Cone Motility Research Articles

Enhancing Network Anomaly Intrusion Detection with IoT Data-Driven BOA-CNN-BiGRU-AAM -Net Classification

Network security is one of the key components of cybersecurity anomaly intrusion detection, which is responsible for identifying unusual behaviours or activities within a network that might indicate possible security breaches or threats. In this suggested intrusion detection system (IDS), network traffic data is continuously monitored via anomaly detection. The study makes utilising one of the most recent datasets to spot unusual behaviour in networks connected to the Internet of Things, the IoTID20 dataset, to facilitate this process. The preprocessing stage involves painstaking steps for smoothing, filtering, and cleaning the data. The Pine Cone Optimisation algorithm (PCOA), a novel optimizer inspired by nature, is introduced in this study for the feature selection process. PCOA seeks to increase the effectiveness of feature selection while drawing inspiration from the various ways that pine trees reproduce, such as pollination and the movement of pine cones by animals and gravity. Moreover, IDS is classified using Bidirectional Gated Recurrent Unit–Additive Attention Mechanism Based on Convolutional Neural Networks (CNN-BiGRU-AAM), which makes use of deep learning's capabilities for efficient classification tasks. In addition, this work presents the Botox Optimisation Algorithm (BOA) for hyperparameter tuning, which is modelled after the way Botox functions in human anatomy. BOA uses a human-based method to adjust the hyperparameters of the model to attain the best accuracy. The results of the experiments show that the suggested methodologies are effective in improving network anomaly intrusion detection systems, with a maximum accuracy of 99.45%.

Manipulating generalized Dirac cones in subwavelength dipolar arrays

We discuss the emergence and manipulation of generalized Dirac cones in the subradiant collective modes of a subwavelength dipolar array. We consider a collection of single quantum emitters modeled as point dipoles arranged in a honeycomb lattice with subwavelength periodicity. While conventional honeycomb arrays host bound modes that display Dirac cones at the $K$ and ${K}^{\ensuremath{'}}$ points, we show that introducing uniaxial anisotropy in the lattice results in modified dispersion relations. These include the tilting of Dirac cones arising purely due to long-range, retarded, electromagnetic coupling in the lattice, which changes the local density of states at the Dirac point from vanishing (type I) to diverging (types II and III), the emergence of semi-Dirac points, with linear and quadratic dispersions in orthogonal directions, and the anisotropic movement of Dirac cones away from the $K$ and ${K}^{\ensuremath{'}}$ points. Such energy dispersions can modify substantially the dynamics of local probes, such as quantum emitters, for which they have been shown to induce anisotropic power-law interactions.

Neuronal paxillin and drebrin mediate BDNF-induced force transduction and growth cone turning in a soft-tissue-like environment.

Soft tissue environments govern neuronal morphogenesis. However, the precise molecular mechanisms underlying chemotropism-directed axonal growth cone movement in extremely soft environments remain unclear. Here, we show that drebrin, a growth cone T-zone protein, modulates growth cone turning in response to brain-derived neurotrophic factor (BDNF) coated on a soft substrate. Structurally, axonal growth cones of rodent hippocampal neurons grown on 0.1kPa hydrogels possess an expanded T zone in which drebrin is highly integrated with both F-actin and microtubules. Biochemically, we identify paxillin as interacting with drebrin in cells grown on 0.1kPa hydrogels but not on glass coverslips. When grown on 0.1kPa substrates, growth cones asymmetrically exposed to BDNF-bound stripes exhibit enhanced paxillin-drebrin interaction on the side facing the stripes, an activity that is PKA and AAK1 dependent but independent of Src kinase. Functionally, we show that BDNF-induced growth cone turning and force generation on soft substrates require drebrin phosphorylation and paxillin-drebrin association.

Bio-inspired water resistant and fast multi-responsive Janus actuator assembled by cellulose nanopaper and graphene with lignin adhesion

Flexible actuators with responses to various environmental stimuli have attracted great attention, but the issues of weak layer-to-layer bonding and low water resistance of cellulose-based actuators severely restrict their practical application. Herein, inspired by the internal structure of lignocellulose and reversible opening movement of pine cones by external humidity stimuli, a novel Janus film consisting of the insulated lignin-containing cellulose nanopaper (CNP) layer and the conductive reduced graphene oxide (rGO) layer was delicately designed and well fabricated through lignin adhesion between the two layers. Characterization showed that the obtained Janus film with a tensile strength of 141 MPa could be used as a flexible actuator, which could be operated based on water absorption and dehydration of the CNP layer as well as the light-to-heat conversion and high conductivity of rGO layer. Thus, the as-fabricated Janus film with excellent durability (folding resistance (>1000 times), good wet stability, and durable electrical actuation (>500 cycles)) had quick multi-responses to humidity, near-infrared radiation and electrical stimulation. Particularly, the resultant Janus film had the fastest response speed (1.875°/s/V) under the electrical stimuli compared to the reported carbon/polymer-based flexible actuators with comparable weights. Therefore, this CNP-based Janus film can be potentially used in many fields such as humidity sensor, bionic artificial arm/driving motor, and it could be helpful to develop facile and environmentally friendly strategies for the construction of multi-responsive Janus actuator/intelligent devices.

PFTAIRE Kinase L63 Interactor 1A (Pif1A Protein) Is Required for Actin Cone Movement during Spermatid Individualization in Drosophila melanogaster.

A useful model for determining the mechanisms by which actin and actin binding proteins control cellular architecture is the Drosophila melanogaster process of spermatogenesis. During the final step of spermatogenesis, 64 syncytial spermatids individualized as stable actin cones move synchronously down the axonemes and remodel the membranes. To identify new genes involved in spermatid individualization, we screened a collection of Drosophila male-sterile mutants and found that, in the line Z3-5009, actin cones formed near to the spermatid nuclei but failed to move, resulting in failed spermatid individualization. However, we show by phalloidin actin staining, electron microscopy and immunocytochemical localization of several actin binding proteins that the early cones had normal structure. We sequenced the genome of the Z3-5009 line and identified mutations in the PFTAIRE kinase L63 interactor 1A (Pif1A) gene. Quantitative real-time PCR showed that Pif1A transcript abundance was decreased in the mutant, and a transgene expressing Pif1A fused to green fluorescent protein (GFP) was able to fully rescue spermatid individualization and male fertility. Pif1A-GFP localized to the front of actin cones before initiation of movement. We propose that Pif1A plays a pivotal role in directing actin cone movement.

Observing movement of Dirac cones from single-photon dynamics

Graphene with honeycomb structure, being critically important in understanding physics of matter, exhibits exceptionally unusual half-integer quantum Hall effect and unconventional electronic spectrum with quantum relativistic phenomena. Particularly, graphene-like structure can be used for realizing topological insulator which inspires an intrinsic topological protection mechanism with strong immunity for maintaining coherence of quantum information. These various peculiar physics arise from the unique properties of Dirac cones which show high hole degeneracy, massless charge carriers and linear intersection of bands. Experimental observation of Dirac cones conventionally focuses on the energy-momentum space with bulk measurement. Recently, the wave function and band structure have been mapped into the real-space in photonic system, and made flexible control possible. Here, we demonstrate a direct observation of the movement of Dirac cones from single-photon dynamics in photonic graphene under different biaxial strains. Sharing the same spirit of wave-particle nature in quantum mechanics, we identify the movement of Dirac cones by dynamically detecting the edge modes and extracting the diffusing distance of the packets with accumulation and statistics on individual single-particle registrations. Our results of observing movement of Dirac cones from single-photon dynamics, together with the method of direct observation in real space by mapping the band structure defined in momentum space, pave the way to understand a variety of artificial structures in quantum regime.

ROCK inhibitor Y‑27632 protects rats against cerebral ischemia/reperfusion‑induced behavioral deficits and hippocampal damage.

Cerebral ischemic injury is a major cause of death and long‑term disability worldwide that leads to neurological and behavioral deficits, and for which successful treatments are still lacking. Ras homolog family member A (RhoA) and Rho‑associated coiled‑coil containing protein kinase (ROCK) are associated with the growth of neurons and the movement of neuronal growth cones. RhoA/ROCK inhibitors have been demonstrated to promote the recovery of motor function following nerve injury, but the underlying mechanism requires further investigation. The present study aimed to investigate the effects of the ROCK inhibitor Y‑27632 on middle cerebral artery occlusion (MCAO)‑induced cerebral ischemic injury. Rats were randomly assigned to the Control, Y‑27632, MCAO+Vehicle or MCAO+Y‑27632 group. Firstly, infarct volume, cognitive ability and cerebral injury were assessed. Secondly, indicators of cerebral inflammation, oxidative stress and apoptosis were evaluated. Finally, the expression of recombinant glial fibrillary acidic protein (GFAP) and allograft inflammatory factor1(AIF1) in the brain were measured to assess the activation of astrocytes and microglia, respectively. The results showed that Y‑27632 effectively increased the survival rate and behavioral performance of rats, and attenuated the cerebral injury, oxidative stress and cerebral inflammation levels following MCAO. The disturbance in hippocampal neurons caused by MCAO was also alleviated following treatment with Y‑27632. Neuronal apoptosis was also decreased following Y‑27632 treatment, as demonstrated by the TUNEL assay and the expression levels of Caspases‑3, 8 and 9 and Bax/Bcl‑2 ratio. The levels of GFAP and AIF1 were increased by MCAO and further promoted by Y‑27632, indicating the activation of astrocytes and microglia. In conclusion, the present study offered evidence of a protective effect of Y‑27632 administration on cerebral ischemia/reperfusion induced behavioral and hippocampal damage by activating astrocytes and microglia.

Organization of Buccal Cone Musculature in the Pteropod Mollusc Clione limacina.

The pteropod mollusc Clione limacina is a feeding specialist, preying on shelled pteropods of the genus Limacina. Specialized prey-capture structures, called buccal cones, are hydraulically everted from within the mouth to capture the prey. Once captured, the prey is manipulated so the shell opening is over the mouth of Clione. Analyses of high-speed cine sequences of prey capture suggest that the mouth is actively opened rather than passively forced open by buccal cone eversion. The inflated buccal cones are initially straight and form a wide angle (maximum, 113°) prior to prey contact. Individual buccal cones bend orally following prey contact, suggesting a sensory trigger. To determine the muscular basis of buccal cone movements, the musculature of the buccal cones is described. Three distinct muscle fiber types include circular smooth muscle, longitudinal smooth muscle, and longitudinal striated muscle. The organization, distribution, and innervation of the muscle types suggest that circular muscle is used during buccal cone eversion, longitudinal smooth muscle is used for buccal cone withdrawal, and longitudinal striated muscle is used for oral bending of the buccal cones after prey contact and for manipulation of the prey.

HEAVY METAL POLLUTANT-INDUCED CYTOTOXICITY INVOLVES PERTURBATIONS OF MITOCHONDRIAL FUNCTION

Abstract BACKGROUND Environmental pollutants like heavy metals pose a tremendous risk to both animal and human health though the mechanisms underlying their cytotoxic actions at the cellular level remain largely unknown. The freshwater mollusc Lymnaea stagnalis carries hemocynin as its oxygen carrier whereby iron is replaced with copper. As such, this species is highly sensitive to its environmental copper contents and has been used as an important indicator of water quality. Studies have shown that miniscule levels of heavy metals (Pb, Ni, Cu, Co) dissolved in aqueous environments lead to detrimental effects on many of the Lymanea’s vital functions – including respiration and cardiac functions. OBJECTIVES The objective was to determine how heavy metal pulliutants target the cell and its vital functions and if the detirioration of cell motility and viability is a result of the reduced functioning and potential of the cells mitochondria. DESIGN/METHODS We tested the effects of Cu (EC20 as low as 1.8 ug L-1) on isolated blood cells (hemocytes) and neurons from Lymnaea. We sought to determine whether Cu2+ affected cellular viability, motility and neuronal growth cone movements involving cytoskeletal proteins such as actin and tubulin. Cells from the brain were harvested and plated on sigma coated dishes and left to incubate for 3 days to adjust to the environement. They were then stained with mitortracker dyes for mitochondrial potential and movement. The results were captured through live cell imaging and were later analyzed using neurite tracer. We demonstrate the effects of Cu on single mitochondrial movements, structure and function. RESULTS This study provides the first direct evidence that heavy metals such as Cu are indeed cytotoxic and that its detrimental effects on animal health likely involve perturbations of mitochondrial structure and function. Mitochondrial accumulation within the cell started detirioraiting within the first hour of live cell imaging. The mitochondria within the tested cells also started chainging how they cluster within an expanding growth cone. Mitochondrial density decreased substantially and clustered mitohochondira became more fragmeneted which is a positive indication of mitochndrial malfunction. The mitochondrial potential dropped substantially too, indicating that the mitochondria were unable to produce energy like they are suppose to in normal conditions. Finally, this also allowed us to show why heavy metal use in the dentistry profession and other medical professions where heavy metals are used can be linked to cell apoptosis and mitochondrial degradation. CONCLUSION Heavy metals indeed cause malfunction within the cells mitochondria and the reduced functioning disables the cells from fulfilling their associated functions. This was observed through the reduction of breathing, mastication, movement, and neuronal firing of the Lymnaea, which shows a direct realtionship to degraded mitochondria within these cells. Similar results were seen within the hemocytes, which demonstrates that their function of circulating and delivering oxygen was also impaired due to faulty mitochondria.

Retraction: A mathematical model explains saturating axon guidance responses to molecular gradients

Correct wiring is crucial for the proper functioning of the nervous system. Molecular gradients provide critical signals to guide growth cones, which are the motile tips of developing axons, to their targets. However, in vitro, growth cones trace highly stochastic trajectories, and exactly how molecular gradients bias their movement is unclear. Here, we introduce a mathematical model based on persistence, bias, and noise to describe this behaviour, constrained directly by measurements of the detailed statistics of growth cone movements in both attractive and repulsive gradients in a microfluidic device. This model provides a mathematical explanation for why average axon turning angles in gradients in vitro saturate very rapidly with time at relatively small values. This work introduces the most accurate predictive model of growth cone trajectories to date, and deepens our understanding of axon guidance events both in vitro and in vivo.

VEGF Triggers the Activation of Cofilin and the Arp2/3 Complex within the Growth Cone.

A crucial neuronal structure for the development and regeneration of neuronal networks is the axonal growth cone. Affected by different guidance cues, it grows in a predetermined direction to reach its final destination. One of those cues is the vascular endothelial growth factor (VEGF), which was identified as a positive effector for growth cone movement. These positive effects are mainly mediated by a reorganization of the actin network. This study shows that VEGF triggers a tight colocalization of cofilin and the Arp2/3 complex to the actin cytoskeleton within chicken dorsal root ganglia (DRG). Live cell imaging after microinjection of GFP (green fluorescent protein)-cofilin and RFP (red fluorescent protein)-LifeAct revealed that both labeled proteins rapidly redistributed within growth cones, and showed a congruent distribution pattern after VEGF supplementation. Disruption of signaling upstream of cofilin via blocking LIM-kinase (LIMK) activity resulted in growth cones displaying regressive growth behavior. Microinjection of GFP-p16b (a subunit of the Arp2/3 complex) and RFP-LifeAct revealed that both proteins redistributed into lamellipodia of the growth cone within minutes after VEGF stimulation. Disruption of the signaling to the Arp2/3 complex in the presence of VEGF by inhibition of N-WASP (neuronal Wiskott–Aldrich–Scott protein) caused retraction of growth cones. Hence, cofilin and the Arp2/3 complex appear to be downstream effector proteins of VEGF signaling to the actin cytoskeleton of DRG growth cones. Our data suggest that VEGF simultaneously affects different pathways for signaling to the actin cytoskeleton, since activation of cofilin occurs via inhibition of LIMK, whereas activation of Arp2/3 is achieved by stimulation of N-WASP.

A growing field: The regulation of axonal regeneration by Wnt signaling.

The canonical Wnt/β-catenin pathway is a highly conserved signaling cascade that plays critical roles during embryogenesis. Wnt ligands regulate axonal extension, growth cone guidance and synaptogenesis throughout the developing central nervous system (CNS). Recently, studies in mammalian and fish model systems have demonstrated that Wnt/β-catenin signaling also promotes axonal regeneration in the adult optic nerve and spinal cord after injury, raising the possibility that Wnt could be developed as a therapeutic strategy. In this review, we summarize experimental evidence that reveals novel roles for Wnt signaling in the injured CNS, and discuss possible mechanisms by which Wnt ligands could overcome molecular barriers inhibiting axonal growth to promote regeneration. A central challenge in the neuroscience field is developing therapeutic strategies that induce robust axonal regeneration. Although adult axons have the capacity to respond to axonal guidance molecules after injury, there are several major obstacles for axonal growth, including extensive neuronal death, glial scars at the injury site, and lack of axonal guidance signals. Research in rodents demonstrated that activation of Wnt/β-catenin signaling in retinal neurons and radial glia induced neuronal survival and axonal growth, but that activation within reactive glia at the injury site promoted proliferation and glial scar formation. Studies in zebrafish spinal cord injury models confirm an axonal regenerative role for Wnt/β-catenin signaling and identified the cell types responsible. Additionally, in vitro and in vivo studies demonstrated that Wnt induces axonal and neurite growth through transcription-dependent effects of its central mediator β-catenin, potentially by inducing regeneration-promoting genes. Canonical Wnt signaling may also function through transcription-independent interactions of β-catenin with cytoskeletal elements, which could stabilize growing axons and control growth cone movement. Therefore, these studies suggest that Wnt-induced pathways responsible for regulating axonal growth during embryogenesis could be repurposed to promote axonal growth after injury.

Dendritic Actin Cytoskeleton: Structure, Functions, and Regulations.

Actin is a versatile and ubiquitous cytoskeletal protein that plays a major role in both the establishment and the maintenance of neuronal polarity. For a long time, the most prominent roles that were attributed to actin in neurons were the movement of growth cones, polarized cargo sorting at the axon initial segment, and the dynamic plasticity of dendritic spines, since those compartments contain large accumulations of actin filaments (F-actin) that can be readily visualized using electron- and fluorescence microscopy. With the development of super-resolution microscopy in the past few years, previously unknown structures of the actin cytoskeleton have been uncovered: a periodic lattice consisting of actin and spectrin seems to pervade not only the whole axon, but also dendrites and even the necks of dendritic spines. Apart from that striking feature, patches of F-actin and deep actin filament bundles have been described along the lengths of neurites. So far, research has been focused on the specific roles of actin in the axon, while it is becoming more and more apparent that in the dendrite, actin is not only confined to dendritic spines, but serves many additional and important functions. In this review, we focus on recent developments regarding the role of actin in dendrite morphology, the regulation of actin dynamics by internal and external factors, and the role of F-actin in dendritic protein trafficking.

Protein interacting with NIMA (never in mitosis A)-1 regulates axonal growth cone adhesion and spreading through myristoylated alanine-rich C kinase substrate isomerization.

Axonal growth cone motility requires precise regulation of adhesion to navigate the complex environment of the nervous system and reach its target. Myristoylated alanine-rich C kinase substrate (MARCKS) protein is enriched in the developing brain and plays an important, phosphorylation-dependent role in the modulation of axonal growth cone adhesion. The ratio of phospho-MARCKS (MARCKS-P) to total MARCKS controls adhesion modulation and spreading of the axonal growth cone. Pin1, a peptidyl-prolyl cis/trans isomerase (PPIase) that recognizes and binds to phosphorylated serine/threonine residues preceded by a proline (pSer/Thr-Pro) is also expressed in the developing brain. Here, we show that Pin1 is present in the growth cone, interacts with MARCKS-P, and regulates its dephosphorylation. We also described morphological alterations in the corpus callosum and cerebral cortex fibers of the Pin1 knockout mouse brain that may be caused by the misregulation of MARCKS-P and alterations of neuronal adhesion. We have shown that MARCKS, a critical protein in the movement of neuronal growth cones, is in turn regulated by both phosphorylation and cis-trans peptidyl isomerization mediated by Pin1. In the absence of Pin1, MARCKS is hyperphosphorylated, leading to loss of adhesions, and collapse of the growth cone. The Pin1 KO mice exhibited disturbed neuronal projections from the cerebral cortex and reduced white matter tracks such as the corpus callosum. This study highlights a novel function of Pin1 in neurodevelopment.

RETRACTED: A mathematical model explains saturating axon guidance responses to molecular gradients

Correct wiring is crucial for the proper functioning of the nervous system. Molecular gradients provide critical signals to guide growth cones, which are the motile tips of developing axons, to their targets. However, in vitro, growth cones trace highly stochastic trajectories, and exactly how molecular gradients bias their movement is unclear. Here, we introduce a mathematical model based on persistence, bias, and noise to describe this behaviour, constrained directly by measurements of the detailed statistics of growth cone movements in both attractive and repulsive gradients in a microfluidic device. This model provides a mathematical explanation for why average axon turning angles in gradients in vitro saturate very rapidly with time at relatively small values. This work introduces the most accurate predictive model of growth cone trajectories to date, and deepens our understanding of axon guidance events both in vitro and in vivo.

Band Gap on/off Switching of Silicene Superlattice

On the basis of density functional theory calculations with generalized gradient approximation, we have investigated in detail the cooperative effects of uniaxial strain and degenerate perturbation on manipulating the band gap in silicene. The uniaxial strain would split π bands into πa and πz bands, resulting in Dirac cone movement. Then, the hexagonal antidot would split πa (πz) bands into πa1 and πa2 (πz1 and πz2) bands, accounting for the band gap opening in the superlattices with the Dirac cone being folded to the Γ point, which is a different mechanism as compared to the sublattice equivalence breaking. The energy interval between the split πa and πz bands could be tuned to switch band gap on and off, suggesting a reversible switch between the high charge carrier velocity properties of massless Fermions attributed to the linear energy dispersion relation around the Dirac point and the high on/off properties associated with a sizable band gap. In addition, the gap width could be continuously tuned by...

The dynamics of growth cone morphology.

BackgroundNormal brain function depends on the development of appropriate patterns of neural connections. A critical role in guiding axons to their targets during neural development is played by neuronal growth cones. These have a complex and rapidly changing morphology; however, a quantitative understanding of this morphology, its dynamics and how these are related to growth cone movement, is lacking.ResultsHere we use eigenshape analysis (principal components analysis in shape space) to uncover the set of five to six basic shape modes that capture the most variance in growth cone form. By analysing how the projections of growth cones onto these principal modes evolve in time, we found that growth cone shape oscillates with a mean period of 30 min. The variability of oscillation periods and strengths between different growth cones was correlated with their forward movement, such that growth cones with strong, fast shape oscillations tended to extend faster. A simple computational model of growth cone shape dynamics based on dynamic microtubule instability was able to reproduce quantitatively both the mean and variance of oscillation periods seen experimentally, suggesting that the principal driver of growth cone shape oscillations may be intrinsic periodicity in cytoskeletal rearrangements.ConclusionsIntrinsically driven shape oscillations are an important component of growth cone shape dynamics. More generally, eigenshape analysis has the potential to provide new quantitative information about differences in growth cone behaviour in different conditions.

Corneal sulfated glycosaminoglycans and their effects on trigeminal nerve growth cone behavior in vitro: roles for ECM in cornea innervation.

Sensory trigeminal nerve growth cones innervate the cornea in a highly coordinated fashion. The purpose of this study was to determine if extracellular matrix glycosaminoglycans (ECM-GAGs), including keratan sulfate (KS), dermatan sulfate (DS), and chondroitin sulfate A (CSA) and C (CSC), polymerized in developing eyefronts, may provide guidance cues to nerves during cornea innervation. Immunostaining using antineuron-specific-β-tubulin and monoclonal antibodies for KS, DS, and CSA/C was performed on eyefronts from embryonic day (E) 9 to E14 and staining visualized by confocal microscopy. Effects of purified GAGs on trigeminal nerve growth cone behavior were tested using in vitro neuronal explant cultures. At E9 to E10, nerves exiting the pericorneal nerve ring grew as tight fascicles, advancing straight toward the corneal stroma. In contrast, upon entering the stroma, nerves bifurcated repeatedly as they extended anteriorly toward the epithelium. KS was localized in the path of trigeminal nerves, whereas DS and CSA/C-rich areas were avoided by growth cones. When E10 trigeminal neurons were cultured on different substrates comprised of purified GAG molecules, their neurite growth cone behavior varied depending on GAG type, concentration, and mode of presentation (immobilized versus soluble). High concentrations of immobilized KS, DS, and CSA/C inhibited neurite growth to varying degrees. Neurites traversing lower, permissive concentrations of immobilized DS and CSA/C displayed increased fasciculation and decreased branching, whereas KS caused decreased fasciculation and increased branching. Enzymatic digestion of sulfated GAGs canceled their effects on trigeminal neurons. Data herein suggest that GAGs may direct the movement of trigeminal nerve growth cones innervating the cornea.

Surface Microstructures on Planar Substrates and Textile Fibers Guide Neurite Outgrowth: A Scaffold Solution to Push Limits of Critical Nerve Defect Regeneration?

The treatment of critical size peripheral nerve defects represents one of the most serious problems in neurosurgery. If the gap size exceeds a certain limit, healing can't be achieved. Connection mismatching may further reduce the clinical success. The present study investigates how far specific surface structures support neurite outgrowth and by that may represent one possibility to push distance limits that can be bridged. For this purpose, growth cone displacement of fluorescent embryonic chicken spinal cord neurons was monitored using time-lapse video. In a first series of experiments, parallel patterns of polyimide ridges of different geometry were created on planar silicon oxide surfaces. These channel-like structures were evaluated with and without amorphous hydrogenated carbon (a-C:H) coating. In a next step, structured and unstructured textile fibers were investigated. All planar surface materials (polyimide, silicon oxide and a-C:H) proved to be biocompatible, i.e. had no adverse effect on nerve cultures and supported neurite outgrowth. Mean growth cone migration velocity measured on 5 minute base was marginally affected by surface structuring. However, surface structure variability, i.e. ridge height, width and inter-ridge spacing, significantly enhanced the resulting net velocity by guiding the growth cone movement. Ridge height and inter-ridge distance affected the frequency of neurites crossing over ridges. Of the evaluated dimensions ridge height, width, and inter-ridge distance of respectively 3, 10, and 10 µm maximally supported net axon growth. Comparable artificial grooves, fabricated onto the surface of PET fibers by using an excimer laser, showed similar positive effects. Our data may help to further optimize surface characteristics of artificial nerve conduits and bioelectronic interfaces.

Matrix Metalloproteinase-8 Is Involved in Dermal Nerve Growth: Implications for Possible Application to Pruritus from In Vitro Models

Cutaneous nerve density is related to abnormal itch perception in dermatoses, such as atopic dermatitis and xerosis. However, the mechanisms underlying the elongation of dermal nerve fibers within the interstitial collagen (CoL) matrix are poorly understood. In this study, a culture system of rat dorsal root ganglion neurons consisting of type I CoL and a Boyden chamber containing a nerve growth factor (NGF) concentration gradient was used. Nerve fibers penetrating into type I CoL gel were observed in the presence of the NGF concentration gradient. Levels of matrix metalloproteinase-8 (MMP-8) mRNA and protein were increased in the cultured neurons and the conditioned medium, respectively. The nerve fiber penetration was dose dependently inhibited by MMP-8 blockers. Moreover, MMP-8 immunoreactivity was partially localized at growth cones in NGF-responsive nerve fibers. Semaphorin 3A stimulation also showed the opposite effects on these NGF-dependent events. Intriguingly, MMP-8 expression was upregulated by type I and III CoLs, which are substrates for this enzyme. These results suggested that MMP-8 is involved in sensory nerve growth within the interstitial CoL matrix through modulation by the axonal guidance molecules and/or extracellular matrix components. These findings provide insight into the development of pruritus involving skin nerve density.