The ciliary GTPase Arl13b regulates cell migration and cell cycle progression

Acknowledgments We acknowledge Prof. Tamara Caspary from Emory University for kindly providing the cell lines, Linda Duncan from the University of Aberdeen Ian Fraser Cytometry Center for help with flow cytometry. MP was funded by the Scottish Universities Life Science Alliance (SULSA) and the University of Aberdeen. Funding This work was supported by grants from British Council China (Sino-UK higher Education for PhD studies) to YD and CM, The Carnegie Trust for the Universities of Scotland (70190) and The NHS Grampian Endowment Funds (14/09) to BL, and National Natural Science Foundation of China (31528011) to BL and YD.Peer reviewedPostprin

The Application of Electric Fields in Biology and Medicine

We discuss a wide range of applications of electric fields in biology and medicine. For example, physiological strength (<500 V/m) fields are used to improve the healing of wounds, the stimulation of neurons, and the positioning and activation of cells on scaffolds for tissue engineering purposes. The brief, strong pulses used in electroporation are used to improve the insertion of drugs into tumors and DNA into cell nuclei. The references direct readers to detailed reviews of these applications. The mechanism by which cells detect physiological strength fields is not well understood. We also describe a field-transduction mechanism that shares features common to the detection of fluid shear by cells. We then provide some experimental evidence that supports our model

The Effect of an Applied Electric Current on Cell Proliferation, Viability, Morphology, Adhesion, and Stem Cell Differentiation

The importance of electrical stimulus is often underrated in cell biology and tissue engineering, although electric fields and currents, both endogenous and applied, play a great role in many cellular functions. Electrical stimulation of the cells causes direct effects on cells, such as rearrangement of the cytoskeleton, redistribution of membrane receptors and changes in calcium dynamics, as well as electrochemical reactions at the electrode/electrolyte interface. In this thesis, the effect of an applied electric current on cell proliferation, viability, morphology, adhesion, and stem cell differentiation was studied. The electric stimulation was applied to two different types of mammalian cells, mouse myoblasts and adipose-derived stem cells that were either in a direct contact with the electrodes or in a contact with the electrodes through the electrolyte.The applied electric current changed the cell spreading characteristics on the electrode, and induced the more elongated cell morphology even when the cells were not cultured directly on the electrode. However, after a certain threshold, the increase in current dose resulted in decrease in the cell viability and sometimes also on the cell proliferation rates. The stimulation influenced the cell adhesion as well, studied by both quantitative and qualitative methods on the electrode and in a biomaterial scaffold. The low currents decreased and higher currents increased the cell-substrate adhesion forces. The highest adhesion forces were related to the poor cell viability and at the highest current values, it was impossible to detach the cell from the substrate. The increase in electric current also decreased the cell migration and adhesion to the scaffold. In addition to the changes in their morphology, the stimulation of the adiposederived stem cells also modified their differentiation pattern. Stimulation of the stem cells with electric current and electrochemically released Cu2+ induced the upregulation of neuron-specific genes and proteins, whereas stimulation with current only mainly induced changes in the cell morphology.As demonstrated in this thesis, electric stimulation induces changes in many cellular functions and might offer an easy and cost-effective method to regulate them in future in vitro and in vivo applications. For instance, electric current could be used for 3 controlled arrangement of cells within the scaffold or for inducing the neuronal differentiation of stem cells

Human dermal fibroblast activation under pulsed electrical stimulation via conductive fabrics : signalling pathways and potential benefit for wound healing

Lors de la cicatrisation, plusieurs types cellulaires dont les kératinocytes et les fibroblastes ainsi que plusieurs facteurs de croissance jouent d’importants rôles. La cicatrisation cutanée peut aussi être activée par des facteurs exogènes, dont la stimulation électrique (SE). La SE peut moduler les fonctions fibroblastiques durant la cicatrisation. Le fibroblaste contribue de façon active à la cicatrisation en sécrétant différentes protéines (collagène, fibronectine, élastine) pour favoriser le comblement tissulaire. Les fibroblastes adoptent aussi un phénotype contractile en exprimant l’α-actine contribuant à la fermeture de la plaie. Notre hypothèse est que certaines de ces fonctions fibroblastiques pourraient être modulées par une stimulation électrique. Pour vérifier cette hypothèse nous avons utilisé une membrane biocompatible et conductrice à base de polyethylene terephthalate (PET) recouvert de polypyrrole (PPy). Les fibroblastes dermiques humains ont été cultivés sur ces membranes conducteurs, puis exposés ou non à un courant pulsé (PES) selon deux régimes : soit 10s PES suivi de 1200s de repos, ou 300s PES suivi de 600s de repos, durant 24 h. Deux intensités électriques ont été étudiées, 50 et 100 mV/mm. Nos travaux démontrent que la SE favorise l’adhésion, la prolifération et la migration des fibroblastes dermiques. Ces activités cellulaires sont consolidées par une sécrétion importante de FGF2 et d’α-SMA. Il est important de noter que l’effet de la SE favorise le changement phénotypique des fibroblastes en myo-fibroblastes grâce à la voie des Smad et de TGFβ/ERK. Nous avons aussi démontré que l’effet de la SE est maintenue à long terme et est transférable de la cellule mère vers les cellules filles. En effet après sous-culture les cellules expriment toujours de façon importante l’α-SMA. En conclusion, nous avons démontré que la stimulation électrique pulsée module positivement les fonctions cicatricielles des fibroblastes humains. Ces travaux démontrent pour la première fois les voies de signalisation (Smad et TGFβ/ERK) sollicitées par la SE pour activer les fibroblastes lors de la cicatrisation. Ces travaux suggèrent l’utilisation de la SE pour favoriser la guérison/cicatrisation des plaies.During skin wound healing, cutaneous cells particularly fibroblasts and keratinocytes as well as several growth factors play important roles. Wound healing can be activated by exogenous factors, including electrical stimulation (ES). ES can also modulate fibroblast functions. Fibroblasts contribute to healing by secreting structural proteins (collagen, fibronectin, elastin) to repair the wound area. Fibroblasts also adopt a contractile phenotype expressing α-actin contributing to wound closure. The hypothesis of the thesis is that fibroblasts proliferate and transdifferentiate into myofibroblasts by sensing pulsed electrical signals and adjusting relevant signalling pathways. To test this hypothesis we used biocompatible polyethylene terephthalate (PET) fabrics coated with electrically conductive polypyrrole (PPy). Human dermal fibroblasts were cultured on these conductive fabrics and exposed to the optimized pulsed ES: either 10s PES in a period of 1200s, or 300s PES in 600s period, for a total of 24 hours. Two electric intensities were studied, 50 and 100 mV/ mm. Our work showed that the PES promoted the adhesion, proliferation and migration of dermal fibroblasts. These cellular activities were consolidated by an elevated level of fibroblast growth factor 2 (FGF2) and the high expression of α-smooth muscle actin (α-SMA). Important findings were that PES promoted the phenotypic change of fibroblasts to myofibroblasts, and such change was coordinated through the Smad and TGFβ/ERK pathways. It also demonstrated that the effect of PES was able to maintain for a long period of time after the end of stimulation, and was transferable from the mother cells to the daughter cells. Following subculture, the electrically stimulated fibroblasts still expressed significant amount of α-SMA. In conclusion, this thesis demonstrates that PES through conductive fabrics can activate the wound healing functions in human dermal fibroblasts. This work revealed for the first time that Smad and TGFβ/ERK pathways are required by the PES-induced fibroblasts-to-myofibroblasts differentiation. This work also demonstrated that the PES activated cells can survive in vivo. These studies suggest the application of the PES in promoting tissue regeneration and wound healing

Preparation and characterization of conductive polymer substrates for electrically stimulated cells

Des membranes conductrices composées de polypyrrole (PPy) dopé à l'héparine (HE) et de polylactide biodégradable (PLLA) ont été produites pour transmettre une stimulation électrique (ES) à des cellules en culture. La préparation de ces membranes constituées de PPy/HE/PLLA nécessite beaucoup de temps ; et la reproductibilité n'était pas satisfaisante. Le premier objectif de cette étude est de raccourcir le temps de préparation, d'améliorer les propriétés conductrices des membranes fabriquées en PPy/HE/PLLA. Le deuxième objectif est d'évaluer la cytotoxicité des nouvelles membranes, et leur utilisation pour délivrer des stimulations électriques aux fibroblastes de peau humaine. Le PPy a été synthétisé par polymérisation oxydative en utilisant l'héparine comme co-dopant. Les particules de PPy ont été mélangées avec le PLLA dans un rapport de 1:9 (p/p) dans du chloroforme. La solution a ensuite été coulée et séchée pour former une fine membrane de PPy/HE/PLLA. Cette membrane a été analysée par microscopie électronique à balayage (MEB) pour la morphologie de surface et par spectroscopie infrarouge de Fourier (FTIR) pour la chimie de surface. Sa conductivité a été mesurée par un système de sonde à quatre points. Sa cytocompatibilité a été évaluée en utilisant des fibroblastes de peau humaine par coloration Hochets et test MTT. La stabilité électrique a été déterminée dans un milieu de culture cellulaire pendant 24 heures. L'effet de la ES a été évalué après 6 et 24 heures d'exposition des fibroblastes à un champ électrique de 200 mV/mm. La membrane en PPy/HE/PLLA a affiché une conductivité d'environ 1,6 × 10⁻⁴ S/cm. Les observations SEM ont montré que les particules de PPy formaient des agrégats uniformes dispersés sur la surface. L'analyse FTIR a confirmé la présence de PPy et de PLLA. Les membranes n'étaient pas cytotoxiques et ont délivré des ES pour augmenter la prolifération des fibroblastes. Le nouveau protocole améliore considérablement l'efficacité et la reproductibilité de la préparation des membranes. La nouvelle membrane PPy/HE/PLLA possède une conductivité et une stabilité adéquates pour soutenir la croissance cellulaire sous stimulation électrique.Electrically conductive membranes made of heparin (HE)-doped polypyrrole (PPy) and biodegradable polylactide (PLLA) have been engineered to mediate electrical stimulation (ES) to cultured cells. The preparation of such PPy/HE/PLLA membranes was time-consuming, and reproducibility was not satisfactory. The first objective of this thesis is to shorten the preparation time, improve the property consistency, and characterize the properties of the new PPy/HE/PLLA membranes. The second objective is to evaluate the new membranes' cytotoxicity and their suitability as a conductive cell culture substrate in electrically stimulating human skin fibroblasts. The PPy was synthesized by oxidative polymerization using heparin as the co-dopant. The PPy particles were mixed with the PLLA at a 1:9 ratio (w/w) in chloroform. The solution was then cast and dried to form a thin PPy/HE/PLLA membrane. This membrane was analyzed by scanning electron microscopy (SEM) for surface morphology and by Fourier transform infrared spectroscopy (FTIR) for surface chemistry. A four-point probe system was used to measure its conductivity. Its cytocompatibility was evaluated using human skin fibroblasts by Hoechst staining and MTT assay. The electrical stability was measured in a cell culture medium for 24 hours. The effect of ES was evaluated after 6- and 24-hour exposures of the fibroblasts to an electrical field of 200 mV/mm. The PPy/HE/PLLA membrane had a conductivity of about 1,6 × 10⁻⁴ S/cm. The SEM observations showed that the PPy particles formed uniform aggregates dispersed as "islands" on the surface. The FTIR analysis confirmed the presence of PPy and PLLA. The membranes were not cytotoxic and delivered ES to increase fibroblast proliferation. The new protocol significantly increases membrane preparation efficiency and reproducibility. The new PPy/HE/PLLA membrane has adequate conductivity and stability to support cell growth under ES

Preparation of multifunctional biodegradable substrate and electrical modulation of osteoblast cellular functions

L'activité cellulaire répond à la stimulation électrique (SE). Le but de cette thèse était le développement d'un composite multifonctionnel et l'étude de la réponse des ostéoblastes à la SE transmise par un tel composite. Les objectifs spécifiques étaient les suivants: a) synthèse des particules de haute conductivité en polypyrroles (PPy) avec des rendements élevés en contrôlant la taille et la régularité moléculaire; b) bioactivation des particules PPy par dopage à l'héparine (HE); c) préparation de composites multifonctionnels électriquement stables et présentant une haute affinité biologique; d) étude de la prolifération et de la minéralisation des ostéoblastes sur un échafaudage conducteur sous SE. Le chapitre I résume les phénomènes bioélectriques chez l'humain à différents niveaux, les mécanismes possibles de l'action de l'électricité sur les cellules, et l'étude de la SE en génie tissulaire osseux. Ce chapitre propose également une revue critique des différentes techniques et des différentes méthodologies de SE utilisées pour des études environnementales, scientifiques et pour les soins cliniques. Les hypothèses et les objectifs de la thèse sont présentés. Le chapitre II décrit la synthèse des nanoparticules en PPy par polymérisation en emulsion en utilisant le réactif de Fenton comme oxydant. Ces nanoparticules présentent une morphologie polygonale creuse, avec une épaisseur approximative de 50 nm et un diamètre de 400-500 nm. Les caractéristiques cristallines de ces nanoparticules ont été démontrées. Un mécanisme plausible de synthèse est proposé. Le chapitre III rapporte la bioactivation des particules en PPy en utilisant F héparine (HE) comme dopant, la préparation d'une membrane conductrice biodégradable, et la culture de fibroblastes sur ces membranes. Le dopage avec HE améliore la stabilité électrique de la membrane conductrice et augmente l'adhésion et la prolifération de cellules. Le chapitre IV démontre que la SE induite par la membrane conductrice peut moduler l'activité des ostéoblastes et accélérer la formation osseuse. Un champ électrique optimal de 200 mV/mm avec une durée de stimulation entre 2 et 8 h a favorisé la prolifération des ostéoblastes et augmenté l'expression et la production de ses marqueurs spécifiques de maturation (ALP) et de minéralisation (CO). Le chapitre V présente une discussion générale, le sommaire des conclusions et les perspectives de recherche pour le futur. L'implication de ces travaux en génie tissulaire et en santé humaine est également abordée

Review of Piezoelectrical Materials Potentially Useful for Peripheral Nerve Repair

It has increasingly been recognized that electrical currents play a pivotal role in cell migration and tissue repair, in a process named "galvanotaxis". In this review, we summarize the current evidence supporting the potential benefits of electric stimulation (ES) in the physiology of peripheral nerve repair (PNR). Moreover, we discuss the potential of piezoelectric materials in this context. The use of these materials has deserved great attention, as the movement of the body or of the external environment can be used to power internally the electrical properties of devices used for providing ES or acting as sensory receptors in artificial skin (e-skin). The fact that organic materials sustain spontaneous degradation inside the body means their piezoelectric effect is limited in duration. In the case of PNR, this is not necessarily problematic, as ES is only required during the regeneration period. Arguably, piezoelectric materials have the potential to revolutionize PNR with new biomedical devices that range from scaffolds and nerve-guiding conduits to sensory or efferent components of e-skin. However, much remains to be learned regarding piezoelectric materials, their use in manufacturing of biomedical devices, and their sterilization process, to fine-tune their safe, effective, and predictable in vivo application.info:eu-repo/semantics/publishedVersio

Nonthermal Plasma Technology as a Versatile Strategy for Polymeric Biomaterials Surface Modification: A Review

In modern technology, there is a constant need to solve very complex problems and to fine-tune existing solutions. This is definitely the case in modern medicine with emerging fields such as regenerative medicine and tissue engineering. The problems, which are studied in these fields, set very high demands on the applied materials. In most cases, it is impossible to find a single material that meets all demands such as biocompatibility, mechanical strength, biodegradability (if required), and promotion of cell-adhesion, proliferation, and differentiation. A common strategy to circumvent this problem is the application of composite materials, which combine the properties of the different constituents. Another possible strategy is to selectively modify the surface of a material using different modification techniques. In the past decade, the use of nonthermal plasmas for selective surface modification has been a rapidly growing research field. This will be the highlight of this review. In a first part of this paper, a general introduction in the field of surface engineering will be given. Thereafter, we will focus on plasma-based strategies for surface modification. The purpose of the present review is twofold. First, we wish to provide a tutorial-type review that allows a fast introduction for researchers into the field. Second, we aim to give a comprehensive overview of recent work on surface modification of polymeric biomaterials, with a focus on plasma-based strategies. Some recent trends will be exemplified. On the basis of this literature study, we will conclude with some future trends for research

Electrospun Nanofibers for Neural Tissue Engineering

Biodegradable nanofibers produced by electrospinning represent a new class of promising scaffolds to support nerve regeneration. We begin with a brief discussion on electrospinning of nanofibers and methods for controlling the structure, porosity, and alignment of the electrospun nanofibers. The methods include control of the nanoscale morphology and microscale alignment for the nanofibers, as well as the fabrication of macroscale, three-dimensional tubular structures. We then highlight recent studies that utilize electrospun nanofibers to manipulate biological processes relevant to nervous tissue regeneration, including stem cell differentiation, guidance of neurite extension, and peripheral nerve injury treatments. The main objective of this feature article is to provide valuable insights into methods for investigating the mechanisms of neurite growth on novel nanofibrous scaffolds and optimization of the nanofiber scaffolds and conduits for repairing peripheral nerve injuries

Application of Nanowires for Retinal Regeneration

Nanowires aim at developing advanced architectures are gaining popularity for damaged neural systems. The retina with a complicated structure is an essential part of our visual nervous system. Any disorder inside retina could lead to blindness due to irregularity in transferring neural signals to the brain. In recent years, the emergence of nanostructures, as well as nanowires, has provided a viable means for enhancing the regeneration of retinal. Nanowires with the ability to sense light and converting it to the electrical signals simulate the extracellular electrical properties, which are the newest nanostructures for the retinal applications. The different structure of nanowires has been examined in vitro, and several others are undergoing in vivo for vision recovery. Among the structures, core-shell nanowires and functionalized nanowires with gold nanoparticles attract the attention for the regeneration of retinal neural systems. Herein, subsequently provide an introduction to the anatomy of the retina, and retinal disorders, the latest progress in the regeneration of retina and vision using nanowires will be reviewed. Also, the different structures, including core-shell and functionalized nanowires with nanoparticles, will be examined. Eventually, the point of view and perspective of applying nanowire in retinal regeneration will be offered