Role of neurotrophic factors in neuronal development

Bioengineering strategy to promote CNS nerve growth and regeneration via chronic glutamate signaling

Being part of the mature mammalian central nervous system, impairments of the retina and optic nerves caused by trauma or diseases often cannot be restored. Progressive degeneration of retinal ganglion cells (RGCs) in glaucoma and other optic neuropathies gradually leads to permanent vision loss, which currently has no cure. The purpose of this study is to develop a biocompatible scaffold to support RGC survival and guide axon growth, facilitating optic nerve repair and regeneration. We here report that electrical stimulation (ES) significantly promoted neurite outgrowth and elongation from primary RGCs, mediated through glutamate receptor signaling. To mimic prolonged glutamate stimulation and facilitate sustained nerve growth, we fabricated biocompatible poly-γ-benzyl-L-glutamate (PBG) scaffolds for controlled glutamate release. These PBG scaffolds supported RGC survival and robust long-distance nerve growth in both retinal explants and isolated RGC cultures. In contrast, control polycaprolactone (PCL) scaffolds with similar physical structures showed little benefits on RGC survival or nerve growth. Moreover, PBG scaffolds promoted the differentiation and neurite outgrowth from embryonic stem cell-derived RGC progenitors. The aligned PBG scaffold drove directed nerve elongation along the fiber alignment. Transplantation of PBG-coated biocompatible conduits induced robust optic nerve regeneration in adult mice following nerve transection. Together, the findings present the exciting possibility of driving optic nerve regeneration and RGC progenitor cell differentiation by imitating ES or glutamate signaling. PBG presents a permissive biomaterial in supporting robust and directed axon growth with promising clinical applications in the future. STATEMENT OF SIGNIFICANCE: We here reported compelling findings that demonstrate the potent regenerative effects of a bioengineered scaffold incorporating poly-γ-benzyl-L-glutamate (PBG) on the optic nerve. Retinal ganglion cell (RGC) axons, which form the optic nerve, are incapable of regenerating in adulthood, posing a significant hurdle in restoring vision for patients with optic nerve diseases or injuries. Built upon the finding that electrical stimulation promotes RGC axonal growth through glutamate signaling, we developed PBG scaffolds to provide sustained glutamate stimulation and showed their exceptional effects on driving directed axonal elongation in cultured RGCs and neural progenitors, as well as supporting robust optic nerve regeneration after transection in vivo. The findings hold great promise for reversing vision loss in patients with optic nerve conditions.

Differential roles of NR4A2 (NURR1) paralogs in the brain and behavior of zebrafish

Dopaminergic (DAnergic) dysfunction and imbalanced dopamine (DA) levels are known contributors to the pathogenesis of numerous psychiatric and neurodegenerative disorders. Of the many identified risk factors for DA-associated disorders, nuclear receptor subfamily 4 group A2 (NR4A2; or nuclear receptor related-1 protein (NURR1)), a transcription factor involved in DAnergic differentiation, has been associated with Parkinson's disease and attention deficit hyperactive disorder (ADHD). In zebrafish, transient loss of nr4a2 was previously shown to decrease tyrosine hydroxylase (TH) expression and impair locomotion. To further characterize the roles of the two zebrafish nr4a2 paralogs, nr4a2a, and nr4a2b, we produced targeted loss-of-function mutants and examined DAnergic neuron regeneration, oxidative respiration, and behavioral traits. The loss of nr4a2a function more closely recapitulated Parkinsonian phenotypes and affected neurotrophic factor gene expression. Conversely, nr4a2b mutants displayed behavioral symptoms reminiscent of mice deficient in Nr4a2 with increased neurotrophic output. In contrast, nr4a2b mutants also displayed increased metabolic input from non-mitochondrial sources indicative of high cytosolic reactive oxygen species and perturbed mitochondrial function. The nr4a2a mutants also showed increased maximal respiration, which may suggest a compensatory mechanism to meet the metabolic requirements of DAnergic neuron health. Overall, the zebrafish mutants generated in this study helped uncover molecular mechanisms involved in DA-related disease pathologies, and in the regeneration of DAnergic neurons.

Nanotechnology Approaches for Prevention and Treatment of Chemotherapy-Induced Neurotoxicity, Neuropathy, and Cardiomyopathy in Breast and Ovarian Cancer Survivors

Nanotechnology has emerged as a promising approach for the targeted delivery of therapeutic agents while improving their efficacy and safety. As a result, nanomaterial development for the selective targeting of cancers, with the possibility of treating off-target, detrimental sequelae caused by chemotherapy, is an important area of research. Breast and ovarian cancer are among the most common cancer types in women, and chemotherapy is an essential treatment modality for these diseases. However, chemotherapy-induced neurotoxicity, neuropathy, and cardiomyopathy are common side effects that can affect breast and ovarian cancer survivors quality of life. Therefore, there is an urgent need to develop effective prevention and treatment strategies for these adverse effects. Nanoparticles (NPs) have extreme potential for enhancing therapeutic efficacy but require continued research to elucidate beneficial interventions for women cancer survivors. In short, nanotechnology-based approaches have emerged as promising strategies for preventing and treating chemotherapy-induced neurotoxicity, neuropathy, and cardiomyopathy. NP-based drug delivery systems and therapeutics have shown potential for reducing the side effects of chemotherapeutics while improving drug efficacy. In this article, the latest nanotechnology approaches and their potential for the prevention and treatment of chemotherapy-induced neurotoxicity, neuropathy, and cardiomyopathy in breast and ovarian cancer survivors are discussed.

The Use of Neurotrophic Factors as a Promising Strategy for the Treatment of Neurodegenerative Diseases (Review)

The review considers the use of exogenous neurotrophic factors in the treatment of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, and others. This group of diseases is associated with the death of neurons and dysfunction of the nervous tissue. Currently, there is no effective therapy for neurodegenerative diseases, and their treatment remains a serious problem of modern medicine. A promising strategy is the use of exogenous neurotrophic factors. Targeted delivery of these factors to the nervous tissue can improve survival of neurons during the development of neurodegenerative processes and ensure neuroplasticity. There are methods of direct injection of neurotrophic factors into the nervous tissue, delivery using viral vectors, as well as the use of gene cell products. The effectiveness of these approaches has been studied in numerous experimental works and in a number of clinical trials. Further research in this area could provide the basis for the creation of an alternative treatment for neurodegenerative diseases.

Biomarkers of fatigue in oncology: A systematic review

Cancer-related fatigue (CRF) is a distressing side effect of cancer and treatment, affecting both patients during active treatment and survivors, negatively impacting quality of life. While its exact cause remains uncertain, various mechanisms such as immune dysfunction, HPA-axis dysfunction, and treatment toxicity are proposed. Inflammatory biomarkers of CRF have been explored in previous research, but non-inflammatory markers have not been comprehensively studied. This systematic review analysed 33 studies to identify non-inflammatory peripheral blood biomarkers associated with CRF. Promising markers included Hb, blood coagulation factors, BDNF, tryptophan, GAA, mtDNA, platinum, CA125, and cystatin-C. Inconsistent findings were observed for other markers like VEGF, leptin, and stress hormones. Most studies focused on adults. Research in pediatrics is limited. This review showed partial evidence for the inflammaging hypothesis (neurotoxicity due to neuro-inflammation) laying at the basis of CRF. Further research, especially in pediatrics, is needed to confirm this hypothesis and guide future biomarker studies.

Mechanisms of microRNA-132 in central neurodegenerative diseases: A comprehensive review

MicroRNA-132 (miR-132) is a highly conserved molecule that plays a crucial regulatory role in central nervous system (CNS) disorders. The expression levels of miR-132 exhibit variability in various neurological disorders and have been closely linked to disease onset and progression. The expression level of miR-132 in the CNS is regulated by a diverse range of stimuli and signaling pathways, including neuronal migration and integration, dendritic outgrowth, and complexity, synaptogenesis, synaptic plasticity, as well as inflammation and apoptosis activation. The aberrant expression of miR-132 in various central neurodegenerative diseases has garnered widespread attention. Clinical studies have revealed altered miR-132 expression levels in both chronic and acute CNS diseases, positioning miR-132 as a potential biomarker or therapeutic target. An in-depth exploration of miR-132 holds the promise of enhancing our understanding of the mechanisms underlying CNS diseases, thereby offering novel insights and strategies for disease diagnosis and treatment. It is anticipated that this review will assist researchers in recognizing the potential value of miR-132 and in generating innovative ideas for clinical trials related to CNS degenerative diseases.

iPSC-derived neural precursor cells engineering GBA1 recovers acid β-glucosidase deficiency and diminishes α-synuclein and neuropathology

Mutations in GBA1, encoding the lysosomal acid β-glucosidase (GCase), cause neuronopathic Gaucher disease (nGD) and promote Parkinson disease (PD). The mutations on GBA1 include deletion and missense mutations that are pathological and lead to GCase deficiency in Gaucher disease. Both nGD and PD lack disease-modifying treatments and are critical unmet medical needs. In this study, we evaluated a cell therapy treatment using mouse iPSC-derived neural precursor cells (NPCs) engineered to overexpress GCase (termed hGBA1-NPCs). The hGBA1-NPCs secreted GCase that was taken up by adjacent mouse Gba -/- neurons and improved GCase activity, reduced GCase substrate accumulation, and improved mitochondrial function. Short-term in vivo effects were evaluated in 9H/PS-NA mice, an nGD mouse model exhibiting neuropathology and α-synuclein aggregation, the typical PD phenotypes. Intravenously administrated hGBA1-NPCs were engrafted throughout the brain and differentiated into neural lineages. GCase activity was increased in various brain regions of treated 9H/PS-NA mice. Compared with vehicle, hGBA1-NPC-transplanted mice showed ∼50% reduction of α-synuclein aggregates in the substantia nigra, significant reduction of neuroinflammation and neurodegeneration in the regions of NPC migration, and increased expression of neurotrophic factors that support neural cell function. Together, these results support the therapeutic benefit of intravenous delivery of iPSC-derived NPCs overexpressing GCase in mitigating nGD and PD phenotypes and establish the feasibility of combined cell and gene therapy for GBA1-associated PD.

Transcriptomic, Proteomic, and Morphologic Characterization of Healing in Volumetric Muscle Loss

Skeletal muscle has a robust, inherent ability to regenerate in response to injury from acute to chronic. In severe trauma, however, complete regeneration is not possible, resulting in a permanent loss of skeletal muscle tissue referred to as volumetric muscle loss (VML). There are few consistently reliable therapeutic or surgical options to address VML. A major limitation in investigation of possible therapies is the absence of a well-characterized large animal model. Here, we present results of a comprehensive transcriptomic, proteomic, and morphologic characterization of wound healing following volumetric muscle loss in a novel canine model of VML which we compare to a nine-patient cohort of combat-associated VML. The canine model is translationally relevant as it provides both a regional (spatial) and temporal map of the wound healing processes that occur in human VML. Collectively, these data show the spatiotemporal transcriptomic, proteomic, and morphologic properties of canine VML healing as a framework and model system applicable to future studies investigating novel therapies for human VML.

Potential of Cellular Therapy for ALS: Current Strategies and Future Prospects

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive upper and lower motor neuron (MN) degeneration with unclear pathology. The worldwide prevalence of ALS is approximately 4.42 per 100,000 populations, and death occurs within 3-5 years after diagnosis. However, no effective therapeutic modality for ALS is currently available. In recent years, cellular therapy has shown considerable therapeutic potential because it exerts immunomodulatory effects and protects the MN circuit. However, the safety and efficacy of cellular therapy in ALS are still under debate. In this review, we summarize the current progress in cellular therapy for ALS. The underlying mechanism, current clinical trials, and the pros and cons of cellular therapy using different types of cell are discussed. In addition, clinical studies of mesenchymal stem cells (MSCs) in ALS are highlighted. The summarized findings of this review can facilitate the future clinical application of precision medicine using cellular therapy in ALS.

Effects of photoperiod and diet on BDNF daily rhythms in diurnal sand rats

Brain-derived neurotrophic factor (BDNF), its receptors and epigenetic modulators, are implicated in the pathophysiology of affective disorders, T2DM and the circadian system function. We used diurnal sand rats, which develop type 2 diabetes (T2DM), anxiety and depressive-like behavior under laboratory conditions. The development of these disorders is accelerated when animals are maintained under short photoperiod (5:19L:D, SP) compared to neutral photoperiod (12:12L:D, NP). We compared rhythms in plasma BDNF as well as BDNF and PER2 expression in the frontal cortex and suprachiasmatic nucleus (SCN) of sand rats acclimated to SP and NP. Acclimation to SP resulted in higher insulin levels, significantly higher glucose levels in the glucose tolerance test, and significantly higher anxiety- and depression-like behaviors compared with animals acclimated to NP. NP Animals exhibited a significant daily rhythm in plasma BDNF levels with higher levels during the night, and in BDNF expression levels in the frontal cortex and SCN. No significant BDNF rhythm was found in the plasma, frontal cortex or SCN of SP acclimated animals. We propose that in sand rats, BDNF may, at least in part, mediate the effects of circadian disruption on the development of anxiety and depressive-like behavior and T2DM.

Neuroprotective Efficiency of Prodigiosins Conjugated with Selenium Nanoparticles in Rats Exposed to Chronic Unpredictable Mild Stress is Mediated Through Antioxidative, Anti-Inflammatory, Anti-Apoptotic, and Neuromodulatory Activities

PURPOSE

Depression is a mood disorder accompanied by intensive molecular and neurochemical alterations. Currently, available antidepressant therapies are not fully effective and are often accompanied by several adverse impacts. Accordingly, the ultimate goal of this investigation was to clarify the possible antidepressant effects of prodigiosins (PDGs) loaded with selenium nanoparticles (PDGs-SeNPs) in chronic unpredictable mild stress (CUMS)-induced depression-like behavior in rats.

METHODS

Sixty Sprague Dawley rats were randomly allocated into six groups: control, CUMS group (depression model), fluoxetine (Flu, 10 mg/kg)+CUMS, PDGs+CUMS (300 mg/kg), sodium selenite (Na2SeO3, 400 mg/kg)+CUMS, and PDGs-SeNPs+CUMS (200 mg/kg). All treatments were applied orally for 28 consecutive days.

RESULTS

PDGs-SeNPs administration prevented oxidative insults in hippocampal tissue, as demonstrated by decreased oxidant levels (nitric oxide and malondialdehyde) and elevated innate antioxidants (glutathione, glutathione peroxidase, glutathione reductase, superoxide dismutase, and catalase), in addition to the upregulated expression of nuclear factor erythroid 2-related factor 2 and heme oxygenase-1 in rats exposed to CUMS. Additionally, PDGs-SeNPs administration suppressed neuroinflammation in hippocampal tissue, as determined by the decreased production of pro-inflammatory cytokines (tumor necrosis factor-alpha, interleukin-1β, and interleukin-6), increased anti-inflammatory cytokine interleukin-10, and decreased inflammatory mediators (prostaglandin E2, cyclooxygenase-2, and nuclear factor kappa B). Moreover, PDGs-SeNPs administration in stressed rats inhibited neuronal loss and the development of hippocampal apoptosis through enhanced levels of B cell lymphoma 2 and decreased levels of caspase 3 and Bcl-2-associated X protein. Interestingly, PDGs-SeNPs administration improved hormonal levels typically disrupted by CUMS exposure and significantly modulated hippocampal levels of monoamines, brain-derived neurotrophic factor, monoamine oxidase, and acetylcholinesterase activities, in addition to upregulating the immunoreactivity of glial fibrillary acidic protein in CUMS model rats.

CONCLUSION

PDGs-SeNPs may serve as a prospective antidepressant candidate due to their potent antioxidant, anti-inflammatory, and neuroprotective potential.

Beneficial Effects of Neurotrophin-4 Supplementation During in vitro Maturation of Porcine Cumulus-Oocyte Complexes and Subsequent Embryonic Development After Parthenogenetic Activation

Neurotrophin-4 (NT-4) is a neurotrophic factor that plays an important role in follicular development and oocyte maturation. However, it is not yet known whether NT-4 is related to oocyte maturation and follicular development in pigs. This study aims to investigate the effects of NT-4 supplementation during in vitro maturation (IVM) of porcine oocytes and subsequent embryonic development after parthenogenetic activation (PA). First, NT-4 and its receptors (TrkB and p75^NTR) were identified through fluorescent immunohistochemistry in porcine ovaries. NT-4 was mainly expressed in theca and granulosa cells; phospho-TrkB and total TrkB were expressed in theca cells, granulosa cells, and oocytes; p75^NTR was expressed in all follicular cells. During IVM, the defined maturation medium was supplemented with various concentrations of NT-4 (0, 1, 10, and 100 ng/mL). After IVM, the nuclear maturation rate was significantly higher in the 10 and 100 ng/mL NT-4 treated groups than in the control. There was no significant difference in the intracellular reactive oxygen species levels in any group after IVM, but the 1 and 10 ng/mL NT-4 treatment groups showed a significant increase in the intracellular glutathione levels compared to the control. In matured cumulus cells, the 10 ng/mL NT-4 treatment group showed significantly increased cumulus expansion-related genes and epidermal growth factor (EGF) signaling pathway-related genes. In matured oocytes, the 10 ng/mL treatment group showed significantly increased expression of cell proliferation-related genes, antioxidant-related genes, and EGF signaling pathway-related genes. We also investigated the subsequent embryonic developmental competence of PA embryos. After PA, the cleavage rates significantly increased in the 10 and 100 ng/mL NT-4 treatment groups. Although there was no significant difference in the total cell number of blastocysts, only the 10 ng/mL NT-4 treatment group showed a higher blastocyst formation rate than the control group. Our findings suggest that supplementation with the 10 ng/mL NT-4 can enhance porcine oocyte maturation by interacting with the EGF receptor signaling pathway. In addition, we demonstrated for the first time that NT-4 is not only required for porcine follicular development, but also has beneficial effects on oocyte maturation and developmental competence of PA embryos.

Conditional Deletion of Activating Rearranged During Transfection Receptor Tyrosine Kinase Leads to Impairment of Photoreceptor Ribbon Synapses and Disrupted Visual Function in Mice

Purpose: The rearranged during transfection (RET) receptor tyrosine kinase plays a key role in transducing signals related to cell growth and differentiation. Ret mutant mice show abnormal retinal activity and abnormal levels and morphology of bipolar cells, yet die on the 21st day after birth as a result of renal underdevelopment. To extend the observation period, we generated the Ret conditional knockout Chx10-Cre;C-Ret lx/lx mouse model and analyzed the retinal function and morphological changes in mature and aging Chx10-Cre;C-Ret lx/lx mice. Methods: Retina-specific depletion of Ret was achieved using mice with floxed alleles of the Ret gene with CHX10-driven Cre recombinase; floxed mice without Cre expression were used as controls. Retinal function was examined using electroretinography (ERG), and 2-, 4-, 12-, and 24-month-old mice were analyzed by hematoxylin staining and immunohistochemistry to evaluate retinal morphological alterations. The ultrastructure of photoreceptor synapses was evaluated using electron microscopy. Results: The results of the ERG testing showed that b-wave amplitudes were reduced in Chx10-Cre;C-Ret lx/lx mice, whereas a-waves were not affected. A histopathological analysis revealed a thinner and disorganized outer plexiform layer at the ages of 12 and 24 months in Chx10-Cre;C-Ret lx/lx mice. Moreover, the data provided by immunohistochemistry showed defects in the synapses of photoreceptor cells. This result was confirmed at the ultrastructural level, thus supporting the participation of Ret in the morphological changes of the synaptic ribbon. Conclusion: Our results provide evidence of the role of Ret in maintaining the function of the retina, which was essential for preserving the structure of the synaptic ribbon and supporting the integrity of the outer plexiform layer.

Localization of Neurotrophin Specific Trk Receptors in Mechanosensory Systems of Killifish (Nothobranchius guentheri)

Neurotrophins (NTs) and their signal-transducing Trk receptors play a crucial role in the development and maintenance of specific neuronal subpopulations in nervous and sensory systems. NTs are supposed to regulate two sensory systems in fish, the inner ear and the lateral line system (LLS). The latter is one of the major mechanosensory systems in fish. Considering that annual fishes of the genus Nothobranchius, with their short life expectancy, have become a suitable model for aging studies and that the occurrence and distribution of neurotrophin Trk receptors have never been investigated in the inner ear and LLS of killifish (Nothobranchius guentheri), our study aimed to investigate the localization of neurotrophin-specific Trk receptors in mechanosensory systems of N. guentheri. For histological and immunohistochemical analysis, adult specimens of N. guentheri were processed using antibodies against Trk receptors and S100 protein. An intense immunoreaction for TrkA and TrkC was found in the sensory cells of the inner ear as well as in the hair cells of LLS. Moreover, also the neurons localized in the acoustic ganglia displayed a specific immunoreaction for all Trk receptors (TrkA, B, and C) analyzed. Taken together, our results demonstrate, for the first time, that neurotrophins and their specific receptors could play a pivotal role in the biology of the sensory cells of the inner ear and LLS of N. guentheri and might also be involved in the hair cells regeneration process in normal and aged conditions.

The Restorative Effect of Gallic Acid on the Experimental Sciatic Nerve Damage Model

Objective

Peripheral nerve injuries occur mostly as a result of mechanical trauma. Due to the microvascular deterioration in peripheral nerve damage, it becomes challenging to remove free oxygen radicals. Gallic acid is a powerful antioxidant with anti-inflammatory effects and a free radical scavenger. The purpose of the study is to show that gallic acid contributes to the restorative effect in mechanical nerve damage, considering its antioxidant and anti-inflammatory effects.

Methods

Thirty male Sprague Dawley albino mature rats were included in the study. Ten of them constituted the control group, 10 out of 20 rats for which sciatic nerve damage was caused, constituted the saline group, and 10 formed the gallic acid group. Post-treatment motor functions, histological, immunohistochemical, and biochemical parameters of the rats were evaluated.

Results

Compared to the surgery+saline group, lower compound muscle action potential (CMAP) latency, higher CMAP amplitude, and higher inclined plane test values were found in the surgery+gallic acid group. Similarly, a higher nerve growth factor (NGF) percentage, a higher number of axons, and a lower percentage of fibrosis scores were observed in the surgery+gallic acid group. Finally, lower tissue malondialdehyde (MDA) and higher heat shock protein-70 (HSP-70) values were determined in the surgery+gallic acid group.

Conclusion

Gallic acid positively affects peripheral nerve injury healing due to its anti-inflammatory and antioxidant effects. It has been thought that gallic acid can be used as a supportive treatment in peripheral nerve damage.

Electrical stimulation of human neural stem cells via conductive polymer nerve guides enhances peripheral nerve recovery

Severe peripheral nerve injuries often result in permanent loss of function of the affected limb. Current treatments are limited by their efficacy in supporting nerve regeneration and behavioral recovery. Here we demonstrate that electrical stimulation through conductive nerve guides (CNGs) enhances the efficacy of human neural progenitor cells (hNPCs) in treating a sciatic nerve transection in rats. Electrical stimulation strengthened the therapeutic potential of NPCs by upregulating gene expression of neurotrophic factors which are critical in augmenting synaptic remodeling, nerve regeneration, and myelination. Electrically-stimulated hNPC-containing CNGs are significantly more effective in improving sensory and motor functions starting at 1-2 weeks after treatment than either treatment alone. Electrophysiology and muscle assessment demonstrated successful re-innervation of the affected target muscles in this group. Furthermore, histological analysis highlighted an increased number of regenerated nerve fibers with thicker myelination in electrically-stimulated hNPC-containing CNGs. The elevated expression of tyrosine kinase receptors (Trk) receptors, known to bind to neurotrophic factors, indicated the long-lasting effect from electrical stimulation on nerve regeneration and distal nerve re-innervation. These data suggest that electrically-enhanced stem cell-based therapy provides a regenerative rehabilitative approach to promote peripheral nerve regeneration and functional recovery.

SARS-CoV-2 Infection in Pregnant Women: Neuroimmune-Endocrine Changes at the Maternal-Fetal Interface

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) has devastating effects on the population worldwide. Given this scenario, the extent of the impact of the disease on more vulnerable individuals, such as pregnant women, is of great concern. Although pregnancy may be a risk factor in respiratory virus infections, there are no considerable differences regarding COVID-19 severity observed between pregnant and nonpregnant women. In these circumstances, an emergent concern is the possibility of neurodevelopmental and neuropsychiatric harm for the offspring of infected mothers. Currently, there is no stronger evidence indicating vertical transmission of SARS-CoV-2; however, the exacerbated inflammatory response observed in the disease could lead to several impairments in the offspring's brain. Furthermore, in the face of historical knowledge on possible long-term consequences for the progeny's brain after infection by viruses, we must consider that this might be another deleterious facet of COVID-19. In light of neuroimmune interactions at the maternal-fetal interface, we review here the possible harmful outcomes to the offspring brains of mothers infected by SARS-CoV-2.

The Contribution of Microglia to the Development and Maturation of the Visual System

Microglia, the resident immune cells of the central nervous system (CNS), were once considered quiescent cells that sat in readiness for reacting to disease and injury. Over the last decade, however, it has become clear that microglia play essential roles in maintaining the normal nervous system. The retina is an easily accessible part of the central nervous system and therefore much has been learned about the function of microglia from studies in the retina and visual system. Anatomically, microglia have processes that contact all synapses within the retina, as well as blood vessels in the major vascular plexuses. Microglia contribute to development of the visual system by contributing to neurogenesis, maturation of cone photoreceptors, as well as refining synaptic contacts. They can respond to neural signals and in turn release a range of cytokines and neurotrophic factors that have downstream consequences on neural function. Moreover, in light of their extensive contact with blood vessels, they are also essential for regulation of vascular development and integrity. This review article summarizes what we have learned about the role of microglia in maintaining the normal visual system and how this has helped in understanding their role in the central nervous system more broadly.

Expression of neurotrophic factor genes by human adipose stem cells post-induction by deprenyl

Human adipose stem cells (hASCs) were introduced as appropriate candidate due to advantages like ease of isolation, in vitro expansion and lack of immune response. Deprenyl (Dep) was used to induce bone marrow stem cells into neuron-like cells. We investigated the Dep effect on neurotrophin genes expression in hASCs and their differentiation into neuron-like cells. The cells were isolated from small pieces of abdominal adipose tissue and subjected to flow cytometry to confirm purification. The osteogenic and adipogenic differentiation were identified. The proliferation rate and neurotrophin genes expression of treated cells were evaluated by MTT, TH immunostaining and RT-PCR. hASCs had positive response to CD44, CD73, CD90, CD105 markers and negative response to CD34 and CD45 markers and differentiated into adipocytes and osteocytes. Exposure to 10–7 M of Dep for 24 hours caused a significant increase of viable cells and BDNF, NTF-3 genes expression as compared to cultured cells in serum free medium and had no effect on the expression of NGF and GDNF genes. Based on our results, Dep is able to induce BDNF, NTF-3 and NTF-4 genes expression and neroun-like morphology in hASCs.

Interrupting Neuron-Tumor Interactions to Overcome Treatment Resistance

Neurons in the tumor microenvironment release neurotransmitters, neuroligins, chemokines, soluble growth factors, and membrane-bound growth factors that solid tumors leverage to drive their own survival and spread. Tumors express nerve-specific growth factors and microRNAs that support local neurons and guide neuronal growth into tumors. The development of feed-forward relationships between tumors and neurons allows tumors to use the perineural space as a sanctuary from therapy. Tumor denervation slows tumor growth in animal models, demonstrating the innervation dependence of growing tumors. Further in vitro and in vivo experiments have identified many of the secreted signaling molecules (e.g., acetylcholine, nerve growth factor) that are passed between neurons and cancer cells, as well as the major signaling pathways (e.g., MAPK/EGFR) involved in these trophic interactions. The molecules involved in these signaling pathways serve as potential biomarkers of disease. Additionally, new treatment strategies focus on using small molecules, receptor agonists, nerve-specific toxins, and surgical interventions to target tumors, neurons, and immune cells of the tumor microenvironment, thereby severing the interactions between tumors and surrounding neurons. This article discusses the mechanisms underlying the trophic relationships formed between neurons and tumors and explores the emerging therapies stemming from this work.

Neuronal MT1-MMP mediates ECM clearance and Lrp4 cleavage for agrin deposition and signaling in presynaptic development

Agrin is a crucial factor that induces postsynaptic differentiation at neuromuscular junctions (NMJs), but how secreted agrin is locally deposited in the context of extracellular matrix (ECM) environment and its function in presynaptic differentiation remain largely unclear. Here, we report that the proteolytic activity of neuronal membrane-type 1 matrix metalloproteinase (MT1-MMP; also known as MMP14) facilitates agrin deposition and signaling during presynaptic development at NMJs. Firstly, agrin deposition along axons exhibits a time-dependent increase in cultured neurons that requires MMP-mediated focal ECM degradation. Next, local agrin stimulation induces the clustering of mitochondria and synaptic vesicles, two well-known presynaptic markers, and regulates vesicular trafficking and surface insertion of MT1-MMP. MMP inhibitor or MT1-MMP knockdown suppresses agrin-induced presynaptic differentiation, which can be rescued by treatment with the ectodomain of low-density lipoprotein receptor-related protein 4 (Lrp4). Finally, neuronal MT1-MMP knockdown inhibits agrin deposition and nerve-induced acetylcholine receptor clustering in nerve-muscle co-cultures and affects synaptic structures at Xenopus NMJs in vivo Collectively, our results demonstrate a previously unappreciated role of agrin, as well as dual functions of neuronal MT1-MMP proteolytic activity in orchestrating agrin deposition and signaling, in presynaptic development.

Targeting neurotrophic factors: Novel approaches to musculoskeletal pain

Chronic pain represents a substantial unmet medical need globally. In recent years, the quest for a new generation of novel, safe, mechanism-based analgesic treatments has focused on neurotrophic factors, a large group of secreted proteins that control the growth and survival of different populations of neurons, but that postnatally are involved in the genesis and maintenance of pain, with biological activity in both the periphery and the central nervous system. In this narrative review, we discuss the two families of neurotrophic proteins that have been extensively studied for their role in pain: first, the neurotrophins, nerve growth factor (NGF) and brain-derived growth factor (BDNF), and secondly, the GDNF family of ligands (GFLs). We provide an overview of the pain pathway, and the pain-producing effects of these different proteins. We summarize accumulating preclinical and clinical findings with a focus on musculoskeletal pain, and on osteoarthritis in particular, because the musculoskeletal system is the most prevalent source of chronic pain and of disability, and clinical testing of these novel agents - often biologics- is most advanced in this area.

Controlling properties of human neural progenitor cells using 2D and 3D conductive polymer scaffolds

Human induced pluripotent stem cell-derived neural progenitor cells (hNPCs) are a promising cell source for stem cell transplantation to treat neurological diseases such as stroke and peripheral nerve injuries. However, there have been limited studies investigating how the dimensionality of the physical and electrical microenvironment affects hNPC function. In this study, we report the fabrication of two- and three-dimensional (2D and 3D respectively) constructs composed of a conductive polymer to compare the effect of electrical stimulation of hydrogel-immobilized hNPCs. The physical dimension (2D vs 3D) of stimulating platforms alone changed the hNPCs gene expression related to cell proliferation and metabolic pathways. The addition of electrical stimulation was critical in upregulating gene expression of neurotrophic factors that are important in regulating cell survival, synaptic remodeling, and nerve regeneration. This study demonstrates that the applied electrical field controls hNPC properties depending on the physical nature of stimulating platforms and cellular metabolic states. The ability to control hNPC functions can be beneficial in understanding mechanistic changes related to electrical modulation and devising novel treatment methods for neurological diseases.

Intravenous infusion of iPSC-derived neural precursor cells increases acid β-glucosidase function in the brain and lessens the neuronopathic phenotype in a mouse model of Gaucher disease

Gaucher disease (GD) is caused by GBA1 mutations leading to functional deficiency of acid-β-glucosidase (GCase). No effective treatment is available for neuronopathic GD (nGD). A subclass of neural stem and precursor cells (NPCs) expresses VLA4 (integrin α4β1, very late antigen-4) that facilitates NPC entry into the brain following intravenous (IV) infusion. Here, the therapeutic potential of IV VLA4+NPCs was assessed for nGD using wild-type mouse green fluorescent protein (GFP)-positive multipotent induced pluripotent stem cell (iPSC)-derived VLA4+NPCs. VLA4+NPCs successfully engrafted in the nGD (4L;C*) mouse brain. GFP-positive cells differentiated into neurons, astrocytes and oligodendrocytes in the brainstem, midbrain and thalamus of the transplanted mice and significantly improved sensorimotor function and prolonged life span compared to vehicle-treated 4L;C* mice. VLA4+NPC transplantation significantly decreased levels of CD68 and glial fibrillary acidic protein, as well as TNFα mRNA levels in the brain, indicating reduced neuroinflammation. Furthermore, decreased Fluoro-Jade C and NeuroSilver staining suggested inhibition of neurodegeneration. VLA4+NPC-engrafted 4L;C* midbrains showed 35% increased GCase activity, reduced substrate [glucosylceramide (GC, -34%) and glucosylsphingosine (GS, -11%)] levels and improved mitochondrial oxygen consumption rates in comparison to vehicle-4L;C* mice. VLA4+NPC engraftment in 4L;C* brain also led to enhanced expression of neurotrophic factors that have roles in neuronal survival and the promotion of neurogenesis. This study provides evidence that iPSC-derived NPC transplantation has efficacy in an nGD mouse model and provides proof of concept for autologous NPC therapy in nGD.

Neuroprotective effects of lovastatin in the pilocarpine rat model of epilepsy according to the expression of neurotrophic factors

Studies have suggested that neurotrophic factors (NTFs) are involved in the status epilepticus development. This indicates their essential role in mediating acquired epileptic conditions. Therefore, modulating the expression of NTFs may inhibit seizure-induced cell loss in the epileptic lesions. In this study, we examined the anti-apoptotic, anti-necrotic and regulatory effects of lovastatin on the expression of NTFs in the pilocarpine rat model of temporal lobe epilepsy (TLE). A total of 32 male Wistar rats were divided into 4 groups (n = 8 per group): i) normal; ii) non-treated epileptic group [intraperitoneal (i.p.) administration of 350-400 mg/kg pilocarpine]; iii) treatment group (pilocarpine-treated rats treated followed by 5 mg/kg lovastatin); and iv) vehicle epileptic rats treated with Carboxymethyl cellulose (CMC). Animals that had a behavioral score of 4-5 according to the Racine scale were selected for study participation. Three days after the first seizure, pilocarpine-treated rats received i.p. injections of lovastatin for 14 days. The rats were killed and prepared for histopathologic analysis as well as real-time RT-PCR 17 days after the first seizure. The results of this study showed increased mRNA expression of glial cell line-derived neurotrophic factor (GDNF) and Ciliary neurotrophic factor (CNTF) and decreased expressions of Brain-derived neurotrophic factor (BDNF), Neurotrophin-3 (NT-3), and Neurotrophin-4 (NT-4) mRNA in the epileptic rats treated with lovastatin. Histological analysis of neurodegeneration in the brain sections showed that the number of hippocampal apoptotic and necrotic cells significantly decreased in the treatment groups. Furthermore, numerical density of neurons per area was significantly higher in the treated groups compared with the untreated groups. Collectively, the results of this study have shown that lovastatin could attenuate seizure-induced expression of neurotrophic factors and consequently reduce hippocampal cell death in the pilocarpine rat model of TLE.

FGF family members differentially regulate maturation and proliferation of stem cell-derived astrocytes

The glutamate transporter 1 (GLT1) is upregulated during astrocyte development and maturation in vivo and is vital for astrocyte function. Yet it is expressed at low levels by most cultured astrocytes. We previously showed that maturation of human and mouse stem cell-derived astrocytes – including functional glutamate uptake – could be enhanced by fibroblast growth factor (FGF)1 or FGF2. Here, we examined the specificity and mechanism of action of FGF2 and other FGF family members, as well as neurotrophic and differentiation factors, on mouse embryonic stem cell-derived astrocytes. We found that some FGFs – including FGF2, strongly increased GLT1 expression and enhanced astrocyte proliferation, while others (FGF16 and FGF18) mainly affected maturation. Interestingly, BMP4 increased astrocytic GFAP expression, and BMP4-treated astrocytes failed to promote the survival of motor neurons in vitro. Whole transcriptome analysis showed that FGF2 treatment regulated multiple genes linked to cell division, and that the mRNA encoding GLT1 was one of the most strongly upregulated of all astrocyte canonical markers. Since GLT1 is expressed at reduced levels in many neurodegenerative diseases, activation of this pathway is of potential therapeutic interest. Furthermore, treatment with FGFs provides a robust means for expansion of functionally mature stem cell-derived astrocytes for preclinical investigation.

Exploring the potential role of sonic hedgehog cell signalling pathway in antidepressant effects of nicotine in chronic unpredictable mild stress rat model

Nicotine is the most common and highly addictive drug of abuse, associated with several life-threatening diseases and high mortality. Nicotine abuse is the concerted effort to feel reward and fight depression in depressed individuals. The underlying mechanism of nicotine is to activate the brain reward system in the central nervous system and provide an antidepressant effect. Antidepressants provide their therapeutic effect by stimulating hippocampal neurogenesis, which can be correlated with brain derived neurotrophic factor (BDNF) expression in the hippocampus. BDNF interacts with Wnt/β-catenin and sonic hedgehog (Shh) signalling cascade to stimulate hippocampal neurogenesis. Shh is the marker of hippocampal neurogenesis and also involved in the neuropathology of depression. But knowledge in this area to identify the potential therapeutic target is limited. In our study, we explored the role of BDNF, Wnt/β-catenin and Shh signalling in depression and the involvement of these signalling pathways in providing an antidepressant effect by nicotine. Our investigations showed that chronic unpredictable mild stress induced depression results declined expression of BDNF, Wnt/β-catenin, Shh and its downstream transcription factors GLI1/2/3 and NKX2.2 in the hippocampus of male Wistar rat. Moreover, we also observed that nicotine administration increased the expression of these signalling molecules in providing the antidepressant effects.

Theobromine Improves Working Memory by Activating the CaMKII/CREB/BDNF Pathway in Rats

Theobromine (TB) is a primary methylxanthine found in cacao beans. cAMP-response element-binding protein (CREB) is a transcription factor, which is involved in different brain processes that bring about cellular changes in response to discrete sets of instructions, including the induction of brain-derived neurotropic factor (BDNF). Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) has been strongly implicated in the memory formation of different species as a key regulator of gene expression. Here we investigated whether TB acts on the CaMKII/CREB/BDNF pathway in a way that might improve the cognitive and learning function in rats. Male Wistar rats (5 weeks old) were divided into two groups. For 73 days, the control rats (CN rats) were fed a normal diet, while the TB-fed rats (TB rats) received the same food, but with a 0.05% TB supplement. To assess the effects of TB on cognitive and learning ability in rats: The radial arm maze task, novel object recognition test, and Y-maze test were used. Then, the brain was removed and the medial prefrontal cortex (mPFC) was isolated for Western Blot, real-time PCR and enzyme-linked immunosorbent assay. Phosphorylated CaMKII (p-CaMKII), phosphorylated CREB (p-CREB), and BDNF level in the mPFC were measured. In all the behavior tests, working memory seemed to be improved by TB ingestion. In addition, p-CaMKII and p-CREB levels were significantly elevated in the mPFC of TB rats in comparison to those of CN rats. We also found that cortical BDNF protein and mRNA levels in TB rats were significantly greater than those in CN rats. These results suggest that orally supplemented TB upregulates the CaMKII/CREB/BDNF pathway in the mPFC, which may then improve working memory in rats.

Neurotrophic Factors and Their Receptors Are Altered by the Mere Partial IGF-1 Deficiency

Neurotrophic factors (NTFs) are a relevant group of secreted proteins that modulate growth, differentiation, repair, and survival of neurons, playing a role in the maintenance of the synaptic unions, dendrites, and axons and also being crucial for peripheral nervous system development and regulating plasticity in the adult central nervous system. On the other hand, insulin-like growth factor 1 (IGF-1) has been ascertained multiple beneficial actions in the brain: neuro-development, -protection, -genesis and plasticity. To further investigate the possible mechanisms underlying IGF-1 deficiency in the establishment of neurological disease, microarray and reverse transcription polymerase chain reaction gene expression analyses coupled with in silico processing were performed in an experimental model of partial IGF-1 deficiency. Results show that the mere IGF-1 deficiency seems to be responsible for an altered expression of genes coding for neurotrophic factors (particularly ciliary neurotrophic factor and mesencephalic astrocyte-derived neurotrophic factor), their receptors and signaling pathways (specially RET). The presented findings support that IGF-1 deficiency might be involved in the establishment and progression of neurodegenerative disorders.

Screening of brain-derived neurotrophic factor (BDNF) single nucleotide polymorphisms and plasma BDNF levels among Malaysian major depressive disorder patients

Background

Brain-derived neurotrophic factor (BDNF) is a neurotrophin found in abundance in brain regions such as the hippocampus, cortex, cerebellum and basal forebrain. It has been associated with the risk of susceptibility to major depressive disorder (MDD). This study aimed to determine the association of three BDNF variants (rs6265, rs1048218 and rs1048220) with Malaysian MDD patients.

Methods

The correlation of these variants to the plasma BDNF level among Malaysian MDD patients was assessed. A total of 300 cases and 300 matched controls recruited from four public hospitals within the Klang Valley of Selangor State, Malaysia and matched for age, sex and ethnicity were screened for BDNF rs6265, rs1048218 and rs1048220 using high resolution melting (HRM).

Findings

BDNF rs1048218 and BDNF rs1048220 were monomorphic and were excluded from further analysis. The distribution of the alleles and genotypes for BDNF rs6265 was in Hardy-Weinberg equilibrium for the controls (p = 0.13) but was in Hardy Weinberg disequilibrium for the cases (p = 0.011). Findings from this study indicated that having BDNF rs6265 in the Malaysian population increase the odds of developing MDD by 2.05 folds (95% CI = 1.48–3.65). Plasma from 206 cases and 206 controls were randomly selected to measure the BDNF level using enzyme-linked immunosorbent assay (ELISA). A significant decrease in the plasma BDNF level of the cases as compared to controls (p<0.0001) was observed. However, there was no evidence of the effect of the rs6265 genotypes on the BDNF level indicating a possible role of other factors in modulating the BDNF level that warrants further investigation.

Conclusion

The study indicated that having the BDNF rs6265 allele (A) increase the risk of developing MDD in the Malaysian population suggesting a possible role of BDNF in the etiology of the disorder.

Sprouty1 regulates neuritogenesis and survival of cortical neurons

In multicellular organisms, receptor tyrosine kinases (RTKs) control a variety of cellular processes, including cell proliferation, differentiation, migration, and survival. Sprouty (SPRY) proteins represent an important class of ligand-inducible inhibitors of RTK-dependent signaling pathways. Here, we investigated the role of SPRY1 in cells of the central nervous system (CNS). Expression of SPRY1 was substantially higher in neural stem cells than in cortical neurons and was increased during neuronal differentiation of cortical neurons. We found that SPRY1 was a direct target gene of the CNS-specific microRNA, miR-124 and miR-132. In primary cultures of cortical neurons, the neurotrophic factors brain-derived neurotrophic factor (BDNF) and Basic fibroblast growth factor (FGF2) downregulated SPRY1 expression to positively regulate their own functions. In immature cortical neurons and mouse N₂ A cells, we found that overexpression of SPRY1 inhibited neurite development, whereas knockdown of SPRY1 expression promoted neurite development. In mature neurons, overexpression of SPRY1 inhibited the prosurvival effects of both BDNF and FGF2 on glutamate-mediated neuronal cell death. SPRY1 was also upregulated upon glutamate treatment in mature neurons and partially contributed to the cytotoxic effect of glutamate. Together, our results indicate that SPRY1 contributes to the regulation of CNS functions by influencing both neuronal differentiation under normal physiological processes and neuronal survival under pathological conditions.

Effects of Taurine on Alterations of Neurobehavior and Neurodevelopment Key Proteins Expression in Infant Rats by Exposure to Hexabromocyclododecane

Hexabromocyclododecanes (HBCDs) is a widely used flame retardant. Studies have found that HBCDs has toxic effects on endocrine and neural development, leading to adverse effects on behavior, learning and memory. This study aimed to investigate the protective effects of taurine on cognitive function, neurotrophic factors expression of infant rats exposured to HBCDs. Sprague-Dawley rats of 10-days old were oral gavaged of different doses (0.3, 3 and 30 mg/kg) of HBCDs and 30 mg/kg HBCDs with 300 mg/kg taurine for 60 consecutive days. Rat cognitive function was detected by the method of Morris water maze test. The protein expressions of brain derived neurotrophic factor (BDNF), nerve growth factor (NGF) and fibroblast growth factor (FGF) were assayed by Western-blotting. Results showed that rats exposed to HBCDs significantly declined rats spatial learning and memory ability by increasing the latency time of seeking the platform (P < 0.05), decreasing the numbers that each rat had crossed the non-exits and the time spent in the target quadrant as compared with those in control rats (P < 0.05). Taurine treatment significantly reversed the effects of HBCDs. Western-blotting results showed that expression of BDNF, NGF and FGF proteins in the low dose group were obviously increased compared with those in control rats (P < 0.01), and middle-dose and high dose groups significantly decreased. Taurine treatment increased BDNF and NGF expression as compared with high dose groups while Taurine seemed to have no effects on FGF. These result suggested that higher doses of HBCDs early exposure in the developing rats could decrease neurotrophic factors including BDNF, NGF, FGF, which have an impact on neural development, damage on learning and memory.

Neurodegenerative Diseases: Regenerative Mechanisms and Novel Therapeutic Approaches

Regeneration refers to regrowth of tissue in the central nervous system. It includes generation of new neurons, glia, myelin, and synapses, as well as the regaining of essential functions: sensory, motor, emotional and cognitive abilities. Unfortunately, regeneration within the nervous system is very slow compared to other body systems. This relative slowness is attributed to increased vulnerability to irreversible cellular insults and the loss of function due to the very long lifespan of neurons, the stretch of cells and cytoplasm over several dozens of inches throughout the body, insufficiency of the tissue-level waste removal system, and minimal neural cell proliferation/self-renewal capacity. In this context, the current review summarized the most common features of major neurodegenerative disorders; their causes and consequences and proposed novel therapeutic approaches.

Neurobiology of depression: A neurodevelopmental approach

OBJECTIVES

The main aims of this paper are to review and evaluate the neurobiology of the depressive syndrome from a neurodevelopmental perspective.

METHODS

An English language literature search was performed using PubMed.

RESULTS

Depression is a complex syndrome that involves anatomical and functional changes that have an early origin in brain development. In subjects with genetic risk for depression, early stress factors are able to mediate not only the genetic risk but also gene expression. There is evidence that endocrine and immune interactions have an important impact on monoamine function and that the altered monoamine signalling observed in the depressive syndrome has a neuro-endocrino-immunological origin early in the development.

CONCLUSIONS

Neurodevelopment is a key aspect to understand the whole neurobiology of depression.

Methamphetamine augment HIV-1 Tat mediated memory deficits by altering the expression of synaptic proteins and neurotrophic factors

Methamphetamine (METH) abuse is common among individuals infected with HIV-1 and has been shown to affect HIV replication and pathogenesis. These HIV-1 infected individuals also exhibit greater neuronal injury and higher cognitive decline. HIV-1 proteins, specifically gp120 and HIV-1 Tat, have been earlier shown to affect neurocognition. HIV-1 Tat, a viral protein released early during HIV-1 replication, contributes to HIV-associated neurotoxicity through various mechanisms including production of pro-inflammatory cytokines, reactive oxygen species and dysregulation of neuroplasticity. However, the combined effect of METH and HIV-1 Tat on neurocognition and its potential effect on neuroplasticity mechanisms remains largely unknown. Therefore, the present study was undertaken to investigate the combined effect of METH and HIV-1 Tat on behavior and on the expression of neuroplasticity markers by utilizing Doxycycline (DOX)-inducible HIV-1 Tat (1-86) transgenic mice. Expression of Tat in various brain regions of these mice was confirmed by RT-PCR. The mice were administered with an escalating dose of METH (0.1 mg/kg to 6 mg/kg, i.p) over a 7-day period, followed by 6 mg/kg, i.p METH twice a day for four weeks. After three weeks of METH administration, Y maze and Morris water maze assays were performed to determine the effect of Tat and METH on working and spatial memory, respectively. Compared with controls, working memory was significantly decreased in Tat mice that were administered METH. Moreover, significant deficits in spatial memory were also observed in Tat-Tg mice that were administered METH. A significant reduction in the protein expressions of synapsin 1, synaptophysin, Arg3.1, PSD-95, and BDNF in different brain regions were also observed. Expression levels of Calmodulin kinase II (CaMKII), a marker of synaptodendritic integrity, were also significantly decreased in HIV-1 Tat mice that were treated with METH. Together, this data suggests that METH enhances HIV-1 Tat-induced memory deficits by reducing the expression of pre- and postsynaptic proteins and neuroplasticity markers, thus providing novel insights into the molecular mechanisms behind neurocognitive impairments in HIV-infected amphetamine users.

Brain-derived neurotrophic factor Val66Met genotype and ovarian steroids interactively modulate working memory-related hippocampal function in women: a multimodal neuroimaging study

Preclinical evidence suggests that the actions of ovarian steroid hormones and brain-derived neurotrophic factor (BDNF) are highly convergent on brain function. Studies in humanized mice document an interaction between estrus cycle-related changes in estradiol secretion and BDNF Val⁶⁶Met genotype on measures of hippocampal function and anxiety-like behavior. We believe our multimodal imaging data provide the first demonstration in women that the effects of the BDNF Val/Met polymorphism on hippocampal function are selectively modulated by estradiol. In a 6-month pharmacological hormone manipulation protocol, healthy, regularly menstruating, asymptomatic women completed positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) scans while performing the n-back working memory task during three hormone conditions: ovarian suppression induced by the gonadotropin-releasing hormone agonist, leuprolide acetate; leuprolide plus estradiol; and leuprolide plus progesterone. For each of the three hormone conditions, a discovery data set was obtained with oxygen-15 water regional cerebral blood flow PET in 39 healthy women genotyped for BDNF Val⁶⁶Met, and a confirmatory data set was obtained with fMRI in 27 women. Our results, in close agreement across the two imaging platforms, demonstrate an ovarian hormone-by-BDNF interaction on working memory-related hippocampal function (PET: F_2,37=9.11, P=0.00026 uncorrected, P=0.05, familywise error corrected with small volume correction; fMRI: F_2,25=5.43, P=0.01, uncorrected) that reflects differential hippocampal recruitment in Met carriers but only in the presence of estradiol. These findings have clinical relevance for understanding the neurobiological basis of individual differences in the cognitive and behavioral effects of ovarian steroids in women, and may provide a neurogenetic framework for understanding neuropsychiatric disorders related to reproductive hormones as well as illnesses with sex differences in disease expression and course.

Pathobiological expression of the brain-derived neurotrophic factor (BDNF) in cerebellar cortex of sudden fetal and infant death victims

Brain-derived neurotrophic factor (BDNF), a neurotrophin of the central nervous system, is able to regulate neuronal differentiation and modulate synaptic plasticity, being particularly involved in the development of the cerebellar cortical structure. The main aim of this study was to delineate, by immunohistochemistry, the BDNF expression in human cerebellar cortex of victims of fetal and infant death. The study was performed on a total of 45 cases, aged between 25 gestational weeks and 6 postnatal months, including 29 victims of sudden fetal and infant death and 16 age-matched subjects who died of known causes (Controls). We observed, in sudden death groups compared with Controls, a significantly higher incidence of defective BDNF expression in granule layers of the cerebellar cortex, which was particularly evident in the posterior lobule, a region that participates in respiratory control. These results were related to maternal smoking, allowing to speculate that nicotine, in addition to the well-known damages, can exert adverse effects during cerebellar cortex development, in particular in hindering the BDNF expression in the posterior lobule. This implies modifications of synaptic transmission in the respiratory circuits, with obvious deleterious consequences on survival.

miRNA profiling of NurOwn®: mesenchymal stem cells secreting neurotrophic factors

BACKGROUND

MSC-NTF cells are Mesenchymal Stromal Cells (MSC) induced to express high levels of neurotrophic factors (NTFs) using a culture-medium based approach. MSC-NTF cells have been successfully studied in clinical trials for Amyotrophic Lateral Sclerosis (ALS) patients. MicroRNAs (miRNA) are short non-coding RNA molecules that coordinate post-transcriptional regulation of multiple gene targets. The purpose of this study was to determine whether the miRNA profile could provide a tool for MSC-NTF cell characterization and to distinguish them from the matched MSC from which they are derived.

METHODS

NTF secretion in the culture supernatant of MSC-NTF cells was evaluated by ELISA assays. The Agilent microarray miRNA platform was used for pairwise comparisons of MSC-NTF cells to MSC. The differentially expressed miRNAs and putative mRNA targets were validated using qPCR analyses.

RESULTS

Principal component analysis revealed two distinct clusters based on cell type (MSC and MSC-NTFs). Nineteen miRNAs were found to be upregulated and 22 miRNAs were downregulated in MSC-NTF cells relative to the MSC cells of origin. Further validation of differentially expressed miRNAs confirmed that miR-3663 and miR-132 were increased 18.5- and 4.06-fold, respectively while hsa-miR-503 was reduced more than 15-fold, suggesting that miRNAs could form the basis of an MSC-NTF cell characterization assay. In an analysis of the miRNA mRNA targets, three mRNA targets of hsa-miR-132-3p (HN-1, RASA1 and KLH-L11) were found to be significantly downregulated.

CONCLUSIONS

We have demonstrated that MSC-NTF cells can be distinguished from their MSCs of origin by a unique miRNA expression profile.

TRIAL REGISTRATION

Clinicaltrial.gov identifier NCT01777646 . Registered 12 December 2012.

Association analysis between mitogen-activated protein/extracellular signal-regulated kinase (MEK) gene polymorphisms and depressive disorder in the Han Chinese population

BACKGROUND

Recent research findings suggest that BDNF and BDNF signaling pathways participate in the development of major depressive disorder. Mitogen-activated extracellular signal-regulated kinase (MEK) is the most important kinase in the extracellular signal-regulated kinase pathway, and the extracellular signal-regulated kinase pathway is the key signaling pathway of BDNF, so it may play a role in development of depressive disorder. The aim of this study is to investigate the association between polymorphisms of the MAP2K1 (also known as MEK) gene and depressive disorder.

RESULTS

Three single nucleotide polymorphisms (SNPs), were significantly associated with depressive disorder: rs1549854 (p = 0.006), rs1432441 (p = 0.025), and rs7182853 (p = 0.039). When subdividing the sample by gender, two of the SNPs remained statistically associated with depressive disorder in females: rs1549854 (p = 0.013) and rs1432441 (p = 0.04).

CONCLUSION

The rs1549854 and rs1432441 polymorphisms of the MAP2K1 gene may be associated with major depressive disorder, especially in females. This study is the first to report that the MAP2K1 gene may be a genetic marker for depressive disorder.

Ciliary neurotrophic factor (CNTF) delivery to retina: an overview of current research advancements

The intraocular administration of the ciliary neurotrophic factor (CNTF) has been found to attenuate the photoreceptor degeneration and preserve retinal functions in the animal research models of the inherited or induced retinal disease. Studies with the aim of CNTF transfer to the posterior segment inside the eye have been directed to determine the best method for its administration. An ideal delivery method would overcome the eye drug elimination mechanisms or barriers and provide the sustained release of the CNTF into retina in the safest fashion with the minimum harm to the quality of life. This review focuses on the present state of CNTF delivery to retina, also provides an overview of available technologies and their challenges.

Neuronal survival in the brain: neuron type-specific mechanisms

Neurogenic regions of mammalian brain produce many more neurons that will eventually survive and reach a mature stage. Developmental cell death affects both embryonically produced immature neurons and those immature neurons that are generated in regions of adult neurogenesis. Removal of substantial numbers of neurons that are not yet completely integrated into the local circuits helps to ensure that maturation and homeostatic function of neuronal networks in the brain proceed correctly. External signals from brain microenvironment together with intrinsic signaling pathways determine whether a particular neuron will die. To accommodate this signaling, immature neurons in the brain express a number of transmembrane factors as well as intracellular signaling molecules that will regulate the cell survival/death decision, and many of these factors cease being expressed upon neuronal maturation. Furthermore, pro-survival factors and intracellular responses depend on the type of neuron and region of the brain. Thus, in addition to some common neuronal pro-survival signaling, different types of neurons possess a variety of 'neuron type-specific' pro-survival constituents that might help them to adapt for survival in a certain brain region. This review focuses on how immature neurons survive during normal and impaired brain development, both in the embryonic/neonatal brain and in brain regions associated with adult neurogenesis, and emphasizes neuron type-specific mechanisms that help to survive for various types of immature neurons. Importantly, we mainly focus on in vivo data to describe neuronal survival specifically in the brain, without extrapolating data obtained in the PNS or spinal cord, and thus emphasize the influence of the complex brain environment on neuronal survival during development.

Circadian Rhythms in Plasma Brain-derived Neurotrophic Factor Differ in Men and Women

The measurement of circulating levels of brain-derived neurotrophic factor (BDNF) has been proposed to be a marker of disease and an indicator of recovery. Thus, knowing the temporal pattern and influence of potential circadian rhythms is important. Although several studies have measured BDNF at different times of day, no studies have done so while controlling for potential masking influences such as sleep and activity. Further, no previous study has examined circadian rhythms within individuals. We examined circadian rhythms in plasma BDNF while minimizing masking from behavioral and environmental factors using a 30-h constant routine (CR) protocol. In a sample of 39 healthy adults, we found significant circadian rhythms in 75% of women and 52% of men. The timing of the acrophase of the BDNF rhythm, however, was unrelated to clock time in women, while it was related to clock time in men. These results indicate that the use of single-sample measures of plasma BDNF as a marker of disease will be unreliable, especially in women. Repeated plasma BDNF samples over a 24-h period within individuals would be needed to reveal abnormalities related to disease states.

Brain-derived Neurotrophic Factor Is Associated With Disease Severity and Clinical Outcome in Ugandan Children Admitted to Hospital With Severe Malaria

BACKGROUND

Malaria remains a leading cause of childhood death and neurologic disability in sub-Saharan Africa. Here, we test the hypothesis that malaria-induced alterations to circulating brain-derived neurotrophic factor (BDNF) are associated with poor clinical outcomes in children with severe malaria.

METHODS

We quantified BDNF (by enzyme-linked immunosorbent assay) in plasma samples collected [at presentation (day 1), day 3 and day 14], during a prospective study of Ugandan children admitted to hospital with severe malaria (n = 179).

RESULTS

BDNF concentration at presentation (day 1) was lower in children with cerebral malaria (P < 0.01), coma (P < 0.01), Lambaréné Organ Dysfunction Score >1 (P < 0.05) and respiratory distress (P < 0.01). Higher BDNF concentration at presentation was associated with shorter time to coma recovery [hazard ratio = 1.655 (1.194-2.293); P = 0.002] and a reduced odds ratio of disability [0.50 (0.27-0.94); P = 0.047] and death [0.45 (0.22-0.92); P = 0.035]. BDNF concentration was lower on day 1 and increased in children surviving severe malaria (day 14; P < 0.0001).

CONCLUSIONS

Our findings provide the new evidence linking circulating BDNF with disease severity, coma recovery and clinical outcome in children with severe malaria.

Resveratrol ameliorates chronic unpredictable mild stress-induced depression-like behavior: involvement of the HPA axis, inflammatory markers, BDNF, and Wnt/β-catenin pathway in rats

Classic antidepressant drugs are modestly effective across the population and most are associated with intolerable side effects. Recently, numerous lines of evidence suggest that resveratrol (RES), a natural polyphenol, possesses beneficial therapeutic activity for depression. The aim of the present study was to explore whether RES exhibits an antidepressant-like effect in a depression model and to explore the possible mechanism. A depression model was established via chronic unpredictable mild stress (CUMS), after which the model rats in the RES and fluoxetine groups received a daily injection of RES or fluoxetine, respectively. The sucrose preference test, open field test, and forced swimming test were used to explore the antidepressant-like effects of RES. The activity of the hypothalamic-pituitary-adrenal (HPA) axis was evaluated by detecting the plasma corticosterone concentration and hypothalamic mRNA expression of corticotrophin-releasing hormone. The plasma interleukin-6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor-α (TNF-α) concentrations were measured by enzyme-linked immunosorbent assay. Hippocampal protein expression of brain-derived neurotrophic factor (BDNF) and the Wnt/β-catenin pathway were analyzed by western blot. The results showed that RES relieved depression-like behavior of CUMS rats, as indicated by the increased sucrose preference and the decreased immobile time. Rats that received RES treatment exhibited reduced plasma corticosterone levels and corticotrophin-releasing hormone mRNA expression in the hypothalamus, suggesting that the hyperactivity of the HPA axis in CUMS rats was reversed by RES. Moreover, after RES treatment, the rats exhibited increased plasma IL-6, CRP, and TNF-α concentrations. Furthermore, RES treatment upregulated the hippocampal protein levels of BDNF and the relative ratio of p-β-catenin/β-catenin while downregulating the relative ratio of p-GSK-3β/GSK-3β. Our findings suggest that RES improved depressive behavior in CUMS rats by downregulating HPA axis hyperactivity, increasing BDNF expression and plasma IL-6, CRP, and TNF-α concentrations, and regulating the hippocampal Wnt/β-catenin pathway.

Neurogenesis in Stroke Recovery

Stroke, resulting from limited blood flow to the brain, is one of the most important causes of morbidity and mortality worldwide. Stroke is classified as ischemic, due to lack of blood flow, or hemorrhagic, due to bleeding. Because 87 % of strokes are classified as ischemic, this type will be the predominant focus of this review. Except for thrombolytic therapy, there is no established treatment to reduce the neurological deficits caused by ischemic stroke. Therefore, it is necessary to develop new therapeutic strategies designed to improve neurological functions after ischemic stroke. Recently, therapies to enhance neurogenesis after ischemic stroke have been investigated. However, these approaches have not led to successful clinical outcomes. This review addresses the pathophysiology of stroke, neurogenesis after stroke, and how to stimulate these processes based on the current literature. Finally, ongoing clinical trials to improve neurological functions after stroke by enhancing neurogenesis are discussed in this review.

The progress in optic nerve regeneration, where are we?

Optic nerve regeneration is an important area of research. It can be used to treat patients suffering from optic neuropathy and provides insights into the treatment of numerous neurodegenerative diseases. There are many hurdles impeding optic regeneration in mammals. The mammalian central nervous system is non-permissive to regeneration and intrinsically lacks the capacity for axonal regrowth. Any axonal injury also triggers a vicious cycle of apoptosis. Understanding these hurdles provides us with a rough framework to appreciate the essential steps to bring about optic nerve regeneration: enhancing neuronal survival, axon regeneration, remyelination and establishing functional synapses to the original neuronal targets. In this review article, we will go through current potential treatments for optic nerve regeneration, which includes neurotrophic factor provision, inflammatory stimulation, growth inhibition suppression, intracellular signaling modification and modeling of bridging substrates.

BDNF promotes the growth of human neurons through crosstalk with the Wnt/β-catenin signaling pathway via GSK-3β

Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal growth; however, the downstream regulatory mechanisms remain unclear. In this study, we investigated whether BDNF exerts its neurotrophic effects through the Wnt/β-catenin signaling pathway in human embryonic spinal cord neurons in vitro. We found that neuronal growth (soma size and average neurite length) was increased by transfection with a BDNF overexpression plasmid. Western blotting and real-time quantitative PCR showed that expression of the BDNF pathway components TrkB, PI3K, Akt and PLC-γ was increased by BDNF overexpression. Furthermore, the Wnt signaling factors Wnt, Frizzled and Dsh and the downstream target β-catenin were upregulated, whereas GSK-3β was downregulated. In contrast, when BDNF signaling was downregulated with BDNF siRNA, the growth of neurons was decreased. Furthermore, BDNF signaling factors, Wnt pathway components and β-catenin were all downregulated, whereas GSK-3β was upregulated. This suggests that BDNF affects the growth of neurons in vitro through crosstalk with Wnt signaling, and that GSK-3β may be a critical factor linking these two pathways. To evaluate this possibility, we treated neurons with 6-bromoindirubin-3'-oxime (BIO), a small molecule GSK-3β inhibitor. BIO reduced the effects of BDNF upregulation/downregulation on soma size and average neurite length, and suppressed the impact of BDNF modulation on the Wnt signaling pathway. Taken together, our findings suggest that BDNF promotes the growth of neurons in vitro through crosstalk with the Wnt/β-catenin signaling pathway, and that this interaction may be mediated by GSK-3β.

Back and forth in time: Directing age in iPSC-derived lineages

The advent of induced pluripotent stem cells (iPSC) has transformed the classic approach of studying human disease, providing in vitro access to disease-relevant cells from patients for the study of disease pathogenesis and for drug screening. However, in spite of the broad repertoire of iPSC-based disease models developed in recent years, increasing evidence suggests that this technology might not be fully suitable for the study of conditions of old age, such as neurodegeneration. The difficulty in recapitulating late-stage features of disease in cells of pluripotent origin is believed to be a discrepancy between the fetal-like nature of iPSC-progeny and the advanced age of onset of neurodegenerative syndromes. In parallel to the issue of functional immaturity known to affect derivatives of pluripotent cells, latest findings suggest that reprogramming also subjects cells to a process of "rejuvenation", giving rise to cells that are too "young" to manifest phenotypes of age-related diseases. Thus, following the significant progress in manipulating cellular fate, the stem cell field will now have to face the new challenge of controlling cellular age, in order to fully harness the potential of iPSC-technology to advance the research and cure of diseases of the aging brain. This article is part of a Special Issue entitled SI: Exploiting human neurons.

Brain-derived neurotrophic factor correlates with functional and cognitive impairment in non-disabled older individuals

We used a complete battery of geriatric and psychometric tests to evaluate whether plasma-borne brain-derived neurotrophic factor (BDNF), a master molecule in neuroplasticity, is associated with the severity of functional and cognitive impairment in non-disabled older individuals. There was a significant positive correlation between BDNF plasma concentrations and the Barthel index, a measurement of the ability of individuals to perform the activities of daily living (p=0.03) and the concentration subcategory measured with the mini mental state examination (MMSE) test (p = 0.01). Furthermore, plasma BDNF inversely and significantly correlated with the blood eosinophil count (p = 0.01), the total cholesterol concentration (p = 0.04), and high-density lipoprotein cholesterol (p=0.04). However, BDNF did not correlate with any other socio-demographic or clinical characteristics, other analytical parameters measured in the blood, or any other geriatric assessment scales. Our results suggest that BDNF may play a role in the pathophysiology of functional impairment in the elderly and in some aspects of cognitive function. However, more studies are needed to understand the relationship between circulating BDNF and functional impairment to determine if BDNF represents a candidate biomarker for this type of cognitive impairment.