L’étude a été financée par des subventions de la Fondazione Bambino Gesù et de Ricerca Corrente (ministère italien de la Santé) à C.C.  Nous tenons à remercier le Dr Enrico Bertini (Département de neurosciences, Unité des maladies neuromusculaires et neurodégénératives, Laboratoire de médecine moléculaire, Hôpital de recherche pour enfants Bambino Gesù), le Dr Stefania Petrini (Centre central de microscopie confocale, Laboratoires de recherche, Hôpital de recherche pour enfants Bambino Gesù), Giulia Pericoli (Département d’onco-hématologie, thérapie génique et cellulaire, Hôpital de recherche pour enfants Bambino Gesù) et Roberta Ferretti (Département d’onco-hématologie, thérapie génique et cellulaire, Hôpital de recherche pour enfants Bambino Gesù) pour des discussions scientifiques et une aide technique. Maria Vinci est récipiendaire d’une bourse « Children with Cancer UK ».

1. Revêtement de 96 plaques de puits
REMARQUE : Différents revêtements ont été testés dans la même plaque, mais dans des puits distincts (voir le dossier supplémentaire).
<ol><li>Diluer le Matrigel 1:100 dans DMEM. Ajouter 100 μL par puits aux plaques de 96 puits et incuber pendant 1 h à température ambiante. Ensuite, retirez la solution et lavez les puits avec 100 μL de DMEM deux fois.</li>
	<li>Laminine diluée (20 μg/mL, LN-521) dans du PBS (avec calcium et magnésium). Ajouter 100 μL au puits et incuber à 4 °C pendant la nuit. Le lendemain, effectuez deux lavages avec DMEM avant d’ensemencer les cellules.</li>
	<li>Diluer la vitronectine (10 μg/mL) dans un tampon de dilution. Ajouter 100 μL par puits à la plaque de 96 puits et incuber pendant 1 heure à température ambiante. Lavez les puits avec du PBS (sans calcium ni magnésium) avant de plaquer les cellules.</li>
	<li>Diluer la HU-fibronectine (30 μg/mL) dans le ddH2O. Ajouter 100 μL dans les puits et incuber à température ambiante pendant 45 minutes. Ensuite, lavez les puits avec le milieu avant d’ensemencer les cellules.</li>
</ol>2. Maintien des CSPi en culture
REMARQUE : Les CSPi ont été achetées dans le commerce. Les CSPi ont été dérivées de fibroblastes humains sains et reprogrammées à l’aide de la technologie épisomique.
<ol><li>À partir du congélateur à -80 °C ou de l’azote liquide, décongeler les CSPi cryoconservés dans un bain-marie à 37 °C. Nettoyez le flacon contenant les cellules avec de l’éthanol à 70 % avant de le déposer dans l’enceinte de sécurité biologique.</li>
	<li>Ajouter goutte à goutte la suspension cellulaire à 5 mL de milieu de culture cellulaire préchauffé (p. ex. mTeSR1) goutte à goutte à l’aide d’une pipette de 1000 μL dans un tube conique stérile de 15 mL.</li>
	<li>Centrifuger les cellules à 304 x g pendant 5 min à température ambiante (RT).</li>
	<li>Retirer le milieu et remettre en suspension la pastille cellulaire dans 4 mL de milieu de culture cellulaire.</li>
	<li>Plaquer la suspension cellulaire dans deux puits des 6 plaques de puits (105 CSPi par boîte de culture cellulaire à 6 puits), où les fibroblastes embryonnaires de souris (MEF) ont été plaqués précédemment. Semencez des MEF deux jours avant le placage de CSPi à une densité de 2,4 x 104/cm2 dans du DMEM (contenant 10 % de sérum fœtal bovin, 1 % de L-glutamine et 1 % de pénicilline-streptomycine).</li>
	<li>Après l’ensemencement, compléter le milieu cellulaire avec 10 μM d’inhibiteur de ROCK Y-27632.</li>
	<li>Cultiver les CSPi sur MEF pendant les 4-5 premières semaines, puis à l’état sans alimentation (condition sans MEF), en utilisant l’un des revêtements d’intérêt (voir l’étape 1 et le tableau 1) dans mTeSR1.</li>
	<li>Lorsque les CSPi sont confluentes à 70-80%, passage 1:4 en utilisant un traitement EDTA de 0,5 mM pendant 3-5 min à TA. Ajouter 1 mL d’EDTA 0,5 mM pour une plaque à 6 puits (ou des quantités proportionnelles pour les autres types de plaques). Transférer dans de nouveaux puits dans des conditions sans alimentation et incuber à 37 °C, 5% CO2, 20% O2.</li>
	<li>Changez le support avec mTeSR1 frais tous les jours et divisez les cellules tous les 2 jours.</li>
</ol>3. Caractérisation de la confluence cellulaire
<ol><li>Utilisez 96 plaques de puits pour les expériences.</li>
	<li>Ensemencer 10 000 cellules par puits après au moins 1 mois de culture en conditions exemptes de mangeoire afin de s’assurer que les MEF n’ont pas été transmis. Utilisez des lames de comptage jetables pour compter les cellules avec le microscope optique.</li>
	<li>Effectuez les expériences en trois exemplaires. Par conséquent, testez chaque condition d’ensemencement dans trois puits.</li>
	<li>Effectuer l’acquisition automatisée d’images dès le jour 1 suivant l’ensemencement à l’aide d’un cytomètre en mode fond clair. Effectuez une acquisition d’image automatisée toutes les 24 heures pendant 5 jours. Pour obtenir des informations détaillées sur les paramètres expérimentaux, reportez-vous au fichier supplémentaire.</li>
	<li>Utilisez le contraste automatique et l’exposition automatique pour mieux visualiser les cellules.</li>
	<li>Définissez le paramètre d’analyse (voir Fichier supplémentaire) pour l’analyse de confluence afin d’appliquer un masque de 60%, 80% et 100% par puits, afin d’évaluer les changements de focalisation dus à la réfraction de la lumière à la limite des puits. Utilisez les différents paramètres d’analyse de masque mentionnés ci-dessus pour analyser la confluence cellulaire à chaque point temporel.</li>
</ol>4. Analyses statistiques
<ol><li>Déclarez les résultats quantitatifs sous forme de moyennes ±'erreur-type de la moyenne (MEB).</li>
	<li>Pour comparer les différences globales des différentes conditions de revêtement, obtenez des données en utilisant les mêmes échantillons et effectuez le test t de l’échantillon apparié de Student. Les valeurs de p inférieures à 0,05 sont considérées comme statistiquement significatives, et toutes les valeurs p déclarées sont recto verso.</li>
</ol>5. Caractérisation des microfilaments cytosquelettiques
<ol><li>Fixer les cellules avec 4% de paraformaldéhyde (4% PFA) dans PBS pendant 10 min à TA, suivi de deux lavages dans PBS (10 min au total).</li>
	<li>Ajouter 100 μL de solution de blocage (composée de 5% de BSA, 0,1% de Triton dans PBS) à chaque puits pendant 1 h à TA.</li>
	<li>Retirer la solution bloquante et laver les échantillons deux fois avec du PBS pendant 10 min.</li>
	<li>Ajouter 100 μL de la solution de travail conjuguée phalloïdine-conjuguée par échantillon et incuber pendant 1 h à TA.</li>
	<li>Lavez les cellules deux fois avec du PBS (10 min à TA).</li>
	<li>Colorer les noyaux avec Hoechst 33342 dilué 1:10000 dans PBS pendant 10 min à TA.</li>
	<li>Retirez la solution Hoechst et lavez les cellules deux fois avec du PBS pendant 10 minutes à chaque fois.</li>
	<li>Laver l’échantillon avec H2O et laisser sécher sous une hotte chimique.</li>
	<li>Ajouter 100 μL de support de montage (c.-à-d. PBS:glycérol, 1:1) pour couvrir les cellules et préserver la fluorescence des échantillons.</li>
	<li>Observez la cellule à Ex/Em 493/517 nm sur un microscope confocal à balayage laser équipé d’une source laser à lumière blanche (WLL) et d’un laser à diode de 405 nm. Acquérir des images confocales séquentielles à l’aide d’un objectif d’immersion dans l’huile HC PLAPO 40x. Utilisez la même puissance laser, les mêmes séparateurs de faisceau, les mêmes réglages de filtre, les mêmes diamètres de trous d’épingle et le même mode de balayage pour tous les échantillons examinés.</li>
</ol>

<ol>
	<li>Masotti, A., 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=Aged+iPSCs+display+an+uncommon+mitochondrial+appearance+and+fail+to+undergo+in+vitro+neurogenesis.">Aged iPSCs display an uncommon mitochondrial appearance and fail to undergo in vitro neurogenesis.</a> Aging (Albany NY). 6 (12), 1094-1108 (2014).</li><li>Xu, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Feeder-free+growth+of+undifferentiated+human+embryonic+stem+cells.">Feeder-free growth of undifferentiated human embryonic stem cells.</a> Nature Biotechnology. 19, 971-974 (2001).</li><li>Kleinman, H. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+characterization+of+type+IV+procollagen,+laminin,+and+heparan+sulfate+proteoglycan+from+the+EHS+sarcoma.">Isolation and characterization of type IV procollagen, laminin, and heparan sulfate proteoglycan from the EHS sarcoma.</a> Biochemistry. 21 (24), 6188-6193 (1982).</li><li>Rodin, S., 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=Clonal+culturing+of+human+embryonic+stem+cells+on+laminin-521/E-cadherin+matrix+in+defined+and+xeno-free+environment.">Clonal culturing of human embryonic stem cells on laminin-521/E-cadherin matrix in defined and xeno-free environment.</a> Nature Communications. 5, 3195 (2014).</li><li>Rodin, S., Antonsson, L., Hovatta, O., Tryggvason, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monolayer+culturing+and+cloning+of+human+pluripotent+stem+cells+on+laminin-521+based+matrices+under+xeno-free+and+chemically+defined+conditions.">Monolayer culturing and cloning of human pluripotent stem cells on laminin-521 based matrices under xeno-free and chemically defined conditions.</a> Nature Protocols. 9 (10), 2354-2368 (2014).</li><li>Laperle, A., 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=&#945;-5+Laminin+Synthesized+by+Human+Pluripotent+Stem+Cells+Promotes+Self-Renewal.">&#945;-5 Laminin Synthesized by Human Pluripotent Stem Cells Promotes Self-Renewal.</a> Stem Cell Reports. 5 (2), 195-206 (2015).</li><li>Albalushi, H., 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=Laminin+521+stabilizes+the+pluripotency+expression+pattern+of+human+embryonic+stem+cells+initially+derived+on+feeder+cells.">Laminin 521 stabilizes the pluripotency expression pattern of human embryonic stem cells initially derived on feeder cells.</a> Stem Cell International. 2018, 7127042 (2018).</li><li>Zhang, D., 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=Niche-derived+laminin-511+promotes+midbrain+dopaminergic+neuron+survival+and+differentiation+through+YAP.">Niche-derived laminin-511 promotes midbrain dopaminergic neuron survival and differentiation through YAP.</a> Science Signaling. 10 (493), (2017).</li><li>Lu, H. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+defined+xeno-free+and+feeder-free+culture+system+for+the+derivation,+expansion+and+direct+differentiation+of+transgene-free+patient-specific+induced+pluripotent+stem+cells.">A defined xeno-free and feeder-free culture system for the derivation, expansion and direct differentiation of transgene-free patient-specific induced pluripotent stem cells.</a> Biomaterials. 35 (9), 2816-2826 (2015).</li><li>Miyazaki, T., Nakatsuji, N., Suemori, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimization+of+slow+cooling+cryopreservation+for+human+pluripotent+stem+cells.">Optimization of slow cooling cryopreservation for human pluripotent stem cells.</a> Genesis. 52 (1), 49-55 (2014).</li><li>Bergstr&#246;m, R., Str&#246;m, S., Holm, F., Feki, A., Hovatta, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Xeno-free+culture+of+human+pluripotent+stem+cells.">Xeno-free culture of human pluripotent stem cells.</a> Methods in Molecular Biology. 767, 125-136 (2011).</li><li>Braam, S. 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=Recombinant+vitronectin+is+a+functionally+defined+substrate+that+supports+human+embryonic+stem+cell+self-renewal+via+alphavbeta5+integrin.">Recombinant vitronectin is a functionally defined substrate that supports human embryonic stem cell self-renewal via alphavbeta5 integrin.</a> Stem Cells. 26 (9), 2257-2265 (2008).</li><li>Chen, G., 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=Chemically+defined+conditions+for+human+iPSC+derivation+and+culture.">Chemically defined conditions for human iPSC derivation and culture.</a> Nature Methods. 8 (5), 424-429 (2008).</li><li>Li, J., 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=Impact+of+vitronectin+concentration+and+surface+properties+on+the+stable+propagation+of+human+embryonic+stem+cells.">Impact of vitronectin concentration and surface properties on the stable propagation of human embryonic stem cells.</a> Biointerphases. 5 (3), 132-142 (2010).</li><li>Prowse, A. B., 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=Long-term+culture+of+human+embryonic+stem+cells+on+recombinant+vitronectin+in+ascorbate+free+media.">Long-term culture of human embryonic stem cells on recombinant vitronectin in ascorbate free media.</a> Biomaterials. 31 (32), 8281-8288 (2010).</li><li>Rowland, T. J., 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=Roles+of+integrins+in+human+induced+pluripotent+stem+cell+growth+on+Matrigel+and+vitronectin.">Roles of integrins in human induced pluripotent stem cell growth on Matrigel and vitronectin.</a> Stem Cells and Development. 19 (8), 1231-1240 (2010).</li><li>Ruoslahti, E., Engvall, E., Hayman, E. G., Spiro, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+studies+on+amniotic+fluid+and+plasma+fibronectins.">Comparative studies on amniotic fluid and plasma fibronectins.</a> Biochemistry. 193 (1), 295-299 (1981).</li><li>Ni, H., Li, A., Simonsen, N., Wilkins, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrin+activation+by+dithiothreitol+or+Mn2++induces+a+ligand-occupied+conformation+and+exposure+of+a+novel+NH2-terminal+regulatory+site+on+the+beta1+integrin+chain.">Integrin activation by dithiothreitol or Mn2+ induces a ligand-occupied conformation and exposure of a novel NH2-terminal regulatory site on the beta1 integrin chain.</a> Biological Chemistry. 273 (14), 7981-7987 (1998).</li><li>Seltana, A., Basora, N., Beaulieu, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intestinal+epithelial+wound+healing+assay+in+an+epithelial-mesenchymal+co-culture+system.">Intestinal epithelial wound healing assay in an epithelial-mesenchymal co-culture system.</a> Wound Repair &amp; Regeneration. 18 (1), 114-122 (2010).</li><li>Amit, M., Shariki, C., Margulets, V., Itskovitz-Eldor, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Feeder+layer-and+serum-free+culture+of+human+embryonic+stem+cells.">Feeder layer-and serum-free culture of human embryonic stem cells.</a> Biology of Reproduction. 70 (3), 837-845 (2004).</li><li>Vaheri, A., Mosher, D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+molecular+weight,+cell+surface-associated+glyco-protein+(fibronectin)+lost+in+malignant+transformation.">High molecular weight, cell surface-associated glyco-protein (fibronectin) lost in malignant transformation.</a> Biochimica et Biophysica Acta. 516 (1), 1-25 (1978).</li><li>Mao, Y., Schwarzbauer, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fibronectin+fibrillogenesis,+a+cell-mediated+matrix+assembly+process.">Fibronectin fibrillogenesis, a cell-mediated matrix assembly process.</a> Matrix Biology. 24 (6), 389-399 (2005).</li><li>Polyak, K., Weinberg, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transitions+between+epithelial+and+mesenchymal+states:+acquisition+of+malignant+and+stem+cell+traits.">Transitions between epithelial and mesenchymal states: acquisition of malignant and stem cell traits.</a> Nature Reviews Cancer. 9 (4), 265-273 (2009).</li><li>Kadler, K. E., Hill, A., Canty-Laird, E. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collagen+fibrillogenesis:+fibronectin,+integrins,+and+minor+collagens+as+organizers+and+nucleators.">Collagen fibrillogenesis: fibronectin, integrins, and minor collagens as organizers and nucleators.</a> Current Opinion in Cell Biology. 20 (5), 495-501 (2008).</li><li>Hunt, G. C., Schwarzbauer, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tightening+the+connections+between+cadherins+and+fibronectin+matrix.">Tightening the connections between cadherins and fibronectin matrix.</a> Developmental Cell. 16 (3), 327-328 (2009).</li><li>Villa-Diaz, L. G., Ross, A. M., Lahann, J., Krebsbach, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concise+review:+The+evolution+of+human+pluripotent+stem+cell+culture:+from+feeder+cells+to+synthetic+coatings.">Concise review: The evolution of human pluripotent stem cell culture: from feeder cells to synthetic coatings.</a> Stem Cells. 31 (1), 1-7 (2013).</li><li>Engler, A. J., Sen, S., Sweeney, H. L., Discher, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matrix+elasticity+directs+stem+cell+lineage+specification.">Matrix elasticity directs stem cell lineage specification.</a> Cell. 126 (4), 677-689 (2006).</li><li>Vigilante, A., 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=Identifying+Extrinsic+versus+Intrinsic+Drivers+of+Variation+in+Cell+Behavior+in+Human+iPSC+Lines+from+Healthy+Donors.">Identifying Extrinsic versus Intrinsic Drivers of Variation in Cell Behavior in Human iPSC Lines from Healthy Donors.</a> Cell Reports. 26 (8), 2078-2087 (2019).</li></ol>

Les auteurs n’ont rien à divulguer.

L’utilisation des CSPi pour la modélisation des maladies et le dépistage futur des médicaments, ainsi que leur application possible en médecine de précision, en font une technologie d’une grande pertinence et, pour cette raison, nous pensons qu’il est nécessaire de comprendre clairement les conditions de culture in vitro qui ressemblent mieux à la situation physiologique des cellules souches embryonnaires. Dans ce contexte, nous avons testé différents revêtements ECM utilisant des CSPi de type sauvage afi...

Les cellules souches pluripotentes induites (CSPi) sont obtenues à partir de cellules somatiques et peuvent être différenciées en différents types de cellules. Ils sont souvent utilisés comme système pour modéliser la pathogenèse des maladies ou effectuer le dépistage de médicaments, et offrent également le potentiel d’être utilisés dans le contexte de la médecine personnalisée. Étant donné que les CSPi ont un grand potentiel, il est important de les caractériser pleinement pour les utiliser en tant que système modèle fiable. Nous avons déjà montré l’importance de cultiver des CSPi dans un environnement hypoxique, car ces cellules dépendent de la glycolyse et un environnement aérobie peut provoquer un déséquilibre redox1. Les CSPi sont également vulnérables à d’autres conditions de culture, en particulier l’environnement extracellulaire. L’optimisation des conditions de culture est un enjeu clé pour les maintenir en bonne santé et proliférer. Une culture saine de CSPi conduira à des cellules différenciées saines qui sont généralement le point final du modèle utilisé pour comprendre les caractéristiques moléculaires, cellulaires et fonctionnelles de troubles humains ou de processus cellulaires spécifiques.
Dans cette étude, un protocole simple a été utilisé pour tester la confluence des CSPi en utilisant différentes conditions de revêtement dans des puits séparés. Les CSPi nécessitent une couche nourricière de fibroblastes embryonnaires murins (MEF) pour se fixer correctement, mais la coexistence des CSPi et du MEF rend difficile l’analyse comme l’extraction d’ARN ou de protéines puisque deux populations de cellules sont présentes. Afin d’éviter la couche nourricière, différentes protéines appartenant à la matrice extracellulaire (ECM) ont été utilisées pour recréer la niche cellulaire naturelle et pour avoir une culture iPSC sans nourrisseur. En particulier, Matrigel est une préparation solubilisée de membrane basale extraite du sarcome de souris Engelbreth-Holm-Swarm (EHS), qui est enrichie en protéines de la matrice extracellulaire (c.-à-d. laminine, collagène IV, protéoglycanes sulfate d’héparane, entactine/nidogène et facteurs de croissance)2,3. Les autres conditions de revêtement utilisées sont plutôt des protéines purifiées dont la pertinence dans la construction des ECM est connue : la laminine-521 est connue pour être sécrétée par les cellules souches pluripotentes humaines (CSPh) dans la masse cellulaire interne de l’embryon et c’est l’une des laminines les plus courantes dans le corps après la naissance 4,5,6,7,8,9, 10,11; la vitronectine est une matrice de culture cellulaire exempte de xéno connue pour soutenir la croissance et la différenciation desCSPh 12,13,14,15,16; La fibronectine est une protéine ECM importante pour le développement des vertébrés et la fixation et le maintien des cellules souches embryonnaires à l’état pluripotent 17,18,19,20,21,22,23,24,25. Étant donné que différentes conditions de revêtement sont disponibles, nous les comparons en termes d’effet sur la confluence des CSPi.

<table border="0" cellpadding="0" cellspacing="0" style="width:1124px;" width="1123">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:589px;">10 mL Stripette Serological Pipets, Polystyrene, Individually Paper/Plastic Wrapped, Sterile</td>
			<td style="width:281px;">Corning</td>
			<td style="width:77px;">4488</td>
			<td style="width:176px;">Tool</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">15 mL high-clarity polypropylene (PP) conical centrifuge tubes</td>
			<td>Falcon</td>
			<td>352097</td>
			<td>Tool</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;">1x PBS (With Ca2+; Mg2+)</td>
			<td>Thermofisher</td>
			<td>14040133</td>
			<td>Medium</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;">1x PBS (without Ca2+; Mg2+)</td>
			<td>Euroclone</td>
			<td>ECB4004L</td>
			<td>Medium</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">5 mL Stripette Serological Pipets, Polystyrene, Individually Paper/Plastic Wrapped, Sterile</td>
			<td>Corning</td>
			<td>4487</td>
			<td>Tool</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Cell culture microplate, 96 WELL, PS, F-Bottom</td>
			<td>Greiner Bio One</td>
			<td>655090</td>
			<td>Support</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Cell culture plate, 6 well</td>
			<td>Costar</td>
			<td>3516</td>
			<td>Support</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">DMEM (Dulbecco&#39;s Modified Eagle&#39;s Medium- high glucose)</td>
			<td>Sigma</td>
			<td>D5671</td>
			<td>Medium</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">EDTA</td>
			<td>Sigma</td>
			<td>ED4SS-500g</td>
			<td>Reagent</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Epi Episomal iPSC Reprogramming Kit</td>
			<td>Invitrogen</td>
			<td>A15960</td>
			<td>Reagent</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">FAST - READ 102</td>
			<td>Biosigma</td>
			<td>BVS100</td>
			<td>Tool</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fetal Bovine Serum (FBS)</td>
			<td>Gibco</td>
			<td>10270106</td>
			<td>Medium</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fibronectin</td>
			<td>Merck</td>
			<td>FC010</td>
			<td>Coating</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Glycerol</td>
			<td>Sigma</td>
			<td>G5516</td>
			<td>Reagent</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">H2O</td>
			<td></td>
			<td>MILLIQ</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hoechst</td>
			<td>Thermofisher</td>
			<td>33342</td>
			<td>Reagent</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Laminin 521</td>
			<td>Stem Cell Technologies</td>
			<td>77003</td>
			<td>Coating</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">L-Glutamine (200 mM)</td>
			<td>Gibco</td>
			<td>LS25030081</td>
			<td>Reagent</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Matrigel</td>
			<td>Corning Matrigel hESC-Qualified Matrix</td>
			<td>354277</td>
			<td>Coating</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:589px;">Mouse embryonic fibroblasts (MEF)</td>
			<td>Life Technologies</td>
			<td>A24903</td>
			<td>Coating</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">MTESR1 Medium</td>
			<td>Stem Cell Technologies</td>
			<td>85851</td>
			<td>Medium</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">MTESR1 Supplement</td>
			<td>Stem Cell Technologies</td>
			<td>85852</td>
			<td>Medium</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Penicillin-Streptomycin (10,000 U/mL)</td>
			<td>Gibco</td>
			<td>15140122</td>
			<td>Reagent</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Phalloidin</td>
			<td>Sigma</td>
			<td>P1951</td>
			<td>Reagent</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Vitronectin</td>
			<td>Stem Cell Technologies</td>
			<td>7180</td>
			<td>Coating</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Y-27632</td>
			<td>Sigma</td>
			<td>Y0503</td>
			<td>Reagent</td>
		</tr>
	</tbody>
</table>

measuring the confluence of ipscs using an automated imaging system

Cette étude vise à comprendre comment la croissance des CSPi sur différents substrats de revêtement ECM peut affecter la confluence cellulaire. Un protocole permettant d’évaluer la confluence des CSPi en temps réel a été établi sans qu’il soit nécessaire de compter les cellules en suspension unicellulaire pour éviter toute perturbation de la croissance. Un système d’analyse d’images à haut contenu a été utilisé pour évaluer de manière automatisée la confluence iPCS sur 4 ECM différents au fil du temps. Différents paramètres d’analyse ont été utilisés pour évaluer la confluence cellulaire des CSPi adhérentes et seule une légère différence (à 24 et 48 heures avec la laminine) a été observée si un masque à 60, 80 ou 100% a été appliqué. Nous montrons également que la laminine conduit à la meilleure confluence par rapport à Matrigel, la vitronectine et la fibronectine.

Dans cette étude, nous avons étudié la confluence des CSPi lorsqu’elles sont cultivées dans différentes conditions de revêtement. À l’aide d’un cytomètre, nous avons pu obtenir des résultats facilement informatifs en trois exemplaires en 5 jours. Étant donné que les CSPi se fixent à peine aux récipients en plastique et qu’un revêtement est nécessaire pour favoriser leur prolifération, nous avons décidé de surveiller la confluence des CSPi humaines car elle indique la santé de la culture cellula...

Watch this Scientific Journal Video about Measuring the Confluence of iPSCs Using an Automated Imaging System at JoVE.com

Measuring the Confluence of iPSCs Using an Automated Imaging System

L’objectif du protocole est de comparer différentes conditions de revêtement de la matrice extracellulaire (ECM) afin d’évaluer comment le revêtement différentiel affecte le taux de croissance des cellules souches pluripotentes induites (CSPi). En particulier, nous visons à mettre en place les conditions pour obtenir une croissance optimale des cultures iPSC.

Mesure de la confluence des CSPi à l’aide d’un système d’imagerie automatisé.

This study focuses on understanding how growing iPSCs on different ECM coating substrates can affect cell confluence. A protocol to assess iPSC confluence ...

measuring-the-confluence-of-ipscs-using-an-automated-imaging-system

Research

JoVE Journal

Biology

1.9K vues.  Ospedale Pediatrico Bambino Gesù, IRCCS. L’objectif du protocole est de comparer différentes conditions de revêtement de la matrice extracellulaire (ECM) afin d’évaluer comment le revêtement différentiel affecte le taux de croissance des cellules souches pluripotentes induites (CSPi). En particulier, nous visons à mettre en place les conditions pour obtenir une croissance optimale des cultures iPSC.

Vidéo: Measuring the Confluence of iPSCs Using an Automated Imaging System

Bioelectric Analyses of an Osseointegrated Intelligent Implant Design System for Amputees

The projected number of American amputees is expected to rise to 3.6 million by 2050.  Many of these individuals depend on artificial limbs to perform routine activities, but prosthetic suspensions using traditional socket technology can prove to be cumbersome and uncomfortable for a person with limb loss.  Moreover, for those with high proximal amputations, limited residual limb length may prevent exoprosthesis attachment all together. Osseointegrated implant technology is a novel operative procedure which allows firm skeletal attachment between the host bone and an implant. Preliminary results in European amputees with osseointegrated implants have shown improved clinical outcomes by allowing direct transfer of loads to the bone-implant interface.  Despite the apparent advantages of osseointegration over socket technology, the current rehabilitation procedures require long periods of restrictive load bearing prior which may be reduced with expedited skeletal attachment via electrical stimulation.  The goal of the osseointegrated intelligent implant design (OIID) system is to make the implant part of an electrical system to accelerate skeletal attachment and help prevent periprosthetic infection. To determine optimal electrode size and placement, we initiated proof of concept with computational modeling of the electric fields and current densities that arise during electrical stimulation of amputee residual limbs.  In order to provide insure patient safety, subjects with retrospective computed tomography scans were selected and three dimensional reconstructions were created using customized software programs to ensure anatomical accuracy (Seg3D and SCIRun) in an IRB and HIPAA approved study.  These software packages supported the development of patient specific models and allowed for interactive manipulation of electrode position and size. Preliminary results indicate that electric fields and current densities can be generated at the implant interface to achieve the homogenous electric field distributions   required to induce osteoblast migration, enhance skeletal fixation and may help prevent periprosthetic infections.  Based on the electrode configurations experimented with in the model, an external two band configuration will be advocated in the future.

There is a need to develop alternative prosthesis attachment due to limb loss attributed to vascular occlusive diseases and trauma. The goal of the work is to introduce an osseointegrated intelligent implant design system to increase skeletal fixation and reduce periprosthetic infection rates for patients needing osseointegrated technology.

Analyses Bioelectric d&#39;un système ostéo-intégrés Implant Intelligent Design pour amputés

The projected number of American amputees is expected to rise to 3.6 million by 2050.  Many of these individuals depend on artificial limbs to perform ...

Recherche

Biologie

Measuring the Bending Stiffness of Bacterial Cells Using an Optical Trap

We developed a protocol to measure the bending rigidity of filamentous rod-shaped bacteria. Forces are applied with an optical trap, a microscopic three-dimensional spring made of light that is formed when a high-intensity laser beam is focused to a very small spot by a microscope's objective lens. To bend a cell, we first bind live bacteria to a chemically-treated coverslip. As these cells grow, the middle of the cells remains bound to the coverslip but the growing ends are free of this restraint. By inducing filamentous growth with the drug cephalexin, we are able to identify cells in which one end of the cell was stuck to the surface while the other end remained unattached and susceptible to bending forces. A bending force is then applied with an optical trap by binding a polylysine-coated bead to the tip of a growing cell. Both the force and the displacement of the bead are recorded and the bending stiffness of the cell is the slope of this relationship.

We present a protocol for bending filamentous bacterial cells attached to a cover-slip surface with an optical trap to measure the cellular bending stiffness.

Mesure de la rigidité à la flexion des cellules bactériennes utilisant un piège optique

We developed a protocol to measure the bending rigidity of filamentous rod-shaped bacteria. Forces are applied with an optical trap, a microscopic ...

A Simple Method for Imaging Arabidopsis Leaves Using Perfluorodecalin as an Infiltrative Imaging Medium

The problem of acquiring high-resolution images deep into biological samples is widely acknowledged1. In air-filled tissue such as the spongy mesophyll of plant leaves or vertebrate lungs further difficulties arise from multiple transitions in refractive index between cellular components, between cells and airspaces and between the biological tissue and the rest of the optical system. Moreover, refractive index mismatches lead to attenuation of fluorophore excitation and signal emission in fluorescence microscopy. We describe here the application of the perfluorocarbon, perfluorodecalin (PFD), as an infiltrative imaging medium which optically improves laser scanning confocal microscopy (LSCM) sample imaging at depth, without resorting to damaging increases in laser power and has minimal physiological impact2. We describe the protocol for use of PFD with Arabidopsis thaliana leaf tissue, which is optically complex as a result of its structure (Figure 1). PFD has a number of attributes that make it suitable for this use3. The refractive index of PFD (1.313) is comparable with that of water (1.333) and is closer to that of cytosol (approx. 1.4) than air (1.000). In addition, PFD is readily available, non-fluorescent and is non-toxic. The low surface tension of PFD (19 dynes cm-1) is lower than that of water (72 dynes cm-1) and also below the limit (25 - 30 dyne cm-1) for stomatal penetration4, which allows it to flood the spongy mesophyll airspaces without the application of a potentially destructive vacuum or surfactant. Finally and crucially, PFD has a great capacity for dissolving CO2 and O2, which allows gas exchange to be maintained in the flooded tissue, thus minimizing the physiological impact on the sample. These properties have been used in various applications which include partial liquid breathing and lung inflation5,6, surgery7, artificial blood8, oxygenation of growth media9, and studies of ice crystal formation in plants10. Currently, it is common to mount tissue in water or aqueous buffer for live confocal imaging. We consider that the use of PFD as a mounting medium represents an improvement on existing practice and allows the simple preparation of live whole leaf samples for imaging.

A Simple Method for Imaging Arabidopsis Leaves Using Perfluorodecalin as an Infiltrative Imaging Medium

We describe the use of perfluorodecalin as an infiltrative mounting medium. This is a simple method for improving depth of imaging in Arabidopsis thaliana leaf tissue with minimal physiological impact.

Une méthode simple pour l&#39;imagerie Arabidopsis Feuilles utilisant perfluorodécaline comme un moyen d&#39;imagerie infiltratives

The problem of acquiring high-resolution images deep into biological samples is widely acknowledged1. In air-filled tissue such as the spongy mesophyll of ...

Using an Automated 3D-tracking System to Record Individual and Shoals of Adult Zebrafish

Like many aquatic animals, zebrafish (Danio rerio) moves in a 3D space. It is thus preferable to use a 3D recording system to study its behavior. The presented automatic video tracking system accomplishes this by using a mirror system and a calibration procedure that corrects for the considerable error introduced by the transition of light from water to air. With this system it is possible to record both single and groups of adult zebrafish. Before use, the system has to be calibrated. The system consists of three modules: Recording, Path Reconstruction, and Data Processing. The step-by-step protocols for calibration and using the three modules are presented. Depending on the experimental setup, the system can be used for testing neophobia, white aversion, social cohesion, motor impairments, novel object exploration etc. It is especially promising as a first-step tool to study the effects of drugs or mutations on basic behavioral patterns. The system provides information about vertical and horizontal distribution of the zebrafish, about the xyz-components of kinematic parameters (such as locomotion, velocity, acceleration, and turning angle) and it provides the data necessary to calculate parameters for social cohesions when testing shoals.

The use of a 3D automatic video system that can track individual and groups of zebrafish is described. As application example we explore the effects of the NMDA-receptor antagonist MK-801 on shoals of zebrafish.

Like many aquatic animals, zebrafish (Danio rerio) moves in a 3D space. It is thus preferable to use a 3D recording system to study its behavior. The ...

Measuring the Effects of Bacteria on C. Elegans Behavior Using an Egg Retention Assay

C. elegans egg-laying behavior is affected by environmental cues such as osmolarity1 and vibration2. In the total absence of food C. elegans also cease egg-laying and retain fertilized eggs in their uterus3. However, the effect of different sources of food, especially pathogenic bacteria and particularly Enterococcus faecalis, on egg-laying
	behavior is not well characterized. The egg-in-worm (EIW) assay is a useful tool to quantify the effects of different types of bacteria, in this case E. faecalis, on egg- laying behavior.
	
	EIW assays involve counting the number of eggs retained in the uterus of C. elegans4. The EIW assay involves bleaching staged, gravid adult C. elegans to remove the cuticle and separate the retained eggs from the animal. Prior to bleaching, worms are exposed to bacteria (or any type of environmental cue) for a fixed period of time. After bleaching, one is very easily able to count the number of eggs retained inside the uterus of the worms. In this assay, a quantifiable increase in egg retention after E. faecalis exposure can be easily measured. The EIW assay is a behavioral assay that may be used to screen for potentially pathogenic bacteria or the presence of environmental toxins. In addition, the EIW assay may be a tool to screen for drugs that affect neurotransmitter signaling since egg-laying behavior is modulated by neurotransmitters such as serotonin and acetylcholine5-9.

Measuring the Effects of Bacteria on C. Elegans Behavior Using an Egg Retention Assay

An egg-in-worm (EIW) assay is a useful method to quantify egg-laying behavior. Alterations in egg laying can be a behavioral response of the model organism Caenorhabditis elegans to potentially harmful environmental substances such as those produced by pathogenic bacteria.

Mesurer les effets des bactéries sur<em&gt; C. Elegans</em&gt; Comportement aide d&#39;un test de rétention d&#39;oeufs

C. elegans egg-laying behavior is  affected by environmental cues such as osmolarity1 and  vibration2. In the total absence of food C. elegans also cease ...

Imaging Spatial Reorganization of a MAPK Signaling Pathway Using the Tobacco Transient Expression System

Visualization of dynamic signaling events in live cells has been a challenge. We expanded an established transient expression system, the biomolecular fluorescent complementation (BiFC) assay in tobacco epidermal cells, from testing protein-protein interaction to monitoring spatial distribution of signal transduction in plant cells. In this protocol, we used the BiFC assay to show that the interaction and the signaling between the Arabidopsis MAPKKK YODA and MAPK6 occur at the plasma membrane. When the scaffold protein BASL was co-expressed, the YODA-MAPK interaction redistributed and spatially co-polarized with CFP-BASL. This modified tobacco expression system allows for quick examination of signaling localization and dynamic changes (less than 4 days) and can accommodate multiple of fluorescent protein colors (at least three). We also presented detailed methods to quantify protein distribution (asymmetric spatial localization, or &#34;polarization&#34;) in tobacco cells. This advanced tobacco expression system has a potential to be used widely for quick testing of dynamic signaling events in live plant cells.

At the subcellular level, signaling events are dynamically modulated by developmental and environmental cues. Here we describe a protocol that employs the tobacco transient expression system to monitor dynamic protein-protein interaction and to disclose spatial organization of signal transduction in plant cells.

Imagerie réorganisation spatiale d&#39;une voie de signalisation MAPK Utilisation du système d&#39;expression transitoire du tabac

Visualization of dynamic signaling events in live cells has been a challenge. We expanded an established transient expression system, the biomolecular ...

Studying the Protein Quality Control System of D. discoideum Using Temperature-controlled Live Cell Imaging

The complex lifestyle of the social amoebae Dictyostelium discoideum makes it a valuable model for the study of various biological processes. Recently, we showed that D. discoideum is remarkably resilient to protein aggregation and can be used to gain insights into the cellular protein quality control system. However, the use of D. discoideum as a model system poses several challenges to microscopy-based experimental approaches, such as the high motility of the cells and their susceptibility to photo-toxicity. The latter proves to be especially challenging when studying protein homeostasis, as the phototoxic effects can induce a cellular stress response and thus alter to behavior of the protein quality control system. 
Temperature increase is a commonly used way to induce cellular stress. Here, we describe a temperature-controllable imaging protocol, which allows observing temperature-induced perturbations in D. discoideum. Moreover, when applied at normal growth temperature, this imaging protocol can also noticeably reduce photo-toxicity, thus allowing imaging with higher intensities. This can be particularly useful when imaging proteins with very low expression levels. Moreover, the high mobility of the cells often requires the acquisition of multiple fields of view to follow individual cells, and the number of fields needs to be balanced against the desired time interval and exposure time.

Studying the Protein Quality Control System of D. discoideum Using Temperature-controlled Live Cell Imaging

The social amoebae Dictyostelium discoideum has recently been established as a system to study protein misfolding and proteostasis. Here, we describe a new imaging-based methodology to study temperature-induced protein aggregation and the cellular stress response in D. discoideum.

L&#39;étude de la protéine système de contrôle de la qualité des<em&gt; D. discoideum</em&gt; Utilisation de cellules vivantes d&#39;imagerie à température contrôlée

The complex lifestyle of the social amoebae Dictyostelium discoideum makes it a valuable model for the study of various biological processes. Recently, we ...

A Rapid Automated Protocol for Muscle Fiber Population Analysis in Rat Muscle Cross Sections Using Myosin Heavy Chain Immunohistochemistry

Quantification of muscle fiber populations provides a deeper insight into the effects of disease, trauma, and various other influences on skeletal muscle composition. Various time-consuming methods have traditionally been used to study fiber populations in many fields of research. However, recently developed immunohistochemical methods based on myosin heavy chain protein expression provide a quick alternative to identify multiple fiber types in a single section. Here, we present a rapid, reliable and reproducible protocol for improved staining quality, allowing automatic acquisition of whole cross sections and automatic quantification of fiber populations with ImageJ. For this purpose, embedded skeletal muscles are cut in cross sections, stained using myosin heavy chains antibodies with secondary fluorescent antibodies and DAPI for cell nuclei staining. Whole cross sections are then scanned automatically using a slide scanner to obtain high-resolution composite pictures of the entire specimen. Fiber population analyses are subsequently performed to quantify slow, intermediate and fast fibers using an automated macro for ImageJ. We have previously shown that this method can identify fiber populations reliably to a degree of &#177;4%. In addition, this method reduces inter-user variability and time per analyses significantly using the open source platform ImageJ.

Here, we present a protocol for rapid muscle fiber analyses, which allows improved staining quality, and thereby automatic acquisition and quantification of fiber populations using the freely available software ImageJ.

Un protocole automatisé pour l&#39;analyse rapide de la population de fibre musculaire chez le rat Muscle Sections Cross Utilisation myosine chaîne lourde immunohistochimie

Quantification of muscle fiber populations provides a deeper insight into the effects of disease, trauma, and various other influences on skeletal muscle ...

Flexible Measurement of Bioluminescent Reporters Using an Automated Longitudinal Luciferase Imaging Gas- and Temperature-optimized Recorder (ALLIGATOR)

Luciferase-based reporters of cellular gene expression are in widespread use for both longitudinal and end-point assays of biological activity. In circadian rhythms research, for example, clock gene fusions with firefly luciferase give rise to robust rhythms in cellular bioluminescence that persist over many days. Technical limitations associated with photomultiplier tubes (PMT) or conventional microscopy-based methods for bioluminescence quantification have typically demanded that cells and tissues be maintained under quite non-physiological conditions during recording, with a trade-off between sensitivity and throughput. Here, we report a refinement of prior methods that allows long-term bioluminescence imaging with high sensitivity and throughput which supports a broad range of culture conditions, including variable gas and humidity control, and that accepts many different tissue culture plates and dishes. This automated longitudinal luciferase imaging gas- and temperature-optimized recorder (ALLIGATOR) also allows the observation of spatial variations in luciferase expression across a cell monolayer or tissue, which cannot readily be observed by traditional methods. We highlight how the ALLIGATOR provides vastly increased flexibility for the detection of luciferase activity when compared with existing methods.

Flexible Measurement of Bioluminescent Reporters Using an Automated Longitudinal Luciferase Imaging Gas- and Temperature-optimized Recorder ALLIGATOR

Genetically encoded luciferase is a popular non-invasive reporter of gene expression. Use of an automated longitudinal luciferase imaging gas- and temperature-optimized recorder (ALLIGATOR) enables longitudinal recording from bioluminescent cells under a wide range of conditions. Here we show how ALLIGATOR may be used in the context of circadian rhythms research.

Mesure souples de Reporters bioluminescents utilisant une luciférase longitudinale automatisé d’imagerie enregistreur de gaz et la température-optimisé (ALLIGATOR)

Luciferase-based reporters of cellular gene expression are in widespread use for both longitudinal and end-point assays of biological activity. In ...

Establishment of an Extracellular Acidic pH Culture System

Conditions of the tumor microenvironment, such as hypoxia or nutrient starvation, play critical roles in cancer progression and malignancy. However, the role of acidic extracellular pH in tumor aggressiveness and its underlying mechanism has not been extensively studied compared to hypoxic or nutrient starvation conditions. In addition, a well-defined culture method to mimic the acidic extracellular tumor microenvironment has not been fully reported.
Here we present a simple in vitro culture method to maintain acidic extracellular pH using reduced bicarbonate and increased lactate or HCl concentrations in the culture medium. The medium pH was sustained for at least 24 h and gradually decreased by 72 h following culture of PANC-1 and AsPC-1 pancreatic cancer cells. Three distinct acidic media conditions in this study highly upregulated pH-responsive genes such as MSMO1, INSIG1, and IDI1 compared to hypoxia or nutrient starvation. The upregulation of these genes can be used as a marker of acidic pH. These simple techniques are beneficial to elucidate underlying mechanisms of tumor malignancy under acidic tumor microenvironment. Therefore, our extracellular acidic pH culture system enables discovery of cellular acidic pH responses not only in cancer cells but also in primary cells, such as renal tubular cells, in relation to the other acidic disorders including, diabetic ketoacidosis, lactic acidosis, renal tubular acidosis, and respiratory acidosis.

The acidic tumor microenvironment plays critical roles in tumor progression. To assess the effects of acidic extracellular pH on cancer cells in vitro, we established simple acidic culture systems.

Mise en place d’un pH extracellulaire acide système de Culture

Conditions of the tumor microenvironment, such as hypoxia or nutrient starvation, play critical roles in cancer progression and malignancy. However, the ...