255 In vivo detection of non-occlusive thrombi in drug-eluting stents by scintigraphy and radio-labelled annexin V in a rabbit model

IntroductionThrombi in contact with non re-endothelialized stent struts associated with drug-eluting stent (DES) thrombosis. Hence, detection of thrombi in DES could help to evaluate the risk of DES thrombosis. Annexin V radio-labelled with 99mTechnetium (99mTc) is a radio-tracer with a high affinity for activated platelets.ObjectivesOur objectives were: 1) to develop an animal model of non-occlusive thrombosis of stents, 2) to evaluate the ability of annexin V 99mTc for the detection of in-stent thrombi using scintigraphy.MethodsRight carotid arteries of NZW rabbits (n=14) fed a high cholesterol diet were implanted with overlapping DES (n=7) or bare-metal stents (BMS; n=7). Four weeks after stent implantation, rabbits underwent a first scintigraphy 3 hours after injection of 200 MBq of radio-labelled annexin V 99mTc. At the end of the first scintigraphy, a suture was placed surgically proximal to the stented carotid arteries in order to induce a thrombus-prone flow limiting stenosis. Four days later, a second scintigraphy was performed. After the second scintigraphy, stents were excised, imaged ex vivo and then fixed for histological examination and scanning electron microscopy (SEM).ResultsActivities measured in vivo in the stented carotid arteries after injection of annexin V 99mTc were higher on the second scintigraphy after creation of a surgical stenosis as compared to the first scintigraphy (0.24 vs. 0.15 counts/pixel/MBq, respectively; p<0.05). On the second scintigraphy, activities were higher in DES vs. BMS (0.26 vs. 0.19 counts/pixel/MBq, respectively; p < 0.005). High activities measured in stents in vivo were associated with the detection of thrombi on corresponding histological sections and SEM.ConclusionsIn this work, we developed a rabbit model of non-occlusive thrombosis of stents in carotid arteries. In this model, in-stent thrombi could be detected using annexin V 99mTc scintigraphy

In vitro studies and preliminary in vivo evaluation of silicified concentrated collagen hydrogels

Hybrid and nanocomposite silicacollagen materials derived from concentrated collagen hydrogels were evaluated in vitro and in vivo to establish their potentialities for biological dressings. Silicification significantly improved the mechanical and thermal stability of the collagen network within the hybrid systems. Nanocomposites were found to favor the metabolic activity of immobilized human dermal fibroblastswhile decreasing the hydrogel contraction. Cell adhesion experiments suggested that in vitro cell behavior was dictated by mechanical properties and surface structure of the scaffold. First-to-date in vivo implantation of bulk hydrogels in subcutaneous sites of rats was performed over the vascular inflammatory period. These materials were colonized and vascularized without inducing strong inflammatory response. These data raise reasonable hope for the future application of silicacollagen biomaterials as biological dressings.Fil: Desimone, Martín Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Hélary, Christophe. Université Pierre et Marie Curie; FranciaFil: Quignard, Sandrine. Université Pierre et Marie Curie; FranciaFil: Rietveld, Ivo B. Universite de Paris; FranciaFil: Bataille, Clement. Université de Versailles Saint-quentin-en-yvelines.; FranciaFil: Copello, Guillermo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Mosser, Gervaise. Université Pierre et Marie Curie; FranciaFil: Giraud Guille, Marie-Madeleine. Université Pierre et Marie Curie; FranciaFil: Livage, Jacques. Université Pierre et Marie Curie; FranciaFil: Meddahi Pellé, Anne. Université de Versailles Saint-quentin-en-yvelines.; FranciaFil: Coradin, Thibaud. Université Pierre et Marie Curie; Franci

Biomatériaux vasculaires : du génie biologique et médical au génie tissulaire

Les biomatériaux sont au centre d’innovations importantes dans le traitement des traumatismes, de certaines affections (en particulier cardio-vasculaires) ou du vieillissement. Des progrès se poursuivent actuellement dans le cadre du génie tissulaire en s’intégrant dans une approche plus large qui fait appel aux avancées techniques de la chimie des polymères, des biotechnologies, et de la thérapie cellulaire et génique. Cette approche pluridisciplinaire vise à associer dans une même unité fonctionnelle un matériau (synthétique ou naturel) si possible dégradable, et une composante cellulaire, dans une architecture tridimensionnelle. Il s’agit de favoriser avec ces nouveaux biomatériaux hybrides, l’aptitude de l’organisme à se réparer. De ce champ d’investigations, des innovations importantes sont attendues, en particulier dans le domaine du remplacement des vaisseaux. Du génie biologique et médical au génie tissulaire, les biomatériaux occupent toujours une place centrale.Biomaterials are already widely used in medical sciences. The field of biomaterials began to shift to produce materials able to stimulate specific cellular responses at the molecular level. The combined efforts of cell biologists, engineers, materials scientists, mathematicians, geneticists, and clinicians are now used in tissue engineering to restore, maintain, or improve tissue functions or organs. This rapidly expanding approach combines the fields of material sciences and cell biology for the molecular design of polymeric scaffolds with appropriate 3D configuration and biological responses. Future developments for new blood vessels will require improvements in technology of materials and biotechnology together with the increased knowledge of the interactions between materials, blood, and living tissues. Biomaterials represent a crucial mainstay for all these studies

Nesting and fate of transplanted stem cells in hypoxic/ischemic injured tissues: The role of HIF1α/sirtuins and downstream molecular interactions.

International audienceThe nesting mechanisms and programming for the fate of implanted stem cells in the damaged tissue have been critical issues in designing and achieving cell therapies. The fracture site can induce senescence or apoptosis based on the surrounding harsh conditions, hypoxia, and oxidative stress (OS). Respiration deficiency, disruption in energy metabolism, and consequently OS induction change the biophysical, biochemical, and cellular components of the native tissue. Additionally, the homeostatic molecular players and cell signaling might be changed. Despite all aforementioned issues, in the native stem cell niche, physiological hypoxia is not toxic; rather, it is vitally required for homing, self-renewal, and differentiation. Hence, the key macromolecular players involved in the support of stem cell survival and re-adaptation to a new dysfunctional niche must be understood for managing the cell therapy outcome. Hypoxia-inducible factor 1-alpha is the master transcriptional regulator, involved in the cell response to hypoxia and the adaptation of stem cells to a new niche. This protein is regulated by interaction with sirtuins. Sirtuins are highly conserved NAD+-dependent enzymes that monitor the cellular energy status and modulate gene transcription, genome stability, and energy metabolism in response to environmental signals to modulate the homing and fate of stem cells. Herein, new insights into the nesting of stem cells in hypoxic-ischemic injured tissues were provided and their programming in a new dysfunctional niche along with the involved complex macromolecular players were critically discussed

Evaluation of dense collagen matrices as medicated wound dressing for the treatment of cutaneous chronic wounds

International audienceCutaneous chronic wounds are characterized by an impaired wound healing which may lead to infection and amputation. When current treatments are not effective enough, the application of wound dressings is required. To date, no ideal biomaterial is available. In this study, highly dense collagen matrices have been evaluated as novel medicated wound dressings for the treatment of chronic wounds. For this purpose, the structure, mechanical properties, swelling ability and in vivo stability of matrices concentrated from 5 to 40 mg mL(-1) were tested. The matrix stiffness increased with the collagen concentration and was associated with the fibril density and thickness. Increased collagen concentration also enhanced the material resistance against accelerated digestion by collagenase. After subcutaneous implantation in rats, dense collagen matrices exhibited high stability without any degradation after 15 days. The absence of macrophages and neutrophils evidenced their biocompatibility. Subsequently, dense matrices at 40 mg mL(-1) were evaluated as drug delivery system for ampicillin release. More concentrated matrices exhibited the best swelling abilities and could absorb 20 times their dry weight in water, allowing for an efficient antibiotic loading from their dried form. They released efficient doses of antibiotics that inhibited the bacterial growth of Staphylococcus Aureus over 3 days. In parallel, they show no cytotoxicity towards human fibroblasts. These results show that dense collagen matrices are promising materials to develop medicated wound dressings for the treatment of chronic wounds

Gelatin-polytrimethylene carbonate blend based electrospun tubular construct as a potential vascular biomaterial.

International audienceThe present work details the fabrication of electrospun tubular scaffolds based on the biocompatible and unexploited blend of gelatin and polytrimethylene carbonate (PTMC) as a media (middle layer of blood vessel) equivalent for blood vessel regeneration. An attempt to resemble the media stimulated the selection of gelatin as a matrix (substitution for collagen) with the inclusion of the biodegradable elastomer PTMC (substitution for elastin). -The work highlights the variation of electrospinning parameters and its assiduous selection based on fiber diameter distribution and pore size distribution to obtain smooth microfibers and micropores which is reported for the first time for this blend. Electrospun conduits of gelatin-PTMC blend had fibers sized 6-8 μm and pores sized ~100-150 μm. Young's modulus of 0.40 ± 0.045 MPa was observed, resembling the tunica media of the native artery (~0.5 MPa). An evaluation of the surface properties, topography, and mechanical properties validated its physical requirements for inclusion in a vascular graft. Preliminary biological tests confirmed its minimal in-vitro toxicity and in-vivo biocompatibility. MTT assay (indirect) elucidated cell viability above 70% with scaffold extract, considered to be non-toxic according to the EN ISO-10993-5/12 protocol. The in-vivo subcutaneous implantation in rat showed a marked reduction in macrophages within 15 days revealing its biocompatibility and its possibility for host integration. This comprehensive study presents for the first time the potential of microporous electrospun gelatin and PTMC blend based tubular construct as a potential biomaterial for vascular tissue engineering. The proposed media equivalent included in a bilayer or trilayer polymeric construct can be a promising off-shelf vascular graft

Recent advances in Fe-based bioresorbable stents: Materials design and biosafety

Fe-based materials have received more and more interests in recent years as candidates to fabricate bioresorbable stents due to their appropriate mechanical properties and biocompatibility. However, the low degradation rate of Fe is a serious limitation for such application. To overcome this critical issue, many efforts have been devoted to accelerate the corrosion rate of Fe-based stents, through the structural and surface modification of Fe matrix. As stents are implantable devices, the released corrosion products (Fe2+ ions) in vessels may alter the metabolism, by generating reactive oxygen species (ROS), which might in turn impact the biosafety of Fe-based stents. These considerations emphasize the importance of combining knowledge in both materials and biological science for the development of efficient and safe Fe-based stents, although there are still only limited numbers of reviews regarding this interdisciplinary field. This review aims to provide a concise overview of the main strategies developed so far to design Fe-based stents with accelerated degradation, highlighting the fundamental mechanisms of corrosion and the methods to study them as well as the reported approaches to accelerate the corrosion rates. These approaches will be divided into four main sections, focusing on (i) increased active surface areas, (ii) tailored microstructures, (iii) creation of galvanic reactions (by alloying, ion implantation or surface coating of noble metals) and (iv) decreased local pH induced by degradable surface organic layers. Recent advances in the evaluation of the in vitro biocompatibility of the final materials and ongoing in vivo tests are also provided

Astaxanthin Complexes to Attenuate Muscle Damage after In Vivo Femoral Ischemia-Reperfusion.

International audience(1) Background: Reperfusion injury refers to the cell and tissue damage induced, when blood flow is restored after an ischemic period. While reperfusion reestablishes oxygen supply, it generates a high concentration of radicals, resulting in tissue dysfunction and damage. Here, we aimed to challenge and achieve the potential of a delivery system based on astaxanthin, a natural antioxidant, in attenuating the muscle damage in an animal model of femoral hind-limb ischemia and reperfusion. (2) Methods: The antioxidant capacity and non-toxicity of astaxanthin was validated before and after loading into a polysaccharide scaffold. The capacity of astaxanthin to compensate stress damages was also studied after ischemia induced by femoral artery clamping and followed by varied periods of reperfusion. (3) Results: Histological evaluation showed a positive labeling for CD68 and CD163 macrophage markers, indicating a remodeling process. In addition, higher levels of Nrf2 and NQO1 expression in the sham group compared to the antioxidant group could reflect a reduction of the oxidative damage after 15 days of reperfusion. Furthermore, non-significant differences were observed in non-heme iron deposition in both groups, reflecting a cell population susceptible to free radical damage. (4) Conclusions: Our results suggest that the in situ release of an antioxidant molecule could be effective in improving the antioxidant defenses of ischemia/reperfusion (I/R)-damaged muscles