Vinculina-GFP plasmídeo foi um presente de Kenneth Yamada, National Institutes of Health, Instituto Nacional de Pesquisa Dental e Craniofacial, Bethesda, Maryland, e actina-MRFP plasmídeo foi um presente de Michael Davidson, Universidade Estadual da Flórida, Tallahassee, Florida. Este trabalho foi financiado pela NSF Prémio Carreira # 0747334 e AHA-Nacional SDG # 0835205N a Andreea Trache.

1. Visão Geral do Sistema Integrado de Microscopia O sistema de microscópio que é usado para estes estudos tem sido descrito em detalhe 1. Resumidamente, um microscópio invertido Olympus IX-81 com TIRF anexo (Olympus, Center Valley, PA) é combinado com CSU-22 Yokogawa cabeça de leitura (Yokogawa Electric Inc, Japão). A Bioscope SZ microscópio de força atômica (Veeco Instruments Inc, Santa Barbara, CA) é montado em cima do microscópio óptico invertido, e todo o sistema é colocado em cima de uma mesa de grade de pesquisa óptico (Newport, Irvine, CA). A montagem confocal compostas a partir da verificação do disco de fiação, roda de filtros externos e sua câmera EMCCD (Roper Scientific-fotométricos, Tucson, AZ) são rigidamente conectados com uma placa base de alumínio colocada sobre uma almofada de silício necessária para amortecimento de vibrações. O scanner confocal se conecta com o microscópio através de uma flange com um colar treaded que pode ser dissociado do microscópio AFM durante as medições, de forma que nenhuma vibração do scanner disco girando vai afetar as medidas AFM. Um laser de argônio-Krypton (Spectra Physics, Mountain View, CA) é usado como fonte de excitação para ambos TIRF e modos de imagem confocal, e podem ser acoplados, em alternativa, duas fibras ópticas que entregar a laser para o acessório TIRF ou a cabeça de leitura, respectivamente . Dois computadores de controle do sistema: Slidebook software controla a imagem óptica e software Nanoscope controla o AFM. 2. Cultura de células Células vivas expressando GFP constrói direcionados contra proteínas específicas deve ser colocado em um copo placa de cultura de células de fundo 24 horas antes do experimento de estimulação mecânica. No dia do experimento substituir o meio de cultura celular com o meio-vermelho de fenol livre. O prato de cultura de células é montado no palco AFM com um colar magnético. 3. Dica AFM Preparação e Microscópio Set-up A ponta do AFM personalizado com um micron 2 biotinilado conta de vidro vai ser lavadas cinco vezes com DPBS e em seguida incubadas 5 min com avidina (1 mg / ml), lavado novamente com DPBS cinco vezes, e em seguida incubadas 5 min com 1 mg / mL biotinilado fibronectina. A dica vai ser lavadas cinco vezes mais no final 2, montada no scanner AFM, e então a saia de silicone de proteção serão colocadas ao redor do portador. Definir o microscópio para visualização de vídeo para alinhar a ponta do AFM no centro do campo de visão. Alinhar a alavanca óptica, colocando o feixe de laser no final do cantilever e altere o objetivo de um objetivo de alta ampliação adequada para imagens de células individuais. A constante da mola da ponta deve ser determinado antes de iniciar o experimento. Esse parâmetro será medido através do método sintonia térmica disponível no software Nanoscope. Mudar de câmera de vídeo para câmera EMCCD para permitir imagens de fluorescência. Em seguida, escolha uma célula e trazer a ponta do AFM em contato com essa célula específica. Após 20 min tempo de espera, que é necessário para uma forte adesão focal para formar no ponto de AFM de contacto com a superfície da célula, o procedimento de estimulação mecânica será iniciado. 4. A estimulação mecânica da Célula Viva TIRF imagem 04/03 será o método de escolha para a visualização e quantificação de aderências focal, e girando-disk confocal imagem 5 será usado para visualizar o citoesqueleto de actina em todo o corpo celular. O AFM 6 vai ser usado em modo de imagem de contato com líquidos. Uma imagem TIRF ou confocal da célula será adquirido antes de iniciar o procedimento de estimulação mecânica. A estimulação mecânica será induzido pela sonda AFM funcionalizados que será movido para cima em passos discretos cada 3-5 min ao longo de um período de tempo (1-1,5 horas). A célula reativa-resposta será gravada continuamente em software Nanoscope como uma série de imagens de altura, cada linha na imagem que representa uma unidade de tempo de 1 seg. Enquanto a aquisição dos dados AFM, o operador monitores em todas as vezes o z-posição da ponta do AFM para determinar o momento adequado para a atração seguinte. Após cada estimulação mecânica é possível adquirir uma imagem TIRF ou confocal da célula em Slidebook software, enquanto a aquisição de dados continuamente AFM. As imagens ópticas podem ser processadas off-line para criar filmes que mostram citoesqueleto de actina e reorganização aderências focal. Além disso, cada imagem pode ser processado para determinar quantitativamente área de células, área de proteína específica, e analisar a morfologia das células em geral. No final do experimento a ponta do AFM é retirado da cela e sensibilidade da ponta AFM será medido no software Nanoscope. O experimento é muito sensíveis ao ruído! Qualquer falar ou tocar em microscópio durante o exmentam devem ser evitados. Para minimizar o ruído nas medidas AFM, o confocal de disco de fiação deve ser dissociado do microscópio. O tempo de espera para formar uma forte adesão focal entre a superfície da célula e a ponta do AFM pode variar dependendo do tipo celular utilizado e as revestidas de matriz na ponta. 5. Resultados representante <img src="/files/ftp_upload/2072/2072fig1.jpg" alt="Figura 1" /> Figura 1. Mesma célula muscular lisa vascular (VSMC) transfectadas com actina-MRFP e vinculina-GFP foi fotografada por: (A) AFM na superfície da célula apical; (B) TIRF na superfície da célula basal e (C) A microscopia confocal girando em disco em todo o corpo celular. A imagem confocal é mostrado como projeção máxima de uma pilha de 3-D. Sobrepõe boa entre o AFM e TIRF ou girando-disk imagens são mostradas em confocal (D) e (E), respectivamente. Tamanho da imagem é de 64 x 50 mícron. <img src="/files/ftp_upload/2072/2072fig2.jpg" alt="Figura 2" /> Figura 2. A VSMC transfectadas com actina-MRFP era mecanicamente estimulada pela AFM e fotografada por fiação de disco microscopia confocal As setas indicam as fibras de actina que:. (A) polimerizar / engrossar, (b) despolimerizar / desaparecer, ou (c) pacote em conjunto, devido para a reestruturação da actina. Linhas brancas tracejadas representam a ponta do AFM acima da célula. Tamanho da imagem 91 x 91 micron.

<ol>
	<li>Trache, A., Lim, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrated+microscopy+for+real-time+imaging+of+mechanotransduction+studies+in+live+cells.">Integrated microscopy for real-time imaging of mechanotransduction studies in live cells.</a> J Biomed Opt. 14, 034024-03 (2009).</li><li>Trache, A., Meininger, G. A., Coico, R., Kowalik, T., Quarles, J. M., Stevenson, B., Taylor, R. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tension+development+during+contractile+stimulation+of+smooth+muscle+requires+recruitment+of+paxillin+and+vinculin+to+the+membrane.">Tension development during contractile stimulation of smooth muscle requires recruitment of paxillin and vinculin to the membrane.</a> Am J Physiol Cell Physiol. 286, C433-C447 (2004).</li><li>Alenghat, F. J., 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:+all+signals+point+to+cytoskeleton,+matrix+and+integrins.">Mechanotransduction: all signals point to cytoskeleton, matrix and integrins.</a> Sciences STKE. 119, pe6-pe6 (2002).</li><li>Zamir, E., Geiger, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+complexity+and+dynamics+of+cell-matrix+adhesions.">Molecular complexity and dynamics of cell-matrix adhesions.</a> J Cell Sci. 114, 3583-3590 (2001).</li><li>Geiger, B., Bershdsky, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assembly+and+mechanosensory+function+of+focal+contacts.">Assembly and mechanosensory function of focal contacts.</a> Curr Opin Cell Biol. 13, 584-592 (2001).</li><li>Sastry, S. K., Burridge, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Focal+Adhesions:+a+nexus+for+intracellular+signaling+and+cytoskeletal+dynamics.">Focal Adhesions: a nexus for intracellular signaling and cytoskeletal dynamics.</a> Exp Cell Res. 261, 25-36 (2000).</li><li>Orr, A. W., Helmke, B. P., Blackman, B. R., 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=Mechanisms+of+mechanotransduction.">Mechanisms of mechanotransduction.</a> Dev Cell. 10, 11-20 (2006).</li></ol>

Não há conflitos de interesse declarados.

Aderências citoesqueleto 10/07 e 16/11 focal são estruturas dinâmicas que montar, dispersar e virar as células migram ou responder a força mecânica 17. Eles têm funções importantes na regulação do crescimento celular, sobrevivência e expressão gênica. Sabendo sua distribuição e dinâmicas específicas fornece uma melhor compreensão de como as células se comunicam com a matriz e entre si. Este sistema novo microscópio é amplamente aplicável em uma ampla gama de estudos de dinâmica molecular em qualquer células aderentes ao vivo. O microscópio integrado permite o monitoramento quantitativo de rápida sub-celular alterações e fornece uma nova ferramenta importante para compreender o processo fundamental de remodelação celular em resposta à força mecânica.

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		<th>Material Name</th>
		<th>Type</th>
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		<th>Catalogue Number</th>
		<th>Comment</th>
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<td>AFM tip</td>
<td>&nbsp;</td>
<td>Novascan Technologies</td>
<td>&nbsp;</td>
<td>2 micron Borosilicate bead, 0.01N/m, Biotin Surface</td>
</tr>
<tr>
<td>avidin</td>
<td>&nbsp;</td>
<td>Sigma Aldrich</td>
<td>A9275</td>
<td>1mg/mL in DPBS</td>
</tr>
<tr>
<td>Fibronectin</td>
<td>&nbsp;</td>
<td>Sigma Aldrich</td>
<td>F4759</td>
<td>1 mg/mL</td>
</tr>
<tr>
<td>DPBS</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>21600-051</td>
<td>&nbsp;</td>
<tr>
<td>Amaxa transfection kit for Smooth Muscle Cells</td>
<td>&nbsp;</td>
<td>Lonza</td>
<td>VPI-1004</td>
<td>&nbsp;</td>
<tr>
<td>Mattek glass bottom dishes</td>
<td>&nbsp;</td>
<td>MatTek Corporation</td>
<td>P60G-1.5-30-F</td>
<td>Sterile 60mm Falcon dishes with glass bottom coverslip no. 1.5</td>
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live cell response to mechanical stimulation studied by integrated optical and atomic force microscopy

Para entender o mecanismo pelo qual as células vivas sentido forças mecânicas, e como eles reagem e se adaptam ao seu ambiente, uma nova tecnologia capaz de investigar o comportamento de células em sub-nível celular com resolução espacial e temporal alta foi desenvolvido. Assim, um microscópio de força atômica (AFM) foi integrado com um total reflexão interna de fluorescência microscopia (TIRF) e velocidade de rotação do disco (FSD) microscopia confocal. O sistema integrado é amplamente aplicável em uma ampla gama de estudos de dinâmica molecular em qualquer células aderentes ao vivo, permitindo que imagens ópticas direta de respostas das células ao estímulo mecânico em tempo real. Reorganização significativa dos filamentos de actina e aderências focal foi mostrado devido à estimulação mecânica local na superfície da célula apical, que induziu alterações na estrutura celular em todo o corpo da célula. Estas técnicas inovadoras irá fornecer novas informações para a compreensão de reestruturação de células vivas e dinâmicas em resposta à força mecânica. Um protocolo detalhado e um conjunto de dados representativos que mostram a resposta de células vivas ao estímulo mecânico são apresentados.

Watch this Scientific Journal Video about Live Cell Response to Mechanical Stimulation Studied by Integrated Optical and Atomic Force Microscopy at JoVE.com

Live Cell Response to Mechanical Stimulation Studied by Integrated Optical and Atomic Force Microscopy

Este trabalho tem como objetivo instruir o leitor na operação de um sistema integrado de força atômica-microscópio óptico de imagem para a estimulação mecânica de células vivas em cultura. Um protocolo passo a passo é apresentado. Um representante conjunto de dados que mostra a resposta de células vivas ao estímulo mecânico é apresentado.

Resposta celular ao vivo para Estimulação mecânicas estudadas por Microscopia de Força Atômica e Óptica Integrada

To understand the mechanism by which living cells sense mechanical forces, and how they respond and adapt to their environment, a new technology able to ...

live-cell-response-to-mechanical-stimulation-studied-integrated

Nanyang Technological University

Research

JoVE Journal

Biology

11.2K visualizações.  Texas A&M Health Science Center. Este trabalho tem como objetivo instruir o leitor na operação de um sistema integrado de força atômica-microscópio óptico de imagem para a estimulação mecânica de células vivas em cultura. Um protocolo passo a passo é apresentado. Um representante conjunto de dados que mostra a resposta de células vivas ao estímulo mecânico é apresentado.

Vídeo: Live Cell Response to Mechanical Stimulation Studied by Integrated Optical and Atomic Force Microscopy

Phase Contrast and Differential Interference Contrast (DIC) Microscopy

Phase-contrast microscopy is often used to produce contrast for transparent, non light-absorbing, biological specimens. The technique was discovered by Zernike, in 1942, who received the Nobel prize for his achievement. DIC microscopy, introduced in the late 1960s, has been popular in biomedical research because it highlights edges of specimen structural detail, provides high-resolution optical sections of thick specimens including tissue cells, eggs, and embryos and does not suffer from the  phase halos  typical of phase-contrast images. This protocol highlights the principles and practical applications of these microscopy techniques.

Phase Contrast and Differential Interference Contrast DIC Microscopy

This protocol highlights the principles and practical applications of Phase and Differential Interference Contrast (DIC) Microscopy

Contraste de fase e de interferência diferencial Contrast Microscopy (DIC)

Phase-contrast microscopy is often used to produce contrast for transparent, non light-absorbing, biological specimens. The technique was discovered by ...

Biologia

Micro-Mechanical Characterization of Lung Tissue Using Atomic Force Microscopy

Matrix stiffness strongly influences growth, differentiation and function of adherent cells1-3. On the macro scale the stiffness of tissues and organs within the human body span several orders of magnitude4. Much less is known about how stiffness varies spatially within tissues, and what the scope and spatial scale of stiffness changes are in disease processes that result in tissue remodeling. To better understand how changes in matrix stiffness contribute to cellular physiology in health and disease, measurements of tissue stiffness obtained at a spatial scale relevant to resident cells are needed. This is particularly true for the lung, a highly compliant and elastic tissue in which matrix remodeling is a prominent feature in diseases such as asthma, emphysema, hypertension and fibrosis. To characterize the local mechanical environment of lung parenchyma at a spatial scale relevant to resident cells, we have developed methods to directly measure the local elastic properties of fresh murine lung tissue using atomic force microscopy (AFM) microindentation. With appropriate choice of AFM indentor, cantilever, and indentation depth, these methods allow measurements of local tissue shear modulus in parallel with phase contrast and fluorescence imaging of the region of interest. Systematic sampling of tissue strips provides maps of tissue mechanical properties that reveal local spatial variations in shear modulus. Correlations between mechanical properties and underlying anatomical and pathological features illustrate how stiffness varies with matrix deposition in fibrosis. These methods can be extended to other soft tissues and disease processes to reveal how local tissue mechanical properties vary across space and disease progression.

The stiffness of the extracellular matrix strongly influences multiple behaviors of adherent cells. Matrix stiffness varies spatially throughout a tissue, and undergoes modification in various disease conditions. Here we develop methods to characterize spatial variations in stiffness in normal and fibrotic mouse lung tissue using atomic force microscopy microindentation.

Micro-Mecânica Caracterização do tecido pulmonar Usando Microscopia de Força Atômica

Matrix stiffness strongly influences growth, differentiation and function of adherent cells1-3.  On the macro scale the stiffness of tissues and organs ...

Mechanical Stimulation of Chondrocyte-agarose Hydrogels

Articular cartilage suffers from a limited repair capacity when damaged by mechanical insult or degraded by disease, such as osteoarthritis. To remedy this deficiency, several medical interventions have been developed. One such method is to resurface the damaged area with tissue-engineered cartilage; however, the engineered tissue typically lacks the biochemical properties and durability of native cartilage, questioning its long-term survivability. This limits the application of cartilage tissue engineering to the repair of small focal defects, relying on the surrounding tissue to protect the implanted material. To improve the properties of the developed tissue, mechanical stimulation is a popular method utilized to enhance the synthesis of cartilaginous extracellular matrix as well as the resultant mechanical properties of the engineered tissue. Mechanical stimulation applies forces to the tissue constructs analogous to those experienced in vivo. This is based on the premise that the mechanical environment, in part, regulates the development and maintenance of native tissue1,2. The most commonly applied form of mechanical stimulation in cartilage tissue engineering is dynamic compression at physiologic strains of approximately 5-20% at a frequency of 1 Hz1,3. Several studies have investigated the effects of dynamic compression and have shown it to have a positive effect on chondrocyte metabolism and biosynthesis, ultimately affecting the functional properties of the developed tissue4-8. In this paper, we illustrate the method to mechanically stimulate chondrocyte-agarose hydrogel constructs under dynamic compression and analyze changes in biosynthesis through biochemical and radioisotope assays. This method can also be readily modified to assess any potentially induced changes in cellular response as a result of mechanical stimuli.

The biosynthesis of cartilaginous extracellular matrix by chondrocytes can be affected by application of mechanical stimuli. This method describes the technique of applying dynamic compressive strains to chondrocytes encapsulated in 3D constructs and the evaluation of induced changes in chondrocyte metabolism.

A estimulação mecânica de condrócitos-agarose Hidrogéis

Articular cartilage suffers from a limited repair capacity when damaged by mechanical insult or degraded by disease, such as osteoarthritis. To remedy ...

Sample Preparation for Single Virion Atomic Force Microscopy and Super-resolution Fluorescence Imaging

Immobilization of virions to glass surfaces is a critical step in single virion imaging. Here we present a technique&#160;adopted from single molecule imaging assays which allows adhesion of single virions to glass surfaces with specificity. This preparation is based on grafting the surface of the glass with a mixture of PLL-g-PEG and PLL-g-PEG-Biotin, adding a layer of avidin, and finally creating virion anchors through attachment of biotinylated virus specific antibodies. We have applied this technique across a range of experiments including atomic force microscopy (AFM) and super-resolution fluorescence imaging. This sample preparation method results in a control adhesion of the virions to the surface.

The attachment of virions to a surface is a requirement for single virion imaging by Super-resolution fluorescence imaging or atomic force microscopy (AFM). Here we demonstrate a sample preparation method for controlled adhesion of virions to glass surfaces suitable for use in AFM and super-resolution fluorescence imaging.

Preparação da amostra para microscopia da força atômica de virion único e imagem de fluorescência de super-resolução

Immobilization of virions to glass surfaces is a critical step in single virion imaging. Here we present a technique&#160;adopted from single molecule ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

In Vivo Rastreamento 4-Dimensional de tronco hematopoéticas e células progenitoras em adultos mouse na calota craniana de Medula Óssea

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a versatile analytical tool for characterizing viscoelastic mechanical properties for a variety of materials ranging from hard (plastic, glass, metal, etc.) surfaces to cells on any substrate. It has been widely used to measure the stiffness of cells, but less frequently used to measure the stiffness of aortas. In this paper, we will describe the procedures for using AFM in contact mode to measure the ex vivo elastic modulus of unloaded mouse arteries. We describe our procedure for isolation of mouse aortas, and then provide detailed information for the AFM analysis. This includes step-by-step instructions for alignment of the laser beam, calibration of the spring constant and deflection sensitivity of the AFM probe, and acquisition of force curves. We also provide a detailed protocol for data analysis of the force curves.

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

We present detailed protocols for isolation of aortas from mouse and measurement of their elastic modulus using atomic force microscopy.

Medindo a rigidez<em&gt; Ex Vivo</em&gt; Mouse aortas Usando Microscopia de Força Atômica

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a ...

Analyzing Cell Surface Adhesion Remodeling in Response to Mechanical Tension Using Magnetic Beads

Mechanosensitive cell surface adhesion complexes allow cells to sense the mechanical properties of their surroundings. Recent studies have identified both force-sensing molecules at adhesion sites, and force-dependent transcription factors that regulate lineage-specific gene expression and drive phenotypic outputs. However, the signaling networks converting mechanical tension into biochemical pathways have remained elusive. To explore the signaling pathways engaged upon mechanical tension applied to cell surface receptor, superparamagnetic microbeads can be used. Here we present a protocol for using magnetic beads to apply forces to cell surface adhesion proteins. Using this approach, it is possible to investigate not only force-dependent cytoplasmic signaling pathways by various biochemical approaches, but also adhesion remodeling by magnetic isolation of adhesion complexes attached to the ligand-coated beads. This protocol includes the preparation of ligand-coated superparamagnetic beads, and the application of define tensile forces followed by biochemical analyses. Additionally, we provide a representative sample of data demonstrating that tension applied to integrin-based adhesion triggers adhesion remodeling and alters protein tyrosine phosphorylation.

Cell surface adhesions are central in mechanotransduction, as they transmit mechanical tension and initiate the signaling pathways involved in tissue homeostasis and development. Here, we present a protocol for dissecting the biochemical pathways that are activated in response to tension, using ligand-coated magnetic microbeads and force application to adhesion receptors.

Analisando celular superfície de adesão remodelação em resposta à tensão mecânica usando pérolas magnéticas

Mechanosensitive cell surface adhesion complexes allow cells to sense the mechanical properties of their surroundings. Recent studies have identified both ...

Glucose Uptake Measurement and Response to Insulin Stimulation in In Vitro Cultured Human Primary Myotubes

Skeletal muscle is the largest glucose deposit in mammals and largely contributes to glucose homeostasis. Assessment of insulin sensitivity of muscle cells is of major relevance for all studies dedicated to exploring muscle glucose metabolism and characterizing metabolic alterations. In muscle cells, glucose transporter type 4 (GLUT4) proteins translocate to the plasma membrane in response to insulin, thus allowing massive entry of glucose into the cell. The ability of muscle cells to respond to insulin by increasing the rate of glucose uptake is one of the standard readouts to quantify muscle cell sensitivity to insulin. Human primary myotubes are a suitable in vitro model, as the cells maintain many features of the donor phenotype, including insulin sensitivity. This in vitro model is also suitable for the test of any compounds that could impact insulin responsiveness. Measurements of the glucose uptake rate in differentiated myotubes reflect insulin sensitivity.
In this method, human primary muscle cells are cultured in vitro to obtain differentiated myotubes, and glucose uptake rates with and without insulin stimulation are measured. We provide a detailed protocol to quantify passive and active glucose transport rates using radiolabeled [3H] 2-deoxy-D-Glucose ([3H]2dG). Calculation methods are provided to quantify active basal and insulin-stimulated rates, as well as stimulation fold.

Glucose Uptake Measurement and Response to Insulin Stimulation in In Vitro Cultured Human Primary Myotubes

In this method, human primary muscle cells are cultured in vitro to obtain differentiated myotubes and glucose uptake rates are measured. We provide a detailed protocol to quantify rates in basal and insulin-stimulated states using radiolabeled [3H] 2-deoxy-D-Glucose.

Medição da captação de glicose e resposta à estimulação de insulina em miotubos primários humanos cultivados in vitro

Skeletal muscle is the largest glucose deposit in mammals and largely contributes to glucose homeostasis. Assessment of insulin sensitivity of muscle ...

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Chemotaxis, or migration up a gradient of a chemoattractant, is the best understood mode of directed migration. Studies using social amoeba Dictyostelium discoideum revealed that a complex signal transduction network of parallel pathways amplifies the response to chemoattractants, and leads to biased actin polymerization and protrusion of a pseudopod in the direction of a gradient. In contrast, molecular mechanisms driving other types of directed migration, for example, due to exposure to shear flow or electric fields, are not known. Many regulators of chemotaxis exhibit localization at the leading or lagging edge of a migrating cell, as well as show transient changes in localization or activation following global stimulation with a chemoattractant. To understand the molecular mechanisms of other types of directed migration we developed a method that allows examination of cellular response to acute mechanical stimulation based on brief (2 - 5 s) exposure to shear flow. This stimulation can be delivered in a channel while imaging cells expressing fluorescently-labeled biosensors to examine individual cell behavior. Additionally, cell population can be stimulated in a plate, lysed, and immunoblotted using antibodies that recognize active versions of proteins of interest. By combining both assays, one can examine a wide array of molecules activated by changes in subcellular localization and/or phosphorylation. Using this method we determined that acute mechanical stimulation triggers activation of the chemotactic signal transduction and actin cytoskeleton networks. The ability to examine cellular responses to acute mechanical stimulation is important for understanding the initiating events necessary for shear flow-induced motility. This approach also provides a tool for studying the chemotactic signal transduction network without the confounding influence of the chemoattractant receptor.

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Here we describe methods for assessing cellular response to acute mechanical stimulation. In the microscopy-based assay, we examine localization of fluorescently-labeled biosensors following brief stimulation with shear flow. We also test activation of various proteins of interest in response to acute mechanical stimulation biochemically.

Avaliação de Dictyostelium discoideum resposta à estimulação mecânica aguda

Chemotaxis, or migration up a gradient of a chemoattractant, is the best understood mode of directed migration. Studies using social amoeba Dictyostelium ...

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

In numerous biological contexts, animal cells need to interact physically with their environment by developing mechanical forces. Among these, traction forces have been well-characterized, but there is a lack of techniques allowing the measurement of the protrusion forces exerted by cells orthogonally to their substrate. We designed an experimental setup to measure the protrusion forces exerted by adherent cells on their substrate. Cells plated on a compliant Formvar sheet deform this substrate and the resulting topography is mapped by atomic force microscopy (AFM) at the nanometer scale. Force values are then extracted from an analysis of the deformation profile based on the geometry of the protrusive cellular structures. Hence, the forces exerted by the individual protruding units of a living cell can be measured over time. This technique will enable the study of force generation and its regulation in the many cellular processes involving protrusion. Here, we describe its application to measure the protrusive forces generated by podosomes formed by human macrophages.

Here, we detail the experimental techniques used to evaluate the protrusion forces that podosomes apply on a compliant film, from the preparation of the film to the automated analysis of topographical images.

Microscopia de força de protrusão: Um método para quantificar as forças desenvolvidas pela célula saliências

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