Low calcium levels in serum-free media maintain chondrocyte phenotype in monolayer culture and reduce chondrocyte aggregation in suspension culture

SummaryObjectiveExtracellular calcium influences chondrocyte differentiation and synthesis of extracellular matrix. Previously, calcium concentrations ranging from 0.1mM to 2mM have been used in vitro and these studies indicated that low calcium concentrations were generally favorable for chondrocyte culture. Our objective was to extend these findings to yet lower calcium concentrations and to comprehensively examine effects on morphology and phenotype in two culture systems.MethodsSerum-free media containing 1mM, 50μM or 15μM of calcium and a serum-containing medium were used to culture chondrocytes in suspension and in monolayer, at high and low inoculation density.ResultsIn monolayer, at low and high density, removing serum and decreasing calcium concentration decreased cell spreading and lowered collagen type I expression whereas collagen type II expression remained stable. In suspension, cells aggregated for all media tested; however, aggregates were smaller and looser in the absence of serum.ConclusionThe serum-free 50μM and 1mM calcium media provide good alternatives to classical media for monolayer culture since both growth and chondrocyte phenotype were maintained. In suspension culture, the serum-free 1mM calcium medium also possesses the beneficial properties of limiting aggregate size while maintaining growth and phenotype

Firm dynamics in an global and uncertain economy

In this dissertation, I study firm dynamics in the context of a global and uncertain economy. In the first chapter, I show how uncertainty generates reallocation among French multinationals. In a second chapter, I study how an increase in demand uncertainty negatively impacts firm growth and how the persistence of this effect depends on the synchronicity of the firm dynamic with that of the other firms in its sector. Finally in the third chapter, I highlight how the extensive margin of international trade contribute to shape the direction, quantity and content of the international transmission of knowledge

Optimisation et caractérisation de la culture de chondrocytes en suspension

Revue de la littérature -- Objectifs et organisation générale du document -- Article -- Low calcium levels in serum-free media maintain chondrocyte phenotype in monolayer culture and reduce chodrocyte aggregation in suspension culture -- Article-chondrocyte cultured in stirred suspension with serum-free medium containing pluronic-68 aggregate and proliferate while maintaining their differentiated phenotype -- Article -- the fate of pluronic F-68 in chondrocytes and CHO cells -- Chondrocyte aggregation in suspension culture is GFOGER-GPP and gbs1 integrin dependent -- Discussion générale

Firm dynamics in an global and uncertain economy

In this dissertation, I study firm dynamics in the context of a global and uncertain economy. In the first chapter, I show how uncertainty generates reallocation among French multinationals. In a second chapter, I study how an increase in demand uncertainty negatively impacts firm growth and how the persistence of this effect depends on the synchronicity of the firm dynamic with that of the other firms in its sector. Finally in the third chapter, I highlight how the extensive margin of international trade contribute to shape the direction, quantity and content of the international transmission of knowledge

Exporting ideas: knowledge flows from expanding trade in goods

We examine the effect of entry by French firms into a new export market on the dynamics of their patents' citations received from that destination. Applying a difference-in-differences identification strategy with a staggered treatment design, we show that: (i) entering a new foreign market has a significant impact on the long-run flow of citations; (ii) the impact is mostly driven by the extensive margin; (iii) inventors in destination countries patent mostly in products that do not directly compete with those of the exporting firm; (iv) the spillover intensity decreases with the technological distance between the exporting firm and the destination

Rapport de mission au Ghana : Participation à la réunion d'experts organisée par la FAO sur FAW (18 au 20 juillet 2017).

L'expertise collégiale réalisée pour le compte de la FAO m'a amené à participer, sur invitation, à la réunion d'experts organisée à Accra, au Ghana, du 18 au 20 juillet 2017, sur le thème de l'invasion sur le continent africain de l'espèce exotique envahissante Spodoptera frugiperda (Fall armyworm-FAW). J'avais en effet rédigé une fiche synthétique sur cette espèce présente notamment au Brésil sur le cotonnier. Lors de cette réunion, des collègues d'Amérique du sud (Brésil - Celso Omoto/ESALQ et Ivan Cruz/Embrapa Milho e sorgo), du Mexique (Helda Morales/Ecosur), du Royaume-Uni (Ken Wilson/Lancaster University) et des États-Unis (Rob Meagher/USDA et Fred Gould, ce dernier par Skype) ont été conviés à partager leur expérience. Le second jour, les exposés des chercheurs du Zimbabwe, d'Ouganda, du Bénin et du Cameroun ont permis d'actualiser les connaissances sur la situation dans ces pays d'Afrique sub-saharienne. J. van den Berg, chercheur d'Afrique du Sud, n'a pas pu se déplacer, ni Dominic Reisig des USA. Non programmé initialement, j'ai néanmoins pu y faire un exposé en trois parties, juste avant celui de Georg Goergen, chercheur de l'IITA qui avait identifié le premier l'espèce à Cotonou. La première partie de ma présentation a montré la variabilité des agroécosystèmes à base de maïs, tandis que la seconde partie abordait des composantes de la lutte intégrée pour voir celles réellement intéressantes à appliquer. Dans une troisième partie j'ai dressé l'état des lieux des forces francophones pouvant contribuer potentiellement à de futures études, forces basées tant dans des pays africains francophones qu'en métropole. Le dernier jour a été consacré à la synthèse des connaissances mises à disposition les jours d'avant et aux perspectives de développement des activités destinées à mieux gérer les infestations à toutes les échelles de décision, en particulier à celle des petits agriculteurs. Un programme basé sur trois piliers (1. FAW sustainable management, 2. Impact assessment, 3. Communication, training and awareness) est en cours d'élaboration à la FAO dans lequel le Cirad pourrait être appelé à contribuer si la demande lui en est faite. (Résumé d'auteur

Translational strategies in drug development for knee osteoarthritis.

Osteoarthritis (OA) is a common disease worldwide with large unmet medical needs. To bring innovative treatments to OA patients, we at Merck have implemented a comprehensive strategy for drug candidate evaluation. We have a clear framework for decision-making in our preclinical pipeline, to design our clinical proof-of-concept trials for OA patients. We have qualified our strategy to define and refine dose and dosing regimen, for treatments administered either systemically or intra-articularly (IA). We do this through preclinical in vitro and in vivo studies, and by back-translating results from clinical studies in OA patients

Sequential therapy of anti-Nogo-A antibody treatment and treadmill training leads to cumulative improvements after spinal cord injury in rats

Intense training is the most clinically successful treatment modality following incomplete spinal cord injuries (SCIs). With the advent of plasticity enhancing treatments, understanding how treatments might interact when delivered in combination becomes critical. Here, we investigated a rational approach to sequentially combine treadmill locomotor training with antibody mediated suppression of the fiber growth inhibitory protein Nogo-A. Following a large but incomplete thoracic lesion, rats were immediately treated with either anti-Nogo-A or control antibody (2 weeks) and then either left untrained or step-trained starting 3 weeks after injury for 8 weeks. It was found that sequentially combined therapy improved step consistency and reduced toe dragging and climbing errors, as seen with training and anti-Nogo-A individually. Animals with sequential therapy also adopted a more parallel paw position during bipedal walking and showed greater overall quadrupedal locomotor recovery than individual treatments. Histologically, sequential therapy induced the greatest corticospinal tract sprouting caudally into the lumbar region and increased the number of serotonergic synapses onto lumbar motoneurons. Increased primary afferent sprouting and synapse formation onto lumbar motoneurons observed with anti-Nogo-A antibody were reduced by training. Animals with sequential therapy also showed the highest reduction of lumbar interneuronal activity associated with walking (c-fos expression). No treatment effects for thermal nociception, mechanical allodynia, or lesion volume were observed. The results demonstrate that sequential administration of anti-Nogo-A antibody followed in time with intensive locomotor training leads to superior recovery of lost locomotor functions, which is probably mediated by changes in the interaction between descending sprouting and local segmental networks after SCI