New Approach to Identify the Physiological State of Bone Cells at the Surface of Hydroxyapatite Bioceramics

The aim of this work was to identify robust and reproducible signatures characterizing the different steps of bone cell differentiation, from precursors to mature bone cells, using approaches allowing characterization by label-free imaging. Human mesenchymal stromal cells (hMSCs) were cultured either in a growth medium (GM), unable to induce cell differentiation by itself, or in an osteogenic differentiation medium (ODM) on hydroxyapatite ceramics or borosilicate glass. Cell density as well as cell structure, size, and morphology were investigated. A fluorescence microscopy-based approach was followed, using fluorescent labelling of cell features. Some early morphological changes of hMSC during osteogenic differentiation were identified as soon as 48h that were accentuated after 7 days of culture. Cell density was higher when cells were cultured in GM and the cells exhibited significantly smaller nuclei (size ratio about 1.3-1.5) than those cultured in ODM, regardless of the culture support. In ODM, the cells were also of bigger size (1.2 to 1.5 times) and their focal adhesions were reinforcedType I collagen, a gold standard marker of osteogenic differentiation, appeared more intense in ODM. These cell features can be determined using multimodal label-free imaging methods to characterize the differentiation state of hMSCs at the biomaterial surface. They give rise to new cost-effective approaches to investigate cell behavior by suppressing the chemical markers and reducing both the number of needed samples and the requested time to do so

Microporous Hydroxyapatite-Based Ceramics Alter the Physiology of Endothelial Cells through Physical and Chemical Cues

Incorporation of silicate ions in calcium phosphate ceramics (CPC) and modification of their multiscale architecture are two strategies for improving the vascularization of scaffolds for bone regenerative medicine. The response of endothelial cells, actors for vascularization, to the chemical and physical cues of biomaterial surfaces is little documented, although essential. We aimed to characterize in vitro the response of an endothelial cell line, C166, cultivated on the surface CPCs varying either in terms of their chemistry (pure versus silicon-doped HA) or their microstructure (dense versus microporous). Adhesion, metabolic activity, and proliferation were significantly altered on microporous ceramics, but the secretion of the pro-angiogenic VEGF-A increased from 262 to 386 pg/mL on porous compared to dense silicon-doped HA ceramics after 168 h. A tubulogenesis assay was set up directly on the ceramics. Two configurations were designed for discriminating the influence of the chemistry from that of the surface physical properties. The formation of tubule-like structures was qualitatively more frequent on dense ceramics. Microporous ceramics induced calcium depletion in the culture medium (from 2 down to 0.5 mmol/L), which is deleterious for C166. Importantly, this effect might be associated with the in vitro static cell culture. No influence of silicon doping of HA on C166 behavior was detected

Roches ornées, roches dressées

Jean Abélanet peut être considéré comme le pionnier de l'archéologie actuelle sur les terres nord-catalanes. Ce rôle de précurseur dans la découverte de sites majeurs, mais aussi sa contribution savante à l'avancée des études préhistoriques, tant sur le mégalithisme en Pyrénées que sur l'art rupestre post-glaciaire en Europe occidentale, justifient l'hommage qui lui est rendu par la communauté des chercheurs. Cet hommage a pris la forme d'un colloque placé sous l'égide de l'Association Archéologique des Pyrénées-Orientales, dont il fut membre fondateur, et de l'Université de Perpignan, dont il fut le premier enseignant en Préhistoire. Sont rassemblées dans cet ouvrage les contributions de 74 auteurs et co-auteurs. Ces 576 pages, abondamment illustrées par près de 300 figures, abordent des sujets très divers qui reflètent les différents champs d'études balayés par son insatiable et humaniste curiosité. Une première partie, remontant aux sources des arts et des mythes, éclaire certains aspects de l'art rupestre et du mégalithisme, depuis leurs origines jusqu'à nos jours, à partir de recherches récentes menées dans l'Ancien monde, des terres australes d'Afrique jusqu'en Europe de l'Ouest. Le second thème, tout en laissant une large place à l'étude des arts et des traditions funéraires, rassemble des travaux pluridisciplinaires menés à l'orient des Pyrénées, travaux d'historiographie, de palynologie, de géologie, d'archéologie préhistorique et historique, d'histoire ou d'ethnologie