Conductive tissues are main routes of resource transport, that are crucial for the growth of fleshy fruit. Yet, very few quantitative data of xylem and phloem areas are available and their variabilities are unknown. This study aimed at better understanding and quantifying the structural and functional properties of the conductive tissues in tomato pedicel. 11 contrasting genotypes were described and the impact of water deficit was studied depending on stress intensity and stage of application. In parallel, MRI was used to assess the proportion and size of active xylem vessels in the stem. Results were implemented in a Virtual Fruit model to assess the potential contribution of pedicel conductive tissues in the variability of fruit fresh and dry masses. On their whole, results suggested that variations in the properties of conducting tissues are involved in the genotypic and environmental variations of fruit mass. The study also highlights the interest to combine methods and to integrate knowledge to better understand plant functioning, and finally to improve plant models. Flow-MRI was shown to be an easy non-destructive method to measure the functional properties of conducting tissues such as the proportion of active vessels and their diameter.

Les acouphènes sont caractérisés comme étant des sons "parasites" (crépitement, bourdonnement, sifflement) provoqués en absence de stimulus externes. Ce trouble est présent dans plus de 10% (12 à 30%) de la population adulte dans le monde. La prévalence des acouphènes montre une courbe de croissance inquiétante. Les nouveaux modes de vie des pays développés et émergents (exposition au bruit, urbanisation, ect) accélèrent cette tendance et en fait un problème de santé publique majeur. La détermination de marqueurs physiologiques des acouphènes chez l'homme et chez l'animal reste un défi pour la communauté scientifique. L’objectif principal pour les chercheurs étudiant les acouphènes est de pouvoir fournir une mesure objective afin de quantifier les caractéristiques acoustiques/perceptives des acouphènes. Au cours des dernières années, les possibilités apportées par la résonance magnétique sont de plus en plus exploitées avec l’utilisation d’une variété de techniques IRM (Imagerie par Résonance Magnétique). De plus, des améliorations techniques et méthodologiques innovantes chez l’animal ont été apportées, notamment par l'utilisation de nouveaux agents de contraste à base de chlorure de manganèse (MEMRI) ou le sodium (23NaMRI).Dans cette étude, nous avons développé une méthode d’analyse quantitative innovante basée sur le taux de relaxation transverse (R2). Le but de cette méthode est de détecter précisément l'accumulation d'ions paramagnétiques Mn2+ accumulés dans les neurones actifs principalement au travers des canaux calciques voltage-dépendants. La mesure directe du signal RMN dans des régions spécifiques du cerveau permet de déterminer le pourcentage de changement de R2 entre les zones auditives d'intérêt par rapport aux régions non auditives. Nous avons démontré une absorption de Mn2+ nettement plus élevée dans le colliculus inférieur et le noyau cochléaire du côté ipsilatéral et controlatéral chez le groupe de rat traité au salicylate de sodium. Nous avons ensuite comparé la méthode ∆R2/R2 aux méthodes d’analyse MEMRI « standards », à savoir le rapport signal sur bruit (SNR) et le rapport d'intensité du signal (SIR). La méthode de ∆R2/R2 est la seule technique à avoir révélé des résultats statistiquement significatifs dans les colliculus inférieurs et les noyaux cochléaires de manière bilatérale.Puis, dans un second temps, nous avons développé une méthode d’analyse basée sur l’ion sodium (23Na IRM) sur un modèle animal induisant des acoupènes. Le sodium joue un rôle important dans le métabolisme et occupe donc une place importante dans les applications cliniques (tumeurs, accidents vasculaires cérébraux, et certaines maladies neurodégénératives). Les résultats préliminaires obtenus ont montré une potentielle augmentation du volume de l’espace extracellulaire dans les colliculus inférieurs chez le rat, en présence d’acouphènes. Néanmoins, cette augmentation du volume extracellulaire ne semble pas spécifique au système auditif en présence de salicylate de sodium.

Biological activities of cells such as survival and differentiation processes are mainly maintained by a specific extracellular matrix (ECM). Hydrogels have recently been employed successfully in tissue engineering applications. In particular, scaffolds made of gelatin methacrylate-based hydrogels (GelMA) showed great potential due to their biocompatibility, biofunctionality, and low mechanical strength. The development of a hydrogel having tunable and appropriate mechanical properties as well as chemical and biological cues was the aim of this work. A synthetic and biological hybrid hydrogel was developed to mimic the biological and mechanical properties of native ECM. A combination of gelatin methacrylate and acrylamide (GelMA-AAm)-based hydrogels was studied, and it showed tunable mechanical properties upon changing the polymer concentrations. Different GelMA-AAm samples were prepared and studied by varying the concentrations of GelMA and AAm (AAm2.5% + GelMA3%, AAm5% + GelMA3%, and AAm5% + GelMA5%). The swelling behavior, biodegradability, physicochemical and mechanical properties of GelMA-AAm were also characterized. The results showed a variation of swelling capability and a tunable elasticity ranging from 4.03 to 24.98 kPa depending on polymer concentrations. Moreover, the podocyte cell morphology, cytoskeleton reorganization and differentiation were evaluated as a function of GelMA-AAm mechanical properties. We concluded that the AAm2.5% + GelMA3% hydrogel sample having an elasticity of 4.03 kPa can mimic the native kidney glomerular basement membrane (GBM) elasticity and allow podocyte cell attachment without the functionalization of the gel surface with adhesion proteins compared to synthetic hydrogels (PAAm). This work will further enhance the knowledge of the behavior of podocyte cells to understand their biological properties in both healthy and diseased states.

Photobiomodulation (PBM) has been shown to improve cell proliferation and cell migration. Many cell types have been 
investigated, with most studies using deep penetrating red light irradiation. Considering the interest of surface biostimulation 
of oral mesenchymal cells after surgical wound, the present study aimed to assess green light irradiation effects on Dental Pulp 
Stem Cells’ (DPSC) proliferation and migration. To understand the mechanisms underlying these effects, we investigated 
cytoskeleton organization and subsequent cell shape and stiffness. 
A 532-nm wavelength Nd:YAG laser (30 mW) was applied 
between 30 and 600 s on DPSC in vitro. Cell proliferation was analyzed at 24, 48, and 72 h after irradiation, by cell counting and enzymatic activity quantification (paranitrophenylphosphate phosphatase (pNPP) test). A wound healing assay was used to study 
cell migration after irradiation. Effects of PBM on cytoskeleton organization and cell shape were assessed by actin filaments 
staining. Elasticity changes after irradiation were quantified in terms of Young’s modulus measured using Atomic Force 
Microscopy (AFM) force spectroscopy. Green light significantly improved DPSC proliferation with a maximal effect obtained after 300-s irradiation (energy fluence 5 J/cm2). This irradiation had a significant impact on cell migration, improving wound 
healing after 24 h. These results were concomitant with a decrease of cells’ Young’s modulus after irradiation. This cell softening 
was explained by actin cytoskeleton reorganization, with diminution of cell circularity and more abundant pseudopodia. This 
study highlights the interest of green laser PMB for the proliferation and migration of mesenchymal stem cells, with encouraging 
results for clinical application, especially for surgical wound healing procedures.