Les auteurs souhaitent remercier que Fedex Institut de technologie de l&#39;Université de Memphis pour leur soutien. Les auteurs tiennent à remercier les étudiants du groupe de projet de conception principal au Département de génie mécanique à l&#39;Université de Memphis (David Butler, Jackie Carter, Dominick Cleveland, Jacob Shaffer), Daniel Kohn du département Université de Memphis Technologie du génie pour le contrôle moteur , et le Dr Bin Teng et Mme Charlean Luellen pour leur aide dans la culture cellulaire. Ce travail a été soutenu par K01 HL120912 (ER) et R01 HL123540 (CMW).

1. Construction de la membrane avec le bien Murs pour la rétention de Cell Culture, des Médias (voir la figure 1D pour le produit final) <ol><li> Utilisation de polydiméthylsiloxane (PDMS) tôles revêtues avec collagène I, découper le contour de la membrane flexible avec un scalpel ou une filière. </li><li> Placez chaque membrane dans une boîte de 60 mm de Pétri pour le stockage. </li><li> Création de murs: <ol><li> Mélanger PDMS à un ratio de 10: 1 en poids d&#39;élastomère élastomère A à B (durcisseur). </li><li> Verser 5 ml de PDMS entièrement mixtes en tubes de 50 ml. </li><li> Passer tubes de 50 ml avec PDMS non durcies à l&#39;horizontale dans un four à hybridation. </li><li> Utiliser la fonction de rotor pour revêtir les parois intérieures des tubes à huit tours par minute pendant le temps de durcissement. A température ambiante, le PDMS seront entièrement durcies dans les 2 jours. </li><li> Retirer les PDMS à partir du tube dans une hotte de culture cellulaire stérile. </li><li> Utilisation d&#39;une nouvelle lame de rasoir, partitionner le cylindre de PDMS en sections de 4 mm de hauteur. </li><li> Placez les sections, qui serviront de wa membranells, dans un plat contenant Petri sans permettre les murs pour se froisser. </li></ol></li><li> Sélectionnez et le centre d&#39;un mur de PDMS sur une membrane, tout en maintenant les deux dans la boîte de Pétri. </li><li> Placez délicatement PDMS non durcis (10: 1 ratio) sur le périmètre extérieur de la paroi pour être utilisés comme de la colle. Eviter la formation de lacunes entre le mur et la membrane, car il est là pour retenir le liquide. </li><li> Placer chaque boîte de Pétri contenant la membrane rempli et recouvert dans un four à 70 ° C pendant 24 heures pour durcir. </li></ol> 2. Corrélation des rotations moteur avec Clamp déplacement ou Radial croissance pour l&#39;étalonnage (Figure 2) <ol><li> Démarrez le logiciel de commande du moteur. </li><li> Déplacer les mâchoires de l&#39;appareil à l&#39;aide du réglage manuel dans le logiciel de moteur. </li><li> Mesurez la distance et enregistrer la position de comptage du moteur entre des pinces opposées à la fois le déplacement minimum et maximum des pinces. </li><li> Calculer le changement de pour cent dans la distance entre les pinces en fonction du comptage de moteur (~ 0-75k des chiffres). Cela indiquera la souche potentielle maximale atteinte sur la membrane. </li></ol> 3. Application du Plan sur la souris des cellules épithéliales du poumon Ligne (MLE12) <ol><li> Seed MLE12 cellules à 2,5 millions de cellules sur la membrane souple (étape 1) par puits à être confluentes dans les deux jours. La densité d&#39;ensemencement peut varier pour différents types de cellules. </li><li> Assurez-vous que l&#39;actionneur mécanique est dans une position complètement détendue. <ol><li> Retirer milieux de culture cellulaire. </li><li> Utilisation de 1,5 mm poinçons de biopsie, punch deux trous dans chacune des six pince (voir figure 1D) onglets de la membrane. Le positionnement radial des trous détermine la quantité de pré-tension de l&#39;expérience de la membrane initialement. Percez les trous dans un rayon de 20,5 mm sur les onglets de la membrane si aucune pré-tension est souhaitée. </li><li> Placer la membrane sur la civière avec les trous perforés alignant avec les broches à l&#39;intérieur des pinces.Placez pinces supérieures en place. Serrer les vis une par une alternance côtés. </li><li> Ajouter 1 ml de milieu de culture cellulaire. </li></ol></li><li> Placer l&#39;appareil sur la platine du microscope de centrage au milieu de la membrane avec le trajet de la lumière. </li><li> Utilisez du ruban adhésif ou des aimants (si possible) pour fixer le dispositif à la scène. Une fois fixé, le contrôle de l&#39;en-plan (parallèle à la membrane) et verticale (direction z) du dispositif mécanique avec le contrôleur de platine du microscope. </li><li> Appliquer tronçon avec le logiciel fourni par le fabricant en commandant manuellement la position et la vitesse de rotation du moteur 20. </li></ol> 4. Mesure de mitochondriales Reactive Oxygen Species (ROS) <ol><li> Une fois que les cellules sont confluentes, ajouter 2.1 ml de DMEM avec indicateur RT superoxyde mitochondrial (5 uM de concentration finale) directement sur les cellules. </li><li> Incuber pendant 10 min à 37 ° C. </li><li> Laver les cellules doucement trois fois avec un tampon réchauffé dans un bain d&#39;eau pour37 ° C. </li><li> Immédiatement placer la membrane flexible sur la civière (Étape 2.2) déjà en place en vertu d&#39;un microscope confocal verticale. </li><li> Ajouter 1 ml de DMEM avec du milieu sans rouge de phénol et 25 mM de HEPES. </li><li> Définir des filtres d&#39;excitation / émission de 510/580 nm. </li><li> Plusieurs champs image toutes les 15 min pour créer l&#39;évolution temporelle souhaitée de la production de superoxyde mitochondrial. </li><li> A partir d&#39;images capturées, l&#39;intensité de fluorescence fiche histogrammes à chaque intervalle de temps en utilisant un logiciel capable de quantifier l&#39;intensité de fluorescence. </li></ol> 5. Application de stretch et de microscopie à force atomique (AFM) Remarque: Ces étapes sont prévues pour un AFM spécifique et la combinaison de microscope optique (Figure 4 et liste des matières). <ol><li> Préparer l&#39;AFM pour l&#39;expérience. <ol><li> Augmentation de la hauteur de la tête AFM à sa position maximale dans la direction z. </li><li> Mettre diluants sur les jambes de l&#39;AFM àsoulever l&#39;avion à laquelle AFM contacts en porte à faux de l&#39;échantillon. L&#39;échantillon et la tête AFM doit être soulevé pour accueillir la hauteur du dispositif mécanique. </li></ol></li><li> Préparer le microscope optique (si disponible). <ol><li> Retirer la plaque du scanner de l&#39;AFM. Retirer l&#39;objectif souhaité. </li><li> Ajouter une entretoise à l&#39;objectif. La hauteur de l&#39;entretoise dépendrait de l&#39;objectif et l&#39;AFM spécifique set-up, mais il est nécessaire si l&#39;imagerie optique est souhaitée depuis plan d&#39;observation sera changement dans la direction z par un montant égal à la civière et la hauteur de l&#39;adaptateur (Figure 5A). Notez que l&#39;AFM fournit habituellement l&#39;imagerie à faible grossissement d&#39;un chemin optique au-dessus du dispositif. </li><li> Montez le dos objectif souhaité dans son emplacement. Placez le scanner à l&#39;AFM. </li><li> Démarrez le logiciel de l&#39;AFM. Lancer toutes les sources de lumière nécessaires, y compris la source de lumière pour les mesures de fluorescence. </li><li> Monter une puce avec un faisceau cantileverest approprié pour les mesures souhaitées. 200 PN / rigidité nm ou moins est préférable lorsque l&#39;on mesure le module d&#39;élasticité de cellules vivantes. </li><li> Aligner le laser et calibrer la rigidité en porte à faux selon les suggestions du fabricant sur une lamelle de verre monté sur le dispositif. </li></ol></li><li> Préparer une membrane comme dans l&#39;étape 1, mais avec les modifications suivantes. <ol><li> Immédiatement avant le montage de la membrane sur le dispositif d&#39;étirement, couper les murs à environ 1 mm de hauteur. Ceci permet d&#39;éviter les interférences entre les parois connu de membrane et la cellule de charge. </li><li> Monter la membrane sur le dispositif mécanique comme décrit 3.2.1-3.2.3. </li><li> Retirez le support de culture cellulaire pour éviter d&#39;endommager le scanner de l&#39;AFM en cas de déversement. </li><li> Couple l&#39;appareil avec un adaptateur (figure 5A). Placez le dispositif mécanique avec l&#39;adaptateur sur le scanner. </li><li> Étirer la membrane au niveau de la contrainte de traction désirée. </li></ol></li><li&gt; Nano-indentation des cellules étirées. <ol><li> Ajouter un limité (&lt;0,5 ml) du volume des médias sur les cellules pour éviter scanner AFM ou des dommages en raison d&#39;un microscope déversement. </li><li> Engager la poutre en porte à faux avec la membrane. </li><li> Suivez le protocole de l&#39;appareil de l&#39;AFM particulière à balayer des zones d&#39;intérêt. </li></ol></li></ol>

<ol>
	<li>Tschumperlin, D. J., Boudreault, F., Liu, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+and+new+opportunities+in+lung+mechanobiology.">Recent advances and new opportunities in lung mechanobiology.</a> J Biomech. 43, 99-107 (2010).</li><li>Waters, C. M., Roan, E., Navajas, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Comprehensive Physiology. , (2011).</li><li>Majkut, S., Dingal, P. C. D. P., Discher, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stress+Sensitivity+and+Mechanotransduction+during+Heart+Development.">Stress Sensitivity and Mechanotransduction during Heart Development.</a> Current Biology. 24, R495-R501 (2014).</li><li>Hoffman, B. D., Grashoff, C., Schwartz, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+molecular+processes+mediate+cellular+mechanotransduction.">Dynamic molecular processes mediate cellular mechanotransduction.</a> Nature. 475, 316-323 (2011).</li><li>Wang, N., Butler, J. P., Ingber, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanotransduction+across+the+cell-surface+and+through+the+cytoskeleton.">Mechanotransduction across the cell-surface and through the cytoskeleton.</a> Science. 260, 1124-1127 (1993).</li><li>Liu, M., Tanswell, A. K., Post, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+force-induced+signal+transduction+in+lung+cells.">Mechanical force-induced signal transduction in lung cells.</a> Am J Physiol. 277, L667-L683 (1999).</li><li>Janmey, P. A., McCulloch, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+mechanics:+integrating+cell+responses+to+mechanical+stimuli.">Cell mechanics: integrating cell responses to mechanical stimuli.</a> Annu Rev Biomed Eng. 9, 1-34 (2007).</li><li>Waters, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactive+oxygen+species+in+mechanotransduction.">Reactive oxygen species in mechanotransduction.</a> Am J Physiol Lung Cell Mol Physiol. 287, L484-L485 (2004).</li><li>Chapman, K. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cyclic+mechanical+strain+increases+reactive+oxygen+species+production+in+pulmonary+epithelial+cells.">Cyclic mechanical strain increases reactive oxygen species production in pulmonary epithelial cells.</a> Am J Physiol Lung Cell Mol Physiol. 289, L834-L841 (2005).</li><li>Chu, E. K., Whitehead, T., Slutsky, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+cyclic+opening+and+closing+at+low-+and+high-volume+ventilation+on+bronchoalveolar+lavage+cytokines.">Effects of cyclic opening and closing at low- and high-volume ventilation on bronchoalveolar lavage cytokines.</a> Crit Car Med. 32, 168-174 (2004).</li><li>Tschumperlin, D., Margulies, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Equibiaxial+deformation-induced+injury+of+alveolar+epithelial+cells+in+vitro.">Equibiaxial deformation-induced injury of alveolar epithelial cells in vitro.</a> Am J Physiol. 275, L1173-L1183 (1998).</li><li>Vlahakis, N. E., Hubmayr, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+stress+failure+in+ventilator-injured+lungs.">Cellular stress failure in ventilator-injured lungs.</a> Am J Respir Crit Care Med. 171, 1328-1342 (2005).</li><li>Roan, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperoxia+alters+the+mechanical+properties+of+alveolar+epithelial+cells.">Hyperoxia alters the mechanical properties of alveolar epithelial cells.</a> Am J Physiol Lung Cell Mol Physiol. 302, L1235-L1241 (2012).</li><li>Gamerdinger, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+load+and+mechanical+integrity+of+lung+cells+-+Experimental+mechanostimulation+of+epithelial+cell-+and+fibroblast-monolayers.">Mechanical load and mechanical integrity of lung cells - Experimental mechanostimulation of epithelial cell- and fibroblast-monolayers.</a> J Mech Behav Biomed Mater. 4, 201-209 (2014).</li><li>Hayashi, K., Naiki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptation+and+remodeling+of+vascular+wall;+biomechanical+response+to+hypertension.">Adaptation and remodeling of vascular wall; biomechanical response to hypertension.</a> J Mech Behav Biomed Mater. 2, 3-19 (2009).</li><li>Villemure, I., Stokes, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+plate+mechanics+and+mechanobiology.+A+survey+of+present+understanding.">Growth plate mechanics and mechanobiology. A survey of present understanding.</a> J Biomech. 42, 1793-1803 (2009).</li><li>Waters, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+system+to+impose+prescribed+homogenous+strains+on+cultured+cells.">A system to impose prescribed homogenous strains on cultured cells.</a> J Appl Physiol (1985). 91, 1600-1610 (2001).</li><li>Gerstmair, A., Fois, G., Innerbichler, S., Dietl, P., Felder, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+device+for+simultaneous+live+cell+imaging+during+uni-axial+mechanical+strain+or+compression.">A device for simultaneous live cell imaging during uni-axial mechanical strain or compression.</a> J Appl Physiol (1985). 107, 613-620 (1985).</li><li>Dassow, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+method+to+measure+mechanical+properties+of+pulmonary+epithelial+cell+layers.">A method to measure mechanical properties of pulmonary epithelial cell layers.</a> J. Biomed. Mater. Res. Part B Appl. Biomater. 101, 1164-1171 (2013).</li><li>Chapman, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cyclic+mechanical+strain+increases+reactive+oxygen+species+production+in+pulmonary+epithelial+cells.">Cyclic mechanical strain increases reactive oxygen species production in pulmonary epithelial cells.</a> Am J Physiol Lung Cell Mol Physiol. 289, L834-L841 (2005).</li><li>Birukov, K. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cyclic+stretch,+reactive+oxygen+species,+and+vascular+remodeling.">Cyclic stretch, reactive oxygen species, and vascular remodeling.</a> Antioxid Redox Signal. 11, 1651-1667 (2009).</li><li>Turrens, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+formation+of+reactive+oxygen+species.">Mitochondrial formation of reactive oxygen species.</a> J Physiol. 552, 335-344 (2003).</li><li>Wang, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Superoxide+flashes+in+single+mitochondria.">Superoxide flashes in single mitochondria.</a> Cell. 134, 279-290 (2008).</li><li>Pouvreau, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Superoxide+flashes+in+mouse+skeletal+muscle+are+produced+by+discrete+arrays+of+active+mitochondria+operating+coherently.">Superoxide flashes in mouse skeletal muscle are produced by discrete arrays of active mitochondria operating coherently.</a> PLoS One. 5, (2010).</li><li>Yalcin, H. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+cytoskeletal+structure+and+mechanics+on+epithelial+cell+injury+during+cyclic+airway+reopening.">Influence of cytoskeletal structure and mechanics on epithelial cell injury during cyclic airway reopening.</a> Am J Physiol Lung Cell Mol Physiol. 297, L881-L891 (2009).</li><li>Jacob, A. M., Gaver, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atelectrauma+disrupts+pulmonary+epithelial+barrier+integrity+and+alters+the+distribution+of+tight+junction+proteins+ZO-1+and+claudin+4.">Atelectrauma disrupts pulmonary epithelial barrier integrity and alters the distribution of tight junction proteins ZO-1 and claudin 4.</a> J Appl Physiol. 113, 1377-1387 (2012).</li><li>DiPaolo, B. C., Lenormand, G., Fredberg, J. J., Margulies, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stretch+magnitude+and+frequency-dependent+actin+cytoskeleton+remodeling+in+alveolar+epithelia.">Stretch magnitude and frequency-dependent actin cytoskeleton remodeling in alveolar epithelia.</a> Am J Physiol Cell Physiol. 299, C345-C353 (2010).</li></ol>

Les auteurs déclarent qu&#39;ils ont aucun intérêt financier concurrentes.

Un dispositif unique pour l&#39;imagerie de cellules vivantes au cours stretch mécanique a été développé; et ce dispositif a été utilisé dans un protocole d&#39;étudier épithéliale du poumon cellule mécanobiologie. Dans des études préliminaires, on a constaté que seul un tronçon tenue stimulé la production de superoxyde mitochondriale dans les cellules épithéliales bronchiques. En outre, il a été démontré que l&#39;augmentation des niveaux de contrainte mécanique causé des dommages directs à l&...

Les cellules sont soumises à des contraintes mécaniques dans de nombreux tissus, et cette stimulation mécanique a été montré pour promouvoir des changements dans les profils d&#39;expression de gène, la libération de facteurs de croissance, des cytokines, ou le remodelage de la matrice extracellulaire et du cytosquelette 4.1. Les signaux intracellulaires transduction de ces stimuli mécaniques se produisent à travers le processus de mécanotransduction 5-7. Dans le système respiratoire, une issue de mécanotransduction est l&#39;augmentation des espèces réactives de l&#39;oxygène (ROS) et 8,9 cytokines pro-inflammatoires dans 10 les cellules epitheliales pulmonaires en présence de contrainte de traction cyclique. Des preuves solides suggère également que la contrainte de tension excessive conduit à diriger un dommage à l&#39;épithélium alvéolaire, en plus des réactions biochimiques de cellules 11-14. Bien que l&#39;accent est mis ici principalement sur la réponse des cellules pulmonaires à la déformation mécanique, voies induites par mécanotransduction jouent un rôle clé dans les basic fonction de nombreux tissus dans le corps humain, y compris la régulation du tonus vasculaire 15 et le développement de la plaque de croissance 16. L&#39;intérêt croissant pour mécanotransduction a donné lieu à la mise au point de nombreux dispositifs pour l&#39;application de contraintes mécaniques physiologiquement pertinentes à des cellules en culture et des tissus. En particulier, les dispositifs en appliquant une contrainte de traction, qui est une forme courante de chargement mécanique subi par le tissu, sont populaires 11,17-19. Cependant, de nombreux dispositifs disponibles sont soit conçu comme un bioréacteur pour les applications d&#39;ingénierie tissulaire ou ne sont pas propices à une véritable imagerie de temps avec étirement. En tant que tel, il est nécessaire de développer des outils et des méthodes qui permettent de visualiser les cellules et les tissus en tension pour faciliter l&#39;étude des voies de transduction mécanique. Ici, un dispositif d&#39;étirement mécanique dans le plan a été conçu et protocoles ont été élaborés pour appliquer multiples formes de la souche de tissus et de cellules, tout en permettant l&#39;imagerie des réponses biochimiques et mécaniques en temps réel (figure 1A-D). Le dispositif utilise six pinces régulièrement espacées disposées circonférentiellement pour saisir une membrane flexible et d&#39;appliquer une dans le plan, une distension radiale jusqu&#39;à environ 20% (figure 1B). Le dispositif d&#39;actionnement peut être placé dans un incubateur de culture cellulaire pendant une période prolongée de temps, tandis que le moteur (Figure 1C) est placée à l&#39;extérieur de l&#39;incubateur et contrôlé par un logiciel propriétaire fourni par le fournisseur du moteur. Le moteur est connecté à un conducteur linéaire, ce qui fait tourner une came interne, entraînant les six pinces Châssis uniformément en tension et de détente. En plus du dispositif mécanique, les membranes flexibles personnalisés ont été créés à partir de culture disponibles dans le commerce des membranes de cellules prêtes à être utilisé dans le système mécanique. Ensuite, les parois circulaires (avec un diamètre d&#39;environ28 mm) ont été faites sur et fixé à la membrane souple de sorte que les cellules peuvent être cultivées seulement dans cette région de bien décrit le profil de contrainte. Afin de déterminer si le placement de ces membranes dans le dispositif d&#39;actionnement de fournir souche uniforme et isotrope dans le centre de la membrane flexible, l&#39;analyse d&#39;éléments finis a été réalisée en utilisant un logiciel disponible dans le commerce (figure 1E-F). La membrane flexible a été modélisée avec des conditions aux limites symétriques et en utilisant tous les éléments quadrilatères pour la maille. Les anneaux concentriques vu dans le tracé de contour de la souche maximum principal illustré à la figure 1F indiquent la distribution isotrope de la souche. La souche subie par la membrane a été mesurée en enregistrant des images des repères à travers chargement (figure 2). La figure 2D montre que la souche de membrane moyenne mesurée dans les directions radiale et axiale est approximativement linéaireen ce qui concerne le moteur appliqué compte jusqu&#39;à une déformation linéaire maximum de 20%. Il n&#39;y avait aucune différence significative entre les niveaux de déformation mesurées pendant la distension par rapport à celles mesurées pendant la rétraction à la position de repos. Ensuite, le déplacement de cellules epitheliales bronchiques humaines (16HBE) et de leurs noyaux de culture sur la membrane souple sur mesure ont été mesurées. Marqué par fluorescence (DAPI) noyaux des cellules ont été imagées 16HBE en utilisant un objectif 20X sous un microscope confocal, alors que le déplacement de la cellule entière a été mesuré à l&#39;aide des images à contraste de phase enregistrées avec un microscope numérique. Comme on le voit sur ​​la figure 3, la déformation mesurée par déplacement des noyaux était similaire à celle mesurée par déplacement de marquage sur la membrane, jusqu&#39;à environ 20% de déformation linéaire. Cela confirme que la contrainte appliquée aux membranes a été transmis aux cellules adhérentes. Les protocoles décrivant l&#39;utilisation de l&#39;appareil de mesure sur un microscope traditionnelle et un microscop à force atomiquee sont fournies dans les étapes suivantes.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>SmartMotor NEMA 34: 3400 Series</td>
			<td>MOOG Animatics</td>
			<td>SM3416D</td>
			<td>Integrated motor, controller, amplifier, encoder and communications bus</td>
		</tr>
		<tr>
			<td>Flexcell Membrane (Collagen I coated)</td>
			<td>Flexcell International Corp</td>
			<td>SM2-1010C</td>
			<td>3.5x5.25x0.020&#34;</td>
		</tr>
		<tr>
			<td>Sylgard 184&#160;</td>
			<td>Dow Corning Corporation</td>
			<td></td>
			<td>10:1</td>
		</tr>
		<tr>
			<td>Hoechst 33342&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>H1399</td>
			<td>DAPI stain</td>
		</tr>
		<tr>
			<td>MitoSOX</td>
			<td>Sigma-Aldrich</td>
			<td>M36008</td>
			<td></td>
		</tr>
		<tr>
			<td>Tiron</td>
			<td>Sigma-Aldrich</td>
			<td>D7389&#160;</td>
			<td>mitochondrial superoxide label</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td></td>
			<td></td>
			<td>superoxide inhibitor</td>
		</tr>
		<tr>
			<td>FBS</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>50 ml tubes</td>
			<td>Fisher Scientific</td>
			<td>06-443-19</td>
			<td>Any centriguge tube can be used to create an area for imaging.</td>
		</tr>
		<tr>
			<td>Hybridization oven</td>
			<td>Bellco Glass</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MLE12 Cells</td>
			<td>ATCC</td>
			<td>CRL-2110</td>
			<td>Mouse Lung Epithelial Cells&#160;</td>
		</tr>
		<tr>
			<td>16HBE cells</td>
			<td>ATCC</td>
			<td>CRL-2741</td>
			<td>Human Bronchial Epithelial Cells</td>
		</tr>
		<tr>
			<td>AFM Indentation Experiments</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cantilever Beams for Nano-indentation</td>
			<td>Budget Sensors</td>
			<td>Si-Ni30</td>
			<td></td>
		</tr>
		<tr>
			<td>AFM&#160;</td>
			<td>Asylum Research</td>
			<td>MFP3D</td>
			<td></td>
		</tr>
		<tr>
			<td>Olympus microscope</td>
			<td>Olympus</td>
			<td>IX-71</td>
			<td>Inverted microscope with 20X and 40X objectives.</td>
		</tr>
		<tr>
			<td>AFM Leg Extenders</td>
			<td>Asylum Research</td>
			<td>Not available</td>
			<td>AFM microscope</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Finite Element Analyses</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ABAQUS</td>
			<td>Simulia</td>
			<td>6.12</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td>NIH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microscopes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Digital microscope</td>
			<td>Life Technologies</td>
			<td>EVOS XL Core</td>
			<td>Initially a self standing company, now owned by Life Technologies.</td>
		</tr>
		<tr>
			<td>Confocal microscope</td>
			<td>Zeiss</td>
			<td>LSM 710</td>
			<td>2-photon upright microscope</td>
		</tr>
	</tbody>
</table>

live cell imaging during mechanical stretch

There is currently a significant interest in understanding how cells and tissues respond to mechanical stimuli, but current approaches are limited in their capability for measuring responses in real time in live cells or viable tissue. A protocol was developed with the use of a cell actuator to distend live cells grown on or tissues attached to an elastic substrate while imaging with confocal and atomic force microscopy (AFM). Preliminary studies show that tonic stretching of human bronchial epithelial cells caused a significant increase in the production of mitochondrial superoxide. Moreover, using this protocol, alveolar epithelial cells were stretched and imaged, which showed direct damage to the epithelial cells by overdistention simulating one form of lung injury in vitro. A protocol to conduct AFM nano-indentation on stretched cells is also provided.

Reactive Oxygen Species et Déformation Des études antérieures ont démontré une augmentation des espèces réactives de l&#39;oxygène (ROS) dans les voies aériennes et les cellules épithéliales alvéolaires en réponse à l&#39;étirement cyclique 21. Les espèces réactives de l&#39;oxygène comprennent des molécules et de radicaux libres dérivés de l&#39;oxygène moléculaire avec une haute réactivité pour les lipides, les protéines, les polysaccharides et...

Watch this Scientific Journal Video about Live Cell Imaging during Mechanical Stretch at JoVE.com

Live Cell Imaging during Mechanical Stretch

A novel imaging protocol was developed using a custom motor-driven mechanical actuator to allow the measurement of real time responses to mechanical strain in live cells. Relevant to mechanobiology, the system can apply strains up to 20% while allowing near real-time imaging with confocal or atomic force microscopy.

Imagerie sur cellule vivante pendant stretch mécanique

There is currently a significant interest in understanding how cells and tissues respond to mechanical stimuli, but current approaches are limited in ...

live-cell-imaging-during-mechanical-stretch

Research

JoVE Journal

Bioengineering

10.3K vues.  University of Tennessee Health Science Center. A novel imaging protocol was developed using a custom motor-driven mechanical actuator to allow the measurement of real time responses to mechanical strain in live cells. Relevant to mechanobiology, the system can apply strains up to 20% while allowing near real-time imaging with confocal or atomic force microscopy. 

Vidéo: Live Cell Imaging during Mechanical Stretch

Axon Stretch Growth: The Mechanotransduction of Neuronal Growth

During pre-synaptic embryonic development, neuronal processes traverse short distances to reach their targets via growth cone. Over time, neuronal somata are separated from their axon terminals due to skeletal growth of the enlarging organism (Weiss 1941; Gray, Hukkanen et al. 1992). This mechanotransduction induces a secondary mode of neuronal growth capable of accommodating continual elongation of the axon (Bray 1984; Heidemann and Buxbaum 1994; Heidemann, Lamoureux et al. 1995; Pfister, Iwata et al. 2004).
Axon Stretch Growth (ASG) is conceivably a central factor in the maturation of short embryonic processes into the long nerves and white matter tracts characteristic of the adult nervous system. To study ASG in vitro, we engineered bioreactors to apply tension to the short axonal processes of neuronal cultures (Loverde, Ozoka et al. 2011). Here, we detail the methods we use to prepare bioreactors and conduct ASG. First, within each stretching lane of the bioreactor, neurons are plated upon a micro-manipulated towing substrate. Next, neurons regenerate their axonal processes, via growth cone extension, onto a stationary substrate. Finally, stretch growth is performed by towing the plated cell bodies away from the axon terminals adhered to the stationary substrate; recapitulating skeletal growth after growth cone extension.
Previous work has shown that ASG of embryonic rat dorsal root ganglia neurons are capable of unprecedented growth rates up to 10mm/day, reaching lengths of up to 10cm; while concurrently resulting in increased axonal diameters (Smith, Wolf et al. 2001; Pfister, Iwata et al. 2004; Pfister, Bonislawski et al. 2006; Pfister, Iwata et al. 2006; Smith 2009). This is in dramatic contrast to regenerative growth cone extension (in absence of mechanical stimuli) where growth rates average 1mm/day with successful regeneration limited to lengths of less than 3cm (Fu and Gordon 1997; Pfister, Gordon et al. 2011). Accordingly, further study of ASG may help to reveal dysregulated growth mechanisms that limit regeneration in the absence of mechanical stimuli.

A unique tissue engineering method was developed to elongate numerous nerve fibers in culture by recapitulating axon stretch growth; a form of nervous system growth whereby nerves elongate in conjunction with growth of the enlarging body.

Croissance stretch Axon: La mécanotransduction de croissance neuronale

During pre-synaptic embryonic development, neuronal processes traverse short distances to reach their targets via growth cone. Over time, neuronal somata ...

Recherche

Bio-ingénierie

Live-cell Imaging of Migrating Cells Expressing Fluorescently-tagged Proteins in a Three-dimensional Matrix

Traditionally, cell migration has been studied on two-dimensional, stiff plastic surfaces. However, during important biological processes such as wound healing, tissue regeneration, and cancer metastasis, cells must navigate through complex, three-dimensional extracellular tissue. To better understand the mechanisms behind these biological processes, it is important to examine the roles of the proteins responsible for driving cell migration. Here, we outline a protocol to study the mechanisms of cell migration using the epithelial cell line (MDCK), and a three-dimensional, fibrous, self-polymerizing matrix as a model system. This optically clear extracellular matrix is easily amenable to live-cell imaging studies and better mimics the physiological, soft tissue environment. This report demonstrates a technique for directly visualizing protein localization and dynamics, and deformation of the surrounding three-dimensional matrix. 
Examination of protein localization and dynamics during cellular processes provides key insight into protein functions. Genetically encoded fluorescent tags provide a unique method for observing protein localization and dynamics. Using this technique, we can analyze the subcellular accumulation of key, force-generating cytoskeletal components in real-time as the cell maneuvers through the matrix. In addition, using multiple fluorescent tags with different wavelengths, we can examine the localization of multiple proteins simultaneously, thus allowing us to test, for example, whether different proteins have similar or divergent roles. Furthermore, the dynamics of fluorescently tagged proteins can be quantified using Fluorescent Recovery After Photobleaching (FRAP) analysis. This measurement assays the protein mobility and how stably bound the proteins are to the cytoskeletal network.
By combining live-cell imaging with the treatment of protein function inhibitors, we can examine in real-time the changes in the distribution of proteins and morphology of migrating cells. Furthermore, we also combine live-cell imaging with the use of fluorescent tracer particles embedded within the matrix to visualize the matrix deformation during cell migration. Thus, we can visualize how a migrating cell distributes force-generating proteins, and where the traction forces are exerted to the surrounding matrix. Through these techniques, we can gain valuable insight into the roles of specific proteins and their contributions to the mechanisms of cell migration.

Cellular processes such as cell migration have traditionally been studied on two-dimensional, stiff plastic surfaces. This report describes a technique for directly visualizing protein localization and analyzing protein dynamics in cells migrating in a more physiologically relevant, three-dimensional matrix.

Imagerie des cellules vivantes des cellules exprimant des protéines par fluorescence Migration-étiquetés dans une matrice tridimensionnelle

Traditionally, cell migration has been studied on two-dimensional, stiff plastic surfaces. However, during important biological processes such as wound ...

Monitoring the Wall Mechanics During Stent Deployment in a Vessel

Clinical trials have reported different restenosis rates for various stent designs1. It is speculated that stent-induced strain concentrations on the arterial wall lead to tissue injury, which initiates restenosis2-7. This hypothesis needs further investigations including better quantifications of non-uniform strain distribution on the artery following stent implantation. A non-contact surface strain measurement method for the stented artery is presented in this work. ARAMIS stereo optical surface strain measurement system uses two optical high speed cameras to capture the motion of each reference point, and resolve three dimensional strains over the deforming surface8,9. As a mesh stent is deployed into a latex vessel with a random contrasting pattern sprayed or drawn on its outer surface, the surface strain is recorded at every instant of the deformation. The calculated strain distributions can then be used to understand the local lesion response, validate the computational models, and formulate hypotheses for further in vivo study.

Stent-induced arterial strain distributions are characterized using an optical surface strain measurement system. This visualization technique is used to gain insights into the impact of stent implantation on the host vessel.

Suivi des Mécanique mur pendant le déploiement du stent dans un vaisseau

Clinical trials have reported different restenosis rates for various stent designs1. It is speculated that stent-induced strain concentrations on the ...

High Throughput Single-cell and Multiple-cell Micro-encapsulation

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement from a bulk fluid environment with applications in high throughput screening, cytometry, and mass spectrometry. We describe a method to not only encapsulate single cells, but to repeatedly capture a set number of cells (here we demonstrate one- and two-cell encapsulation) to study both isolation and the interactions between cells in groups of controlled sizes. By combining drop generation techniques with cell and particle ordering, we demonstrate controlled encapsulation of cell-sized particles for efficient, continuous encapsulation. Using an aqueous particle suspension and immiscible fluorocarbon oil, we generate aqueous drops in oil with a flow focusing nozzle. The aqueous flow rate is sufficiently high to create ordering of particles which reach the nozzle at integer multiple frequencies of the drop generation frequency, encapsulating a controlled number of cells in each drop. For representative results, 9.9 &mu;m polystyrene particles are used as cell surrogates. This study shows a single-particle encapsulation efficiency Pk=1 of 83.7% and a double-particle encapsulation efficiency Pk=2 of 79.5% as compared to their respective Poisson efficiencies of 39.3% and 33.3%, respectively. The effect of consistent cell and particle concentration is demonstrated to be of major importance for efficient encapsulation, and dripping to jetting transitions are also addressed. 
Introduction 
Continuous media aqueous cell suspensions share a common fluid environment which allows cells to interact in parallel and also homogenizes the effects of specific cells in measurements from the media. High-throughput encapsulation of cells into picoliter-scale drops confines the samples to protect drops from cross-contamination, enable a measure of cellular diversity within samples, prevent dilution of reagents and expressed biomarkers, and amplify signals from bioreactor products. Drops also provide the ability to re-merge drops into larger aqueous samples or with other drops for intercellular signaling studies.1,2 The reduction in dilution implies stronger detection signals for higher accuracy measurements as well as the ability to reduce potentially costly sample and reagent volumes.3 Encapsulation of cells in drops has been utilized to improve detection of protein expression,4 antibodies,5,6 enzymes,7 and metabolic activity8 for high throughput screening, and could be used to improve high throughput cytometry.9 Additional studies present applications in bio-electrospraying of cell containing drops for mass spectrometry10 and targeted surface cell coatings.11 Some applications, however, have been limited by the lack of ability to control the number of cells encapsulated in drops. Here we present a method of ordered encapsulation12 which increases the demonstrated encapsulation efficiencies for one and two cells and may be extrapolated for encapsulation of a larger number of cells.
To achieve monodisperse drop generation, microfluidic "flow focusing" enables the creation of controllable-size drops of one fluid (an aqueous cell mixture) within another (a continuous oil phase) by using a nozzle at which the streams converge.13 For a given nozzle geometry, the drop generation frequency f and drop size can be altered by adjusting oil and aqueous flow rates Qoil and Qaq. As the flow rates increase, the flows may transition from drop generation to unstable jetting of aqueous fluid from the nozzle.14 
When the aqueous solution contains suspended particles, particles become encapsulated and isolated from one another at the nozzle. For drop generation using a randomly distributed aqueous cell suspension, the average fraction of drops Dk containing k cells is dictated by Poisson statistics, where Dk = &lambda;k exp(-&lambda;)/(k!) and &lambda; is the average number of cells per drop. The fraction of cells which end up in the "correctly" encapsulated drops is calculated using Pk = (k x Dk)/&Sigma;(k' x Dk'). The subtle difference between the two metrics is that Dk relates to the utilization of aqueous fluid and the amount of drop sorting that must be completed following encapsulation, and Pk relates to the utilization of the cell sample. As an example, one could use a dilute cell suspension (low &lambda;) to encapsulate drops where most drops containing cells would contain just one cell. While the efficiency metric Pk would be high, the majority of drops would be empty (low Dk), thus requiring a sorting mechanism to remove empty drops, also reducing throughput.15
Combining drop generation with inertial ordering provides the ability to encapsulate drops with more predictable numbers of cells per drop and higher throughputs than random encapsulation. Inertial focusing was first discovered by Segre and Silberberg16 and refers to the tendency of finite-sized particles to migrate to lateral equilibrium positions in channel flow. Inertial ordering refers to the tendency of the particles and cells to passively organize into equally spaced, staggered, constant velocity trains. Both focusing and ordering require sufficiently high flow rates (high Reynolds number) and particle sizes (high Particle Reynolds number).17,18 Here, the Reynolds number Re =uDh/&nu; and particle Reynolds number Rep =Re(a/Dh)2, where u is a characteristic flow velocity, Dh [=2wh/(w+h)] is the hydraulic diameter, &nu; is the kinematic viscosity, a is the particle diameter, w is the channel width, and h is the channel height. Empirically, the length required to achieve fully ordered trains decreases as Re and Rep increase. Note that the high Re and Rep requirements (for this study on the order of 5 and 0.5, respectively) may conflict with the need to keep aqueous flow rates low to avoid jetting at the drop generation nozzle. Additionally, high flow rates lead to higher shear stresses on cells, which are not addressed in this protocol. The previous ordered encapsulation study demonstrated that over 90% of singly encapsulated HL60 cells under similar flow conditions to those in this study maintained cell membrane integrity.12 However, the effect of the magnitude and time scales of shear stresses will need to be carefully considered when extrapolating to different cell types and flow parameters. The overlapping of the cell ordering, drop generation, and cell viability aqueous flow rate constraints provides an ideal operational regime for controlled encapsulation of single and multiple cells.
Because very few studies address inter-particle train spacing,19,20 determining the spacing is most easily done empirically and will depend on channel geometry, flow rate, particle size, and particle concentration. Nonetheless, the equal lateral spacing between trains implies that cells arrive at predictable, consistent time intervals. When drop generation occurs at the same rate at which ordered cells arrive at the nozzle, the cells become encapsulated within the drop in a controlled manner. This technique has been utilized to encapsulate single cells with throughputs on the order of 15 kHz,12 a significant improvement over previous studies reporting encapsulation rates on the order of 60-160 Hz.4,15 In the controlled encapsulation work, over 80% of drops contained one and only one cell, a significant efficiency improvement over Poisson (random) statistics, which predicts less than 40% efficiency on average.12
In previous controlled encapsulation work,12 the average number of particles per drop &lambda; was tuned to provide single-cell encapsulation. We hypothesize that through tuning of flow rates, we can efficiently encapsulate any number of cells per drop when &lambda; is equal or close to the number of desired cells per drop. While single-cell encapsulation is valuable in determining individual cell responses from stimuli, multiple-cell encapsulation provides information relating to the interaction of controlled numbers and types of cells. Here we present a protocol, representative results using polystyrene microspheres, and discussion for controlled encapsulation of multiple cells using a passive inertial ordering channel and drop generation nozzle.

Combining monodisperse drop generation with inertial ordering of cells and particles, we describe a method to encapsulate a desired number of cells or particles in a single drop at kHz rates. We demonstrate efficiencies twice exceeding those of unordered encapsulation for single- and double-particle drops.

High Throughput unicellulaire et multiples cellules de micro-encapsulation

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement ...

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 3rd 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.

Using Microfluidics Chips for Live Imaging and Study of Injury Responses in Drosophila Larvae

Drosophila larvae are an attractive model system for live imaging due to their translucent cuticle and powerful genetics. This protocol describes how to utilize a single-layer PDMS device, called the &#39;larva chip&#39; for live imaging of cellular processes within neurons of 3rd instar Drosophila larvae.

L&#39;utilisation de puces microfluidiques pour l&#39;imagerie en direct et l&#39;étude des réponses blessures en<em&gt; Drosophila</em&gt; Larves

Live imaging is an important technique for studying cell biological processes, however this can be challenging in live animals. The translucent cuticle of ...

A Microfluidic Technique to Probe Cell Deformability

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an efficient manner. Typically, data for ~102 cells can be acquired within a 1 hr experiment. An automated image analysis program enables efficient post-experiment analysis of image data, enabling processing to be complete within a few hours. Our device geometry is unique in that cells must deform through a series of micron-scale constrictions, thereby enabling the initial deformation and time-dependent relaxation of individual cells to be assayed. The applicability of this method to human promyelocytic leukemia (HL-60) cells is demonstrated. Driving cells to deform through micron-scale constrictions using pressure-driven flow, we observe that human promyelocytic (HL-60) cells momentarily occlude the first constriction for a median time of 9.3 msec before passaging more quickly through the subsequent constrictions with a median transit time of 4.0 msec per constriction. By contrast, all-trans retinoic acid-treated (neutrophil-type) HL-60 cells occlude the first constriction for only 4.3 msec before passaging through the subsequent constrictions with a median transit time of 3.3 msec. This method can provide insight into the viscoelastic nature of cells, and ultimately reveal the molecular origins of this behavior.

We demonstrate a microfluidics-based assay to measure the timescale for cells to transit through a sequence of micron-scale constrictions.

Une technique microfluidique à la sonde cellulaire Déformabilité

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an ...

From Fast Fluorescence Imaging to Molecular Diffusion Law on Live Cell Membranes in a Commercial Microscope

It has become increasingly evident that the spatial distribution and the motion of membrane components like lipids and proteins are key factors in the regulation of many cellular functions. However, due to the fast dynamics and the tiny structures involved, a very high spatio-temporal resolution is required to catch the real behavior of molecules. Here we present the experimental protocol for studying the dynamics of fluorescently-labeled plasma-membrane proteins and lipids in live cells with high spatiotemporal resolution. Notably, this approach doesn&#8217;t need to track each molecule, but it calculates population behavior using all molecules in a given region of the membrane. The starting point is a fast imaging of a given region on the membrane. Afterwards, a complete spatio-temporal autocorrelation function is calculated correlating acquired images at increasing time delays, for example each 2, 3, n repetitions. It is possible to demonstrate that the width of the peak of the spatial autocorrelation function increases at increasing time delay as a function of particle movement due to diffusion. Therefore, fitting of the series of autocorrelation functions enables to extract the actual protein mean square displacement from imaging (iMSD), here presented in the form of apparent diffusivity vs average displacement. This yields a quantitative view of the average dynamics of single molecules with nanometer accuracy. By using a GFP-tagged variant of the Transferrin Receptor (TfR) and an ATTO488 labeled 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine (PPE) it is possible to observe the spatiotemporal regulation of protein and lipid diffusion on &#181;m-sized membrane regions in the micro-to-milli-second time range.

Spatial distribution and temporal dynamics of plasma membrane proteins and lipids is a hot topic in biology. Here this issue is addressed by a spatio-temporal image fluctuation analysis that provides conceptually the same physical quantities of single particle tracking, but it uses small molecular labels and standard microscopy setups.

De Fluorescence Imaging rapide à moléculaire loi Diffusion sur les membranes cellulaires en direct dans un microscope commercial

It has become increasingly evident that the spatial distribution and the motion of membrane components like lipids and proteins are key factors in the ...

Isokinetic Robotic Device to Improve Test-Retest and Inter-Rater Reliability for Stretch Reflex Measurements in Stroke Patients with Spasticity

Measuring spasticity is important in treatment planning and determining efficacy after treatment. However, the current tool used in clinical settings has been shown to be limited in inter-rater reliability. One factor in this poor inter-rater reliability is the variability of passive motion while measuring the angle of catch (AoC) measurements. Therefore, an isokinetic device has been proposed to standardize the manual joint motion; however, the benefits of isokinetic motion for AoC measurements has not been tested in a standardized manner. This protocol investigates whether isokinetic motion itself can improve inter-rater reliability for AoC measurements. For this purpose, a robotic isokinetic device was developed that is combined with surface electromyography (EMG). Two conditions, manual and isokinetic motions, are compared with the standardized method to measure the angle and subjective feeling of catch. It is shown that in 17 stroke patients with mild elbow flexor spasticity, isokinetic motion improved the intraclass correlation coefficient (ICC) for inter-rater reliability of AoC measurements to 0.890 [95% confidence interval (CI): 0.685&#8211;0.961] by the EMG criteria, and 0.931 (95% CI: 0.791&#8211;0.978) by the torque criteria, from 0.788 (95% CI: 0.493&#8211;0.920) by manual motion. In conclusion, isokinetic motion itself can improve inter-rater reliability of AoC measurements in stroke patients with mild spasticity. Given that this system may provide greater standardized angle measurements and catch of feeling, it may be a good option for the evaluation of spasticity in a clinical setting.

Using a robotic isokinetic device with electromyography (EMG) measurements, this protocol illustrates that isokinetic motion itself can improve inter-rater reliability for the angle of catch measurements in stroke patients with mild elbow flexor spasticity.

Dispositif robotique Isokinetic pour améliorer la fiabilité de test-retest et d'inter-rater pour des mesures de réflexe d'étirement dans les patients de course avec la spasticité

Measuring spasticity is important in treatment planning and determining efficacy after treatment. However, the current tool used in clinical settings has ...

Controlled Strain of 3D Hydrogels under Live Microscopy Imaging

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized in vitro stretching methods. Various available systems use 2D substrate-based stretchers, while the accessibility of 3D techniques to strain soft hydrogels, is more restricted. Here, we describe a method that allows external stretching of soft hydrogels from their circumference, using an elastic silicone strip as the sample carrier. The stretching system utilized in this protocol is constructed from 3D-printed parts and low-cost electronics, making it simple and easy to replicate in other labs. The experimental process begins with polymerizing thick (&#62;100 &#956;m) soft fibrin hydrogels (Elastic Modulus of ~100 Pa) in a cut-out at the center of a silicone strip. Silicone-gel constructs are then attached to the printed-stretching device and placed on the confocal microscope stage. Under live microscopy the stretching device is activated, and the gels are imaged at various stretch magnitudes. Image processing is then used to quantify the resulting gel deformations, demonstrating relatively homogenous strains and fiber alignment throughout the gel&#8217;s 3D thickness (Z-axis). Advantages of this method include the ability to strain extremely soft hydrogels in 3D while executing in situ microscopy, and the freedom to manipulate the geometry and size of the sample according to the user&#8217;s needs. Additionally, with proper adaptation, this method can be used to stretch other types of hydrogels (e.g., collagen, polyacrylamide or polyethylene glycol) and can allow for analysis of cells and tissue response to external forces under more biomimetic 3D conditions.

The presented method involves uniaxial stretching of 3D soft hydrogels embedded in silicone rubber while allowing live confocal microscopy. Characterization of the external and internal hydrogel strains as well as fiber alignment are demonstrated. The device and protocol developed can assess the response of cells to various strain regimes.

Souche contrôlée d’hydrogels 3D sous imagerie par microscopie dynamique

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized ...

A Microphysiological System to Study Leukocyte-Endothelial Cell Interaction during Inflammation

Leukocyte-endothelial cell interactions play an important role in inflammatory diseases such as sepsis. During inflammation, excessive migration of activated leukocytes across the vascular endothelium into key organs can lead to organ failure. A physiologically relevant biomimetic microfluidic assay (bMFA) has been developed and validated using several experimental and computational techniques, which can reproduce the entire leukocyte rolling/adhesion/migration cascade to study leukocyte-endothelial cell interactions. Microvascular networks obtained from in vivo images in rodents were digitized using a Geographic Information System (GIS) approach and microfabricated with polydimethylsiloxane (PDMS) on a microscope slide. To study the effect of shear rate and vascular topology on leukocyte-endothelial cell interactions, a Computational Fluid Dynamics (CFD) model was developed to generate a corresponding map of shear rates and velocities throughout the network. The bMFA enables the quantification of leukocyte-endothelial cells interactions, including rolling velocity, number of adhered leukocytes in response to different shear rates, number of migrated leukocytes, endothelial cell permeability, adhesion molecule expression and other important variables. Furthermore, by using human-related samples, such as human endothelial cells and leukocytes, bMFA provides a tool for rapid screening of potential therapeutics to increase their clinical translatability.

In this protocol, a biomimetic microfluid assay, which can reproduce a physiologically relevant microvascular environment and reproduce the entire leukocyte adhesion/migration cascade, is employed to study leukocyte-endothelial cell interactions in inflammatory disease.

Un système microphysiologique pour étudier l’interaction leucocytaire-endothéliale pendant l’inflammation

Leukocyte-endothelial cell interactions play an important role in inflammatory diseases such as sepsis. During inflammation, excessive migration of ...