The RITS Conference: A Major Event of Biomedical Engineering in France

International audienceResearch in Imaging and HealTh TechnologieS (RITS) is a French scientific meeting dedicated to Biomedical Engineering. This biennial event has given rise to four special issues of IRBM since 2009. The present issue collects some research works presented by young researchers (first author being less than 32 years old). All of them submitted a full paper (instead of a long abstract) to the meeting in order to participate in the SFGBM competition. All the published papers followed the standard reviewing process

Advanced Gene Therapy Strategies for the Repair of ACL Injuries

The anterior cruciate ligament (ACL), the principal ligament for stabilization of the knee, is highly predisposed to injury in the human population. As a result of its poor intrinsic healing capacities, surgical intervention is generally necessary to repair ACL lesions, yet the outcomes are never fully satisfactory in terms of long-lasting, complete, and safe repair. Gene therapy, based on the transfer of therapeutic genetic sequences via a gene vector, is a potent tool to durably and adeptly enhance the processes of ACL repair and has been reported for its workability in various experimental models relevant to ACL injuries in vitro, in situ, and in vivo. As critical hurdles to the effective and safe translation of gene therapy for clinical applications still remain, including physiological barriers and host immune responses, biomaterial-guided gene therapy inspired by drug delivery systems has been further developed to protect and improve the classical procedures of gene transfer in the future treatment of ACL injuries in patients, as critically presented here

rAAV TGF-β and FGF-2 Overexpression via pNaSS-Grafted PCL Films Stimulates the Reparative Activities of Human ACL Fibroblasts

Lesions in the human anterior cruciate ligament (ACL) are frequent, unsolved clinical issues due to the limited self-healing ability of the ACL and lack of treatments supporting full, durable ACL repair. Gene therapy guided through the use of biomaterials may steadily activate the processes of repair in sites of ACL injury. The goal of the present study was to test the hypothesis that functionalized poly(sodium styrene sulfonate)-grafted poly(ε-caprolactone) (pNaSS-grafted PCL) films can effectively deliver recombinant adeno-associated virus (rAAV) vectors as a means of overexpressing two reparative factors (transforming growth factor beta-TGF-β and basic fibroblast growth factor-FGF-2) in primary human ACL fibroblasts. Effective, durable rAAV reporter red fluorescent protein and candidate TGF-β and FGF-2 gene overexpression was achieved in the cells for at least 21 days, especially when pNaSS-grafted PCL films were used versus control conditions, such as ungrafted films and systems lacking vectors or films (between 1.8- and 5.2-fold differences), showing interactive regulation of growth factor production. The expression of TGF-β and FGF-2 from rAAV via PCL films safely enhanced extracellular matrix depositions of type-I/-III collagen, proteoglycans/decorin, and tenascin-C (between 1.4- and 4.5-fold differences) in the cells over time with increased levels of expression of the specific transcription factors Mohawk and scleraxis (between 1.7- and 3.7-fold differences) and without the activation of the inflammatory mediators IL-1β and TNF-α, most particularly with pNaSS-grafted PCL films relative to the controls. This work shows the value of combining rAAV gene therapy with functionalized PCL films to enhance ACL repair

Enhanced Chondrogenic Differentiation Activities in Human Bone Marrow Aspirates via sox9 Overexpression Mediated by pNaSS-Grafted PCL Film-Guided rAAV Gene Transfer

Background: The delivery of therapeutic genes in sites of articular cartilage lesions using non-invasive, scaffold-guided gene therapy procedures is a promising approach to stimulate cartilage repair while protecting the cargos from detrimental immune responses, particularly when targeting chondroreparative bone marrow-derived mesenchymal stromal cells in a natural microenvironment like marrow aspirates. Methods: Here, we evaluated the benefits of providing a sequence for the cartilage-specific sex-determining region Y-type high-mobility group box 9 (SOX9) transcription factor to human marrow aspirates via recombinant adeno-associated virus (rAAV) vectors delivered by poly(ε-caprolactone) (PCL) films functionalized via grafting with poly(sodium styrene sulfonate) (pNaSS) to enhance the marrow chondrogenic potential over time. Results: Effective sox9 overexpression was observed in aspirates treated with pNaSS-grafted or ungrafted PCL films coated with the candidate rAAV-FLAG-hsox9 (FLAG-tagged rAAV vector carrying a human sox9 gene sequence) vector for at least 21 days relative to other conditions (pNaSS-grafted and ungrafted PCL films without vector coating). Overexpression of sox9 via rAAV sox9/pNaSS-grafted or ungrafted PCL films led to increased biological and chondrogenic differentiation activities (matrix deposition) in the aspirates while containing premature osteogenesis and hypertrophy without impacting cell proliferation, with more potent effects noted when using pNaSS-grafted films. Conclusions: These findings show the benefits of targeting patients’ bone marrow via PCL film-guided therapeutic rAAV (sox9) delivery as an off-the-shelf system for future strategies to enhance cartilage repair in translational applications

Etude des interactions entre des copolymères statistiques dérivés du polystyrène et des particules virales

PARIS13-BU Sciences (930792102) / SudocSudocFranceF

Evaluation d une nouvelle prothèse ligamentaire du genou biointégrable en PET (la réponse fibroblastique in vitro et la réponse de l hôte in vivo)

Le greffage a été réalisé à la surface du PET par ozonation et polymérisation radicalaire du monomère, styrène sulfonate de sodium (SSNa). La caractérisation des échantillons par différentes techniques a permis de mettre en évidence la reproductibilité du greffage. L étude in vitro a été réalisée avec des fibroblastes primaires cultivés sur les échantillons de PET greffé et le PET témoin non greffé. Des différences significatives de la réponse cellulaire ont été observées entre les surfaces greffées et non greffées. Les prothèses ligamentaires greffées et non greffées ont été implantées chez la brebis. Un suivi clinique et biologique a été réalisé pendant les premiers 3 mois en montrant que le greffage du polymère bioactif n engendre pas de réaction inflammatoire supplémentaire. L analyse en biologie moléculaire réalisée sur les explants des prothèses ligamentaires 1 an après l intervention met en évidence une transduction améliorée du signal cellulaire.The grafting was performed on PET surface by ozonation and radical polymerization of a monomer, sodium styrene sulfonate (NaSS). Characterization of the samples by various techniques has highlighted the success and the reproducibility of the grafting. The in vitro study was performed with primary fibroblasts cultured on grafted and non grafted PET fabrics and fibers. Significant differences of the cell response were systematically observed between the grafted and non grafted surfaces. The grafted and non grafted PET ligament prostheses were implanted in sheep. A clinical and biological monitoring was performed during the first 3 months after the surgery. The results showed that no additional chronic inflammatory response can be attributed the grafting. Molecular biological analyses by real time RT-PCR were performed on explanted ligament prostheses one year after surgery. Results showed that an improvement of the cell signal transduction.PARIS13-BU Sciences (930792102) / SudocSudocFranceF

ETUDE DE L'ADSORPTION DE LA THROMBINE SUR UN COPOLYMERE A BASE DE CHLORURE DE VINYLE PRESENTANT UNE ACTIVITE ANTICOAGULANTE HEPARIN-LIKE

PARIS13-BU Sciences (930792102) / SudocSudocFranceF

Activité anticoagulante de copolymères à base de poly(chlorure de vinyle), mécanisme de la réaction d'inhibition de la thrombine par l'antithrombine à la surface de ces matériaux

PARIS13-BU Sciences (930792102) / SudocSudocFranceF

Residual stress measurement in veneering ceramic

L émaillage des prothèses dentaires génère des contraintes résiduelles dans la céramique d émaillage et l infrastructure durant le procédé de refroidissement. La connaissance de leur distribution en fonction de la profondeur peut aider à comprendre les échecs,notamment l écaillage de la céramique cosmétique, une complication fréquente avec les prothèses à infrastructure zircone. Le premier objectif de ce travail a été d adapter une méthode industrielle, la méthode du trou incrémental, à l usage dentaire, et de démontrer sa validité pour mesurer les contraintes résiduelles dans des disques en métal (VM) ou en zircone (VZr) émaillés. La méthode développée, présentée dans les premiers chapitres, permet de mesurer des contraintes de très faible module notamment grâce au développement d une chaîne électrique de mesure très sensible. Le second objectif était d étudier l influence de la vitesse de refroidissement, de l épaisseur de la céramique d émaillage et de l infrastructure, et de comparer les mesures dans les échantillons VM et VZr. Les résultats décrits dans les chapitres suivants révèlent que les échantillons VM ont toujours montré un profil qui commence par des contraintes en compression à la surface, ces contraintes diminuant progressivement avec la profondeur, puis ré-augmentant à nouveau. Les échantillons VZr ont montré des profils de contraintes variables,certains décrivant une courbe plus défavorable,dans laquelle les contraintes en compression à la surface deviennent des contraintes en tension en profondeur. Une théorie en deux étapes est décrite pour expliquer le développement des contraintes dans les échantillons métal, et une théorie en trois étapes, comprenant l hypothèse de la transformation de phase, est proposée pour les échantillons zircone. Le ratio adéquat entre l épaisseur d émaillage et de zircone est difficile à définir, et les procédures de refroidissement lent ne semblent pas bénéfiques pour les échantillons VZr.The manufacture of dental crowns and bridges generates residual stresses within the veneering ceramic and framework during the cooling process. Knowing the stress distribution within the veneering ceramic as a function of depth can help the optimizing of manufacturing processes and the understanding of failures, particularly chipping, a frequent complication with zirconia-based fixed partial dentures. The first objective of this work was to transfer and to adapt an effective industrial method, the hole-drilling method, for measuring residual stresses to dental use,and to demonstrate the method for measurement of residual stresses in veneer-metal (VM) and veneer-zirconia (VZr) disks. The adapted method, presented in the earliest chapters, enables the very low stresses measurement in comparison with industrial applications, notably due to the development of a high sensitivity electrical measurement chain. The second objective was to study the influence of cooling rate, veneer thickness, and framework thickness on residual stress profile, and to compare measurements in VM and VZr structures. Results described in the following chapters reveal that VM samples always exhibited the same type of favorable stress vs. depth profile, starting with compressive stresses at the ceramic surface, decreasing with depth, and then becoming compressive again. VZr samples showed varying stress profiles, some describing a worse curve, where the in-surface compressive stresses were found to turn into tensile stresses in the interior.A chronological two-step approach is discussed to explain residual stress development in metal-based samples,and a three-step approach,comprising the hypothesis of the phase transformation, is proposed for zirconia-based samples. The results highlighted the difficulty of defining the adequate ratio between veneer and zirconia framework thickness,and the slow cooling procedures were shown to promote tensile stress development in VZr samples.PARIS13-BU Sciences (930792102) / SudocSudocFranceF

Revêtements polymères bioactifs de fibres en PET pour prothèses ligamentaires (greffage "depuis" la surface et évaluation des propriétés biologiques)

[Résumé en français]La première partie de notre travail a consisté dans le greffage de poly(styrène sulfonate) de sodium et de poly(acide méthacrylique) sur des échantillons de tissus et de fibres d'une prothèse en PET de la Société LARS par la méthode du "grafting from", et dans la caractérisation du greffage par différentes méthodes physico-chimiques. Pendant la deuxième partie nous avons vérifié si l'activité biologique des fibroblastes humains du genou était améliorée suite au greffage. L'étude d'adhérence cellulaire en conditions normales de culture (SVF), plasma et collagène nous a permis de mettre en évidence la présence des importantes forces d'adhérence sur les tissus greffés avec le poly(NaSS) et poly(AM) par rapport aux tissus non greffés. La morphologie cellulaire ainsi que la synthèse du collagène de type I et de type III ont été aussi améliorés sur les échantillons greffés par rapport aux échantillons non greffés.PARIS13-BU Sciences (930792102) / SudocSudocFranceF