Strontium-loaded mineral bone cements as sustained release systems : Compositions, release properties, and effects on human osteoprogenitor cells

This study aims to evaluate in vitro the release properties and biological behavior of original compositions of strontium (Sr)-loaded bone mineral cements. Strontium was introduced into vaterite CaCO3-dicalcium phosphate dihydrate cement via two routes: as SrCO3 in the solid phase (SrS cements), and as SrCl2 dissolved in the liquid phase (SrL cements), leading to different cement compositions after setting. Complementary analytical techniques implemented to thoroughly investigate the release/dissolution mechanism of Sr-loaded cements at pH 7.4 and 37°C during 3 weeks revealed a sustained release of Sr and a centripetal dissolution of the more soluble phase (vaterite) limited by a diffusion process. In all cases, the initial burst of the Ca and Sr release (highest for the SrL cements) that occurred over 48 h did not have a significant effect on the expression of bone markers (alkaline phosphatase, osteocalcin), the levels of which remained overexpressed after 15 days of culture with human osteoprogenitor (HOP) cells. At the same time, proliferation of HOP cells was significantly higher on SrS cements. Interestingly, this study shows that we can optimize the sustained release of Sr2þ, the cement biodegradation and biological activity by controlling the route of introduction of strontium in the cement paste

Development of an injectable composite for bone regeneration

With the development of minimally invasive surgical techniques, there is a growing interest in the research and development of injectable biomaterials especially for orthopedic applications. In a view to enhance the overall surgery benefits for the patient, the BIOSINJECT project aims at preparing a new generation of mineral-organic composites for bone regeneration exhibiting bioactivity, therapeutic activity and easiness of use to broaden the application domains of the actual bone mineral cements and propose an alternative strategy with regard to their poor resorbability, injectability difficulties and risk of infection. First, a physical-chemical study demonstrated the feasibility of self-setting injectable composites associating calcium carbonate-calcium phosphate cement and polysaccharides (tailor-made or commercial polymer) in the presence or not of an antibacterial agent within the composite formulation. Then, bone cell response and antimicrobial activity of the composite have been evaluated in vitro. Finally, in order to evaluate resorption rate and bone tissue response an animal study has been performed and the histological analysis is still in progress. These multidisciplinary and complementary studies led to promising results in a view of the industrial development of such composite for dental and orthopaedic applications

Effects of dynamic cell culture conditions on 3D spatial reogarnization of MSCS/HUVECS spheroids in the context of bone tissue

We aim to observe the development and reorganization of MSCs and HUVECs in Pullulan/Dextran hydrogels supplied with nHAp under dynamic culture conditions in a perfusion bioreactor.Hydrogel poreux sous perfusion : modélisation et optimisation d'un modèle in vitro de reconstruction de défaut osseu

Effect of silver and strontium incorporation route on hydroxyapatite coatings elaborated by rf-SPS

Hydroxyapatite coatings have been currently used on hip prostheses for their ability to promote faster osseointe- gration and bone growth. Nevertheless, post-operative infections remain a recurring problem. To overcome this issue, doping with antibacterial elements has become a new trend. In this work, hydroxyapatite coatings elab- orated by radio-frequency suspension plasma spraying (rf-SPS) were doped with silver and strontium. Several doping strategies were explored thanks to the versatility offered by SPS compared with conventional spraying. First way: calcium phosphate doped powders were synthesized by coprecipitation and then dispersed into water before plasma spraying; second way: undoped powder was dispersed into aqueous medium in which nitrates or nanoparticles of the dopant(s) were respectively dissolved/dispersed. XRD revealed a high level of crystallinity ratio (ISO 13 779) and hydroxyapatite proportion for most of the coatings, with the presence of Ag/Ag 2 O nanopar- ticles whatever the doping route. SEM-EDS and STEM have demonstrated a more homogeneous distribution of the strontium within the coating made from the doped powder. Adherence of the coatings was estimated via a 3-point bending test, while bacteriological tests with S. aureus and proliferation of mesenchymal stem cells (hMSC) were performed. The results indicated a preferential incorporation of strontium into the secondary phases, showed efficient bactericidal properties, excellent mechanical properties in comparison with an APS reference coating, and no evidence of cytotoxic effect. This opens the way of a new type of coatings with a finer structure and a higher homogeneity through a better control of physicochemical properties using a suspension as the precursor

Fabrication par impression 3D d'un matériau composite associant un phosphate de calcium et des cellules humaines pour des applications en ingénierie tissulaire osseuse.

L’approche classique de l’ingénierie du tissu osseux vise à concevoir un substitut tissulaire associant des cellules ostéoprogénitrices à une matrice tridimensionnelle phosphocalcique capable de promouvoir la reconstruction osseuse. Le développement de l’impression 3D dans le domaine de la recherche en biomédical et plus particulièrement dans le domaine de la reconstruction osseuse a permis ces vingt dernières années, d’envisager de nouvelles solutions technologiques visant à améliorer les lacunes bien identifiées de l’approche classique : absence de hiérarchisation cellulaire, néovascularisation limitée, faible diffusion des nutriments et de l’oxygène.Malheureusement, les matériaux commerciaux disponibles pour l’impression 3D du tissu osseux sont peu développés et ne présentent pas à la fois une bonne biocompatibilité cellulaire et à la fois des propriétés mécaniques proches de celle du tissu osseux.L’objectif principal de ce travail a consisté à évaluer in vitro la faisabilité d’une co-impression d’un matériau phosphocalcique constituant l’ossature de la construction (scaffold) et d’une encre biologique. L’objectif secondaire de ce travail était le développement d’un matériau phosphocalcique imprimable et biocompatible.Pour répondre à ces problématiques, nous proposons de développer un matériau phosphocalcique à base de gélatine méthacrylée avec une synthèse d’hydroxyapatite directement dans la gélatine. Cette approche permet d’obtenir un matériau photopolymérisable post impression ayant une phase minérale répartie de façon homogène dans le matériau évitant ainsi l’obstruction de la seringue d’impression. L’encre cellulaire est composée de cellules MG63 issues d’un ostéosarcome humain associé à un hydrogel vecteur composé d’alginate et d’acide hyaluronique. Ce modèle cellulaire simple et bien décrit in vitro permet de répondre aux demandes de l’impression 3D qui nécessite un volume cellulaire important.Nos résultats montrent qu’il est possible d’imprimer sur la même imprimante, par extrusion, ce matériau avec une encre cellulaire composée de cellules MG63. Cette co-impression permet d’obtenir de façon organisée, une construction composée d’une part d’un matériau phosphocalcique recréant le micro-environnement mécanique et chimique de l’os, et d’autre part d’une encre cellulaire préservant la viabilité cellulaire lors de l’impression. De plus, les résultats des tests d’ostéodifférenciation semblent suggérer un potentiel ostéo-inducteur du matériau scaffold qui serait pertinent de confirmer avec un modèle cellulaire plus proche de la cellule ostéoblastique primaire

How hydrodynamics and species transport influence the 3D microenvironment of cells seeded in hydrogel scaffolds

International audienc

How hydrodynamics and species transport influence the 3D microenvironment of cells seeded in hydrogel scaffolds

International audienc

Qualification of labeled Endothelial Progenitor cells for tracking in the context of tissue engineering

Congrès sous l’égide de la Société Française de Génie Biologique et Médical (SFGBM).National audienceIn order to track location and distribution of endothelial cells (ECs) within scaffolds, we chose lentiPGK-TdTomato transduction of human Endothelial Progenitor Cells (EPCs). Because transduction could have a functional impact on cell behaviour, we checked different parameters for qualification of labeled-EPCs. After isolation and expansion, EPCs were transduced with the lentiviral vector containing the TdTomato protein gene. Conventional karyotyping, differentiation capacity, viability, proliferation assays and functional assays were performed with labeled and unlabeled EPCs. Results show that cell labeling did not affect cell adhesion nor induce cell death. Cell labeling did not induce more chromosomal aberrations. Phenotypical characterization was not affected. In the context of tissue engineering applications, labeled EPCs maintained their ability to line scaffolds, withstand physiological arterial shear stress and form tubular networks in co-cultures with human osteoblast progenitor cells. So it is possible to label human EPCs with TdTomato without affecting their behaviour by the transduction procedure. This creates an important tool for vascular and bone tissue engineering

Qualification of labeled Endothelial Progenitor cells for tracking in the context of tissue engineering

In order to track location and distribution of endothelial cells (ECs) within scaffolds, we chose lentiPGK-TdTomato transduction of human Endothelial Progenitor Cells (EPCs). Because transduction could have a functional impact on cell behaviour, we checked different parameters for qualification of labeled-EPCs. After isolation and expansion, EPCs were transduced with the lentiviral vector containing the TdTomato protein gene. Conventional karyotyping, differentiation capacity, viability, proliferation assays and functional assays were performed with labeled and unlabeled EPCs. Results show that cell labeling did not affect cell adhesion nor induce cell death. Cell labeling did not induce more chromosomal aberrations. Phenotypical characterization was not affected. In the context of tissue engineering applications, labeled EPCs maintained their ability to line scaffolds, withstand physiological arterial shear stress and form tubular networks in co-cultures with human osteoblast progenitor cells. So it is possible to label human EPCs with TdTomato without affecting their behaviour by the transduction procedure. This creates an important tool for vascular and bone tissue engineering