Clinical Profile and Outcomes of Multisystem Inflammatory Syndrome in Children: A Multicentric Observational Study.

Background and objective Multisystem inflammatory syndrome in children (MIS-C) is a postinfectious, generalized, hyperimmune state and is potentially lethal. There is scarce data on the clinical presentation and epidemiology of MIS-C in India. In light of this, we conducted this study to describe clinical presentations and outcomes in children diagnosed with MIS-C. Methodology This was a 15-month hospital-based prospective observational study conducted in the Departments of Pediatrics at Jagannath Hospital and Hitech Medical College, Bhubaneswar. The study included all patients diagnosed with MIS-C and treated at these hospitals between May 1, 2020, and August 31, 2021. The inclusion criteria were as follows: patients who were reverse transcription-polymerase chain reaction (RT-PCR)-positive, antibody-positive, or had known contact with those infected with coronavirus disease 2019 (COVID-19). We reviewed patient medical records to collect demographic data such as age, sex, body mass index (BMI), duration of illness, clinical symptomatology, findings of initial echocardiography, and outcomes. We followed each case for three months. We analyzed descriptive statistics using percentages and means and conducted the statistical analysis using SPSS Statistics for Windows, Version 25.0. (IBM Corp., Armonk, NY). Results A total of 30 cases were included in the study, consisting of 16 boys (53.3%) and 14 girls (46.7%). The mean age of the study population was 6.7 years, and 43% had a BMI in the overweight range. All patients (100%) had a fever, 66.7% had lethargy (n=20), and 64.3% (n=19) had abdominal symptoms in the form of vomiting, diarrhea, and abdominal pain. Respiratory distress at admission was found in 16 cases (53.3%), while hypotension at admission was found in 18 (60%) cases. Our population's average duration of pediatric ICU stay was 3.7 ± 1.2 days, and the average duration of inotropy was 2.2 ± 0.5 days. Fifteen cases (50%) required only oxygen support; 10 (33%) required noninvasive ventilation, and only one patient required invasive ventilation. Twenty-two patients (74%) needed fluid boluses. Outcomes of coronary artery dilatations were favorable, regressing to normal (Z-score <2.5) in affected patients within 90 days of follow-up. Conclusions MIS-C has myriad presenting signs, symptoms, and severity. It is often associated with circulatory failure or shock. However, most patients demonstrated good early outcomes, improved left ventricle (LV) function, normalization of coronary abnormalities, and no mortality. This study provides additional data on the clinical presentation of MIS-C and highlights the importance of close, long-term follow-up monitoring of this patient population.

Impacts of partial to complete COVID-19 lockdown on NO2 and PM2.5 levels in major urban cities of Europe and USA.

SARS CoV-2 (COVID-19) coronavirus has been causing enormous suffering, death, and economic losses worldwide. There are rigorous containment measures on industries, non-essential business, transportation, and citizen mobility to check the spread. The lockdowns may have an advantageous impact on reducing the atmospheric pollutants. This study has analyzed the change in atmospheric pollutants, based on the Sentinel-5Ps and ground-station observed data during partial to complete lockdown period in 2020. Results revealed that the mean tropospheric NO2 concentration substantially dropped in 2020 due to lockdown against the same period in 2019 by 18-40% over the major urban areas located in Europe (i.e. Madrid, Milan, Paris) and the USA (i.e. New York, Boston, and Springfield). Conversely, urban areas with partial to no lockdown measures (i.e. Warsaw, Pierre, Bismarck, and Lincoln) exhibited a relatively lower dropdown in mean NO2 concentration (3 to 7.5%). The role of meteorological variability was found to be negligible. Nevertheless, the reduced levels of atmospheric pollutants were primarily attributed to the shutdown of vehicles, power plants, and industrial emissions. Improvement in air quality during COVID-19 may be temporary, but regulatory bodies should learn to reduce air pollution on a long-term basis concerning the trade-offs between the environment, society, and economic growth. The intersection of urban design, health, and environment should be addressed by policy-makers to protect public health and sustainable urban policies could be adopted to build urban resilience against any future emergencies.

Clinical Profile and Immediate Outcome of Multisystem Inflammatory Syndrome in Children Associated with COVID-19: A Multicentric Study.

INTRODUCTION: Following an asymptomatic or mildly symptomatic coronavirus disease (COVID-19), otherwise healthy children may develop serious manifestations in the form of cardiac, neurological, respiratory, gastrointestinal, and dermatologic dysfunction. Many such cases were being observed in Odisha, an eastern state of India, and have been reported from different health-care facilities. We related these unexplained serious manifestations to multisystem inflammatory syndrome associated with COVID-19 (MIS-C) and planned this study. METHODS: This retrospective observational study was carried out at the following three tertiary care centers: Kalinga Institute of Medical Sciences, Bhubaneswar; MKCG Medical College, Berhampur; and Jagannath Hospital, Bhubaneswar. The study population included all children aged from 1 month to 18 years admitted to the hospitals with MIS-C according to the WHO diagnostic criteria. All the data were analyzed by SPSS software. RESULTS: A total of 21 children were included in our study. Majority of the cases were male (76.2%), and the predominant age group was 6-10 years (47.6%). Common symptoms and signs in our observation included fever, pain abdomen, seizure, and hypotension. Most of these cases were positive for severe acute respiratory syndrome coronavirus antibody (80.95%). Response to immunotherapy was dramatic. Mortality (9%) of our study was higher than 1.8%-3% from that of Western literature. None of our patients had coronary abnormality, while two patients had mild cardiac dysfunction at discharge comparable to that of other studies. CONCLUSION: MIS-C following exposure to COVID-19 infection in children is a clinical syndrome, which needs early suspicion and appropriate intervention to prevent mortality.

Histone H1 improves regeneration after mouse spinal cord injury and changes shape and gene expression of cultured astrocytes.

BACKGROUND: We have shown that histone H1 is a binding partner for polysialic acid (PSA) and that it improves functional recovery, axon regrowth/sprouting, and target reinnervation after mouse femoral nerve injury. OBJECTIVE: Here, we analyzed whether histone H1 affects functional recovery, axon regrowth/sprouting, and target reinnervation after spinal cord injury of adult mice. Furthermore, we tested in vitro histone H1's effect on astrocytic gene expression, cell shape and migration as well as on cell survival of cultured motoneurons. METHODS: We applied histone H1 to compressed spinal cord and determined functional recovery and number of fibrillary acidic protein (GFAP)- and neuron-glial antigen 2 (NG2)- positive glial cells, which contribute to glial scarring. Histone H1's effect on migration of astrocytes, astrocytic gene expression and motoneuronal survival was determined using scratch-wounded astroglial monolayer cultures, astrocyte cultures for microarray analysis, and motoneuron cell culture under oxidative stress conditions, respectively. RESULTS: Histone H1 application improves locomotor functions and enhances monoaminergic and cholinergic reinnervation of the spinal cord. Expression levels of GFAP and NG2 around the lesion site were decreased in histone H1-treated mice relative to vehicle-treated mice six weeks after injury. Histone H1 reduced astrocytic migration, changed the shape of GFAP- and NG2-positive glial cells and altered gene expression. Gene ontology enrichment analysis indicated that in particular genes coding for proteins involved in proliferation, differentiation, migration and apoptosis are dysregulated. The up- and down-regulation of distinct genes was confirmed by qPCR and Western blot analysis. Moreover, histone H1 reduced hydrogen peroxide-induced cell death of cultured motoneurons. CONCLUSIONS: The combined observations indicate that histone H1 locally applied to the lesion site, improves regeneration after spinal cord injury. Some of these beneficial functions of histone H1 in vivo and in vitro can be attributed to its interaction with PSA-carrying neural cell adhesion molecule.

A combinatorial library of biodegradable polyesters enables non-viral gene delivery to post-mitotic human stem cell-derived polarized RPE monolayers.

Safe and effective delivery of DNA to post-mitotic cells, especially highly differentiated cells, remains a challenge despite significant progress in the development of gene delivery tools. Biodegradable polymeric nanoparticles (NPs) offer an array of advantages for gene delivery over viral vectors due to improved safety, carrying capacity, ease of manufacture, and cell-type specificity. Here we demonstrate the use of a high-throughput screening (HTS) platform to synthesize and screen a library of 148 biodegradable polymeric nanoparticles, successfully identifying structures that enable efficient transfection of human pluripotent stem cell differentiated human retinal pigment epithelial (RPE) cells with minimal toxicity. These NPs can deliver plasmid DNA (pDNA) to RPE monolayers more efficiently than leading commercially available transfection reagents. Novel synthetic polymers are described that enable high efficacy non-viral gene delivery to hard-to-transfect polarized human RPE monolayers, enabling gene loss- and gain-of-function studies of cell signaling, developmental, and disease-related pathways. One new synthetic polymer in particular, 3,3'-iminobis(N,N-dimethylpropylamine)-end terminated poly(1,5-pentanediol diacrylate-co-3 amino-1-propanol) (5-3-J12), was found to form self-assembled nanoparticles when mixed with plasmid DNA that transfect a majority of these human post-mitotic cells with minimal cytotoxicity. The platform described here can be utilized as an enabling technology for gene transfer to human primary and stem cell-derived cells, which are often fragile and resistant to conventional gene transfer approaches.

The polysialic acid mimetics idarubicin and irinotecan stimulate neuronal survival and neurite outgrowth and signal via protein kinase C.

Polysialic acid (PSA) is a large, negatively charged, linear homopolymer of alpha2-8-linked sialic acid residues. It is generated by two polysialyltransferases and attached to N- and/or O-linked glycans, and its main carrier is the neural cell adhesion molecule (NCAM). PSA controls the development and regeneration of the nervous system by enhancing cell migration, axon pathfinding, synaptic targeting, synaptic plasticity, by regulating the differentiation of progenitor cells and by modulating cell-cell and cell-matrix adhesions. In the adult, PSA plays a role in the immune system, and PSA mimetics promote functional recovery after nervous system injury. In search for novel small molecule mimetics of PSA that are applicable for therapy, we identified idarubicin, an antineoplastic anthracycline, and irinotecan, an antineoplastic agent of the topoisomerase I inhibitor class, as PSA mimetics using a competition enzyme-linked immunosorbent assay. Idarubicin and irinotecan compete with the PSA-mimicking peptide and colominic acid, the bacterial analog of PSA, for binding to the PSA-specific monoclonal antibody 735. Idarubicin and irinotecan stimulate neurite outgrowth and survival of cultured cerebellar neurons after oxidative stress via protein kinase C and Erk1/2 in a similar manner as colominic acid, whereas Fyn, casein kinase II and the phosphatase and tensin homolog are only involved in idarubicin and irinotecan-stimulated neurite outgrowth. These novel results show that the structure and function of PSA can be mimicked by the small organic compounds irinotecan and idarubicin which trigger the same signaling cascades as PSA, thus introducing the possibility of retargeting these drugs to treat nervous system injuries.

REEP6 mediates trafficking of a subset of Clathrin-coated vesicles and is critical for rod photoreceptor function and survival.

In retinal photoreceptors, vectorial transport of cargo is critical for transduction of visual signals, and defects in intracellular trafficking can lead to photoreceptor degeneration and vision impairment. Molecular signatures associated with routing of transport vesicles in photoreceptors are poorly understood. We previously reported the identification of a novel rod photoreceptor specific isoform of Receptor Expression Enhancing Protein (REEP) 6, which belongs to a family of proteins involved in intracellular transport of receptors to the plasma membrane. Here we show that loss of REEP6 in mice (Reep6-/-) results in progressive retinal degeneration. Rod photoreceptor dysfunction is observed in Reep6-/- mice as early as one month of age and associated with aberrant accumulation of vacuole-like structures at the apical inner segment and reduction in selected rod phototransduction proteins. We demonstrate that REEP6 is detected in a subset of Clathrin-coated vesicles and interacts with the t-SNARE, Syntaxin3. In concordance with the rod degeneration phenotype in Reep6-/- mice, whole exome sequencing identified homozygous REEP6-E75K mutation in two retinitis pigmentosa families of different ethnicities. Our studies suggest a critical function of REEP6 in trafficking of cargo via a subset of Clathrin-coated vesicles to selected membrane sites in retinal rod photoreceptors.

Genetic components in diabetic retinopathy.

Diabetic retinopathy (DR) is a serious complication of diabetes, which is fast reaching epidemic proportions worldwide. While tight glycemic control remains the standard of care for preventing the progression of DR, better insights into DR etiology require understanding its genetic basis, which in turn may assist in the design of novel treatments. During the last decade, genomic medicine is increasingly being applied to common multifactorial diseases such as diabetes and age-related macular degeneration. The contribution of genetics to the initiation and progression of DR has been recognized for some time, but the involvement of specific genes and genetic variants remains elusive. Several investigations are currently underway for identifying DR susceptibility loci through linkage studies, candidate gene approaches, and genome-wide association studies. Advent of next generation sequencing and high throughput genomic technologies, development of novel bioinformatics tools and collaborations among research teams should facilitate such investigations. Here, we review the current state of genetic studies in DR and discuss reported findings in the context of biochemical, cell biological and therapeutic advances. We propose the development of a consortium in India for genetic studies with large cohorts of patients and controls from limited geographical areas to stratify the impact of the environment. Uniform guidelines should be established for clinical phenotyping and data collection. These studies would permit identification of genetic loci for DR susceptibility in the Indian population and should be valuable for better diagnosis and prognosis, and for clinical management of this blinding disease.

Vinorelbine and epirubicin share common features with polysialic acid and modulate neuronal and glial functions.

Polysialic acid (PSA), a large, linear glycan composed of 8 to over 100 α2,8-linked sialic acid residues, modulates development of the nervous system by enhancing cell migration, axon pathfinding, and synaptic targeting and by regulating differentiation of progenitor cells. PSA also functions in developing and adult immune systems and is a signature of many cancers. In this study we identified vinorelbine, a semi-synthetic third generation vinca alkaloid, and epirubicin, an anthracycline and 4'-epimer of doxorubicin, as PSA mimetics. Similar to PSA, vinorelbine and epirubicin bind to the PSA-specific monoclonal antibody 735 and compete with the bacterial analog of PSA, colominic acid in binding to monoclonal antibody 735. Vinorelbine and epirubicin stimulate neurite outgrowth of cerebellar neurons via the neural cell adhesion molecule, via myristoylated alanine-rich C kinase substrate, and via fibroblast growth factor receptor, signaling through Erk pathways. Furthermore, the two compounds enhance process formation of Schwann cells and migration of cerebellar neurons in culture, and reduce migration of astrocytes after injury. These novel results show that the structure and function of PSA can be mimicked by the small organic compounds vinorelbine and epirubicin, thus raising the possibility to re-target drugs used in treatment of cancers to nervous system repair. Vinorelbine and epirubicin, identified as PSA mimetics, enhance, like PSA, neuronal migration, neuritogenesis, and formation of Schwann cell processes, and reduce astrocytic migration. Ablating NCAM, inhibiting fibroblast growth factor (FGFR) receptor, or adding the effector domain of myristoylated alanine-rich C kinase substrate (MARCKS) minimize the vinorelbine and epirubicin effects, indicating that they are true PSA mimetics triggering PSA-mediated functions.

Using microfluidics chips for live imaging and study of injury responses in Drosophila larvae.

Live imaging is an important technique for studying cell biological processes, however this can be challenging in live animals. The translucent cuticle of the Drosophila larva makes it an attractive model organism for live imaging studies. However, an important challenge for live imaging techniques is to noninvasively immobilize and position an animal on the microscope. This protocol presents a simple and easy to use method for immobilizing and imaging Drosophila larvae on a polydimethylsiloxane (PDMS) microfluidic device, which we call the 'larva chip'. The larva chip is comprised of a snug-fitting PDMS microchamber that is attached to a thin glass coverslip, which, upon application of a vacuum via a syringe, immobilizes the animal and brings ventral structures such as the nerve cord, segmental nerves, and body wall muscles, within close proximity to the coverslip. This allows for high-resolution imaging, and importantly, avoids the use of anesthetics and chemicals, which facilitates the study of a broad range of physiological processes. Since larvae recover easily from the immobilization, they can be readily subjected to multiple imaging sessions. This allows for longitudinal studies over time courses ranging from hours to days. This protocol describes step-by-step how to prepare the chip and how to utilize the chip for live imaging of neuronal events in 3(rd) instar larvae. These events include the rapid transport of organelles in axons, calcium responses to injury, and time-lapse studies of the trafficking of photo-convertible proteins over long distances and time scales. Another application of the chip is to study regenerative and degenerative responses to axonal injury, so the second part of this protocol describes a new and simple procedure for injuring axons within peripheral nerves by a segmental nerve crush.

Nonyloxytryptamine mimics polysialic acid and modulates neuronal and glial functions in cell culture.

Polysialic acid (PSA) is a major regulator of cell-cell interactions in the developing nervous system and in neural plasticity in the adult. As a polyanionic molecule with high water-binding capacity, PSA increases the intercellular space generating permissive conditions for cell motility. PSA enhances stem cell migration and axon path finding and promotes repair in the lesioned peripheral and central nervous systems, thus contributing to regeneration. As a next step in developing an improved PSA-based approach to treat nervous system injuries, we searched for small organic compounds that mimic PSA and identified as a PSA mimetic 5-nonyloxytryptamine oxalate, described as a selective 5-hydroxytryptamine receptor 1B (5-HT1B ) agonist. Similar to PSA, 5-nonyloxytryptamine binds to the PSA-specific monoclonal antibody 735, enhances neurite outgrowth of cultured primary neurons and process formation of Schwann cells, protects neurons from oxidative stress, reduces migration of astrocytes and enhances myelination in vitro. Furthermore, nonyloxytryptamine treatment enhances expression of the neural cell adhesion molecule (NCAM) and its polysialylated form PSA-NCAM and reduces expression of the microtubule-associated protein MAP2 in cultured neuroblastoma cells. These results demonstrate that 5-nonyloxytryptamine mimics PSA and triggers PSA-mediated functions, thus contributing to the repertoire of molecules with the potential to improve recovery in acute and chronic injuries of the mammalian peripheral and central nervous systems. Polysialic acid (PSA) plays important roles in nervous system development, as well as synaptic plasticity and regeneration in the adult. 5-Nonyloxytryptamine oxalate (5-NOT) mimics PSA and triggers PSA-mediated functions in neurons and glial cells. 5-NOT stimulates neuritogenesis, myelination and Schwann cell migration. This study sets the basis to develop a PSA-mediated therapy of acute and chronic nervous system diseases.

Sodium and potassium currents influence Wallerian degeneration of injured Drosophila axons.

Axons degenerate after injury and in neuropathies and disease via a self-destruction program whose mechanism is poorly understood. Axons that have lost connection to their cell bodies have altered electrical and synaptic activities, but whether such changes play a role in the axonal degeneration process is not clear. We have used a Drosophila model to study the Wallerian degeneration of motoneuron axons and their neuromuscular junction synapses. We found that degeneration of the distal nerve stump after a nerve crush is greatly delayed when there is increased potassium channel activity (by overexpression of two different potassium channels, Kir2.1 and dORKΔ-C) or decreased voltage-gated sodium channel activity (using mutations in the para sodium channel). Conversely, degeneration is accelerated when potassium channel activity is decreased (by expressing a dominant-negative mutation of Shaker). Despite the effect of altering voltage-gated sodium and potassium channel activity, recordings made after nerve crush demonstrated that the distal stump does not fire action potentials. Rather, a variety of lines of evidence suggest that the sodium and potassium channels manifest their effects upon degeneration through changes in the resting membrane potential, which in turn regulates the level of intracellular free calcium within the isolated distal axon.

Dermatan 4-O-sulfotransferase1 ablation accelerates peripheral nerve regeneration.

Chondroitin sulfate (CS) and dermatan sulfate (DS) proteoglycans are major components of the extracellular matrix implicated in neural development, plasticity and regeneration. While it is accepted that CS are major inhibitors of neural regeneration, the contributions of DS to regeneration have not been assessed. To enable a novel approach in studies on DS versus CS roles during development and regeneration, we generated a mouse deficient in the dermatan 4-O-sulfotransferase1 (Chst14(-/-)), a key enzyme in the synthesis of iduronic acid-containing modules found in DS but not CS. In wild-type mice, Chst14 is expressed at high levels in the skin and in the nervous system, and is enriched in astrocytes and Schwann cells. Ablation of Chst14, and the assumed failure to produce DS, resulted in smaller body mass, reduced fertility, kinked tail and increased skin fragility compared with wild-type (Chst14(+/+)) littermates, but brain weight and gross anatomy were unaffected. Neurons and Schwann cells from Chst14(-/-) mice formed longer processes in vitro, and Chst14(-/-) Schwann cells proliferated more than Chst14(+/+) Schwann cells. After femoral nerve transection/suture, functional recovery and axonal regrowth in Chst14(-/-) mice were initially accelerated but the final outcome 3months after injury was not better than that in Chst14(+/+) littermates. These results suggest that while Chst14 and its enzymatic products might be of limited importance for neural development, they may contribute to the regeneration-restricting environment in the adult mammalian nervous system.

Functional role of the interaction between polysialic acid and myristoylated alanine-rich C kinase substrate at the plasma membrane.

Polysialic acid (PSA) is a homopolymeric glycan that plays crucial roles in the developing and adult nervous system. So far only a few PSA-binding proteins have been identified. Here, we identify myristoylated alanine-rich C kinase substrate (MARCKS) as novel PSA binding partner. Binding assays showed a direct interaction between PSA and a peptide comprising the effector domain of MARCKS (MARCKS-ED). Co-immunoprecipitation of PSA-carrying neural cell adhesion molecule (PSA-NCAM) with MARCKS and co-immunostaining of MARCKS and PSA at the cell membrane of hippocampal neurons confirm the interaction between PSA and MARCKS. Co-localization and an intimate interaction of PSA and MARCKS at the cell surface was seen by confocal microscopy and fluorescence resonance energy transfer (FRET) analysis after the addition of fluorescently labeled PSA or PSA-NCAM to live CHO cells or hippocampal neurons expressing MARCKS as a fusion protein with green fluorescent protein (GFP). Cross-linking experiments showed that extracellularly applied PSA or PSA-NCAM and intracellularly expressed MARCKS-GFP are in close contact, suggesting that PSA and MARCKS interact with each other at the plasma membrane from opposite sides. Insertion of PSA and MARCKS-ED peptide into lipid bilayers from opposite sides alters the electric properties of the bilayer confirming the notion that PSA and the effector domain of MARCKS interact at and/or within the plane of the membrane. The MARCKS-ED peptide abolished PSA-induced enhancement of neurite outgrowth from cultured hippocampal neurons indicating an important functional role for the interaction between MARCKS and PSA in the developing and adult nervous system.

The Highwire ubiquitin ligase promotes axonal degeneration by tuning levels of Nmnat protein.

Axonal degeneration is a hallmark of many neuropathies, neurodegenerative diseases, and injuries. Here, using a Drosophila injury model, we have identified a highly conserved E3 ubiquitin ligase, Highwire (Hiw), as an important regulator of axonal and synaptic degeneration. Mutations in hiw strongly inhibit Wallerian degeneration in multiple neuron types and developmental stages. This new phenotype is mediated by a new downstream target of Hiw: the NAD+ biosynthetic enzyme nicotinamide mononucleotide adenyltransferase (Nmnat), which acts in parallel to a previously known target of Hiw, the Wallenda dileucine zipper kinase (Wnd/DLK) MAPKKK. Hiw promotes a rapid disappearance of Nmnat protein in the distal stump after injury. An increased level of Nmnat protein in hiw mutants is both required and sufficient to inhibit degeneration. Ectopically expressed mouse Nmnat2 is also subject to regulation by Hiw in distal axons and synapses. These findings implicate an important role for endogenous Nmnat and its regulation, via a conserved mechanism, in the initiation of axonal degeneration. Through independent regulation of Wnd/DLK, whose function is required for proximal axons to regenerate, Hiw plays a central role in coordinating both regenerative and degenerative responses to axonal injury.

Microfluidic chips for in vivo imaging of cellular responses to neural injury in Drosophila larvae.

With powerful genetics and a translucent cuticle, the Drosophila larva is an ideal model system for live imaging studies of neuronal cell biology and function. Here, we present an easy-to-use approach for high resolution live imaging in Drosophila using microfluidic chips. Two different designs allow for non-invasive and chemical-free immobilization of 3(rd) instar larvae over short (up to 1 hour) and long (up to 10 hours) time periods. We utilized these 'larva chips' to characterize several sub-cellular responses to axotomy which occur over a range of time scales in intact, unanaesthetized animals. These include waves of calcium which are induced within seconds of axotomy, and the intracellular transport of vesicles whose rate and flux within axons changes dramatically within 3 hours of axotomy. Axonal transport halts throughout the entire distal stump, but increases in the proximal stump. These responses precede the degeneration of the distal stump and regenerative sprouting of the proximal stump, which is initiated after a 7 hour period of dormancy and is associated with a dramatic increase in F-actin dynamics. In addition to allowing for the study of axonal regeneration in vivo, the larva chips can be utilized for a wide variety of in vivo imaging applications in Drosophila.

Functional role of the interaction between polysialic acid and extracellular histone H1.

Polysialic acid (PSA) is a large and highly negatively charged glycan that plays crucial roles in nervous system development and function in the adult. It has been suggested to facilitate cell migration, neurite outgrowth, and synaptic plasticity because its hydration volume could enhance flexibility of cell interactions. Evidence for receptors of PSA has so far been elusive. We now identified histone H1 as binding partner of PSA via a single-chain variable fragment antibody using an anti-idiotypic approach. Histone H1 directly binds to PSA as shown by ELISA. Surface biotinylation of cultured cerebellar neurons indicated an extracellular localization of histone H1. Immunostaining of live cerebellar neurons and Schwann cells confirmed that an extracellular pool of histone H1 colocalizes with PSA at the cell surface. Histone H1 was also detected in detergent-insoluble synaptosomal membrane subfractions and postsynaptic densities. When applied in vitro, histone H1 stimulated neuritogenesis, process formation and proliferation of Schwann cells, and migration of neural precursor cells via a PSA-dependent mechanism, further indicating that histone H1 is active extracellularly. These in vitro observations suggested an important functional role for the interaction between histone H1 and PSA not only for nervous system development but also for regeneration in the adult. Indeed, histone H1 improved functional recovery, axon regrowth, and precision of reinnervation of the motor branch in adult mice with femoral nerve injury. Our findings encourage investigations on the therapeutic potential of histone H1 in humans.

Polysialic acid glycomimetics promote myelination and functional recovery after peripheral nerve injury in mice.

alpha2,8 Polysialic acid (PSA) is a carbohydrate attached to the glycoprotein backbone of the neural cell adhesion molecule (NCAM) and implicated in nervous system development and repair. Here, we investigated whether PSA can improve functional recovery after peripheral nerve lesion in adult mice. We applied a functional PSA mimicking peptide or a control peptide in a polyethylene cuff used to surgically reconnect the severed stumps of the femoral nerve before it bifurcates into the motor and sensory branches. Using video-based motion analysis to monitor motor recovery over a 3 month postoperative period, we observed a better functional outcome in the PSA mimetic-treated than in control mice receiving a control peptide or phosphate buffered saline. Retrograde tracing of regenerated motoneurons and morphometric analyses showed that motoneuron survival, motoneuron soma size and axonal diameters were not affected by treatment with the PSA mimetic. However, remyelination of regenerated axons distal to the injury site was considerably improved by the PSA mimetic indicating that effects on Schwann cells in the denervated nerve may underlie the functional effects seen in motor recovery. In line with this notion was the observation that the PSA mimetic enhanced the elongation of Schwann cell processes and Schwann cell proliferation in vitro, when compared with the control peptide. Moreover, Schwann cell proliferation in vivo was enhanced in both motor and sensory branches of the femoral nerve by application of the PSA mimetic. These effects were likely mediated by NCAM through its interaction with the fibroblast growth factor receptor (FGFR), since they were not observed when the PSA mimetic was applied to NCAM-deficient Schwann cells, and since application of two different FGFR inhibitors reduced process elongation from Schwann cells in vitro. Our results indicate the potential of PSA mimetics as therapeutic agents promoting motor recovery and myelination after peripheral nerve injury.