Name: magnetic resonance elastography methodology for the evaluation of tissue engineered construct growth
Uploaded: 2012-02-09T13:00:00
Description: Watch this Scientific Journal Video about Magnetic Resonance Elastography Methodology for the Evaluation of Tissue Engineered Construct Growth at JoVE.com

Cette recherche a été financée en partie par le NIH-RO3 EB007299-02 et NSF EPSCoR premier prix.

1. Préparation Construct tissus Le tissu de construire processus de préparation se compose de trois étapes principales: l&#39;expansion de la population de la cellule, l&#39;ensemencement de cellules sur un échafaudage biomatériau, et la différenciation par l&#39;utilisation de molécules de signalisation chimiques. La procédure pour la préparation construction est basée sur des méthodes menées par Dennis et al., Hong et al., Et Marion et Mao 8,9,10. </p...

<ol>
	<li>Xu, H., Othman, S. F., Magin, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+tissue+engineering+using+magnetic+resonance+imaging.">Monitoring tissue engineering using magnetic resonance imaging.</a> J. Biosci. Bioeng. 106, 515-527 (2008).</li><li>Xu, H., Othman, S. F., Hong, L., Peptan, I. A., Magin, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetic+resonance+microscopy+for+monitoring+osteogenesis+in+tissue-engineered+construct+in+vitro.">Magnetic resonance microscopy for monitoring osteogenesis in tissue-engineered construct in vitro.</a> Phys. Med. Biol. 51, 719-732 (2006).</li><li>Othman, S. F., Xu, H., Royston, T. J., Magin, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microscopic+magnetic+resonance+elastography+(microMRE.">Microscopic magnetic resonance elastography (microMRE.</a> Magn. Reson. Med. 54, 605-615 (2005).</li><li>Muthupillai, R., Lomas, D. J., Rossman, P. J., Greenleaf, J. F., Manduca, A., Ehman, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetic+resonance+elastography+by+direct+visualization+of+propagating+acoustic+strain+waves.">Magnetic resonance elastography by direct visualization of propagating acoustic strain waves.</a> Science. 269, 1854-1857 (1995).</li><li>Othman, S. F., Curtis, E. T., Plautz, S. A., Pannier, A. P., Xu, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetic+resonance+elastography+monitoring+of+tissue+engineered+constructs.">Magnetic resonance elastography monitoring of tissue engineered constructs.</a> NMR Biomed. , (2011).</li><li>Oliphant, T. E., Manduca, A., Ehman, R. L., Greenleaf, 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=Complex-valued+stiffness+reconstruction+for+magnetic+resonance+elastography+by+algebraic+inversion+of+the+differential+equation.">Complex-valued stiffness reconstruction for magnetic resonance elastography by algebraic inversion of the differential equation.</a> Magn. Reson. Med. 45, 299-310 (2001).</li><li>Ringleb, S. I., Chen, Q., Lake, D. S., Manduca, A., Ehman, R. L., An, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+shear+wave:+comparison+to+a+dynamic+shear+material+test.">Quantitative shear wave: comparison to a dynamic shear material test.</a> Magn. Reson. Med. 53, 1197-1201 (2005).</li><li>Hong, L., Peptan, I., Clark, P., Mao, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+adipose+tissue+engineering+by+human+marrow+stromal+cell+seeded+gelatin+sponge.">Ex vivo adipose tissue engineering by human marrow stromal cell seeded gelatin sponge.</a> Ann. Biomed. Eng. 33, 511-517 (2005).</li><li>Dennis, J. E., Haynesworth, S. E., Young, R. G., Caplan, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteogenesis+in+marrow-derived+mesenchymal+cell+porous+ceramic+composites+transplanted+subcutaneously:+effect+of+fibronectin+and+laminin+on+cell+retention+and+rate+of+osteogenic+expression.">Osteogenesis in marrow-derived mesenchymal cell porous ceramic composites transplanted subcutaneously: effect of fibronectin and laminin on cell retention and rate of osteogenic expression.</a> Cell Transplant. 1, 23-32 (1992).</li><li>Marion, N. W., Mao, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesenchymal+stem+cells+and+tissue+engineering.">Mesenchymal stem cells and tissue engineering.</a> Methods Enzymol. 420, 339-361 (2006).</li><li>Rydberg, J., Grimm, R., Kruse, S., Felmlee, J., McCracken, P., Ehman, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+spin-echo+magnetic+resonance+elastography+of+the+brain.">Fast spin-echo magnetic resonance elastography of the brain.</a> , 1647-1647 (2001).</li><li>Kruse, S. A., Grim, R. C., Lake, D. S., Manduca, A., Ehman, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+EPI+based+3D+MR+elastography+of+the+brain.">Fast EPI based 3D MR elastography of the brain.</a> , 3385-3385 (2006).</li></ol>

Dans cette procédure, le processus de MRE pour les constructions de l&#39;ingénierie tissulaire est démontré, de la préparation cellulaire à la génération d&#39;un élastogramme. En appliquant une méthode d&#39;évaluation non destructive mécanique à la canalisation du génie tissulaire, il est maintenant possible d&#39;évaluer les changements dans les constructions d&#39;ingénierie tout au long de multiples étapes de développement. En outre, s&#39;ajoute à d&#39;autres méthodes d&#39;ERM MR pour les ti...

<table border="1"><tbody><tr><td> Nom du produit </td><td> Type </td><td> Entreprise </td><td> Numéro de catalogue </td><td> Commentaires </td></tr><tr><td> MSCGM-Bullet Kit </td><td> Réactif </td><td> Lonza </td><td> PT-3001 </td><td> Conserver à 4 ° C </td></tr><tr><td> DPBS 1X </td><td> Réactif </td><td> Invitrogen </td><td> 21600-010 </td><td></td></tr><tr><td> 0,05% de trypsine-EDTA </td><td> Réactif </td><td> Gibco, Invitrogen </td><td> 25300-054 </td><td> Conserver à -20 ° C </td></tr><tr><td> Dexaméthasone </td><td> Réactif </td><td> Sigma-Aldrich </td><td> D2915 </td><td></td></tr><tr><td> 3-isobutyl-1-méthylxanthine </td><td> Réactif </td><td> Sigma-Aldrich </td><td> I5879 </td><td> Conserver à -20 ° C </td></tr><tr><td> L&#39;insuline bovine du pancréas </td><td> Réactif </td><td> Sigma-Aldrich </td><td> I6634 </td><td> Conserver à -20 ° C </td></tr><tr><td> Indométhacine </td><td> Réactif </td><td> Sigma-Aldrich </td><td> I7378 </td><td></td></tr><tr><td> Β-glycérophosphate </td><td> Réactif </td><td> Sigma-Aldrich </td><td> G9891 </td><td></td></tr><tr><td> Acide L-ascorbique-2-phosphate </td><td> Réactif </td><td> Sigma-Aldrich </td><td> A8960 </td><td></td></tr><tr><td> Gelfoam </td><td> Échafaud </td><td> Pharmacia &amp; Upjohn Co. </td><td> 09-0315-08 </td><td></td></tr><tr><td> Les cellules souches mésenchymateuses </td><td> Lignée cellulaire </td><td> Lonza </td><td> PT-2501 </td><td></td></tr><tr><td> 9.4T MR scanner </td><td> Équipement </td><td> Agilent </td><td></td><td> 400MHz WB </td></tr><tr><td> 10mm Litz Coil </td><td> Équipement </td><td> Doty scientifique </td><td></td><td></td></tr><tr><td> Laser Doppler Vibromètre </td><td> Équipement </td><td> Polytec </td><td> PDV-100 </td><td></td></tr><tr><td> Vibrosoft (20) </td><td> Logiciel </td><td> Polytec </td><td></td><td></td></tr><tr><td> Générateur de fonctions </td><td> Équipement </td><td> Agilent </td><td> AFG 3022B </td><td></td></tr><tr><td> Amplificateur </td><td> Équipement </td><td> Piezo inc </td><td> EPA-104-115 </td><td></td></tr><tr><td> Piezo flexion du moteur </td><td> Équipement </td><td> Piezo inc. </td><td> T234-A4Cl-203X </td><td></td></tr><tr><td> Computer-Linux </td><td> Équipement </td><td> Processeur: Intel Core 2 Duo E8400 Mémoire: 2G </td><td></td><td></td></tr><tr><td> Computer-Windows </td><td> Équipement </td><td> Processeur: Intel Core 2 Duo E8400 Mémoire: 2G </td><td></td><td></td></tr><tr><td> MATLAB </td><td> Logiciel </td><td> The Mathworks, Inc </td><td></td><td> 2009b </td></tr></tbody></table>

magnetic resonance elastography methodology for the evaluation of tissue engineered construct growth

Traditionnel essais mécaniques se traduit souvent par la destruction de l&#39;échantillon, et dans le cas de tissu à long terme conçu de construire des études, l&#39;utilisation de l&#39;évaluation destructrice n&#39;est pas acceptable. Une alternative proposée est l&#39;utilisation d&#39;un procédé d&#39;imagerie appelée élastographie par résonance magnétique. L&#39;élastographie est une méthode non destructive pour déterminer le résultat d&#39;ingénierie en mesurant les valeurs locales des propriétés mécaniques (c.-à-module complexe de cisaillement), qui sont des marqueurs essentiels pour identifier la structure et la fonctionnalité d&#39;un tissu. Comme un moyen non invasif d&#39;évaluation, le suivi des constructions d&#39;ingénierie avec des modalités d&#39;imagerie telles que l&#39;imagerie par résonance magnétique (IRM) a vu un intérêt croissant dans la dernière décennie 1. Par exemple, les par résonance magnétique (MR) des techniques de diffusion et de relaxométrie ont été en mesure de caractériser les changements dans les propriétés chimiques et physiques au cours du développement de l&#39;ingénierie tissulaire 2. La méthode proposée dansle protocole suivant utilise microscopique élastographie par résonance magnétique (μMRE) en tant que technique MR non invasive permettant de mesurer les propriétés mécaniques de petite tissus mous 3. MRE est réalisé en couplant un actionneur mécanique sonore avec le tissu d&#39;intérêt et l&#39;enregistrement de la propagation des ondes de cisaillement avec un scanner MR 4. Récemment, μMRE a été appliqué dans l&#39;ingénierie tissulaire pour acquérir des informations essentiel de la croissance qui est traditionnellement mesurée à l&#39;aide des techniques macroscopiques mécaniques destructeurs 5. Dans la procédure suivante, l&#39;élastographie est obtenue par l&#39;imagerie de constructions d&#39;ingénierie avec une version modifiée de Hahn spin-séquence d&#39;écho associée à un actionneur mécanique. Comme le montre la figure 1, la séquence modifiée se synchronise avec l&#39;acquisition de l&#39;image de transmission des ondes de cisaillement extérieures; ultérieurement, le mouvement est sensibilisée par l&#39;utilisation de paires oscillant bipolaires. Après la collecte d&#39;images avec un mouvement positif et négatif sensitization, la division complexe des données de produire une image d&#39;onde de cisaillement. Puis, l&#39;image est évaluée en utilisant un algorithme d&#39;inversion pour générer une carte rigidité au cisaillement 6. Les résultats des mesures à chaque voxel a été démontré fortement corrélés (R 2&gt; 0.9914) avec les données recueillies à l&#39;aide l&#39;analyse mécanique dynamique 7. Dans cette étude, l&#39;élastographie est intégré dans le processus de développement du tissu pour le suivi des lignées de cellules souches mésenchymateuses (CSM h) la différenciation dans des constructions adipogéniques et ostéogénique comme le montre la figure 2.

Watch this Scientific Journal Video about Magnetic Resonance Elastography Methodology for the Evaluation of Tissue Engineered Construct Growth at JoVE.com

Magnetic Resonance Elastography Methodology for the Evaluation of Tissue Engineered Construct Growth

La procédure démontre la méthodologie de l&#39;élastographie par résonance magnétique pour le suivi des résultats d&#39;ingénierie du tissu adipeux et les constructions de tissus ostéogéniques d&#39;ingénierie grâce à une évaluation non invasive locale des propriétés mécaniques en utilisant microscopique élastographie par résonance magnétique (μMRE).

Méthodologie élastographie par résonance magnétique pour l&#39;évaluation des tissus Conçu croissance Construct

Traditional mechanical testing often results in the destruction of the sample, and in the case of long term tissue engineered construct studies, the use ...

magnetic-resonance-elastography-methodology-for-evaluation-tissue

Research

JoVE Journal

Bioengineering

Bioluminescence Imaging for Assessment of Immune Responses Following Implantation of Engineered Heart Tissue (EHT)

Various techniques of cardiac tissue engineering have been pursued in the past decades including scaffolding strategies using either native or bioartificial scaffold materials, entrapment of cardiac myocytes in hydrogels such as fibrin or collagen and stacking of myocyte monolayers 1. These concepts aim at restoration of compromised cardiac function (e.g. after myocardial infarction) or as experimental models (e.g. predictive toxicology and substance screening or disease modelling). Precise monitoring of cell survival after implantation of engineered heart tissue (EHT) has now become possible using in-vivo bioluminescence imaging (BLI) techniques 2. Here we describe the generation of fibrin-based EHT from a transgenic rat strain with ubiquitous expression of firefly luciferase (ROSA/luciferase-LEW Tg; 3). Implantation is performed into the greater omentum of different rat strains to assess immune responses of the recipient organism following EHT implantation. Comparison of results generated by BLI and the Enzyme Linked Immuno Spot Technique (ELISPOT) confirm the usability of BLI for the assessment of immune responses.

Bioluminescence Imaging for Assessment of Immune Responses Following Implantation of Engineered Heart Tissue EHT

This video demonstrates the use of in vivo bioluminescence imaging to study immune responses after implantation of Engineered Heart Tissue (EHT) in rats.

Imagerie par bioluminescence pour l&#39;évaluation des réponses immunitaires après l&#39;implantation du tissu cardiaque d&#39;ingénierie (ISE)

Various techniques of cardiac tissue engineering have been pursued in the past decades including scaffolding strategies using either native or ...

Recherche

Bio-ingénierie

Evaluation of Polymeric Gene Delivery Nanoparticles by Nanoparticle Tracking Analysis and High-throughput Flow Cytometry

Non-viral gene delivery using polymeric nanoparticles has emerged as an attractive approach for gene therapy to treat genetic diseases1 and as a technology for regenerative medicine2. Unlike viruses, which have significant safety issues, polymeric nanoparticles can be designed to be non-toxic, non-immunogenic, non-mutagenic, easier to synthesize, chemically versatile, capable of carrying larger nucleic acid cargo and biodegradable and/or environmentally responsive. Cationic polymers self-assemble with negatively charged DNA via electrostatic interaction to form complexes on the order of 100 nm that are commonly termed polymeric nanoparticles. Examples of biomaterials used to form nanoscale polycationic gene delivery nanoparticles include polylysine, polyphosphoesters, poly(amidoamines)s and polyethylenimine (PEI), which is a non-degradable off-the-shelf cationic polymer commonly used for nucleic acid delivery1,3 . Poly(beta-amino ester)s (PBAEs) are a newer class of cationic polymers4 that are hydrolytically degradable5,6 and have been shown to be effective at gene delivery to hard-to-transfect cell types such as human retinal endothelial cells (HRECs)7, mouse mammary epithelial cells8, human brain cancer cells9 and macrovascular (human umbilical vein, HUVECs) endothelial cells10.
A new protocol to characterize polymeric nanoparticles utilizing nanoparticle tracking analysis (NTA) is described. In this approach, both the particle size distribution and the distribution of the number of plasmids per particle are obtained11. In addition, a high-throughput 96-well plate transfection assay for rapid screening of the transfection efficacy of polymeric nanoparticles is presented. In this protocol, poly(beta-amino ester)s (PBAEs) are used as model polymers and human retinal endothelial cells (HRECs) are used as model human cells. This protocol can be easily adapted to evaluate any polymeric nanoparticle and any cell type of interest in a multi-well plate format.

A protocol for nanoparticle tracking analysis (NTA) and high-throughput flow cytometry to evaluate polymeric gene delivery nanoparticles is described. NTA is utilized to characterize the nanoparticle particle size distribution and the plasmid per particle distribution. High-throughput flow cytometry enables quantitative transfection efficacy evaluation for a library of gene delivery biomaterials.

Évaluation de livraison Gene polymère nanoparticules d&#39;analyse de suivi par des nanoparticules et de cytométrie en flux à haut débit

Non-viral gene delivery using polymeric nanoparticles has emerged as an attractive approach for gene therapy to treat genetic diseases1 and as a ...

Protocol for Relative Hydrodynamic Assessment of Tri-leaflet Polymer Valves

Limitations of currently available prosthetic valves, xenografts, and homografts have prompted a recent resurgence of developments in the area of tri-leaflet polymer valve prostheses. However, identification of a protocol for initial assessment of polymer valve hydrodynamic functionality is paramount during the early stages of the design process. Traditional in vitro pulse duplicator systems are not configured to accommodate flexible tri-leaflet materials; in addition, assessment of polymer valve functionality needs to be made in a relative context to native and prosthetic heart valves under identical test conditions so that variability in measurements from different instruments can be avoided. Accordingly, we conducted hydrodynamic assessment of i) native (n = 4, mean diameter, D = 20 mm), ii) bi-leaflet mechanical (n= 2, D = 23 mm) and iii) polymer valves (n = 5, D = 22 mm) via the use of a commercially available pulse duplicator system (ViVitro Labs Inc, Victoria, BC) that was modified to accommodate tri-leaflet valve geometries. Tri-leaflet silicone valves developed at the University of Florida comprised the polymer valve group. A mixture in the ratio of 35:65 glycerin to water was used to mimic blood physical properties. Instantaneous flow rate was measured at the interface of the left ventricle and aortic units while pressure was recorded at the ventricular and aortic positions. Bi-leaflet and native valve data from the literature was used to validate flow and pressure readings. The following hydrodynamic metrics were reported: forward flow pressure drop, aortic root mean square forward flow rate, aortic closing, leakage&#160;and regurgitant volume, transaortic closing, leakage, and total energy losses. Representative results indicated that hydrodynamic metrics from the three valve groups could be successfully obtained by incorporating a custom-built assembly into a commercially available pulse duplicator system and subsequently, objectively compared to provide insights on functional aspects of polymer valve design.

There has been renewed interest in developing polymer valves. Here, the objectives are to demonstrate the feasibility of modifying a commercial pulse duplicator to accommodate tri-leaflet geometries and to define a protocol to present polymer valve hydrodynamic data in comparison to native and prosthetic valve data collected under near-identical conditions.

Protocole pour l&#39;évaluation hydrodynamique relative de Vannes polymères tri-leaflet

Limitations of currently available prosthetic valves, xenografts, and homografts have prompted a recent resurgence of developments in the area of ...

Surgical Technique for the Implantation of Tissue Engineered Vascular Grafts and Subsequent In Vivo Monitoring

The development of Tissue Engineered Vessels (TEVs) is advanced by the ability to routinely and effectively implant TEVs (4-5 mm in diameter) into a large animal model. A step by-step protocol for inter-positional placement of the TEV and real-time digital assessment of the TEV and native carotid arteries is described here. In vivo monitoring is made possible by the implantation of flow probes, catheters and ultrasonic crystals (capable of recording dynamic diameter changes of implanted TEVs and native carotid arteries) at the time of surgery. Once implanted, researchers can calculate arterial blood flow patterns, invasive blood pressure and artery diameter yielding parameters such as pulse wave velocity, augmentation index, pulse pressures and compliance. Data acquisition is accomplished using a single computer program for analysis throughout the duration of the experiment. Such invaluable data provides insight into TEV matrix remodeling, its resemblance to native/sham controls and overall TEV performance in vivo.

Surgical Technique for the Implantation of Tissue Engineered Vascular Grafts and Subsequent In Vivo Monitoring

A step-by-step protocol for the inter-positional placement of Tissue Engineered Vessels (TEVs) into the carotid artery of a sheep using end-to-end anastomosis and real-time digital assessment in vivo until animal sacrifice.

Technique chirurgicale pour l&#39;implantation de l&#39;ingénierie tissulaire vasculaires greffes et suivantes<em&gt; In Vivo</em&gt; Surveillance

The development of Tissue Engineered Vessels (TEVs) is advanced by the ability to routinely and effectively implant TEVs (4-5 mm in diameter) into a large ...

Athymic Rat Model for Evaluation of Engineered Anterior Cruciate Ligament Grafts

Anterior cruciate ligament (ACL) rupture is a common ligamentous injury that often requires surgery because the ACL does not heal well without intervention. Current treatment strategies include ligament reconstruction with either autograft or allograft, which each have their associated limitations. Thus, there is interest in designing a tissue-engineered graft for use in ACL reconstruction. We describe the fabrication of an electrospun polymer graft for use in ACL tissue engineering. This polycaprolactone graft is biocompatible, biodegradable, porous, and is comprised of aligned fibers. Because an animal model is necessary to evaluate such a graft, this paper describes an intra-articular athymic rat model of ACL reconstruction that can be used to evaluate engineered grafts, including those seeded with xenogeneic cells. Representative histology and biomechanical testing results at 16 weeks postoperatively are presented, with grafts tested immediately post-implantation and contralateral native ACLs serving as controls. The present study provides a reproducible animal model with which to evaluate tissue engineered ACL grafts, and demonstrates the potential of a regenerative medicine approach to treatment of ACL rupture.

Animal models are important tools for the evaluation of tissue-engineered grafts. This paper presents the protocol for preparing an electrospun biodegradable polymer graft for use in anterior cruciate ligament tissue engineering, as well as a surgical protocol for implantation in a rat model.

Athymiques Rat Modèle d&#39;évaluation des Engineered ligament croisé antérieur greffes

Anterior cruciate ligament (ACL) rupture is a common ligamentous injury that often requires surgery because the ACL does not heal well without ...

Polyelectrolyte Complex for Heparin Binding Domain Osteogenic Growth Factor Delivery

During reconstructive bone surgeries, supraphysiological amounts of growth factors are empirically loaded onto scaffolds to promote successful bone fusion. Large doses of highly potent biological agents are required due to growth factor instability as a result of rapid enzymatic degradation as well as carrier inefficiencies in localizing sufficient amounts of growth factor at implant sites. Hence, strategies that prolong the stability of growth factors such as BMP-2/NELL-1, and control their release could actually lower their efficacious dose and thus reduce the need for larger doses during future bone regeneration surgeries. This in turn will reduce side effects and growth factor costs. Self-assembled PECs have been fabricated to provide better control of BMP-2/NELL-1 delivery via heparin binding and further potentiate growth factor bioactivity by enhancing in vivo stability. Here we illustrate the simplicity of PEC fabrication which aids in the delivery of a variety of growth factors during reconstructive bone surgeries.

Self-assembled polyelectrolyte complexes (PEC) fabricated from heparin and protamine were deposited on alginate beads to entrap and regulate the release of osteogenic growth factors. This delivery strategy enables a 20-fold reduction of BMP-2 dose in spinal fusion applications. This article illustrates the benefits and fabrication of PECs.

Complexe de polyélectrolyte pour Heparin Binding Domain Growth Factor ostéogénique Livraison

During reconstructive bone surgeries, supraphysiological amounts of growth factors are empirically loaded onto scaffolds to promote successful bone ...

Automated Contraction Analysis of Human Engineered Heart Tissue for Cardiac Drug Safety Screening

Cardiac tissue engineering describes techniques to constitute three dimensional force-generating engineered tissues. For the implementation of these procedures in basic research and preclinical drug development, it is important to develop protocols for automated generation and analysis under standardized conditions. Here, we present a technique to generate engineered heart tissue (EHT) from cardiomyocytes of different species (rat, mouse, human). The technique relies on the assembly of a fibrin-gel containing dissociated cardiomyocytes between elastic polydimethylsiloxane (PDMS) posts in a 24-well format. Three-dimensional, force-generating EHTs constitute within two weeks after casting. This procedure allows for the generation of several hundred EHTs per week and is technically limited only by the availability of cardiomyocytes (0.4-1.0 x 106/EHT). Evaluation of auxotonic muscle contractions is performed in a modified incubation chamber with a mechanical interlock for 24-well plates and a camera placed on top of this chamber. A software controls a camera moved on an XYZ axis system to each EHT. EHT contractions are detected by an automated figure recognition algorithm, and force is calculated based on shortening of the EHT and the elastic propensity and geometry of the PDMS posts. This procedure allows for automated analysis of high numbers of EHT under standardized and sterile conditions. The reliable detection of drug effects on cardiomyocyte contraction is crucial for cardiac drug development and safety pharmacology. We demonstrate, with the example of the hERG channel inhibitor E-4031, that the human EHT system replicates drug responses on contraction kinetics of the human heart, indicating it to be a promising tool for cardiac drug safety screening.

Here, we show the generation of human engineered heart tissue from induced pluripotent stem cells (hiPSC)-derived cardiomyocytes. We present a method to analyze contraction force and exemplary alteration of contraction pattern by the hERG channel inhibitor E-4031. This method shows high level of robustness and suitability for cardiac drug screening.

Automatisé Contraction L&#39;analyse des tissus humains Engineered cardiaque pour le dépistage de la sécurité cardiaque médicaments

Cardiac tissue engineering describes techniques to constitute three dimensional force-generating engineered tissues. For the implementation of these ...

Metabolic Support of Excised, Living Brain Tissues During Magnetic Resonance Microscopy Acquisition

This protocol describes the procedures necessary to support normal metabolic functions of acute brain slice preparations during the collection of magnetic resonance (MR) microscopy data. While it is possible to perform MR collections on living, excised mammalian tissue, such experiments have traditionally been constrained by resolution limits and are thus incapable of visualizing tissue microstructure. Conversely, MR protocols that did achieve microscopic image resolution required the use of fixed samples to accommodate the need for static, unchanging conditions over lengthy scan times. The current protocol describes the first available MR technique that enables imaging of living, mammalian tissue samples at microscopic resolutions. Such data is of great importance to the understanding of how pathology-based contrast changes occurring at the microscopic level influence the content of macroscopic MR scans such as those used in the clinic. Once such an understanding is realized, diagnostic methods with greater sensitivity and accuracy can be developed, which will translate directly to earlier disease treatment, more accurate therapy monitoring and improved patient outcomes.
While the described methodology focuses on brain slice preparations, the protocol is adaptable to any excised tissue slice given that changes are made to the gas and perfusate preparations to accommodate the tissue&#39;s specific metabolic needs. Successful execution of the protocol should result in living, acute slice preparations that exhibit MR diffusion signal stability for periods up to 15.5 h. The primary advantages of the current system over other MR compatible perfusion apparatuses are its compatibility with the MR microscopy hardware required to attain higher resolution images and ability to provide constant, uninterrupted flow with carefully regulated perfusate conditions. Reduced sample throughput is a consideration with this design as only one tissue slice may be imaged at a time.

The current protocol describes a method by which users can maintain viability of acute hippocampal and cortical slice preparations during the collection of magnetic resonance microscopy data.

Soutien métabolique des excisées, les tissus de cerveau vivants lors de l’Acquisition de la microscopie par résonance magnétique

This protocol describes the procedures necessary to support normal metabolic functions of acute brain slice preparations during the collection of magnetic ...

Custom Engineered Tissue Culture Molds from Laser-etched Masters

As the field of tissue engineering has continued to mature, there has been increased interest in a wide range of tissue parameters, including tissue shape. Manipulating tissue shape on the micrometer to centimeter scale can direct cell alignment, alter effective mechanical properties, and address limitations related to nutrient diffusion. In addition, the vessel in which a tissue is prepared can impart mechanical constraints on the tissue, resulting in stress fields that can further influence both the cell and matrix structure. Shaped tissues with highly reproducible dimensions also have utility for in vitro assays in which sample dimensions are critical, such as whole tissue mechanical analysis.
This manuscript describes an alternative fabrication method utilizing negative master molds prepared from laser etched acrylic: these molds perform well with polydimethylsiloxane (PDMS), permit designs with dimensions on the centimeter scale and feature sizes smaller than 25 &#181;m, and can be rapidly designed and fabricated at a low cost and with minimal expertise. The minimal time and cost requirements allow for laser etched molds to be rapidly iterated upon until an optimal design is determined, and to be easily adapted to suit any assay of interest, including those beyond the field of tissue engineering.

Herein we present a rapid, facile, and low-cost method for fabricating custom polydimethylsiloxane molds that can be used for producing hydrogel-based engineered tissues with complex geometries. We additionally describe results from mechanical and histological assessments conducted on engineered cardiac tissues produced using this technique.

Coutume machinée moules de vitroplants de maîtres gravé au Laser

As the field of tissue engineering has continued to mature, there has been increased interest in a wide range of tissue parameters, including tissue ...

Manufacturing Abdominal Aorta Hydrogel Tissue-Mimicking Phantoms for Ultrasound Elastography Validation

Ultrasound (US) elastography, or elasticity imaging, is an adjunct imaging technique that utilizes sequential US images of soft tissues to measure the tissue motion and infer or quantify the underlying biomechanical characteristics. For abdominal aortic aneurysms (AAA), biomechanical properties such as changes in the tissue's elastic modulus and estimates of the tissue stress may be essential for assessing the need for the surgical intervention. Abdominal aortic aneurysms US elastography could be a useful tool to monitor AAA progression and identify changes in biomechanical properties characteristic of high-risk patients.
A preliminary goal in the development of an AAA US elastography technique is the validation of the method using a physically relevant model with known material properties. Here we present a process for the production of AAA tissue-mimicking phantoms with physically relevant geometries and spatially modulated material properties. These tissue phantoms aim to mimic the US properties, material modulus, and geometry of the abdominal aortic aneurysms. Tissue phantoms are made using a polyvinyl alcohol cryogel (PVA-c) and molded using 3D printed parts created using computer aided design (CAD) software. The modulus of the phantoms is controlled by altering the concentration of PVA-c and by changing the number of freeze-thaw cycles used to polymerize the cryogel. The AAA phantoms are connected to a hemodynamic pump, designed to deform the phantoms with the physiologic cyclic pressure and flows. Ultra sound image sequences of the deforming phantoms allowed for the spatial calculation of the pressure normalized strain and the identification of mechanical properties of the vessel wall. Representative results of the pressure normalized strain are presented.

Here we describe a method to manufacture aneurysmal, aortic tissue-mimicking phantoms for the use in testing ultrasound elastography. The combined use of computer-aided design (CAD) and 3-dimensional (3D) printing techniques produce aortic phantoms with predictable, complex geometries to validate the elastographic imaging algorithms with controlled experiments.

Aorte abdominale Hydrogel imitant le tissu de fabrication fantômes pour Validation élastographie par ultrasons

Ultrasound (US) elastography, or elasticity imaging, is an adjunct imaging technique that utilizes sequential US images of soft tissues to measure the ...