreover, the number of neural progenitors was increased following OPN treatment, with the maximum effect on the second day after OPN injection into the healthy brain, and 14 days after OPN injection following ischemia. After ischemia, OPN quantitatively promoted the endogenous, ischemia-induced neuroblast expansion, and additionally recruited progenitors from the contralateral hemisphere.

Conclusions

Our results strongly suggest that OPN constitutes a promising substance for the targeted activation of neurogenesis in ischemic stroke.

Importance of Angiogenin and Endothelial Progenitor Cells After Rehabilitation Both in Ischemic Stroke Patients and in a Mouse Model of Cerebral Ischemia

Background: Rehabilitation therapy is the only available treatment for stroke survivors presenting neurological deficits; however, the underlying molecules and mechanisms associated with functional/motor improvement during rehabilitation are poorly understood. Objective: Our aim is to study the modulation of angiogenin and endothelial progenitor cells (EPCs) as repair-associated factors in a cohort of stroke patients and mouse models of rehabilitation after cerebral ischemia. Methods: The clinical study included 18 ischemic strokes admitted to an intensive rehabilitation therapy (IRT) unit, 18 non-ischemic controls and brain samples from three deceased patients. Angiogenin and EPCs were measured in blood obtained before and up to 6 months after IRT together with an extensive evaluation of the motor/functional status. In parallel, C57BL/6 mice underwent middle cerebral artery occlusion, and the pasta matrix reaching-task or treadmill exercises were used as rehabilitation models. Angiogenin RNA expression was measured after 2 or 12 days of treatment together with cell counts from EPCs cultures. Results: Brain angiogenin was identified in both human and mouse tissue, whereas serum levels increased after 1 month of IRT in association with motor/functional improvement. EPC populations were increased after stroke and remained elevated during follow-up after IRT. The mouse model of rehabilitation by the task-specific pasta matrix exercise increased the number of EPCs at 2 days and increased angiogenin expression after 12 days of rehabilitation. Conclusions: Angiogenin and EPCs are modulated by rehabilitation after cerebral ischemia, suggesting that both angiogenin and EPCs could serve as biomarkers of improvement during rehabilitation or future therapeutic targets.

Macrophage Cytokines Enhance Cell Proliferation of Normal Prostate Epithelial Cells through Activation of ERK and Akt

Macrophage infiltrations (inflammation) are associated with prostate disorders such as prostatitis, prostatic hyperplasia and prostate cancer. All prostate disorders have elevated cell proliferation, and are initiated from normal prostate epithelial cells. To date, the mechanism of how macrophages regulate normal prostate epithelial cell proliferation remains largely unknown. Using a 3D co-culture system, we here show that Raw 264.7 macrophages increased cell proliferation of normal prostate epithelial PZ-HPV-7 cells. In addition, these Raw 264.7 macrophages expressed higher levels of Ym1 and CD206. We further identify macrophage-secreted cytokines including CCL3, IL-1ra, osteopontin, M-CSF1 and GDNF as mediators for potentiating PZ-HPV-7 cell proliferation in 3D. All these cytokines differentially activated ERK and Akt. Blockade of both kinases through their inhibitors hindered macrophage-induced cell proliferation of PZ-HPV-7 cells. Hence, our data provide mechanistic insight of how inflammation may contribute to development of prostatic diseases at a very early stage through augment of cell proliferation of normal prostate epithelial cells.

Transcriptional profiling validates involvement of extracellular matrix and proteinases genes in mouse gonad development

Extracellular matrix (ECM) plays an important scaffolding role in the establishment of organs structure during development. A great number of ECM components and enzymes (proteinases) regulating formation/degradation of ECM during organ remodeling have been identified. In order to study the role of ECM in the mouse gonad development, especially during sexual differentiation of the gonads when the structure of the testis and ovary becomes established, we performed a global analysis of transcriptome in three main cell types of developing gonad (supporting, interstitial/stromal and germ cells) using transgenic mice, cell sorting and microarray. The genes coding for ECM components were mostly expressed in two gonadal cell lines: supporting and interstitial/stromal cells. These two cell lines differed in the expression pattern of ECM components, which suggests that ECM components might be crucial for differentiation of gonad compartments (for example testis cords vs. interstitium in XY gonads). Collagens and proteoglycans coding genes were mainly expressed in the interstitium/stromal cells, while non-collagen glycoproteins and matricellular coding genes were expressed in both cell lines. We also analyzed the expression of genes encoding ECM enzymes that are secreted to the ECM where they remodel the scaffolding of developing organs. We found that the ECM enzyme genes were also mostly expressed in supporting and interstitial/stromal cells. In contrast to the somatic cells, the germ cells expressed only limited number of ECM components and enzymes. This suggests that the germ line cells do not participate, or play only a minor role, in the sculpting of the gonad structure via ECM synthesis and remodeling. Importantly, the supporting cells showed the sex-specific pattern of expression of ECM components. However, the pattern of expression of most ECM enzymes in the somatic and germ cells is independent on the sex of the gonad. Further studies are required to elucidate the exact roles of identified genes in sexual differentiation of the gonads.

Protein profiling identified key chemokines that regulate the maintenance of human pluripotent stem cells

Microenvironment (or niche)-providing chemokines regulate many important biological functions of tissue-specific stem cells. However, to what extent chemokines influence human pluripotent stem cells (hPSCs) is not yet completely understood. In this study, we applied protein array to screen chemokines found within the cytokine pool in the culture supernatant of hPSCs. Our results showed that chemokines were the predominant supernatant components, and came from three sources: hPSCs, feeder cells, and culture media. Chemotaxis analysis of IL-8, SDF-1α, and IP-10 suggested that chemokines function as uniform chemoattractants to mediate in vitro migration of the hPSCs. Chemokines mediate both differentiated and undifferentiated states of hPSCs. However, balanced chemokine signaling tends to enhance their stemness in vitro. These results indicate that chemokines secreted from both stem cells and feeder cells are essential to mobilize hPSCs and maintain their stemness.

Ameliorating Effect of Osteopontin on H2O2-Induced Apoptosis of Human Oligodendrocyte Progenitor Cells

Recently our group used oligodendrocyte progenitor cells (OPCs) as appropriate model cells to pinpoint the mechanism of the progress of neurodegenerative disorders. In the present study, we focused on the therapeutic role of osteopontin (OPN), a secreted glycosylated phosphoprotein, involved in a number of physiological events including bone formation and remodeling, immune responses, and tumor progression. Protective role of OPN, as a negative regulator of tumorigenesis, has already been clarified. Human embryonic stem cell-derived OPCs were pretreated with OPN before induction of apoptosis by H₂O₂. Data indicated that OPN prohibited cell death and enhanced OPC viability. This effect is achieved through reduction of apoptosis and induction of anti-apoptosis markers. In addition OPN induces expression of several integrin subunits, responsible for OPN interaction. Notably, our findings showed that expression of αV β1/β3/β5 and β8 integrins increased in response to OPN, while treatment with H₂O₂ down-regulated αV β1/β5 and β8 integrins expression significantly. In conclusion, OPN may act via αV integrin signaling and trigger suppression of P53-dependent apoptotic cascades. Therefore OPN therapy may be considered as a feasible process to prevent progress of neurodegenerative diseases in human.

Osteopontin Augments M2 Microglia Response and Separates M1- and M2-Polarized Microglial Activation in Permanent Focal Cerebral Ischemia

Background

Focal cerebral ischemia induces distinct neuroinflammatory processes. We recently reported the extracellular phosphor-glyco-protein osteopontin (OPN) to directly affect primary microglia in vitro, promoting survival while shifting their inflammatory profile towards a more neutral phenotype. We here assessed the effects of OPN on microglia after stroke in vivo, with focus on infarct demarcation.

Methods

Animals underwent focal photothrombotic stroke and were injected intracerebroventricularly with 500 μg OPN or vehicle. Immunohistochemistry assessed neuronal damage and infarct volume, neovascularisation, glial scar formation, microglial activation, and M1 and M2 polarisation.

Results

After photothrombotic stroke, areas covered by M1 and M2 microglia substantially overlapped. OPN treatment reduced that overlap, with microglia appearing more spread out and additionally covering the infarct core. OPN additionally modulated the quantity of microglia subpopulations, reducing iNOS+ M1 cells while increasing M2 microglia, shifting the M1/M2 balance towards an M2 phenotype. Moreover, OPN polarized astrocytes towards the infarct.

Conclusion

Microglial activation and M1 and M2 polarization have distinct but overlapping spatial patterns in permanent focal ischemia. Data suggest that OPN is involved in separating M1 and M2 subpopulations, as well as in shifting microglia polarization towards the M2 phenotype modulating beneficially inflammatory responses after focal infarction.

Monocyte depletion early after stroke promotes neurogenesis from endogenous neural stem cells in adult brain

Ischemic stroke, caused by middle cerebral artery occlusion, leads to long-lasting formation of new striatal neurons from neural stem/progenitor cells (NSPCs) in the subventricular zone (SVZ) of adult rodents. Concomitantly with this neurogenic response, SVZ exhibits activation of resident microglia and infiltrating monocytes. Here we show that depletion of circulating monocytes, using the anti-CCR2 antibody MC-21 during the first week after stroke, enhances striatal neurogenesis at one week post-insult, most likely by increasing short-term survival of the newly formed neuroblasts in the SVZ and adjacent striatum. Blocking monocyte recruitment did not alter the volume of the ischemic lesion but gave rise to reduced astrocyte activation in SVZ and adjacent striatum, which could contribute to the improved neuroblast survival. A similar decrease of astrocyte activation was found in and around human induced pluripotent stem cell (iPSC)-derived NSPCs transplanted into striatum at one week after stroke in monocyte-depleted mice. However, there was no effect on neurogenesis in the graft as determined 8weeks after implantation. Our findings demonstrate, for the first time, that a specific cellular component of the early inflammatory reaction in SVZ and adjacent striatum following stroke, i.e., infiltrating monocytes, compromises the short-term neurogenic response neurogenesis from endogenous NSPCs.

Human endothelial cells secrete neurotropic factors to direct axonal growth of peripheral nerves

Understanding how nerves spontaneously innervate tissues or regenerate small injuries is critical to enhance material-based interventions to regenerate large scale, traumatic injuries. During embryogenesis, neural and vascular tissues form interconnected, complex networks as a result of signaling between these tissue types. Here, we report that human endothelial cells (HUVECs) secrete brain-derived neurotrophic factor (BDNF), which significantly stimulated axonal growth from chicken or rat dorsal root ganglia (DRGs). HUVEC-conditioned medium was sufficient to enhance axonal growth, demonstrating that direct cell-cell contact was not required. When BDNF was neutralized, there was a significant reduction in axonal growth when incubated in HUVEC-conditioned medium and in direct co-culture with HUVECs. These data show that HUVECs secrete neurotrophic factors that significantly enhance axonal growth, and can inform future in vivo studies to direct or pattern the angiogenic response in regenerating tissues to encourage re-innervation.

Radial Glia Cells Control Angiogenesis in the Developing Cerebral Cortex Through TGF-β1 Signaling

Neuroangiogenesis in the developing central nervous system is controlled by interactions between endothelial cells (ECs) and radial glia (RG) neural stem cells, although RG-derived molecules implicated in these events are not fully known. Here, we investigated the role of RG-secreted TGF-β1, in angiogenesis in the developing cerebral cortex. By isolation of murine microcapillary brain endothelial cells (MBECs), we demonstrate that conditioned medium from RG cultures (RG-CM) promoted MBEC migration and formation of vessel-like structures in vitro, in a TGF-β1-dependent manner. These events were followed by endothelial regulation of GPR124 and BAI-1 gene expression by RG-CM. Proteome profile of RG-CM identified angiogenesis-related molecules IGFBP2/3, osteopontin, endostatin, SDF1, fractalkine, TIMP1/4, Ang-1, pentraxin3, and Cyr61, some of them modulated by TGF-β1 induction. In vivo gain and loss of function assays targeting RG cells demonstrates a specific TGF-β1-dependent control of blood vessels branching in the cerebral cortex. Together, our results point to TGF-β1 signaling pathway as a potential mediator of the RG-EC interactions and shed light to the key role of RG in paving the brain vascular network.

In Vitro Effects of Lead on Gene Expression in Neural Stem Cells and Associations between Up-regulated Genes and Cognitive Scores in Children

BACKGROUND

Lead (Pb) adversely affects neurodevelopment in children. Neural stem cells (NSCs) play an essential role in shaping the developing brain, yet little is known about how Pb perturbs NSC functions and whether such perturbation contributes to impaired neurodevelopment.

OBJECTIVES

We aimed to identify Pb-induced transcriptomic changes in NSCs and to link these changes to neurodevelopmental outcomes in children who were exposed to Pb.

METHODS

We performed RNA-seq-based transcriptomic profiling in human NSCs treated with 1 μM Pb. We used qRT-PCR, Western blotting, ELISA, and ChIP (chromatin immunoprecipitation) to characterize Pb-induced gene up-regulation. Through interrogation of a genome-wide association study, we examined the association of gene variants with neurodevelopment outcomes in the ELEMENT birth cohort.

RESULTS

We identified 19 genes with significantly altered expression, including many known targets of NRF2-the master transcriptional factor for the oxidative stress response. Pb induced the expression of SPP1 (secreted phosphoprotein 1), which has known neuroprotective effects. We demonstrated that SPP1 is a novel direct NRF2 target gene. Single nucleotide polymorphisms (SNPs) (rs12641001) in the regulatory region of SPP1 exhibited a statistically significant association (p = 0.005) with the Cognitive Development Index (CDI).

CONCLUSION

Our findings revealed that Pb induces an NRF2-dependent transcriptional response in neural stem cells and identified SPP1 up-regulation as a potential novel mechanism linking Pb exposure with neural stem cell function and neurodevelopment in children.