Die Autoren sind dankbar, Anna Labernadie, Guillaume Charrière und Patrick Delobelle für ihren ersten Beitrag zu dieser Arbeit und Matthieu Sanchez und Françoise Viala für ihre Hilfe mit video Dreh und Schnitt. Diese Arbeit wurde von l ' Agence Nationale De La Recherche (ANR14-CE11-0020-02), la Fondation Pour la Recherche Médicale (FRM DEQ2016 0334894), INSERM planen Krebs, Fondation Toulouse Krebs und Human Frontier Science Program (RGP0035/2016) unterstützt.

1. Vorbereitung des Formvar-beschichtete Netze
<ol><li>Reinigen Sie Raster-Elektronen-Mikroskopie mit Aceton und trocknen Sie sie auf Filterpapier. Reinigen Sie anschließend einen Objektträger mit reinem Ethanol, mit einem Objektiv-Papier wischen Sie ab und entfernen Sie den Staub mit einem Gebläse.</li>
	<li>Stellen Sie eine Folie mit Ethanol gereinigt Glas senkrecht in den Trichter eines Film-Casting-Gerätes mit einer Lösung von Formvar im unteren Teil. Decken Sie die Spitze des Trichters.</li>
	<li>Pumpen Sie Formvar Lösung (0,5 % Ethylen Paraquatdichlorid) 100 mL mit Zerstäuber Birne, bis die zwei Drittel der Folie erreicht.</li>
	<li>Halten Sie die Folie in die Lösung für 1 min.</li>
	<li>Öffnen Sie das Ventil des Geräts, um die Formvar-Lösung in einem stetigen Strom abtropfen lassen. Ein Volumenstrom von 10 bis 15 mL/s wird einen Formvar Film von 30-80 nm ergeben. Die Dicke der Folie richtet sich nach der Konzentration der Lösung Formvar und die Entwässerung. Hinweis: Die Entwässerung-Rate kann durch entlüften der Druck über das Ventil Luft-Out durch langsames Öffnen des Ventils gesteuert werden. Je schneller die Entwässerung, je dicker die Folie. In der Praxis weil es schwierig ist, vorherzusagen, die Schichtdicke von Formvar Strömungsgeschwindigkeit, wir bereiten mehrere Chargen Formvar Filme und steuern ihre Stärke von AFM (siehe Schritt2).</li>
	<li>Entfernen Sie die Folie aus der Kammer und trocknen Sie es vorsichtig auf Filterpapier, flüssigen Formvar zu entfernen.</li>
	<li>Schneiden Sie ein Rechteck 20 x 50 mm aus dem Formvar Film mit einer Rasierklinge.</li>
	<li>Ein Becherglas mit destilliertem Wasser füllen und langsam Tauchen die Folie senkrecht ins Wasser schweben aus dem Film: der Film sollte auf der Wasseroberfläche schweben.</li>
	<li>Ort trocken Aceton gereinigt Raster auf dem Film, glänzende stellen.</li>
	<li>Legen Sie eine Runde Glas-Deckglas (Ø 12 mm) auf ein paar der Netze. Das Deckglas wird dazu dienen, die Schichtdicke zu messen (siehe Schritt2).</li>
	<li>Decken Sie einen Objektträger mit einem weißen Aufkleber geändert, um es zu passen. Tauchen Sie die Folie vertikal an der Grenze des schwimmenden Formvar Films, bis der ganze Film auf die Folie haftet. Entfernen Sie überschüssiges Wasser aus der Folie mit Filterpapier und über Nacht bei Raumtemperatur trocknen lassen.</li>
</ol>2. Messung der Schichtdicke
<ol><li>Schneiden Sie Formvar um das Deckglas mit Pinzette, um es von der Folie lösen.</li>
	<li>Markieren Sie die Position des Rasters unter dem Deckglas mit einem Stift.</li>
	<li>Schneiden Sie die Formvar rund um den markierten Gitter um es von dem Deckglas zu lösen. Daher werden ein Loch in die verbleibenden Formvar Blatt, die es erlauben Ihnen, um die Schichtdicke zu messen. Decken Sie das Deckglas mit PBS zu und legen Sie es auf einen Glasobjektträger am Mikroskop.</li>
	<li>Montieren Sie ein Silizium-Nitrid-Freischwinger auf dem AFM Glasblock, sicherstellen, dass die goldenen Streifen, die Spitze der Feder nicht gedeckt ist. Hinweis: Die Empfindlichkeit und die Federkonstante des nadelträgers sollte vorher mit PBS-Puffer kalibriert haben.</li>
	<li>Montieren Sie den Glasblock auf das AFM-Modul, und platzieren Sie das Modul auf das Mikroskop.</li>
	<li>Die Beobachtung Kammer legen Sie Formvar beschichteten deckgläschen auf und bedecken Sie es mit 500 µL PBS.</li>
	<li>Scannen Sie die Grenze des Lochs in der Formvar Blatt mit AFM in Kontakt-Modus und einem 0,5 nN Kraft-Sollwert.</li>
	<li>Verwenden Sie die Glasoberfläche Deckglas als Referenz für Höhenmessungen und bewerten die Formvar Dicke wie die Höhe des Querschnitts (mindestens 10 Messungen pro Formvar Charge).</li>
</ol>3. Aussaat Zellen auf Gittern
<ol><li>Unter einer sterilen Haube legte einen Streifen (12 x 3 mm) doppelseitiges Klebeband auf einem deckgläschen.</li>
	<li>Schneiden Sie ein Raster Formvar beschichtet mit einer Pinzette und legte es kopfüber auf den Klebestreifen (nur der Rand des Rasters muss das Band befestigt werden). Der Formvar Film muss das Deckglas konfrontiert.</li>
	<li>Setzen Sie dieses Gerät in einer Kultur gut.</li>
	<li>Platzieren Sie ein 10 µL Tröpfchen von RPMI ohne FCS mit 104 Makrophagen differenziert aus menschlichen Monozyten16. Hinweis: Stellen Sie sicher nicht, berühren Sie das Gitter mit der Pipettenspitze beschädigen die Formvar Beschichtung zu verhindern.</li>
	<li>Inkubieren Sie für 30 min (37 ° C, 5 % CO2) Zellen haften zu lassen.</li>
	<li>Füllen Sie den Brunnen mit 2 mL RPMI mit 10 % FCS.</li>
	<li>Inkubieren Sie das Gerät für 2 h bei 37 ° C und 5 % CO2 Zellen vor AFM Beobachtung halten zu lassen.</li>
</ol>(4) Topographie Messungen der Podosome-induzierten Verformungen
<ol><li>Ein Glasboden Petrischale zwei Streifen verdoppelt doppelseitigen Klebeband aufkleben. Hinweis: Der Abstand zwischen den beiden Streifen sollte kleiner als der Durchmesser des Rasters.</li>
	<li>Trennen Sie sorgfältig das Raster mit Makrophagen vom Klebeband überzogen.</li>
	<li>Umdrehen Sie die Gitter um die Zellen mit Blick auf das Glas und kleben Sie das Netz zwischen den zwei Klebestreifen.</li>
	<li>Fix das Raster mit zwei neu verdoppelt doppelseitigen Klebstoff Streifen: Raster wird somit zwischen zwei Klebestreifen, verlassen den zentralen Bereich des Rasters für die AFM-Spitze eingeklemmt werden. Hinweis: Stellen Sie sicher, dass die Gitter gut befestigt und nicht verdreht; ansonsten der AFM Cantilever nähern sich die Formvar Oberfläche möglicherweise nicht.</li>
	<li>Füllen Sie die Petrischale mit 2 mL Kulturmedium vorgewärmten 37 ° C (RPMI mit 10 % FCS) mit 10 mM HEPES (pH 7,4) ergänzt.</li>
	<li>Ort der Kulturschale auf 37 ° C Schale Heizung.</li>
	<li>Der Teller wärmer wird auf der AFM-Bühne.</li>
	<li>Lassen Sie das System stabilisieren bei 37 ° C.</li>
	<li>Im Kontakt-Modus mit einer 0,5 nN Kraft einen ersten globalen Bild, Podosomes zu finden, und dann Scannen Formvar Topographie bei 3 Hz mit einer ca. 20 nm große Pixel. Hinweis: Vermeiden Sie Scannen am Rand des Rasters.</li>
</ol>

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<li>Roca-Cusachs, P., Conte, V., Trepat, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Quantifying+Forces+in+Cell+Biology%5BTitle%5D)+AND+%22Nature+Cell+Biology%22%5BJournal%5D)">Quantifying Forces in Cell Biology.</a> Nature Cell Biology. 19, 742-751 (2017).</li>
<li>Labernadie, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Protrusion+Force+Microscopy+Reveals+Oscillatory+Force+Generation+and+Mechanosensing+Activity+of+Human+Macrophage+Podosomes%5BTitle%5D)+AND+%22Nature+Communications%22%5BJournal%5D)">Protrusion Force Microscopy Reveals Oscillatory Force Generation and Mechanosensing Activity of Human Macrophage Podosomes.</a> Nature Communications. 5, 5343(2014).</li>
<li>Proag, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Working+Together%3A+Spatial+Synchrony+in+the+Force+and+Actin+Dynamics+of+Podosome+First+Neighbors%5BTitle%5D)+AND+%22ACS+Nano%22%5BJournal%5D)">Working Together: Spatial Synchrony in the Force and Actin Dynamics of Podosome First Neighbors.</a> ACS Nano. 9, 3800-3813 (2015).</li>
<li>Proag, A., Bouissou, A., Vieu, C., Maridonneau-Parini, I., Poincloux, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Evaluation+of+the+Force+and+Spatial+Dynamics+of+Macrophage+Podosomes+by+Multi-Particle+Tracking%5BTitle%5D)+AND+%22Methods%22%5BJournal%5D)">Evaluation of the Force and Spatial Dynamics of Macrophage Podosomes by Multi-Particle Tracking.</a> Methods. 94, 75-84 (2016).</li>
<li>Cougoule, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Three-Dimensional+Migration+of+Macrophages+Requires+Hck+for+Podosome+Organization+and+Extracellular+Matrix+Proteolysis%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">Three-Dimensional Migration of Macrophages Requires Hck for Podosome Organization and Extracellular Matrix Proteolysis.</a> Blood. 115, 1444-1452 (2010).</li>
<li>Cougoule, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Blood+Leukocytes+and+Macrophages+of+Various+Phenotypes+Have+Distinct+Abilities+to+Form+Podosomes+and+to+Migrate+in+3d+Environments%5BTitle%5D)+AND+%22European+Journal+of+Cell+Biology%22%5BJournal%5D)">Blood Leukocytes and Macrophages of Various Phenotypes Have Distinct Abilities to Form Podosomes and to Migrate in 3d Environments.</a> European Journal of Cell Biology. 91, 938-949 (2012).</li>
<li>Guiet, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Macrophage+Mesenchymal+Migration+Requires+Podosome+Stabilization+by+Filamin+A%5BTitle%5D)+AND+%22Journal+of+Biological+Chemistry%22%5BJournal%5D)">Macrophage Mesenchymal Migration Requires Podosome Stabilization by Filamin A.</a> Journal of Biological Chemistry. 287, 13051-13062 (2012).</li>
<li>Maridonneau-Parini, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Control+of+Macrophage+3d+Migration%3A+A+Therapeutic+Challenge+to+Limit+Tissue+Infiltration%5BTitle%5D)+AND+%22Immunology+Review%22%5BJournal%5D)">Control of Macrophage 3d Migration: A Therapeutic Challenge to Limit Tissue Infiltration.</a> Immunology Review. 262, 216-231 (2014).</li>
<li>Park, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tyrosine+Phosphorylation+of+Wiskott-Aldrich+Syndrome+Protein+%28Wasp%29+by+Hck+Regulates+Macrophage+Function%5BTitle%5D)+AND+%22Journal+of+Biological+Chemistry%22%5BJournal%5D)">Tyrosine Phosphorylation of Wiskott-Aldrich Syndrome Protein (Wasp) by Hck Regulates Macrophage Function.</a> Journal of Biological Chemistry. 289, 7897-7906 (2014).</li>
<li>Van Goethem, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Macrophage+Podosomes+Go+3d%5BTitle%5D)+AND+%22European+Journal+of+Cell+Biology%22%5BJournal%5D)">Macrophage Podosomes Go 3d.</a> European Journal of Cell Biology. 90, 224-236 (2011).</li>
<li>Van Goethem, E., Poincloux, R., Gauffre, F., Maridonneau-Parini, I., Le Cabec, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Matrix+Architecture+Dictates+Three-Dimensional+Migration+Modes+of+Human+Macrophages%3A+Differential+Involvement+of+Proteases+and+Podosome-Like+Structures%5BTitle%5D)+AND+%22Journal+of+Immunology%22%5BJournal%5D)">Matrix Architecture Dictates Three-Dimensional Migration Modes of Human Macrophages: Differential Involvement of Proteases and Podosome-Like Structures.</a> Journal of Immunology. 184, 1049-1061 (2010).</li>
<li>Verollet, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Hiv-1+Reprograms+the+Migration+of+Macrophages%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">Hiv-1 Reprograms the Migration of Macrophages.</a> Blood. 125, 1611-1622 (2015).</li>
<li>Bouissou, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Podosome+Force+Generation+Machinery%3A+A+Local+Balance+between+Protrusion+at+the+Core+and+Traction+at+the+Ring%5BTitle%5D)+AND+%22ACS+Nano%22%5BJournal%5D)">Podosome Force Generation Machinery: A Local Balance between Protrusion at the Core and Traction at the Ring.</a> ACS Nano. 11, 4028-4040 (2017).</li>
<li>Lizarraga, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Diaphanous-Related+Formins+Are+Required+for+Invadopodia+Formation+and+Invasion+of+Breast+Tumor+Cells%5BTitle%5D)+AND+%22Cancer+Research%22%5BJournal%5D)">Diaphanous-Related Formins Are Required for Invadopodia Formation and Invasion of Breast Tumor Cells.</a> Cancer Research. 69, 2792-2800 (2009).</li>
<li>Carman, C. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transcellular+Diapedesis+Is+Initiated+by+Invasive+Podosomes%5BTitle%5D)+AND+%22Immunity%22%5BJournal%5D)">Transcellular Diapedesis Is Initiated by Invasive Podosomes.</a> Immunity. 26, 784-797 (2007).</li>
<li>Sage, P. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Antigen+Recognition+Is+Facilitated+by+Invadosome-Like+Protrusions+Formed+by+Memory%2FEffector+T+Cells%5BTitle%5D)+AND+%22Journal+of+Immunology%22%5BJournal%5D)">Antigen Recognition Is Facilitated by Invadosome-Like Protrusions Formed by Memory/Effector T Cells.</a> Journal of Immunology. 188, 3686-3699 (2012).</li>
<li>Sens, K. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((An+Invasive+Podosome-Like+Structure+Promotes+Fusion+Pore+Formation+During+Myoblast+Fusion%5BTitle%5D)+AND+%22Journal+of+Cell+Biology%22%5BJournal%5D)">An Invasive Podosome-Like Structure Promotes Fusion Pore Formation During Myoblast Fusion.</a> Journal of Cell Biology. 191, 1013-1027 (2010).</li>
<li>Takito, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Transient+Appearance+of+Zipper-Like+Actin+Superstructures+During+the+Fusion+of+Osteoclasts%5BTitle%5D)+AND+%22Journal+of+Cell+Science%22%5BJournal%5D)">The Transient Appearance of Zipper-Like Actin Superstructures During the Fusion of Osteoclasts.</a> Journal of Cell Science. 125, 662-672 (2012).</li>
<li>Shilagardi, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Actin-Propelled+Invasive+Membrane+Protrusions+Promote+Fusogenic+Protein+Engagement+During+Cell-Cell+Fusion%5BTitle%5D)+AND+%22Science%22%5BJournal%5D)">Actin-Propelled Invasive Membrane Protrusions Promote Fusogenic Protein Engagement During Cell-Cell Fusion.</a> Science. 340, 359-363 (2013).</li>
<li>Freeman, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Integrins+Form+an+Expanding+Diffusional+Barrier+That+Coordinates+Phagocytosis%5BTitle%5D)+AND+%22Cell%22%5BJournal%5D)">Integrins Form an Expanding Diffusional Barrier That Coordinates Phagocytosis.</a> Cell. 164, 128-140 (2016).</li>
</ol>

Keine Interessenkonflikte erklärt.

Materialeigenschaften
Die Wahl des Materials für die verformbare Membran, in unserem Fall Formvar, muss einige Voraussetzungen erfüllen. Das Material muss für sichtbares Licht transparent sein und weisen begrenzt Auto-Fluoreszenz um Beobachtungen im Hellfeld und Fluoreszenz-Mikroskopie erlauben. Die Rauheit des dünnen Films muss deutlich unter 10 nm eine topographische Beeinträchtigung Zelladhäsion zu vermeiden und klare Betrachtung der Zelle-induzierte Vorsprünge von A...

Tierische Zellen interagieren körperlich mit der Matrix und den anderen Zellen, die ihre Umwelt1darstellen. Dies ist erforderlich für sie zu migrieren, Körper zu verinnerlichen, externe Informationen zu erwerben oder zu unterscheiden. In solchen Prozessen muss die Zelle mechanische Kräfte erzeugen, und wie in den letzten Jahren zahlreiche Studien gezeigt haben, beeinflusst die Fähigkeit einer Zelle zu erzeugen Kräfte und seiner Umgebung Sonde sein biologische Verhalten, Regie zum Beispiel Verbreitung oder Differenzierung-2,-3. Die Messung von zellulären Kräften ist wiederum eine große Hilfe für die Regulierung der Truppenaufstellung zu studieren und verstehen seine Auswirkung in Zelle Verhalten und Gewebe Schicksal4,5.
Den letzten Jahren erlebt haben die Entwicklung von zahlreichen Techniken, um die Kräfte zu messen, die eine Zelle auf seine Umwelt6ausüben kann. Die meisten davon haben maßgeblich bei der Enthüllung, dass die Traktion erzwingt, dass Zellen ausüben, wie sie auf mobile Sonden oder einem verformbaren Untergrund ziehen. Jedoch die mechanischen Kräfte beteiligt Vorwölbung in die extrazellulären Umwelt leiden unter einem Mangel an Messtechniken und sind bis heute nicht gut charakterisiert.
Um diese Einschränkung zu umgehen, stellen wir Ihnen eine Methode zur Messung der Kräfte, die orthogonal zum Substrat. Es besteht in der Beschichtung von lebenden Zellen auf eine dünne elastische Folie, die in Richtung orthogonal, die es ermöglichen, Substrat Verformung von Zellen zu messen und daraus die beteiligten Kräfte verformen kann. Substrat Topographie mit nanoskaligen Auflösung mit Rasterkraftmikroskopie gemessen und die Bewertung der Kräfte von Verformung stützt sich auf das Wissen um die Geometrie der hervorstehende Zellstrukturen7,8, 9.
Hier beschreiben wir die Einrichtung und ihre Anwendung auf die erzeugte Podosomes, hervorstehende Adhäsion Strukturen gebildet durch Makrophagen für ihre mesenchymalen Migration in dreidimensionalen Umgebungen10,11Kräfte zu messen, 12,13,14,15,16,17. Wir glauben, dass diese Technik die Krafterzeugung und deren Regulierung in viele zelluläre Prozesse, die mit Vorsprung verstehen wird.

<table><tbody><tr><td>200 mesh nickel grids</td><td>Electron Microscopy Sciences</td><td>G200-Ni</td><td></td></tr><tr><td>Filter paper</td><td>Sigma-Aldrich</td><td>1001-055</td><td></td></tr><tr><td>Microscope slides</td><td>Fisher Scientific</td><td>10235612</td><td></td></tr><tr><td>White stickers 26 x 70 mm</td><td>Avery</td><td>DP033-100</td><td></td></tr><tr><td>Film casting device with valve in its outlet</td><td>Electron Microscopy Sciences</td><td>71305-01</td><td></td></tr><tr><td>Razorblades</td><td>Electron Microscopy Sciences</td><td>72000</td><td></td></tr><tr><td>Ethanol</td><td>VWR</td><td>1.08543.0250</td><td></td></tr><tr><td>Acetone</td><td>VWR</td><td>20066.321</td><td></td></tr><tr><td>Formvar 0.5% solution in ethylene dichloride</td><td>Electron Microscopy Sciences</td><td>15820</td><td></td></tr><tr><td>12 mm coverslips</td><td>VWR</td><td>631-0666</td><td></td></tr><tr><td>Inverted microscope</td><td>Carl Zeiss</td><td>Axiovert 200</td><td></td></tr><tr><td>Atomic Force Microscope</td><td>JPK Instruments</td><td>NanoWizard III</td><td></td></tr><tr><td>Temperature-controlled sample holder&amp;nbsp;</td><td>JPK Instruments</td><td>BioCell</td><td></td></tr><tr><td>Silicon nitride cantilever with a nominal spring constant of 0.01 N/m</td><td>Veeco Instruments</td><td>MLCT-AUHW</td><td></td></tr><tr><td>PBS</td><td>Gibco</td><td>14190-094</td><td></td></tr><tr><td>Double-sided adhesive tape</td><td>APLI AGIPA</td><td>118100</td><td></td></tr><tr><td>RPMI 1640</td><td>Gibco</td><td>31870-025</td><td></td></tr><tr><td>FCS</td><td>Sigma-Aldrich</td><td>F7524</td><td></td></tr><tr><td>HEPES&amp;nbsp;</td><td>Sigma-Aldrich</td><td>H0887</td><td></td></tr><tr><td>35 mm glass-bottom Petri dishes</td><td>WPI</td><td>FD35-100</td><td></td></tr></tbody></table>

protrusion force microscopy: a method to quantify forces developed by cell protrusions

In zahlreichen biologischen zusammenhängen müssen tierische Zellen physisch mit ihrer Umgebung interagieren durch mechanische Kräfte zu entwickeln. Unter diesen Zugkräfte gut charakterisierten gewesen, aber es fehlt an Techniken ermöglichen die Messung der Kräfte, Vorsprung durch Zellen orthogonal zu ihrem Substrat. Wir entwarfen eine Versuchsanordnung, die Kräfte, Vorsprung durch adhärente Zellen auf ihrem Substrat zu messen. Zellen, die auf einem kompatiblen Formvar Blatt vergoldet verformen dieses Substrat und die daraus resultierende Topographie wird durch Rasterkraftmikroskopie (AFM) auf der Nanometerskala zugeordnet. Kraftwerte werden dann von einer Analyse der Verformung Profil basierend auf der Geometrie der hervorstehende zellulären Strukturen extrahiert. Daher können die Kräfte, die von den einzelnen hervorstehenden Einheiten einer lebenden Zelle im Laufe der Zeit gemessen werden. Diese Technik ermöglicht die Untersuchung der Krafterzeugung und deren Regulierung in viele zelluläre Prozesse, die mit Vorsprung. Hier beschreiben wir ihre Anwendung auf die hervorstehende Kräfte erzeugte Podosomes gebildet durch menschliche Makrophagen zu messen.

Das obige Protokoll beschreibt die Vorbereitung der Versuchsaufbau, Vorwölbung Krafteinwirkung durch Makrophagen Podosomes auf einem Formvar Substrat zu quantifizieren. Dies erfolgt über AFM und in Abbildung 1dargestellt ist.
Bei der Analyse der topographischen Bild Ausbuchtungen unter Podosomes mit JPK Datenverarbeitungs-Software sollte ein dritten Grades Polynom passen jede Scanzeile unabhängig...

Watch this Scientific Journal Video about Protrusion Force Microscopy: A Method to Quantify Forces Developed by Cell Protrusions at JoVE.com

Protrusion Force Microscopy: A Method to Quantify Forces Developed by Cell Protrusions

Hier zeigen wir die experimentellen Techniken verwendet, um den Vorsprung Kräfte auszuwerten, die Podosomes auf einem konformen Film, von der Vorbereitung des Films für die automatisierte Analyse von topographische Bilder gelten.

Vorsprung-Kraft-Mikroskopie: Eine Methode, um Kräfte entwickelt von Zelle Vorsprünge zu quantifizieren

In numerous biological contexts, animal cells need to interact physically with their environment by developing mechanical forces. Among these, traction ...

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JoVE Journal

Biology

5.5K Aufrufe.  IPBS, Université de Toulouse, CNRS, UPS. Hier zeigen wir die experimentellen Techniken verwendet, um den Vorsprung Kräfte auszuwerten, die Podosomes auf einem konformen Film, von der Vorbereitung des Films für die automatisierte Analyse von topographische Bilder gelten.

Serie: Protrusion Force Microscopy: A Method to Quantify Forces Developed by Cell Protrusions

Measuring the Mechanical Properties of Living Cells Using Atomic Force Microscopy

Mechanical properties of cells and extracellular matrix (ECM) play important roles in many biological processes including stem cell differentiation, tumor formation, and wound healing. Changes in stiffness of cells and ECM are often signs of changes in cell physiology or diseases in tissues. Hence, cell stiffness is an index to evaluate the status of cell cultures. Among the multitude of methods applied to measure the stiffness of cells and tissues, micro-indentation using an Atomic Force Microscope (AFM) provides a way to reliably measure the stiffness of living cells. This method has been widely applied to characterize the micro-scale stiffness for a variety of materials ranging from metal surfaces to soft biological tissues and cells. The basic principle of this method is to indent a cell with an AFM tip of selected geometry and measure the applied force from the bending of the AFM cantilever. Fitting the force-indentation curve to the Hertz model for the corresponding tip geometry can give quantitative measurements of material stiffness. This paper demonstrates the procedure to characterize the stiffness of living cells using AFM. Key steps including the process of AFM calibration, force-curve acquisition, and data analysis using a MATLAB routine are demonstrated. Limitations of this method are also discussed.

This paper demonstrates a protocol to characterize the mechanical properties of living cells by means of microindentation using an Atomic Force Microscope (AFM).

Messung der mechanischen Eigenschaften von lebenden Zellen mit Atomic Force Microscopy

Mechanical  properties of cells and extracellular matrix (ECM) play important roles in many  biological processes including stem cell differentiation, ...

Forschung

Biotechnik

A Direct Force Probe for Measuring Mechanical Integration Between the Nucleus and the Cytoskeleton

The mechanical properties of the nucleus determine its response to mechanical forces generated in cells. Because the nucleus is molecularly continuous with the cytoskeleton, methods are needed to probe its mechanical behavior in adherent cells. Here, we discuss the direct force probe (DFP) as a tool to apply force directly to the nucleus in a living adherent cell. We attach a narrow micropipette to the nuclear surface with suction. The micropipette is translated away from the nucleus, which causes the nucleus to deform and translate. When the restoring force is equal to the suction force, the nucleus detaches and elastically relaxes. Because the suction pressure is precisely known, the force on the nuclear surface is known. This method has revealed that nano-scale forces are sufficient to deform and translate the nucleus in adherent cells, and identified cytoskeletal elements that enable the nucleus to resist forces. The DFP can be used to dissect the contributions of cellular and nuclear components to nuclear mechanical properties in living cells.

In this protocol, we describe a micropipette method to directly apply a controlled force to the nucleus in a living cell. This assay allows interrogation of nuclear mechanical properties in the living, adherent cell.

Eine direkte Kraft-Sonde zur Messung der mechanischen Integration zwischen dem Kern und dem Zytoskelett

The mechanical properties of the nucleus determine its response to mechanical forces generated in cells. Because the nucleus is molecularly continuous ...

Biochemie

Perturbing Endothelial Biomechanics via Connexin 43 Structural Disruption

Endothelial cells have been established to generate intercellular stresses and tractions, but the role gap junctions play in endothelial intercellular stress and traction generation is currently unknown. Therefore, we present here a mechanics-based protocol to probe the influence of gap junction connexin 43 (Cx43) has on endothelial biomechanics by exposing confluent endothelial monolayers to a known Cx43 inhibitor 2,5-dihydroxychalcone (chalcone) and measuring the impact this inhibitor has on tractions and intercellular stresses. We present representative results, which show a decrease in both tractions and intercellular stresses under a high chalcone dosage (2 &#181;g/mL) when compared to control. This protocol can be applied to not just Cx43, but also other gap junctions as well, assuming the appropriate inhibitor is used. We believe this protocol will be useful in the fields of cardiovascular and mechanobiology research.

Here, we present a mechanics-based protocol to disrupt the gap junction connexin 43 and measure the subsequent impact this has on endothelial biomechanics via observation of tractions and intercellular stresses.

Störende Endothelial Biomechanik über Connexin 43 Strukturelle Störung

Endothelial cells have been established to generate intercellular stresses and tractions, but the role gap junctions play in endothelial intercellular ...

Probing Cell Mechanics with Bead-Free Optical Tweezers in the Drosophila Embryo

Morphogenesis requires coordination between genetic patterning and mechanical forces to robustly shape the cells and tissues. Hence, a challenge to understand morphogenetic processes is to directly measure cellular forces and mechanical properties in vivo during embryogenesis. Here, we present a setup of optical tweezers coupled to a light sheet microscope, which allows to directly apply forces on cell-cell contacts of the early Drosophila embryo, while imaging at a speed of several frames per second. This technique has the advantage that it does not require the injection of beads into the embryo, usually used as intermediate probes on which optical forces are exerted. We detail step by step the implementation of the setup, and propose tools to extract mechanical information from the experiments. By monitoring the displacements of cell-cell contacts in real time, one can perform tension measurements and investigate cell contacts&#39; rheology.

Probing Cell Mechanics with Bead-Free Optical Tweezers in the Drosophila Embryo

We present a setup of optical tweezers coupled to a light sheet microscope, and its implementation to probe cell mechanics without beads in the Drosophila embryo.

Prüfende Zelle Mechanik mit Wulst-freie optische Pinzetten in Drosophila Embryos

Morphogenesis requires coordination between genetic patterning and mechanical forces to robustly shape the cells and tissues. Hence, a challenge to ...

Entwicklungsbiologie

Direct Force Measurements of Subcellular Mechanics in Confinement using Optical Tweezers

During the development of a multicellular organism, a single fertilized cell divides and gives rise to multiple tissues with diverse functions. Tissue morphogenesis goes in hand with molecular and structural changes at the single cell level that result in variations of subcellular mechanical properties. As a consequence, even within the same cell, different organelles and compartments resist differently to mechanical stresses; and mechanotransduction pathways can actively regulate their mechanical properties. The ability of a cell to adapt to the microenvironment of the tissue niche thus is in part due to the ability to sense and respond to mechanical stresses. We recently proposed a new mechanosensation paradigm in which nuclear deformation and positioning enables a cell to gauge the physical 3D environment and endows the cell with a sense of proprioception to decode changes in cell shape. In this article, we describe a new method to measure the forces and material properties that shape the cell nucleus inside living cells, exemplified on adherent cells and mechanically confined cells. The measurements can be performed non-invasively with optical traps inside cells, and the forces are directly accessible through calibration-free detection of light momentum. This allows measuring the mechanics of the nucleus independently from cell surface deformations and allowing dissection of exteroceptive and interoceptive mechanotransduction pathways. Importantly, the trapping experiment can be combined with optical microscopy to investigate the cellular response and subcellular dynamics using fluorescence imaging of the cytoskeleton, calcium ions, or nuclear morphology. The presented method is straightforward to apply, compatible with commercial solutions for force measurements, and can easily be extended to investigate the mechanics of other subcellular compartments, e.g., mitochondria, stress-fibers, and endosomes.

Here, we present a protocol to investigate the intracellular mechanical properties of isolated embryonic zebrafish cells in three-dimensional confinement with direct force measurement by an optical trap.

Direkte Kraftmessungen der subzellulären Mechanik im Einschluss mit optischen Pinzetten

During the development of a multicellular organism, a single fertilized cell divides and gives rise to multiple tissues with diverse functions. Tissue ...

Measurement of Force-Sensitive Protein Dynamics in Living Cells Using a Combination of Fluorescent Techniques

Cells sense and respond to physical cues in their environment by converting mechanical stimuli into biochemically-detectable signals in a process called mechanotransduction. A crucial step in mechanotransduction is the transmission of forces between the external and internal environments. To transmit forces, there must be a sustained, unbroken physical linkage created by a series of protein-protein interactions. For a given protein-protein interaction, mechanical load can either have no effect on the interaction, lead to faster disassociation of the interaction, or even stabilize the interaction. Understanding how molecular load dictates protein turnover in living cells can provide valuable information about the mechanical state of a protein, in turn elucidating its role in mechanotransduction. Existing techniques for measuring force-sensitive protein dynamics either lack direct measurements of protein load or rely on the measurements performed outside of the cellular context. Here, we describe a protocol for the F&#246;rster resonance energy transfer-fluorescence recovery after photobleaching (FRET-FRAP) technique, which enables the measurement of force-sensitive protein dynamics within living cells. This technique is potentially applicable to any FRET-based tension sensor, facilitating the study of force-sensitive protein dynamics in variety of subcellular structures and in different cell types.

Here, we present a protocol for the simultaneous use of F&#246;rster resonance energy transfer-based tension sensors to measure protein load and fluorescence recovery after photobleaching to measure protein dynamics enabling the measurement of force-sensitive protein dynamics within living cells.

Messung von Kraft-und Kleinschreibung Proteindynamik in lebenden Zellen mit einer Kombination von fluoreszierenden Techniken

Cells sense and respond to physical cues in their environment by converting mechanical stimuli into biochemically-detectable signals in a process called ...

Study of the Actin Cytoskeleton in Live Endothelial Cells Expressing GFP-Actin

The microvascular endothelium plays an important role as a selectively permeable barrier to fluids and solutes. The adhesive junctions between endothelial cells regulate permeability of the endothelium, and many studies have indicated the important contribution of the actin cytoskeleton to determining junctional integrity1-5. A cortical actin belt is thought to be important for the maintenance of stable junctions1, 2, 4, 5. In contrast, actin stress fibers are thought to generate centripetal tension within endothelial cells that weakens junctions2-5. Much of this theory has been based on studies in which endothelial cells are treated with inflammatory mediators known to increase endothelial permeability, and then fixing the cells and labeling F-actin for microscopic observation. However, these studies provide a very limited understanding of the role of the actin cytoskeleton because images of fixed cells provide only snapshots in time with no information about the dynamics of actin structures5. 
Live-cell imaging allows incorporation of the dynamic nature of the actin cytoskeleton into the studies of the mechanisms determining endothelial barrier integrity. A major advantage of this method is that the impact of various inflammatory stimuli on actin structures in endothelial cells can be assessed in the same set of living cells before and after treatment, removing potential bias that may occur when observing fixed specimens. Human umbilical vein endothelial cells (HUVEC) are transfected with a GFP-&beta;-actin plasmid and grown to confluence on glass coverslips. Time-lapse images of GFP-actin in confluent HUVEC are captured before and after the addition of inflammatory mediators that elicit time-dependent changes in endothelial barrier integrity. These studies enable visual observation of the fluid sequence of changes in the actin cytoskeleton that contribute to endothelial barrier disruption and restoration. 
Our results consistently show local, actin-rich lamellipodia formation and turnover in endothelial cells. The formation and movement of actin stress fibers can also be observed. An analysis of the frequency of formation and turnover of the local lamellipodia, before and after treatment with inflammatory stimuli can be documented by kymograph analyses. These studies provide important information on the dynamic nature of the actin cytoskeleton in endothelial cells that can used to discover previously unidentified molecular mechanisms important for the maintenance of endothelial barrier integrity.

Microscopic imaging of live endothelial cells expressing GFP-actin allows characterization of dynamic changes in cytoskeletal structures. Unlike techniques that use fixed specimens, this method provides a detailed assessment of temporal changes in the actin cytoskeleton in the same cells before, during, and after various physical, pharmacological, or inflammatory stimuli.

Studie des Aktin-Zytoskeletts in Live Endothelial Cells, die GFP-Aktin

The microvascular endothelium plays an important role as a selectively permeable barrier to fluids and solutes. The adhesive junctions between endothelial ...

Biologie

Fabrication and Implementation of a Reference-Free Traction Force Microscopy Platform

Quantifying cell-induced material deformation provides useful information concerning how cells sense and respond to the physical properties of their microenvironment. While many approaches exist for measuring cell-induced material strain, here we provide a methodology for monitoring strain with sub-micron resolution in a reference-free manner. Using a two-photon activated photolithographic patterning process, we demonstrate how to generate mechanically and bio-actively tunable synthetic substrates containing embedded arrays of fluorescent fiducial markers to easily measure three-dimensional (3D) material deformation profiles in response to surface tractions. Using these substrates, cell tension profiles can be mapped using a single 3D image stack of a cell of interest. Our goal with this methodology is to make traction force microscopy a more accessible and easier to implement tool for researchers studying cellular mechanotransduction processes, especially newcomers to the field.

This protocol provides instructions for implementing multiphoton lithography to fabricate three-dimensional arrays of fluorescent fiducial markers embedded in poly(ethylene glycol)-based hydrogels for use as reference-free, traction force microscopy platforms. Using these instructions, measurement of 3D material strain and calculation of cellular tractions is simplified to promote high-throughput traction force measurements.

Herstellung und Implementierung einer referenzfreien Traktionskraftmikroskopie-Plattform

Quantifying cell-induced material deformation provides useful information concerning how cells sense and respond to the physical properties of their ...

Traction Force Microscopy to Study B Lymphocyte Activation

Traction force microscopy (TFM) enables the measurement of forces produced by a cell on a substrate. This technique infers traction force measurements from an experimentally observed displacement field produced by a cell pulling on an elastic substrate. Here, we adapted TFM to investigate the spatial and temporal structure of the force field exerted by B cells when activated by antigen engagement of the B cell receptor. Gel rigidity, bead density, and protein functionalization must be optimized for the study of relatively small cells (~ 6 &#181;m) that interact with, and respond specifically to ligands for cell surface receptors.

Here we present a protocol used to perform traction force microscopy experiments on B cells. We describe the preparation of soft polyacrylamide gels and their functionalization, as well as data acquisition at the microscope and a summary of data analysis.

Traktionskraftmikroskopie zur Untersuchung der B-Lymphozytenaktivierung

Traction force microscopy (TFM) enables the measurement of forces produced by a cell on a substrate. This technique infers traction force measurements ...

Pattern Generation for Micropattern Traction Microscopy

Micropattern traction microscopy allows control of the shape of single cells and cell clusters. Furthermore, the ability to pattern at the micrometer length scale allows the use of these patterned contact zones for the measurement of traction forces, as each micropatterned dot allows for the formation of a single focal adhesion that then deforms the soft, underlying hydrogel. This approach has been used for a wide range of cell types, including endothelial cells, smooth muscle cells, fibroblasts, platelets, and epithelial cells. 
This review describes the evolution of techniques that allow the printing of extracellular matrix proteins onto polyacrylamide hydrogels in a regular array of dots of prespecified size and spacing. As micrometer-scale patterns are difficult to directly print onto soft substrates, patterns are first generated on rigid glass coverslips that are then used to transfer the pattern to the hydrogel during gelation. First, the original microcontact printing approach to generate arrays of small dots on the coverslip is described. A second step that removes most of the pattern to leave islands of small dots is required to control the shapes of cells and cell clusters on such arrays of patterned dots. 
Next, an evolution of this approach that allows for the generation of islands of dots using a single subtractive patterning step is described. This approach is greatly simplified for the user but has the disadvantage of a decreased lifetime for the master mold needed to make the patterns. Finally, the computational approaches that have been developed for the analysis of images of displaced dots and subsequent cell-generated traction fields are described, and updated versions of these analysis packages are provided.

We describe improvements to a standard method for measuring cellular traction forces, based on microcontact printing with a single subtractive patterning step of dot arrays of extracellular matrix proteins on soft hydrogels. This method allows for simpler and more consistent fabrication of island patterns, essential for controlling cell cluster shape.

Mustergenerierung für die Mikromuster-Traktionsmikroskopie

Micropattern traction microscopy allows control of the shape of single cells and cell clusters. Furthermore, the ability to pattern at the micrometer ...