Este estudio fue apoyado por el NIH financiación de la investigación (DK090868 y GM092930 a TI). No es una patente pendiente en un análogo de la rapamicina enjaulado.

1. La transfección de ADN del plásmido <ol><li> Añadir ADN de plásmido, 0,5 g de membrana anclada FRB (en adelante, LDR) y 0,5 mg FKBP-Tiam1 (la invasión de las células T linfoma y metástasis de inducción de proteínas 1: Rac activador) marcados con la proteína fluorescente a 37,5 l O. DH 2 Añadir 1 l HD FuGENE. </li><li> Vortex y se incuba a temperatura ambiente durante 20 minutos. Mientras tanto, siga con los pasos 1.3-1.8. </li><li> Lavar cada pocillo de una cámara de 8-bien con 50 l de poli-D-lisina. </li><li> Lavar el centro de cada pocillo con dH 2 O. </li><li> Trypsinize 80-85% confluentes células NIH-3T3 y diluir a 10 ml de medio de cultivo (DMEM con FBS al 10%). </li><li> Quitar 375 l de la suspensión y centrifugar a 1750 rpm durante 3 minutos. </li><li> Aspirar los medios de comunicación, teniendo cuidado de no perturbar el sedimento. </li><li> Añadir 750 l de FBS DMEM w / 10% y volver a suspender. </li><li> Añadir suspensión celular a DH 2 O / ADN / solución FuGENE HD y mezclar suavemente. </li><li> Añadir 250l de suspensión de células / ADN a cada pocillo (llenarán hasta 3 pocillos). </li><li> Se incuban las células transfectadas a 37 ° C y 5% de CO 2 durante 15-18 horas. </li></ol> 2. Preparación de la CRB-Una solución <ol><li> Sintetizar enjaulado rapamicina-biotina aducto (CRB). Consulte la sección &quot;esquema de síntesis de la CRB&quot; para más detalles. Brevemente, restos enjaulamiento y biotina se preparan por separado. El resto enjaulamiento es entonces conjugado con rapamicina (LC laboratorio), el producto posteriormente acoplado al resto de biotina por un medio de reacción clic 7 para dar CRB. </li><li> Prepare una solución de 1 mM de valores de CRB en DMSO. </li><li> Disolver 1 mg avidina en 250 l de PBS en un tubo Eppendorf de 0,5 ml. </li><li> Añadir 1 l de solución madre CRB avidina disuelto. Mezclar invirtiendo varias veces. </li><li> Incubar a temperatura ambiente durante 15 minutos para dar CRB-avidina conjugada (CRB-A) Solución. </li><li> Excluir las moléculas pequeñas no consolidados y purificar CRB-A. Utilizando una columna de exclusión por tamaño </li></ol> 3. Microscopía e iluminación de luz en el nivel subcelular <ol><li> Suero de hambre células transfectadas en DMEM sin FBS durante 12 horas. </li><li> Aspire con cuidado los medios de comunicación fuera de las células y añadir 250 ml del preparado 400 nM CRB-Una solución (desde el paso 2.6). </li><li> Para visualizar la dinámica de proteínas en las células vivas en la resolución subcelular antes y después del tratamiento de la luz, la microscopía de disco giratorio se utiliza (figura 2a). Iluminación UV se logró mediante el acoplamiento de la óptica de la luz UV LED (365 nm) con epi-fluorescencia de luz (Figura 2b). </li><li> MetaMorph software se utiliza para capturar imágenes de fluorescencia de las células transfectadas cada 15 segundos. </li><li> Definir las coordenadas y el tamaño de un punto de iluminación mediante el uso de una placa de vidrio recubierta con colorantes fluorescentes excitadas por la luz UV. El tamaño puedeser variada mediante la aplicación de la lente objetivo con diferentes aumentos y mediante la selección de las fibras ópticas con núcleo tamaño diferente. </li><li> Después de determinar los niveles de fondo de la membrana fruncido, la luz irradian rayos UV en la periferia de las células. Los siguientes dos pasos son para contrastar anteriores efectos localizados. </li><li> A nivel mundial irradiar las células con luz de 365 nm proporcionada por una lámpara de mercurio. </li><li> Disolver uncaged, por lo que la rapamicina original en DMSO y luego en PBS (400 mM final), y la solución a la cámara de imágenes para producir efectos globales. </li></ol> 4. Los resultados representativos Un ejemplo de resultados representativos se muestran en la Figura 3. La irradiación de luz UV a una pequeña región cerca de un borde celular inducida rápidamente la formación de volantes localizada sólo en y cerca de la zona irradiada. Para confirmar que éste era de hecho la actividad local, luego a nivel internacional las células irradiadas con UV, o añadidos a los medios de rapamicina a granel, tanto de la WHIch inducida por la formación volante global a lo largo de la membrana. Para un análisis cuantitativo, hemos dividido las células diana en cuatro cuadrantes, y contó con la frecuencia de la formación de volantes en cada cuadrante al local, así como después de la estimulación global bajo diversas condiciones, incluyendo los controles (Figura 4). Es sólo que esta combinación de la radiación UV, CRB-A, y apropiadas FKBP-FRB construcciones que induce fruncido local. <img alt="Figura 1" src="/files/ftp_upload/3794/3794fig1.jpg" /> Figura 1. Esquema de la dimerización de la proteína espacialmente confinados con enjaulado rapamicina-avidina conjugada (CRB-A) y la luz ultravioleta. Irradiación UV escinde el enlazador entre la rapamicina y la biotina, resultando en la liberación de productos químicos dimerizer (HE-rapa, C40-O-(2-hidroxietil) rapamicina) y su subproducto. El dimerizer luego liberado se difunde en las células e induce la dimerización entre FKBP-PDI (proteína de interés) y de plasma membRane anclado FRB sólo en la proximidad de la región irradiada (círculo azul). Sin la radiación UV, FKBP y FRB no asociado (cruz roja), por lo tanto, la producción de ningún efecto. (Derechos de Autor @ ACS2011) 6 <img alt="Figura 2" src="/files/ftp_upload/3794/3794fig2.jpg" /> Figura 2. Imagen del microscopio de fluorescencia confocal personalizado. (A) Vista frontal del microscopio confocal (invertido Axiovert 200 de Zeiss). (B) Primer plano, vista desde arriba de una unidad de acoplamiento para el PAI de fluorescencia y luz UV. <img alt="Figura 3" src="/files/ftp_upload/3794/3794fig3.jpg" /> Figura 3. Formación espacialmente confinado en un volante transfectadas NIH3T3 celular inducida por la irradiación UV localizada. Confocal de imágenes de fluorescencia de un celular de fibroblastos NIH3T3 que se transfectaron con YFP de etiquetado FKBP-Tiam1 (Rac activador) y LDR (anclado a la membrana FRB) fueron sometidos a la irradiación en un área confinada cerca de su borde con LED luz a 365 nm durante 15 segundos a partir de 210 segundos en la presencia de CRB-Un conjugado en los medios a granel. Este tratamiento fue seguido por la iluminación global con lámpara de mercurio de 1 seg a 1063 Además seg y global de rapamicina finales 400 Nm a 1560 segundos. La célula casi no mostraron actividad alborotaba al principio (a), pero mostró espacialmente confinados revolviendo después de la iluminación localizada (círculo amarillo) (b). La célula mostró la formación de volante mundial después de la iluminación global y además de la rapamicina (cd), lo que indica que la formación volante local fue causada por la activación de Rac espacialmente confinados. Barra de escala: 10 m. (Derechos de Autor @ ACS2011) 6 <img alt="Figura 4" src="/files/ftp_upload/3794/3794fig4.jpg" /> Figura 4. Frecuencia de la formación de volantes en los cuadrantes de transfectadas las células NIH3T3. La radiación UV local con CRB-A y después de la irradiación UV mundial se realizaron en 13 celdas. CRB-A </sAdemás Trong&gt; (sin irradiación UV), la irradiación UV local con o sin avidina se aplicaron en las células 13, 5 y 6, respectivamente. Ninguna de las células observadas mostró formación volante con CRB-A sin irradiación UV o irradiación UV local con o sin avidina en los medios a granel. Se recogieron los datos a partir de células con baja formación volante de fondo, pero que tenía la capacidad de la rapamicina inducida por la formación de volante, lo que nos marchamos después de cada experimento, al confirmar la formación de volante global como resultado de la suma de la rapamicina (finales de 400 nm). Estos resultados mostraron que CRB-A y la irradiación UV, son necesarias para la formación de volante local en las células. (Derechos de Autor @ ACS2011) 6 Abreviaturas: FKBP: FK506-proteína de unión FRB: FKBP-rapamicina-proteína de unión Tiam1: la invasión de las células T linfoma y metástasis que induce la proteína 1 (Rac FMAM) LDR: Lyn-DSAG enlazador-FRB (Lyn: N-terminal de 11 aminoácidos de Lyn-quinasa) HE-rapa: C40-O - (2-hidroxietil) rapamicina CRB: la rapamicina con el resto de biotina enjaulado CRB-A: CRB conjugado con avidina

<ol>
	<li>Etienne-Manneville, S., Hall, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rho+GTPases+in+cell+biology.">Rho GTPases in cell biology.</a> Nature. 420, 629-635 (2002).</li><li>Takai, Y., Sasaki, T., Matozaki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small+GTP-binding+proteins.">Small GTP-binding proteins.</a> Physiol. Rev. 81, 153-208 (2001).</li><li>Kiyokawa, E., Aoki, K., Nakamura, T., Matsuda, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatiotemporal+regulation+of+small+GTPases+as+revealed+by+probes+based+on+the+principle+of+Forster+Resonance+Energy+Transfer+(FRET):+Implications+for+signaling+and+pharmacology.">Spatiotemporal regulation of small GTPases as revealed by probes based on the principle of Forster Resonance Energy Transfer (FRET): Implications for signaling and pharmacology.</a> Annu. Rev. Pharmacol. Toxicol. 51, 337-358 (2011).</li><li>Inoue, T., Heo, W. D., Grimley, J. S., Wandless, T. J., Meyer, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+inducible+translocation+strategy+to+rapidly+activate+and+inhibit+small+GTPase+signaling+pathways.">An inducible translocation strategy to rapidly activate and inhibit small GTPase signaling pathways.</a> Nat. Methods. 2, 415-418 (2005).</li><li>Komatsu, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organelle-specific,+rapid+induction+of+molecular+activities+and+membrane+tethering.">Organelle-specific, rapid induction of molecular activities and membrane tethering.</a> Nat. Methods. 7, 206-208 (2010).</li><li>Umeda, N., Ueno, T., Pohlmeyer, C., Nagano, T., Inoue, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+photocleavable+rapamycin+conjugate+for+spatiotemporal+control+of+small+GTPase+activity.">A photocleavable rapamycin conjugate for spatiotemporal control of small GTPase activity.</a> J. Am .Chem. Soc. 133, 12-14 (2011).</li><li>Kolb, H. C., Finn, M. G., Sharpless, K. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Click+Chemistry:+Diverse+Chemical+Function+from+a+Few+Good+Reactions.">Click Chemistry: Diverse Chemical Function from a Few Good Reactions.</a> Angew. Chem. Int. Ed. Engl. 40, 2004-2021 (2001).</li><li>Kennedy, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+blue-light-mediated+induction+of+protein+interactions+in+living+cells.">Rapid blue-light-mediated induction of protein interactions in living cells.</a> Nat. Methods. 7, 973-975 (2010).</li><li>Levskaya, A., Weiner, O. D., Lim, W. A., Voigt, 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=Spatiotemporal+control+of+cell+signalling+using+a+light-switchable+protein+interaction.">Spatiotemporal control of cell signalling using a light-switchable protein interaction.</a> Nature. 461, 997-1001 (2009).</li><li>Wu, Y. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+genetically+encoded+photoactivatable+Rac+controls+the+motility+of+living+cells.">A genetically encoded photoactivatable Rac controls the motility of living cells.</a> Nature. 461, 104-108 (2009).</li><li>Yazawa, M., Sadaghiani, A. M., Hsueh, B., Dolmetsch, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+protein-protein+interactions+in+live+cells+using+light.">Induction of protein-protein interactions in live cells using light.</a> Nat. Biotechnol. 27, 941-945 (2009).</li><li>Fegan, A., White, B., Carlson, J. C., Wagner, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemically+controlled+protein+assembly:+techniques+and+applications.">Chemically controlled protein assembly: techniques and applications.</a> Chem. Rev. 110, 3315-3336 (2010).</li><li>Suh, B. C., Inoue, T., Meyer, T., Hille, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+chemically+induced+changes+of+PtdIns(4,5)P2+gate+KCNQ+ion+channels.">Rapid chemically induced changes of PtdIns(4,5)P2 gate KCNQ ion channels.</a> Science. 314, 1454-1457 (2006).</li><li>Varnai, P., Thyagarajan, B., Rohacs, T., Balla, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapidly+inducible+changes+in+phosphatidylinositol+4,5-bisphosphate+levels+influence+multiple+regulatory+functions+of+the+lipid+in+intact+living+cells.">Rapidly inducible changes in phosphatidylinositol 4,5-bisphosphate levels influence multiple regulatory functions of the lipid in intact living cells.</a> J. Cell. Biol. 175, 377-382 (2006).</li></ol>

No hay conflictos de interés declarado.

Se describe una técnica que emplea un novedoso compuesto enjaulado junto con el sistema heterodimerización FKBP-FRB con el fin de manipular a la actividad GTPasa Rho en un lugar concreto subcelular en una escala de tiempo de segundos. Hay tres limitaciones del enfoque actual. En primer lugar, porque el método se basa en la prevención o permitiendo la difusión de dimerizer través de la membrana plasmática, la ubicación de destino celular necesita ser membrana plasmática o sus proximi...

<table border="1"><tbody><tr><td> Nombre del reactivo / equipo </td><td> Empresa </td><td> Número de catálogo </td></tr><tr><td> La rapamicina </td><td> Tecoland </td><td> RAPA99 </td></tr><tr><td> FuGENE HD </td><td> Roche </td><td> 04709691001 </td></tr><tr><td> Avidina </td><td> Sigma </td><td> A9275-10MG </td></tr><tr><td> DMSO </td><td> Sigma </td><td> D2650-5X5ML </td></tr><tr><td> De exclusión por tamaño de columna </td><td> GE Healthcare </td><td> Giro Trampa G-25 </td></tr><tr><td> Con fondo de cristal y cámara de 8- </td><td> Thermo Scientific </td><td> 12-565-47 </td></tr><tr><td> Microscopio de fluorescencia invertido </td><td> Zeiss </td><td> Axiovert200M </td></tr><tr><td> UV LED fuente de luz </td><td> Rapp optoelectrónica </td><td> UVILED </td></tr><tr><td> Disco giratorio confocal </td><td> Yokogawa Electric Corp. </td><td> CSU10 </td></tr><tr><td> CCD de la cámara </td><td> Hamamatsu Photonics </td><td> ORCA-ER </td></tr><tr><td> Lente objetivo 100x </td><td> Zeiss </td><td> Plan de Apochromat </td></tr></tbody></table> Esquema de síntesis de la CRB (Derechos de Autor ACS2011) 6 <a href="/files/ftp_upload/3794/3794scheme1_lg.jpg"><img src="/files/ftp_upload/3794/3794scheme1.jpg" alt="Esquema 1" /></a> Condiciones sintéticas: (a) BnBr, K 2 CO 3, DMF (b) f.HNO 3, AcOH (c) de TFA (d) propargílico-Br, K 2 CO 3, DMF, (e) de glicerol, gato. PTSA, tolueno (f) NaBH 3 CN, TiCl 4, MeCN (g) Tf 2 O, piridin (h) metanol HCl, (i) LiAlH 4, THF (j) TsCl, piridina, CH 2 Cl 2 (k) NaN 3, DMF (L) 8, 2,6-di-t-butilpiridina, CH 2 Cl 2 (m) 13, CuSO 4, ascorbato, 2-propanol, H 2 O, CH 2 Cl 2.

spatio-temporal manipulation of small gtpase activity at subcellular level and on timescale of seconds in living cells

Regulación dinámica de la familia Rho de pequeños triphosphatases guanosina (GTPasas) con una precisión espacial y temporal grande es esencial para varias funciones celulares y los eventos 1 y 2. Su naturaleza dinámica espaciotemporalmente ha sido revelado por la visualización de su actividad y localización en tiempo real 3. Con el fin de obtener un mayor conocimiento de sus funciones en diversas funciones celulares a nivel molecular, el siguiente paso debería ser la perturbación de las actividades de la proteína en un lugar concreto subcelular y el tiempo. Para lograr este objetivo, hemos desarrollado un método para la inducida por la luz, espacio-temporalmente la activación controlada de pequeñas GTPasas mediante la combinación de dos técnicas: (1) inducida por la rapamicina FKBP-FRB heterodimerización y (2) un método foto-jaulas de la rapamicina. Con el uso de rapamicina mediada FKBP-FRB heterodimerización, hemos desarrollado un método para la rápida inducible activación o inactivación de pequeño includi GTPasasng Rac 4, 4 Cdc42, RhoA 4 y 5 de Ras, en el que la rapamicina induce la translocación de FKBP fusionados GTPasas o sus activadores, a la membrana plasmática, donde está anclado FRB. Para el acoplamiento con este sistema heterodimerización, también hemos desarrollado un sistema de foto-jaulas de los análogos de rapamicina. Un compuesto foto-enjaulado es una pequeña molécula cuya actividad se suprime con un grupo protector conocido photocleavable como un grupo enjaulamiento. Para suprimir la actividad heterodimerización completamente, hemos diseñado un rapamicina enjaulado que está atado a una macromolécula tal que el gran complejo resultante no puede atravesar la membrana plasmática, que conduce a prácticamente ninguna actividad de fondo como una dimerizer química dentro de las células 6. Figura 1 ilustra un esquema de nuestra sistema. Con la combinación de estos dos sistemas, contratación local un activador de Rac a la membrana plasmática en una escala de tiempo de segundos y alcanzar la luz inducida por la activación de Rac a niveles subcelularEl 6.

Watch this Scientific Journal Video about Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells at JoVE.com

Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells

Un método para el control espacio-temporal de la actividad GTPasa pequeña luz se describe. Este método se basa en la rapamicina inducida FKBP-FRB heterodimerización y sistemas de enjaulamiento foto-. Optimización de la luz de la irradiación permite la activación espacio-temporalmente controlada de las pequeñas GTPasas a nivel subcelular.

Espacio-Temporal de manipulación de la actividad GTPasa pequeña en el nivel subcelular y en escala de tiempo de segundos en las células vivas

Dynamic regulation of the Rho family of small guanosine triphosphatases (GTPases) with great spatiotemporal precision is essential for various cellular ...

spatio-temporal-manipulation-small-gtpase-activity-at-subcellular

Research

JoVE Journal

Bioengineering

10.8K vistas.  Johns Hopkins University. Un método para el control espacio-temporal de la actividad GTPasa pequeña luz se describe. Este método se basa en la rapamicina inducida FKBP-FRB heterodimerización y sistemas de enjaulamiento foto-. Optimización de la luz de la irradiación permite la activación espacio-temporalmente controlada de las pequeñas GTPasas a nivel subcelular.

Video: Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells

Fluorescence Lifetime Imaging of Molecular Rotors in Living Cells

Diffusion is often an important rate-determining step in chemical reactions or biological processes and plays a role in a wide range of intracellular events. Viscosity is one of the key parameters affecting the diffusion of molecules and proteins, and changes in viscosity have been linked to disease and malfunction at the cellular level.1-3 While methods to measure the bulk viscosity are well developed, imaging microviscosity remains a challenge. Viscosity maps of microscopic objects, such as single cells, have until recently been hard to obtain. Mapping viscosity with fluorescence techniques is advantageous because, similar to other optical techniques, it is minimally invasive, non-destructive and can be applied to living cells and tissues.
Fluorescent molecular rotors exhibit fluorescence lifetimes and quantum yields which are a function of the viscosity of their microenvironment.4,5 Intramolecular twisting or rotation leads to non-radiative decay from the excited state back to the ground state. A viscous environment slows this rotation or twisting, restricting access to this non-radiative decay pathway. This leads to an increase in the fluorescence quantum yield and the fluorescence lifetime. Fluorescence Lifetime Imaging (FLIM) of modified hydrophobic BODIPY dyes that act as fluorescent molecular rotors show that the fluorescence lifetime of these probes is a function of the microviscosity of their environment.6-8 A logarithmic plot of the fluorescence lifetime versus the solvent viscosity yields a straight line that obeys the F&ouml;rster Hoffman equation.9 This plot also serves as a calibration graph to convert fluorescence lifetime into viscosity.
Following incubation of living cells with the modified BODIPY fluorescent molecular rotor, a punctate dye distribution is observed in the fluorescence images. The viscosity value obtained in the puncta in live cells is around 100 times higher than that of water and of cellular cytoplasm.6,7 Time-resolved fluorescence anisotropy measurements yield rotational correlation times in agreement with these large microviscosity values. Mapping the fluorescence lifetime is independent of the fluorescence intensity, and thus allows the separation of probe concentration and viscosity effects. 
In summary, we have developed a practical and versatile approach to map the microviscosity in cells based on FLIM of fluorescent molecular rotors.

Fluorescence Lifetime Imaging (FLIM) has emerged as a key technique to image the environment and interaction of specific proteins and dyes in living cells. FLIM of fluorescent molecular rotors allows mapping of viscosity in living cells.

Imágenes de fluorescencia vida de rotores moleculares en las células vivas

Diffusion is often an important rate-determining step in chemical reactions or biological processes and plays a role in a wide range of intracellular ...

Investigación

Bioingeniería

Quantitative and Temporal Control of Oxygen Microenvironment at the Single Islet Level

Simultaneous oxygenation and monitoring of glucose stimulus-secretion coupling factors in a single technique is critical for modeling pathophysiological states of islet hypoxia, especially in transplant environments. Standard hypoxic chamber techniques cannot modulate both stimulations at the same time nor provide real-time monitoring of glucose stimulus-secretion coupling factors. To address these difficulties, we applied a multilayered microfluidic technique to integrate both aqueous and gas phase modulations via a diffusion membrane. This creates a stimulation sandwich around the microscaled islets within the transparent polydimethylsiloxane (PDMS) device, enabling monitoring of the aforementioned coupling factors via fluorescence microscopy. Additionally, the gas input is controlled by a pair of microdispensers, providing quantitative, sub-minute modulations of oxygen between 0-21%. This intermittent hypoxia is applied to investigate a new phenomenon of islet preconditioning. Moreover, armed with multimodal microscopy, we were able to look at detailed calcium and KATP channel dynamics during these hypoxic events. We envision microfluidic hypoxia, especially this simultaneous dual phase technique, as a valuable tool in studying islets as well as many ex vivo tissues.

Microfluidic oxygen control confers more than just convenience and speed over hypoxic chambers for biological experiments. Especially when implemented via diffusion through a membrane, microfluidic oxygen can provide simultaneous liquid and gas phase modulations at the microscale-level. This technique enables dynamic multi-parametric experiments critical for studying islet pathophysiology.

Control cuantitativo y temporal del Microambiente oxígeno en el Islote de un solo nivel

Simultaneous oxygenation and monitoring of glucose stimulus-secretion coupling factors in a single technique is critical for modeling pathophysiological ...

Isolation of Primary Human Colon Tumor Cells from Surgical Tissues and Culturing Them Directly on Soft Elastic Substrates for Traction Cytometry

Cancer cells respond to matrix mechanical stiffness in a complex manner using a coordinated, hierarchical mechano-chemical system composed of adhesion receptors and associated signal transduction membrane proteins, the cytoskeletal architecture, and molecular motors1, 2. Mechanosensitivity of different cancer cells in vitro are investigated primarily with immortalized cell lines or murine derived primary cells, not with primary human cancer cells. Hence, little is known about the mechanosensitivity of primary human colon cancer cells in vitro. Here, an optimized protocol is developed that describes the isolation of primary human colon cells from healthy and cancerous surgical human tissue samples. Isolated colon cells are then successfully cultured on soft (2 kPa stiffness) and stiff (10 kPa stiffness) polyacrylamide hydrogels and rigid polystyrene (~3.6 GPa stiffness) substrates functionalized by an extracellular matrix (fibronectin in this case). Fluorescent microbeads are embedded in soft gels near the cell culture surface, and traction assay is performed to assess cellular contractile stresses using free open access software. In addition, immunofluorescence microscopy on different stiffness substrates provides useful information about primary cell morphology, cytoskeleton organization and vinculin containing focal adhesions as a function of substrate rigidity.

A protocol is described to extract primary human cells from surgical colon tumor and normal tissues. The isolated cells are then cultured on soft elastic substrates (polyacrylamide hydrogels) functionalized by an extracellular matrix protein, and embedded with fluorescent microbeads. Traction cytometry is performed to assess cellular contractile stresses.

Aislamiento de células tumorales de colon humanos primarios de tejidos quirúrgicos y cultivándolas Directamente en Elastic sustratos blandos de tracción Citometría

Cancer cells respond to matrix mechanical stiffness in a complex manner using a coordinated, hierarchical mechano-chemical system composed of adhesion ...

A Label-free Technique for the Spatio-temporal Imaging of Single Cell Secretions

Inter-cellular communication is an integral part of a complex system that helps in maintaining basic cellular activities. As a result, the malfunctioning of such signaling can lead to many disorders. To understand cell-to-cell signaling, it is essential to study the spatial and temporal nature of the secreted molecules from the cell without disturbing the local environment. Various assays have been developed to study protein secretion, however, these methods are typically based on fluorescent probes which disrupt the relevant signaling pathways. To overcome this limitation, a label-free technique is required.
In this paper, we describe the fabrication and application of a label-free localized surface plasmon resonance imaging (LSPRi) technology capable of detecting protein secretions from a single cell. The plasmonic nanostructures are lithographically patterned onto a standard glass coverslip and can be excited using visible light on commercially available light microscopes. Only a small fraction of the coverslip is covered by the nanostructures and hence this technique is well suited for combining common techniques such as fluorescence and bright-field imaging.
A multidisciplinary approach is used in this protocol which incorporates sensor nanofabrication and subsequent biofunctionalization, binding kinetics characterization of ligand and analyte, the integration of the chip and live cells, and the analysis of the measured signal. As a whole, this technology enables a general label-free approach towards mapping cellular secretions and correlating them with the responses of nearby cells.

Inter-cellular communication is critical for controlling various physiological activities within and outside the cell. This paper describes a protocol for measuring the spatio-temporal nature of single cell secretions. To achieve this, a multidisciplinary approach is used which integrates label-free nanoplasmonic sensing with live cell imaging.

Una técnica-Label libre para el Imaging espacio-temporal de las secreciones sola célula

Inter-cellular communication is an integral part of a complex system that helps in maintaining basic cellular activities. As a result, the malfunctioning ...

Optical Control of Living Cells Electrical Activity by Conjugated Polymers

Hybrid interfaces between organic semiconductors and living tissues represent a new tool for in-vitro and in-vivo applications. In particular, conjugated polymers display several optimal properties as substrates for biological systems, such as good biocompatibility, excellent mechanical properties, cheap and easy processing technology, and possibility of deposition on light, thin and flexible substrates. These materials have been employed for cellular interfaces like neural probes, transistors for excitation and recording of neural activity, biosensors and actuators for drug release. Recent experiments have also demonstrated the possibility to use conjugated polymers for all-optical modulation of the electrical activity of cells. Several in-vitro study cases have been reported, including primary neuronal networks, astrocytes and secondary line cells. Moreover, signal photo-transduction mediated by organic polymers has been shown to restore light sensitivity in degenerated retinas, suggesting that these devices may be used for artificial retinal prosthesis in the future. All in all, light sensitive conjugated polymers represent a new approach for optical modulation of cellular activity.
In this work, all the steps required to fabricate a bio-polymer interface for optical excitation of living cells are described. The function of the active interface is to transduce the light stimulus into a modulation of the cell membrane potential. As a study case, useful for in-vitro studies, a polythiophene thin film is used as the functional, light absorbing layer, and Human Embryonic Kidney (HEK-293) cells are employed as the biological component of the interface. Practical examples of successful control of the cell membrane potential upon stimulation with light pulses of different duration are provided. In particular, it is shown that both depolarizing and hyperpolarizing effects on the cell membrane can be achieved depending on the duration of the light stimulus. The reported protocol is of general validity and can be straightforwardly extended to other biological preparations.

A method for stimulation of in-vitro cell cultures electrical activity with visible light, based on the use of organic semiconducting polymers is described.

Control óptico de células vivas Actividad Eléctrica por conjugadas Polímeros

Hybrid interfaces between organic semiconductors and living tissues represent a new tool for in-vitro and in-vivo applications. In particular, conjugated ...

Co-culture of Living Microbiome with Microengineered Human Intestinal Villi in a Gut-on-a-Chip Microfluidic Device

Here, we describe a protocol to perform long-term co-culture of multi-species human gut microbiome with microengineered intestinal villi in a human gut-on-a-chip microphysiological device. We recapitulate the intestinal lumen-capillary tissue interface in a microfluidic device, where physiological mechanical deformations and fluid shear flow are constantly applied to mimic peristalsis. In the lumen microchannel, human intestinal epithelial Caco-2 cells are cultured to form a &#39;germ-free&#39; villus epithelium and regenerate small intestinal villi. Pre-cultured microbial cells are inoculated into the lumen side to establish a host-microbe ecosystem. After microbial cells adhere to the apical surface of the villi, fluid flow and mechanical deformations are resumed to produce a steady-state microenvironment in which fresh culture medium is constantly supplied and unbound bacteria (as well as bacterial wastes) are continuously removed. After extended co-culture from days to weeks, multiple microcolonies are found to be randomly located between the villi, and both microbial and epithelial cells remain viable and functional for at least one week in culture. Our co-culture protocol can be adapted to provide a versatile platform for other host-microbiome ecosystems that can be found in various human organs, which may facilitate in vitro study of the role of human microbiome in orchestrating health and disease.

We describe an in vitro protocol to co-culture gut microbiome and intestinal villi for an extended period using a human gut-on-a-chip microphysiological system.

Co-cultivo de estar con microbioma intestinal humana microconstruidos Villi en una Gut-on-a-Chip dispositivo de microfluidos

Here, we describe a protocol to perform long-term co-culture of multi-species human gut microbiome with microengineered intestinal villi in a human ...

Isolation of Mesenchymal Stem Cells from Human Alveolar Periosteum and Effects of Vitamin D on Osteogenic Activity of Periosteum-derived Cells

Mesenchymal stem cells (MSCs) are present in a variety of tissues and can be differentiated into numerous cell types, including osteoblasts. Among the dental sources of MSCs, the periosteum is an easily accessible tissue, which has been identified to contain MSCs in the cambium layer. However, this source has not yet been widely studied.
Vitamin D3 and 1,25-(OH)2D3 have been demonstrated to stimulate in vitro differentiation of MSCs into osteoblasts. In addition, vitamin C facilitates collagen formation and bone cell growth. However, no study has yet investigated the effects of Vitamin D3 and Vitamin C on MSCs.
Here, we present a method of isolating MSCs from human alveolar periosteum and examine the hypothesis that 1,25-(OH)2D3 may exert an osteoinductive effect on these cells. We also investigate the presence of MSCs in the human alveolar periosteum and assess stem cell adhesion and proliferation. To assess the ability of vitamin C (as a control) and various concentrations of 1,25-(OH)2D3 (10&#8722;10, 10&#8722;9, 10&#8722;8, and 10&#8722;7 M) to alter key mRNA biomarkers in isolated MSCs mRNA expression of alkaline phosphatase (ALP), bone sialoprotein (BSP), core binding factor alpha-1 (CBFA1), collagen-1, and osteocalcin (OCN) are measured using real-time polymerase chain reaction (RT-PCR).

We present a protocol to investigate the mRNA expression biomarkers of periosteum-derived cells (PDCs) induced by vitamin C (vitamin C) and 1,25-dihydroxy vitamin D [1,25-(OH)2D3]. In addition, we evaluate the ability of PDCs to differentiate into osteocytes, chondrocytes, and adipocytes.

Aislamiento de células madre mesenquimatosas del periostio Alveolar humano y efectos de la vitamina D en la actividad osteogénica de células derivadas del periostio

Mesenchymal stem cells (MSCs) are present in a variety of tissues and can be differentiated into numerous cell types, including osteoblasts. Among the ...

Light-sheet Fluorescence Microscopy to Capture 4-Dimensional Images of the Effects of Modulating Shear Stress on the Developing Zebrafish Heart

The hemodynamic forces experienced by the heart influence cardiac development, especially trabeculation, which forms a network of branching outgrowths from the myocardium. Genetic program defects in the Notch signaling cascade are involved in ventricular defects such as Left Ventricular Non-Compaction Cardiomyopathy or Hypoplastic Left Heart Syndrome. Using this protocol, it can be determined that shear stress driven trabeculation and Notch signaling are related to one another. Using Light-sheet Fluorescence Microscopy, visualization of the developing zebrafish heart was possible. In this manuscript, it was assessed whether hemodynamic forces modulate the initiation of trabeculation via Notch signaling and thus, influence contractile function occurs. For qualitative and quantitative shear stress analysis, 4-D (3-D+time) images were acquired during zebrafish cardiac morphogenesis, and integrated light-sheet fluorescence microscopy with 4-D synchronization captured the ventricular motion. Blood viscosity was reduced via gata1a-morpholino oligonucleotides (MO) micro-injection to decrease shear stress, thereby, down-regulating Notch signaling and attenuating trabeculation. Co-injection of Nrg1 mRNA with gata1a MO rescued Notch-related genes to restore trabeculation. To confirm shear stress driven Notch signaling influences trabeculation, cardiomyocyte contraction was further arrested via tnnt2a-MO to reduce hemodynamic forces, thereby, down-regulating Notch target genes to develop a non-trabeculated myocardium. Finally, corroboration of the expression patterns of shear stress-responsive Notch genes was conducted by subjecting endothelial cells to pulsatile flow. Thus, the 4-D light-sheet microscopy uncovered hemodynamic forces underlying Notch signaling and trabeculation with clinical relevance to non-compaction cardiomyopathy.

Here, we present a protocol to visualize developing hearts in zebrafish in 4-Dimensions (4-D). 4-D imaging, via light-sheet fluorescence microscopy (LSFM), takes 3-Dimensional (3-D) images over time, to reconstruct developing hearts. We show qualitatively and quantitatively that shear stress activates endocardial Notch signaling during chamber development, which promotes cardiac trabeculation.

Microscopía de fluorescencia de la hoja de luz para capturar imágenes de 4 dimensiones de los efectos de la modulación de la tensión de esquileo en el corazón de pez cebra en desarrollo

The hemodynamic forces experienced by the heart influence cardiac development, especially trabeculation, which forms a network of branching outgrowths ...

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.

Medición de la proteína sensible a la fuerza dinámica en células vivas usando una combinación de técnicas fluorescentes

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

Patterning the Geometry of Human Embryonic Stem Cell Colonies on Compliant Substrates to Control Tissue-Level Mechanics

Human embryonic stem cells demonstrate a unique ability to respond to morphogens in vitro by self-organizing patterns of cell fate specification that correspond to primary germ layer formation during embryogenesis. Thus, these cells represent a powerful tool with which to examine the mechanisms that drive early human development. We have developed a method to culture human embryonic stem cells in confined colonies on compliant substrates that provides control over both the geometry of the colonies and their mechanical environment in order to recapitulate the physical parameters that underlie embryogenesis. The key feature of this method is the ability to generate polyacrylamide hydrogels with defined patterns of extracellular matrix ligand at the surface to promote cell attachment. This is achieved by fabricating stencils with the desired geometric patterns, using these stencils to create patterns of extracellular matrix ligand on glass coverslips, and transferring these patterns to polyacrylamide hydrogels during polymerization. This method is also compatible with traction force microscopy, allowing the user to measure and map the distribution of cell-generated forces within the confined colonies. In combination with standard biochemical assays, these measurements can be used to examine the role mechanical cues play in fate specification and morphogenesis during early human development.

Extracellular matrix ligands can be patterned onto polyacrylamide hydrogels to enable the culture of human embryonic stem cells in confined colonies on compliant substrates. This method can be combined with traction force microscopy and biochemical assays to examine the interplay between tissue geometry, cell-generated forces, and fate specification.

Patrón de la geometría de las colonias de células madre embrionarias humanas en sustratos compatibles para controlar la mecánica de nivel de tejido

Human embryonic stem cells demonstrate a unique ability to respond to morphogens in vitro by self-organizing patterns of cell fate specification that ...