Incorporating strontium enriched amorphous calcium phosphate granules in collagen/collagen-magnesium-hydroxyapatite osteochondral scaffolds improves subchondral bone repair.

Osteochondral defect repair with a collagen/collagen-magnesium-hydroxyapatite (Col/Col-Mg-HAp) scaffold has demonstrated good clinical results. However, subchondral bone repair remained suboptimal, potentially leading to damage to the regenerated overlying neocartilage. This study aimed to improve the bone repair potential of this scaffold by incorporating newly developed strontium (Sr) ion enriched amorphous calcium phosphate (Sr-ACP) granules (100-150 µm). Sr concentration of Sr-ACP was determined with ICP-MS at 2.49 ± 0.04 wt%. Then 30 wt% ACP or Sr-ACP granules were integrated into the scaffold prototypes. The ACP or Sr-ACP granules were well embedded and distributed in the collagen matrix demonstrated by micro-CT and scanning electron microscopy/energy dispersive x-ray spectrometry. Good cytocompatibility of ACP/Sr-ACP granules and ACP/Sr-ACP enriched scaffolds was confirmed with in vitro cytotoxicity assays. An overall promising early tissue response and good biocompatibility of ACP and Sr-ACP enriched scaffolds were demonstrated in a subcutaneous mouse model. In a goat osteochondral defect model, significantly more bone was observed at 6 months with the treatment of Sr-ACP enriched scaffolds compared to scaffold-only, in particular in the weight-bearing femoral condyle subchondral bone defect. Overall, the incorporation of osteogenic Sr-ACP granules in Col/Col-Mg-HAp scaffolds showed to be a feasible and promising strategy to improve subchondral bone repair.

Alternative in vitro models used in the main safety tests of cosmetic products and new challenges.

BACKGROUND: Guided by ethical considerations and regulatory requirements such as the 7th Amendment to the European Cosmetics Directive N° 1223/2009, the cosmetic industry has developed and evaluated alternative test strategies such as in vitro assays, in silico approaches for toxicological endpoints and efficacy of cosmetic products and cosmetics ingredients. In consequence, the European Centre for the Validation of Alternative Methods (ECVAM) has proposed a list of validated cell-based in vitro models for predicting the safety and toxicity of cosmetic ingredients. These models have been demonstrated as valuable and effective tools to overcome the limitations of animal in vivo studies. For example, 3D human skin equivalent models are used to evaluate skin irritation potential; and excised human skin is used as the gold standard for the evaluation of dermal absorption. OBJECTIVE: This review presents, in relation to the regulatory requirements, the main alternative in vitro models used in the safety tests of cosmetic products, focusing on skin sensitization, skin corrosion, skin irritation and skin absorption, with advantages and limitations of each model. Recent innovative 3D cell technologies such as Organ-on-a-Chip (OoC) models that can bring significant improvements for toxicology and efficacy testing are also presented. CONCLUSION: The development of OoC technology is promising for assessing the toxicity of substances contained in cosmetics, particularly for repeated dose toxicity, for which no alternative in vitro methods are currently available. Nevertheless, aside from the challenges, the technology needs to be validated and accepted by regulatory organizations as an effective method. Collaboration between researchers, regulatory organizations and industry would be required to achieve this validation.

CONTEXTE: Guidée par des considérations éthiques et des exigences réglementaires telles que le 7e amendement à la directive européenne sur les cosmétiques N° 1223/2009, l'industrie cosmétique a développé et évalué des stratégies de test alternatives telles que des tests in vitro, des approches in silico pour les paramètres toxicologiques et l'efficacité des produits cosmétiques et ingrédients cosmétiques. En conséquence, le Centre Européen pour la Validation des Méthodes Alternatives (ECVAM) a proposé une liste de modèles cellulaires in vitro validés pour prédire la sécurité et la toxicité des ingrédients cosmétiques. Ces modèles ont été démontrés comme des outils précieux et efficaces pour surmonter les limites des études animales in vivo. Par exemple, des modèles équivalents de peau humaine 3D sont utilisés pour évaluer le potentiel d'irritation de la peau; et la peau humaine excisée est utilisée comme « gold standard ¼ pour l'évaluation de l'absorption cutanée. OBJECTIF: Cette revue présente, en lien avec les exigences réglementaires, les principaux modèles alternatifs in vitro utilisés dans les tests de sécurité des produits cosmétiques, en se concentrant sur la sensibilisation, la corrosion, l'irritation et l'absorption cutanée, avec les avantages et les limites de chaque modèle. Des technologies cellulaires 3D innovantes récentes telles que les modèles Organ-on-a-Chip (OoC) qui peuvent apporter des améliorations significatives pour la toxicologie et les tests d'efficacité sont également présentées. CONCLUSION: Le développement de la technologie OoC est prometteur pour évaluer la toxicité des substances contenues dans les cosmétiques, en particulier pour la toxicité à doses répétées, pour laquelle aucune méthode alternative in vitro n'est actuellement disponible. Néanmoins, outre les défis, la technologie doit être validée et acceptée par les organismes régulateurs comme une méthode efficace. Une collaboration entre les chercheurs, les organismes régulateurs et l'industrie serait nécessaire pour parvenir à cette validation.

Interspecies differences with in vitro and in vivo models of vascular tissue engineering.

In arterial replacement there is a clear clinical need for a functional substitute possessing appropriate haemocompatible properties to be implanted as small diameter artery. Endothelial cell seeding constitutes an appreciated method to improve blood compatibility on the condition that cells firmly adhere to the support. Along this way, an innovative technique based on multilayered polyelectrolyte films (PEM) as cell adhesive substrate was previously validated in vitro and in vivo in a small-animal model. In this study, we extended the work on a larger animal (sheep) to validate furthermore the paradigm of PEM functionalization for vascular substitutes. We tested in vitro: the efficiency of PEM to induce endothelial progenitor differentiation in sheep endothelial cells; the ability of PEM to sustain cell proliferation and allow resistance to shear stress; the fate of PEM-coated de-endothelialized human saphenous veins under flow conditions, a prerequisite step before in vivo experiments. Despite in vitro differences we were encouraged by testing in vivo PEM-coated prosthesis as carotid replacement in sheep, but without success. In order to explain the implantation failure, an in vitro haemocompatibility evaluation was performed that highlighted interspecies differences able to explain, at least in part, the graft failure obtained.

Biocompatible fibrous networks of cellulose nanofibres and collagen crosslinked using genipin: potential as artificial ligament/tendons.

Bio-based fibrous nanocomposites of cellulose nanofibres and non-crosslinked/crosslinked collagen were prepared by in situ pH-induced fibrillation of collagen phase and sterilized using gamma rays at 25 KGy. Collagen phase is crosslinked using genipin, a bio-based crosslinker that introduces flexible crosslinks. Microscopy studies of the prepared materials showed nanostructured fibrous collagen and cellulose dispersed in collagen matrix. Mechanical performance of the sterilized nanocomposites was close to that of natural ligament and tendon, in simulated body conditions. Cytocompatibility studies indicated that these nanocomposites allowed human ligament cell and human endothelial cell adhesion, growth, and differentiation; which is eminently favourable to ligament tissue engineering.

Reduction of biofilm infection risks and promotion of osteointegration for optimized surfaces of titanium implants.

Titanium-based implants are widely used in modern clinical practice; however, complications associated with implants due to bacterial-induced infections arise frequently, caused mainly by staphylococci, streptococci, Pseudomonas spp. and coliform bacteria. Although increased hydrophilicity of the biomaterial surface is known to be beneficial in minimizing the biofilm, quantitative analyses between the actual implant parameters and bacterial development are scarce. Here, the results of in vitro studies of Staphylococcus aureus and Staphylococcus epidermidis proliferation on uncoated and coated titanium materials with different roughness, porosity, topology, and hydrophilicity are shown. The same materials have been tested in parallel with respect to human osteogenic and endothelial cell adhesion, proliferation, and differentiation. The experimental data processed by meta-analysis are indicating the possibility of decreasing the biofilm formation by 80-90% for flat substrates versus untreated plasma-sprayed porous titanium and by 65-95% for other porous titanium coatings. It is also shown that optimized surfaces would lead to 10-50% enhanced cell proliferation and differentiation versus reference porous titanium coatings. This presents an opportunity to manufacture implants with intrinsic reduced infection risk, yet without the additional use of antibacterial substances.