Questo lavoro è sostenuto da NIH R01 GM47607, CA163296 e NSF 1.334.493 di CET. Ringraziamo i membri del laboratorio Turner per la lettura critica del manoscritto. Tutti i dati riportati nella presente relazione sono stati riprodotti da permesso da Wormer et al. 2014 11.

1. Preparazione di Durotaxis Chambers <ol><li> Per preparare un 6-pozzetti di coltura tissutale, tarare la bilancia con un tubo da 50 ml. Pesare circa 10 g della soluzione di base PDMS nel tubo da 50 ml (la soluzione è abbastanza viscoso). </li><li> Per 90: 1 substrato (Compliance di ~ 1 kPa), dividere il peso misurato della soluzione di base PDMS nel tubo 90 per determinare la corretta quantità di soluzione reticolante necessaria. Aggiungere la quantità calcolata di soluzione reticolante PDMS al tubo stesso. Esempio: 10 g / 90 = 0,11 g. Aggiungere 0,11 g della soluzione reticolante PDMS alla soluzione di base PDMS. NOTA: La base e reticolante soluzioni sono entrambi forniti nel kit PDMS. </li><li> Mescolare energicamente la miscela base / reticolante PDMS per 5 minuti a temperatura ambiente usando una piccola spatola. A questo punto la miscela contiene un gran numero di bolle d&#39;aria. </li><li> Centrifugare il substrato PDMS in una centrifuga da banco per 5 min a 50 xg a temperatura ambiente per rimuovere l&#39;bubbles. Se ci sono ancora bolle dopo 5 min, centrifuga di nuovo. </li><li> Pipettare 1 ml di 90: 1 PDMS substrato in ciascun pozzetto della coltura di tessuti trattati 6 pozzetti. Eventuali bolle d&#39;aria residue presenti nei PDMS possono essere eliminate in questa fase estraendo usando un ago 21 G. Lasciare le PDMS a diffondere per 30 minuti nel pozzo. </li><li> Bollire 12 millimetri di vetro # 1 coprioggetto in acqua distillata per 5 min. Ripetere due volte e memorizzare i coprioggetti in acqua distillata. </li><li> Mettere uno, coprioggetto secco in ciascun pozzetto della piastra di coltura tissutale toccando delicatamente un lato del vetrino nella soluzione PDMS poi cadere il vetrino sui PDMS. Come il coprioggetto deposita, PDMS cominceranno ad invadere sui bordi del vetrino, ma non copre completamente. Questo genera un&#39;interfaccia tra le PDMS e vetro dopo la polimerizzazione (vedere Figura 1A, B). </li><li> Incubare la piastra a 70 ° C in un forno per 16 ore per curare (indurimento) PDMS. Posizionare il plate in una cappa di coltura cellulare e UV sterilizzare per 10 min. NOTA: E &#39;meglio per rendere le piastre entro un paio di giorni di utilizzo. Tuttavia, le piastre possono essere avvolte in Parafilm senza tampone e conservati a 4 ° C fino a 2 settimane senza alcuna diminuzione nella qualità. </li></ol> 2. Cella placcatura NOTA: Se studiare l&#39;effetto di knockdown siRNA-mediata, eseguire il colpo con le istruzioni del produttore o il protocollo ottimizzato per il tipo cellulare di scelta. <ol><li> Coat ogni durotaxis camera con 1 ml di 10 mg / ml in PBS fibronectina senza calcio e magnesio per 1 ora a 37 ° C. In alternativa, la fibronectina può essere applicato il giorno prima dell&#39;analisi incubando le PDMS con 10 ug / ml in PBS fibronectina per 16 ore a 4 ° C. Assicurarsi che l&#39;intera superficie è immersa nel fibronectina in soluzione PBS. </li><li> Preparare calore denaturato 1% di BSA. Pesare 0,5 g BSA e scioglierlo in 50 ml di PBS.Filtro sterilizzare la soluzione attraverso un filtro di 0,22 micron e riscaldare a 80 ° C per 12 min. Nota: Preparare questa soluzione il giorno prima cella di placcatura e conservare a 4 ° C. </li><li> Aspirare la soluzione fibronectina e lavare 3 volte con PBS. Aggiungere 1 ml di calore denaturato BSA in PBS ad ogni pozzetto ed incubare per 30 minuti a RT. </li><li> Trypsinize e contare le cellule di scelta, mentre le camere durotaxis stanno bloccando con il calore denaturato BSA. </li><li> Piastra 1 x 10 5 cellule in un volume di 2 ml in ciascun pozzetto della camera durotaxis, utilizzando il supporto desiderato per il particolare tipo di cellula di scelta. Permettono alle cellule di aderire e diffondere sul substrato per 4 ore in un incubatore umidificato a 37 ° C con 5% di CO 2. NOTA: cellule U2OS sono normalmente mantenute in DMEM con 10% FBS, supplementato con 2 mM L-glutammina, 1 mM sodio piruvato, e 10 UI / ml di penicillina, 10 mg / ml di streptomicina. NOTA: il numero di cellule usato in questo esempio è ottimizzato perCellule U2OS. Ottimizzazione per altri tipi di cellule può essere richiesto. Questa densità dà le cellule sufficiente per migrare senza interazioni significative con altre cellule. </li></ol> Imaging 3. Live-cell <ol><li> Eseguire l&#39;imaging cellulare dal vivo su un microscopio invertito, con contrasto di fase con un obiettivo 10X. Il microscopio deve essere dotato di un ambiente, camera umidificata chiusa, permettendo il controllo di temperatura a 37 ° C e 5% CO 2 durante l&#39;imaging a lungo termine. </li><li> Dopo che le cellule si sono diffuse per circa 3,5 ore, montare la placca nella camera microscopio. Lasciare il campione (s) per equilibrare nella camera per 30 min. </li><li> Impostare automatizzato, multi-punto in visita sul microscopio, se disponibile. Focus su l&#39;interfaccia tra le 90: 1 PDMS e il vetrino di vetro e scegliere i punti per l&#39;immagine in tutto l&#39;interfaccia con una media di 40 punti per durotaxis camera. Immagine le cellule ogni 10 min per un massimo di 16 ore. NOTA: Il regione di interesse apparirà come due linee, con la linea esterna corrispondente al bordo del vetrino e la linea interna corrispondente all&#39;interfaccia effettiva tra le PDMS e il vetrino. Vedere la Figura 1B. </li></ol> Analisi 4. I dati <ol><li> Generare un foglio di calcolo come nella tabella 1. </li><li> Contare il numero di eventi di attraversamento dalle PDMS alla superficie di vetro e viceversa da ogni film generato. Registrare il numero di eventi di attraversamento nell&#39;apposita colonna nel foglio di calcolo Excel. NOTA: Un evento di crossing è definito come il nucleo cellulare passando sopra il confine tra le PDMS e vetro in entrambe le direzioni. </li><li> Per quantificare attraversare più, contare il numero di volte che la cella è transitato dall&#39;interfaccia. Tale numero deve essere registrato nella colonna di Excel corrispondente al substrato su cui la cella era situato alla fine del film. Ripetere l&#39;analisi per ogni cellula che attraversa l&#39;interfaccia in tfilm che. Escludere le cellule che migrano fuori dal campo visivo durante l&#39;imaging. NOTA: È anche importante verificare, da cellule contando all&#39;inizio dell&#39;esperimento, che le cellule sono in grado di aderire ugualmente ai PDMS fibronectina rivestite coprioggetto e superfici di vetro. </li><li> Calcolare la percentuale di cellule che migrato da PDMS alla superficie del vetro (cioè, durotaxis subito). Aggiungere il numero di attraversare gli eventi da morbido a duro e gli eventi di attraversamento più che si sono concluse sul disco e dividere per il numero totale di eventi di attraversamento. </li><li> Calcolare la percentuale di attraversare più dividendo il numero di attraversare più volte per il numero totale di incroci. </li></ol>

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R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matrix+crosslinking+forces+tumor+progression+by+enhancing+integrin+signaling.">Matrix crosslinking forces tumor progression by enhancing integrin signaling.</a> Cell. 139 (5), 891-906 (2009).</li><li>Lo, C. M., Wang, H. B., Dembo, M., Wang, Y. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+movement+is+guided+by+the+rigidity+of+the+substrate.">Cell movement is guided by the rigidity of the substrate.</a> Biophysical Journal. 79 (1), 144-152 (2000).</li><li>Plotnikov, S. V., Waterman, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Guiding+cell+migration+by+tugging.">Guiding cell migration by tugging.</a> Current Opinion in Cell Biology. 25 (5), 619-626 (2013).</li><li>Choquet, D., Felsenfeld, D. P., Sheetz, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+matrix+rigidity+causes+strengthening+of+integrin-cytoskeleton+linkages.">Extracellular matrix rigidity causes strengthening of integrin-cytoskeleton linkages.</a> Cell. 88 (1), 39-48 (1997).</li><li>Balaban, N. Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Force+and+focal+adhesion+assembly:+a+close+relationship+studied+using+elastic+micropatterned+substrates.">Force and focal adhesion assembly: a close relationship studied using elastic micropatterned substrates.</a> Nature Cell Biology. 3 (5), 466-472 (2001).</li><li>Provenzano, P. P., Keely, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+signaling+through+the+cytoskeleton+regulates+cell+proliferation+by+coordinated+focal+adhesion+and+Rho+GTPase+signaling.">Mechanical signaling through the cytoskeleton regulates cell proliferation by coordinated focal adhesion and Rho GTPase signaling.</a> Journal of Cell Science. 124 (8), 1195-1205 (2011).</li><li>Wang, Y. L., Pelham, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+a+flexible,+porous+polyacrylamide+substrate+for+mechanical+studies+of+cultured+cells.">Preparation of a flexible, porous polyacrylamide substrate for mechanical studies of cultured cells.</a> Methods in Enzymology. 298, 489-496 (1998).</li><li>Prager-Khoutorsky, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fibroblast+polarization+is+a+matrix-rigidity-dependent+process+controlled+by+focal+adhesion+mechanosensing.">Fibroblast polarization is a matrix-rigidity-dependent process controlled by focal adhesion mechanosensing.</a> Nature Cell Biology. 13 (12), 1457-1465 (2011).</li><li>Wormer, D. B., Davis, K. A., Henderson, J. H., Turner, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+focal+adhesion-localized+CdGAP+regulates+matrix+rigidity+sensing+and+durotaxis.">The focal adhesion-localized CdGAP regulates matrix rigidity sensing and durotaxis.</a> PloS ONE. 9 (3), e91815 (2014).</li><li>Trichet, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+of+a+large-scale+mechanosensing+mechanism+for+cellular+adaptation+to+substrate+stiffness.">Evidence of a large-scale mechanosensing mechanism for cellular adaptation to substrate stiffness.</a> Proceedings of the National Academy of Sciences. 109 (18), 6933-6938 (2012).</li><li>Eyckmans, J., Boudou, T., Yu, X., Chen, C. 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The authors have no conflicts to disclose.

Qui descriviamo un semplice test per studiare durotaxis in migrazione delle cellule. Un punto di forza di questo saggio è la facilità di preparazione delle camere durotaxis con PDMS. La rigidità dei substrati può essere facilmente manipolata modificando il rapporto di soluzione di base PDMS a reticolante per consentire lo studio di varie rigidità nel test. Tuttavia, una potenziale limitazione del sistema è che le cellule sono esposte a un solo cambiamento di rigidità del substrato rispetto a sperimentare un gradi...

La matrice extracellulare (ECM) è costituito da una serie complessa di proteine ​​strutturali e reticolazione compreso collagene, fibronectina e laminina. Anche se è noto che l&#39;ECM fornisce un importante supporto strutturale per tessuti cellulari, ci sono sempre più prove per indicare che le cellule rispondono attivamente ai cambiamenti fisici nel loro ambiente ECM per regolare i processi cellulari diversi, tra cui la sopravvivenza cellulare, la differenziazione e la migrazione delle cellule. Ad esempio, le differenze nella rigidità della ECM può guidare le cellule staminali mesenchimali verso differenti linee, con i substrati molli (~ 1 kPa) promuovono lignaggi neurogene mentre rigidi (~ 25 kPa) substrati di promuovere la differenziazione osteogenica 1. Analogamente, un aumento della rigidità matrice stromale ha dimostrato di promuovere la tumorigenesi mammaria cellule epiteliali ed invasione nel 2,3 tessuto circostante. Un aspetto particolarmente interessante di questo mechanosignrisultati dell&#39;attività aling in un processo noto come durotaxis, in cui le cellule migrano preferenzialmente verso un substrato più rigido 4,5. Le cellule rilevano costantemente le caratteristiche fisiche del loro ambiente extracellulare attraverso recettore integrina legame alla ECM. Questo, a sua volta, promuove l&#39;accumulo di numerose proteine ​​strutturali e segnalazione ai loro domini citoplasmatici per guidare la formazione di strutture adesive note come adesioni focali o contatti focali 6,7. Dal momento che le integrine non hanno attività enzimatica intrinseca, i segnali vengono inoltrati dal ECM attraverso queste proteine ​​accessorie per coordinare la risposta delle cellule al loro ambiente mutevole 8. Di conseguenza, l&#39;identificazione e la caratterizzazione delle proteine ​​chiave coinvolte nella regolazione mechanosignaling e durotaxis è un&#39;importante area di ricerca. Vari sistemi modello sono stati sviluppati per studiare durotaxis in vitro, ma la maggior parte hannoutilizzati collagene rivestite poliacrilammide substrati 4. Tuttavia, la preparazione dei substrati di poliacrilammide può essere tecnicamente impegnativo e il collagene utilizzato in questi saggi deve essere chimicamente reticolato al substrato 9. Polidimetilsilossano (PDMS) substrati hanno dimostrato di presentare proprietà meccaniche paragonabili ai substrati di poliacrilammide 10. Tuttavia, substrati PDMS vengono preparate semplicemente miscelando un rapporto della base di reticolante e questi substrati possono essere rivestiti con proteine ​​ECM senza la necessità di reticolazione chimica, rendendo così più facile PDMS uno strumento per studiare gli effetti di rigidità sul comportamento cellulare. Qui, si descrive come preparare una semplice camera di durotaxis in cui un substrato morbido PDMS è integrato con un coprioggetto vetro rigido. Il saggio, come indicato di seguito, fornisce un metodo rapido e semplice per lo studio durotaxis. Per questo studio abbiamo utilizzato cellule di osteosarcoma U2OS umane combinate con siRNA-mediataatterramento di cdGAP per studiare il ruolo di questa proteina di adesione focale durotaxis 11. È importante sottolineare che questo protocollo può essere facilmente adattato alle esigenze individuali. Altri tipi cellulari possono essere sostituiti per le cellule U2OS e qualsiasi proteina possono essere abbassati o overexpressed per determinare gli effetti sul comportamento cellulare durante durotaxis. Inoltre, questo protocollo può essere adattato per incorporare le proteine ​​fluorescenti tag per analizzare le loro dinamiche e comportamento utilizzando FRAP o preoccuparsi approcci.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Polydimethylsiloxane (PDMS)</td>
			<td>Dow Corning</td>
			<td>3097358-1004</td>
			<td>Sylgard 184 Silicone Elastomer Kit</td>
		</tr>
		<tr>
			<td>#1 Cover glass 12mm</td>
			<td>Fisher Scientific</td>
			<td>12-545-82</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well plate</td>
			<td>Celltreat</td>
			<td>229106</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Cellgro</td>
			<td>15-017-CM</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>Cellgro</td>
			<td>25-005-CI</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Pyruvate</td>
			<td>Fisher Scientific</td>
			<td>BP356-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>Cellgro</td>
			<td>30-002-CI</td>
			<td></td>
		</tr>
		<tr>
			<td>Fibronectin</td>
			<td>BD Biosciences</td>
			<td>610077</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Invitrogen</td>
			<td>21600-044</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon tubes</td>
			<td>Celltreat</td>
			<td>229456</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Atlanta Biologicals</td>
			<td>S11150</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin</td>
			<td>Sigma</td>
			<td>A7906</td>
			<td></td>
		</tr>
		<tr>
			<td>U2OS cells</td>
			<td>ATCC</td>
			<td>HTB-96</td>
			<td></td>
		</tr>
	</tbody>
</table>

a simplified system for evaluating cell mechanosensing and durotaxis in vitro

Le proprietà meccaniche e composizione della matrice extracellulare sono molto variabili tra i tipi di tessuto. Questo connettivo diversità stroma del tessuto notevolmente comportamento impatti cella per regolare i processi normali e patologiche tra cui la proliferazione cellulare, la differenziazione, la segnalazione di adesione e la migrazione direzionale. A questo proposito, la capacità innata di certi tipi di cellule a migrare verso un substrato matrice rigida, o meno compatibile è indicato come durotaxis. Questo fenomeno ha un ruolo importante durante lo sviluppo embrionale, la riparazione delle ferite e l&#39;invasione delle cellule tumorali. Qui, descriviamo un test semplice per studiare durotaxis, in vitro, utilizzando polidimetilsilossano (PDMS) substrati. Preparazione del descritto durotaxis camere crea un&#39;interfaccia tra la rigidità relativamente morbido gel PDMS e un vetrino di vetro rigida. Nell&#39;esempio fornito, abbiamo usato queste durotaxis alloggiamenti per dimostrare un ruolo per il Cdc42 / Rac1 GTPasi prote attivazionein, cdGAP, in mechanosensing e durotaxis regolazione nelle cellule umane U2OS osteosarcoma. Questo test è facilmente adattabile ad altri tipi e / o atterramento di altre proteine ​​di interesse cellulari per esplorare i loro rispettivi ruoli nel mechanosignaling e durotaxis.

Uno schema della camera durotaxis è mostrato nella Figura 1A. Substrato PDMS molle (90: 1 miscela di base di PDMS a reticolante soluzioni) si sviluppa in un piatto 6 pozzo e un vetrino di vetro è posto sulla parte superiore delle PDMS, che poi ricopre parzialmente la superficie superiore del vetrino, creando un&#39;interfaccia tra i due substrati di conformità diverso. La rigidità del substrato PDMS morbido è ~ 1 kPa, che è paragonabile alla conformità tipica del tessuto cerebral...

Watch this Scientific Journal Video about A Simplified System for Evaluating Cell Mechanosensing and Durotaxis In Vitro at JoVE.com

A Simplified System for Evaluating Cell Mechanosensing and Durotaxis In Vitro

Many mammalian cells preferentially migrate towards a more rigid matrix or substrate through durotaxis. The goal of this protocol is to provide a simple in vitro system that can be used to study and manipulate cell durotaxis behaviors by incorporating polydimethylsiloxane (PDMS) substrates of defined rigidity, interfacing with glass coverslips.

Un sistema semplificato per la valutazione delle cellule Mechanosensing e Durotaxis<em&gt; In Vitro</em

The composition and mechanical properties of the extracellular matrix are highly variable between tissue types. This connective tissue stroma diversity ...

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Biology

A Simplified System for Evaluating Cell Mechanosensing and Durotaxis In Vitro

8.1K Views.  SUNY Upstate Medical University. Many mammalian cells preferentially migrate towards a more rigid matrix or substrate through durotaxis. The goal of this protocol is to provide a simple in vitro system that can be used to study and manipulate cell durotaxis behaviors by incorporating polydimethylsiloxane (PDMS) substrates of defined rigidity, interfacing with glass coverslips.

Video: A Simplified System for Evaluating Cell Mechanosensing and Durotaxis In Vitro

Mosaic Zebrafish Transgenesis for Evaluating Enhancer Sequences

The completion of the human genome sequence, along with that of many other species, has highlighted the challenge of ascribing specific function to non coding sequences. One prominent function carried out by the non coding fraction of the genome is to regulate gene transcription; however, there are no effective methods to broadly predict cis-regulatory elements from primary DNA sequence. We have developed an efficient protocol to functionally evaluate potential cis-regulatory elements through zebrafish transgenesis. Our approach offers significant advantages over cell-culture based techniques for developmentally important genes, since it provides information on spatial and temporal gene regulation. Conversely, it is faster and less expensive than similar experiments in transgenic mice, and we routinely apply it to sequences isolated from the human genome. Here we demonstrate our approach to selecting elements for testing based on sequence conservation and our protocol for cloning sequences and microinjecting them into zebrafish embryos.

We demonstrate our approach to finding potential enhancer elements from developmentally regulated genes and evaluating their function through mosaic zebrafish transgenesis.

Mosaico Transgenesi Zebrafish per la valutazione sequenze Enhancer

The completion of the human genome sequence, along with that of many other species, has highlighted the challenge of ascribing specific function to non ...

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Biologia

Efficient Derivation of Human Cardiac Precursors and Cardiomyocytes from Pluripotent Human Embryonic Stem Cells with Small Molecule Induction

To date, the lack of a suitable human cardiac cell source has been the major setback in regenerating the human myocardium, either by cell-based transplantation or by cardiac tissue engineering1-3. Cardiomyocytes become terminally-differentiated soon after birth and lose their ability to proliferate. There is no evidence that stem/progenitor cells derived from other sources, such as the bone marrow or the cord blood, are able to give rise to the contractile heart muscle cells following transplantation into the heart1-3. The need to regenerate or repair the damaged heart muscle has not been met by adult stem cell therapy, either endogenous or via cell delivery1-3. The genetically stable human embryonic stem cells (hESCs) have unlimited expansion ability and unrestricted plasticity, proffering a pluripotent reservoir for in vitro derivation of large supplies of human somatic cells that are restricted to the lineage in need of repair and regeneration4,5. Due to the prevalence of cardiovascular disease worldwide and acute shortage of donor organs, there is intense interest in developing hESC-based therapies as an alternative approach. However, how to channel the wide differentiation potential of pluripotent hESCs efficiently and predictably to a desired phenotype has been a major challenge for both developmental study and clinical translation. Conventional approaches rely on multi-lineage inclination of pluripotent cells through spontaneous germ layer differentiation, resulting in inefficient and uncontrollable lineage-commitment that is often followed by phenotypic heterogeneity and instability, hence, a high risk of tumorigenicity6-8 (see a schematic in Fig. 1A). In addition, undefined foreign/animal biological supplements and/or feeders that have typically been used for the isolation, expansion, and differentiation of hESCs may make direct use of such cell-specialized grafts in patients problematic9-11. To overcome these obstacles, we have resolved the elements of a defined culture system necessary and sufficient for sustaining the epiblast pluripotence of hESCs, serving as a platform for de novo derivation of clinically-suitable hESCs and effectively directing such hESCs uniformly towards clinically-relevant lineages by small molecules12 (see a schematic in Fig. 1B). After screening a variety of small molecules and growth factors, we found that such defined conditions rendered nicotinamide (NAM) sufficient to induce the specification of cardiomesoderm direct from pluripotent hESCs that further progressed to cardioblasts that generated human beating cardiomyocytes with high efficiency (Fig. 2). We defined conditions for induction of cardioblasts direct from pluripotent hESCs without an intervening multi-lineage embryoid body stage, enabling well-controlled efficient derivation of a large supply of human cardiac cells across the spectrum of developmental stages for cell-based therapeutics.

We have established a protocol for induction of cardioblasts direct from pluripotent human embryonic stem cells maintained under defined conditions with small molecules, which enables derivation of a large supply of human cardiac progenitors and functional cardiomyocytes for cardiovascular repair.

Derivazione efficiente dei diritti dell&#39;uomo e precursori cardiaci e cardiomiociti pluripotenti da cellule staminali embrionali umane con induzione piccole molecole

To date, the lack of a suitable human cardiac cell source has been the major setback in regenerating the human myocardium, either by cell-based ...

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the messagefor review see 1. However, it's now widely accepted that synonymous codon usage is the primary cause of non-uniform translational elongation rates1. Synonymous codons are not used with identical frequency. A bias exists in the use of synonymous codons with some codons used more frequently than others2. Codon bias is organism as well as tissue specific2,3. Moreover, frequency of codon usage is directly proportional to the concentrations of cognate tRNAs4. Thus, a frequently used codon will have higher multitude of corresponding tRNAs, which further implies that a frequent codon will be translated faster than an infrequent one. Thus, regions on mRNA enriched in rare codons (potential pause sites) will as a rule slow down ribosome movement on the message and cause accumulation of nascent peptides of the respective sizes5-8. These pause sites can have functional impact on the protein expression, mRNA stability and protein foldingfor review see 9. Indeed, it was shown that alleviation of such pause sites can alter ribosome movement on mRNA and subsequently may affect the efficiency of co-translational (in vivo) protein folding1,7,10,11. To understand the process of protein folding in vivo, in the cell, that is ultimately coupled to the process of protein synthesis it is essential to gain comprehensive insights into the impact of codon usage/tRNA content on the movement of ribosomes along mRNA during translational elongation.
Here we describe a simple technique that can be used to locate major translation pause sites for a given mRNA translated in various cell-free systems6-8. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA. The rationale is that at low-frequency codons, the increase in the residence time of the ribosomes results in increased amounts of nascent peptides of the corresponding sizes. In vitro transcribed mRNA is used for in vitro translational reactions in the presence of radioactively labeled amino acids to allow the detection of the nascent chains. In order to isolate ribosome bound nascent polypeptide complexes the translation reaction is layered on top of 30% glycerol solution followed by centrifugation. Nascent polypeptides in polysomal pellet are further treated with ribonuclease A and resolved by SDS PAGE. This technique can be potentially used for any protein and allows analysis of ribosome movement along mRNA and the detection of the major pause sites. Additionally, this protocol can be adapted to study factors and conditions that can alter ribosome movement and thus potentially can also alter the function/conformation of the protein.

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

A technique to identify translational pause sites on mRNA is described. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA, followed by the size analysis of the nascent chains using a denaturing gel electrophoresis.

Isolamento dei ribosomi Polipeptidi Bound nascenti<em&gt; In vitro</em&gt; Per identificare i siti di pausa traslazione lungo mRNA

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the ...

Assaying Proteasomal Degradation in a Cell-free System in Plants

The ubiquitin-proteasome pathway for protein degradation has emerged as one of the most important mechanisms for regulation of a wide spectrum of cellular functions in virtually all eukaryotic organisms. Specifically, in plants, the ubiquitin/26S proteasome system (UPS) regulates protein degradation and contributes significantly to development of a wide range of processes, including immune response, development and programmed cell death. Moreover, increasing evidence suggests that numerous plant pathogens, such as Agrobacterium, exploit the host UPS for efficient infection, emphasizing the importance of UPS in plant-pathogen interactions.
The substrate specificity of UPS is achieved by the E3 ubiquitin ligase that acts in concert with the E1 and E2 ligases to recognize and mark specific protein molecules destined for degradation by attaching to them chains of ubiquitin molecules. One class of the E3 ligases is the SCF (Skp1/Cullin/F-box protein) complex, which specifically recognizes the UPS substrates and targets them for ubiquitination via its F-box protein component. To investigate a potential role of UPS in a biological process of interest, it is important to devise a simple and reliable assay for UPS-mediated protein degradation. Here, we describe one such assay using a plant cell-free system. This assay can be adapted for studies of the roles of regulated protein degradation in diverse cellular processes, with a special focus on the F-box protein-substrate interactions.

Targeted protein degradation represents a major regulatory mechanism for cell function. It occurs via a conserved ubiquitin-proteasome pathway, which attaches polyubiquitin chains to the target protein that then serve as molecular &#8220;tags&#8221; for the 26S proteasome. Here, we describe a simple and reliable cell-free assay for proteasomal degradation of proteins.

Saggio del proteasoma degradazione in un sistema di libero-Cell nelle piante

The ubiquitin-proteasome pathway for protein degradation has emerged as one of the most important mechanisms for regulation of a wide spectrum of cellular ...

Quantitation of Endothelial Cell Adhesiveness In Vitro

One of the cardinal processes of inflammation is the infiltration of immune cells from the lumen of the blood vessel to the surrounding tissue. This occurs when endothelial cells, which line blood vessels, become adhesive to circulating immune cells such as monocytes. In vitro measurement of this adhesiveness has until now been done by quantifying the total number of monocytes that adhere to an endothelial layer either as a direct count or by indirect measurement of the fluorescence of adherent monocytes. While such measurements do indicate the average adhesiveness of the endothelial cell population, they are confounded by a number of factors, such as cell number, and do not reveal the proportion of endothelial cells that are actually adhesive. Here we describe and demonstrate a method which allows the enumeration of adhesive cells within a tested population of endothelial monolayer. Endothelial cells are grown on glass coverslips and following desired treatment are challenged with monocytes (that may be fluorescently labeled). After incubation, a rinsing procedure, involving multiple rounds of immersion and draining, the cells are fixed. Adhesive endothelial cells, which are surrounded by monocytes are readily identified and enumerated, giving an adhesion index that reveals the actual proportion of endothelial cells within the population that are adhesive.

Quantitation of Endothelial Cell Adhesiveness In Vitro

We report an in vitro method that allows the quantitation of the actual number of adhesive cells within an endothelial cell monolayer.

La quantificazione di adesività delle cellule endoteliali<em&gt; In Vitro</em

One of the cardinal processes of inflammation is the infiltration of immune cells from the lumen of the blood vessel to the surrounding tissue. This ...

An Efficient In Vitro Transposition Method by a Transcriptionally Regulated Sleeping Beauty System Packaged into an Integration Defective Lentiviral Vector

The Sleeping Beauty (SB) transposon is a non-viral integrating system with proven efficacy for gene transfer and functional genomics. To optimize the SB transposon machinery, a transcriptionally regulated hyperactive transposase (SB100X) and T2-based transposon are employed. Typically, the transposase and transposon are provided transiently by plasmid transfection and SB100X expression is driven by a constitutive promoter. Here, we describe an efficient method to deliver the SB components to human cells that are resistant to several physical and chemical transfection methods, to control SB100X expression and stably integrate a gene of interest (GOI) through a &#34;cut and paste&#34; SB mechanism. The expression of hyperactive transposase is tightly controlled by the Tet-ON system, widely used to control gene expression since 1992. The gene of interest is flanked by inverted repeats (IR) of the T2 transposon. Both SB components are packaged in integration defective lentiviral vectors transiently produced in HEK293T cells. Human cells, either cell lines or primary cells from human tissue, are in vitro transiently transduced with viral vectors. Upon addition of doxycycline (dox, tetracycline analog) into the culture medium, a fine-tuning of transposase expression is measured and results in a long-lasting integration of the gene of interest in the genome of the treated cells. This method is efficient and applicable to the cell line (e.g., HeLa cells) and primary cells (e.g., human primary keratinocytes), and thus represents a valuable tool for genetic engineering and therapeutic gene transfer.

An Efficient In Vitro Transposition Method by a Transcriptionally Regulated Sleeping Beauty System Packaged into an Integration Defective Lentiviral Vector

This protocol describes a method to achieve stable integration of a gene of interest into the human genome by the transcriptionally regulated Sleeping Beauty system. Preparation of the integration of defective lentiviral vectors, the in vitro transduction of human cells, and the molecular assay on transduced cells are reported.

Un metodo efficiente In Vitro trasposizione da un sistema di bellezza dormire trascrizionalmente regolata confezionato in un vettore lentivirale difettoso di integrazione

The Sleeping Beauty (SB) transposon is a non-viral integrating system with proven efficacy for gene transfer and functional genomics. To optimize the SB ...

Single Cell Durotaxis Assay for Assessing Mechanical Control of Cellular Movement and Related Signaling Events

Durotaxis is the process by which cells sense and respond to gradients of tension. In order to study this process in vitro, the stiffness of the substrate underlying a cell must be manipulated. While hydrogels with graded stiffness and long-term migration assays have proven useful in durotaxis studies, immediate, acute responses to local changes in substrate tension allow focused study of individual cell movements and subcellular signaling events. To repeatably test the ability of cells to sense and respond to the underlying substrate stiffness, a modified method for application of acute gradients of increased tension to individual cells cultured on deformable hydrogels is used which allows for real time manipulation of the strength and direction of stiffness gradients imparted upon cells in question. Additionally, by fine tuning the details and parameters of the assay, such as the shape and dimensions of the micropipette or the relative position, placement, and direction of the applied gradient, the assay can be optimized for the study of any mechanically sensitive cell type and system. These parameters can be altered to reliably change the applied stimulus and expand the functionality and versatility of the assay. This method allows examination of both long term durotactic movement as well as more immediate changes in cellular signaling and morphological dynamics in response to changing stiffness.

Mechanical forces are important for controlling cell migration. This protocol demonstrates the use of elastic hydrogels that can be deformed using a glass micropipette and a micromanipulator to stimulate cells with a local stiffness gradient to elicit changes in cell structure and migration.

Analisi A singola cella Durotaxis per valutare il controllo meccanico del movimento cellulare e gli eventi di segnalazione correlati

Durotaxis is the process by which cells sense and respond to gradients of tension. In order to study this process in vitro, the stiffness of the substrate ...

Valutazione degli effetti fitochimici su Helicoverpa armigera attraverso il saggio di alimentazione

Developing a Feeding Assay System for Evaluating the Insecticidal Effect of Phytochemicals on Helicoverpa armigera

Helicoverpa armigera, a lepidopteran insect, is a polyphagous pest with a worldwide distribution. This herbivorous insect is a threat to plants and agricultural productivity. In response, plants produce several phytochemicals that negatively impact the insect's growth and survival. This protocol demonstrates an obligate feeding assay method to evaluate the effect of a phytochemical (quercetin) on insect growth, development, and survival. Under controlled conditions, the neonates were maintained until the second instar on a pre-defined artificial diet. These second-instar larvae were allowed to feed on a control and quercetin-containing artificial diet for 10 days. The insects' body weight, developmental stage, frass weight, and mortality were recorded on alternate days. The change in body weight, the difference in feeding pattern, and developmental phenotypes were evaluated throughout the assay time. The described obligatory feeding assay simulates a natural mode of ingestion and can be scaled up to a large number of insects. It permits one to analyze phytochemicals' effect on the growth dynamics, developmental transition, and overall fitness of H. armigera. Furthermore, this setup can also be utilized to evaluate alterations in nutritional parameters and digestive physiology processes. This article provides a detailed methodology for feeding assay systems, which may have applications in toxicological studies, insecticidal molecule screening, and understanding chemical effects in plant-insect interactions.

Autore in primo piano: Sviluppo e sfide dei saggi di alimentazione per la gestione dei parassiti degli insetti 

This protocol describes the obligate feeding assay to evaluate the potentially toxic effect of a phytochemical on the lepidopteran insect larvae. This is a highly scalable insect bioassay, easy to optimize the sublethal and lethal dose, deterrent activity, and physiological effect. This could be used for screening eco-friendly insecticides.

Sviluppo di un sistema di dosaggio per l'alimentazione per la valutazione dell'effetto insetticida di sostanze fitochimiche su Helicoverpa armigera

Helicoverpa armigera, a lepidopteran insect, is a polyphagous pest with a worldwide distribution. This herbivorous insect is a threat to plants and ...