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International audience; The aim of this work was to encapsulate transforming growth factor b1 (TGF-b1) into PLGA microparticles for regenerative medicine applications. TGF-b1 was firstly precipitated to ensure its stability during subsequent encapsulation within microparticles. A novel emulsification/extraction process in CO2 medium under mild conditions of pressure and temperature was used to encapsulate the protein. Interestingly, non-volatile injectable solvents, isosorbide dimethyl ether (DMI) and glycofurol (GF), were employed to precipitate the protein and to dissolve the polymer. Good encapsulation efficiency was obtained with preserved bioactivity of the protein. The microparticles were characterized in terms of size and zeta potential. In addition, the morphology and surface properties were determined using scanning electron microscopy (SEM) and atomic force microscopy (AFM) respectively. In vitro release study of the protein from microparticles was presented to assess the capacity of these systems to control the protein release. Moreover, cytotoxicity study was performed and showed an excellent cytocompatibility of the obtained microparticles. Thus, we described an effective and original process for TGF-b1 encapsulation into PLGA microparticles. The obtained polymeric carriers could be used in many biomedical applications and were more specifically developed for cartilage regeneration.

International audience; Competition is known to be a key driver of plant population dynamics. However, understanding how different types of competitive processes interact with population structure in driving population dynamics remains challenging. Ecologists broadly distinguish between two types of competition: size-asymmetric competition (SAC), related to resource pre-emption, and size-symmetric competition (SSC), related to resource depletion. SAC and SSC are known to influence plant-size population structures differently. Usually, SAC increases size inequality and, in return, changes in size inequality reinforce the role of SAC. On the contrary, SSC generally triggers size structure homogeneity. Although numerous simulations and experimental studies have explored how SAC influences population size structure, there is still no clear way to estimate the reverse effect: how changes in the size structure of a population affects the role of SAC compared to SSC in plant growth. In this article, we propose a modelling approach to estimate how size structure influences the role SAC plays in growth in mono-specific forest stands. First, we show that the role of SAC can be assessed by an equation that involves the Gini index, a well-known size inequality index. We then apply our approach to national forest inventory data in France, focusing on two major species: European beech (Fagus sylvatica L.) and silver fir (Abies alba Mill.). This article discusses the conditions necessary to apply such a modelling approach and gives perspectives for further development in plant ecology.

International audience; An objective of mountain forest management is to increase the ability of forest stands to protect human activities against natural hazards such as rock-falls and snow avalanches in a sustainable way. The challenge is to find a compromise between efficient instantaneous protection, favoured by dense stands, and continuous renewal, minimizing time periods of low protection efficiency. We used a Norway spruce stand dynamics model to compare the respective advantages of individual tree and gap selection silviculture in this context. We simulated stand dynamics over 800 years with either individual tree or gap thinning every 20 years with several thinning intensities. At each time step, we evaluated stand resilience, protection efficiency against rock-falls, protection efficiency against avalanches, and structural complexity with four indicators based on stand structure. Every scenario produced short time periods with low stand resilience and protection efficiency. Such periods can be tolerated if they are sufficiently rare compared to the local disturbance regime. We characterized the permanence of resilience and protection of a forest stand as its ability to remain within boundary values of the different indicators, without going out of them during continuous time periods longer than fixed maximum durations. Permanence of resilience and permanence of protection decreased with thinning intensity. Efficient protection against rock-falls was obtained with gap thinning of intermediate intensity while protection against avalanches was obtained only for very low thinning intensities. For our ecological context, the best compromise between resilience and protection was obtained with three 10 m radius gaps per hectare every 20 years (9.5% of the area of a stand). This strategy led to uneven-aged stand structures with a high diversity of diameters classes. Our results suggest that small gap silviculture may be a good way to combine forest renewal and protection efficiency in mountain regions.

Simulating the dynamics of heterogeneous forests calls for spatially explicit radiation transmission models at the scale of individual trees and requiring only a short computing time. Such a model was developed for spatially heterogeneous coniferous forest canopies. Based on the interception of light rays by parabolic crowns, it simultaneously calculates the radiation intercepted by each tree and the distribution of irradiance on the ground. For every sky direction, parallel rays aim at ground cell centres and are intercepted by tree crowns on their way. Slope and exposure are taken into account eliminating rays coming from above the slope. Optimisation in computing time is obtained by pre-selecting for each ray direction a rectangular cell neighbourhood around the target cell in such a way that potentially intercepting trees can only be found in this neighbourhood. Model evaluation was done by comparing hemispherical photographs with model predictions in a spatially heterogeneous Norway spruce (Picea abies, L. Karst) stand at the upper montane level in the Alps. Thanks to a satisfactory fit between model and data and a reasonably short computing time (about 2 min for 0.25 ha), the model can be considered for integration into a forest dynamics simulator. In the reference stand, 42% of incident radiation was intercepted by the highest trees (132 ha−1). Due to the clumped structure, 23% of incident radiation reached the soil. Interception by individual trees varied considerably as a function of tree size and location (from 0 to 60% of the potential interception of a tree growing in isolation). Irradiance at ground level was also extremely variable (between 0 and 50% of irradiance above the canopy), illustrating the need for spatial models in heterogeneous stands. The interception of radiation by trees was not affected by slope and exposure, unlike irradiance at ground level, which increased for southern exposures. Therefore, in terms of dynamics, regeneration should be the most sensitive to changes in these factors. Because the model produces precise radiation values at the ecosystem level, it allows analysis of the links between the structure of a forest stand and its energetic functioning synthetically.

INTRODUCTION AND OBJECTIVES: Beside its regulatory functions during development, the Notch pathway plays an eminent role in the tumorigenesis of malignancies. There are four different Notch receptors, which demonstrate context-dependent activity and can work antagonistically to each other. We have previously described a role for Notch-2 in promoting EMT and invasion in bladder cancer (BCA). Our objective here was to elucidate the role of Notch-1 and -3 in EMT and invasion, hypothesizing that both promote the epithelial, less invasive phenotype. METHODS: Immunohistochemistry was performed on a tissue microarray (TMA) of 104 tumors from patients with muscle invasive BCA. Notch-1 and -3 expression was assessed in a panel of bladder cancer cell lines by Western blot (WB) and correlated to previously established EMT status (based on E-cadherin and ZEB1) and invasive ability. Notch-1 and -3 were silenced by lentiviral shRNA vector in 3 cell lines with high constitutive Notch-1 and -3 expression (UM-UC1, UMUC6 and UM-UC15). Protein and mRNA expression of genes relevant to EMT, invasion and stemness were profiled by WB, real-time PCR, immunofluorescence and FACS. Proliferation, migration and invasion were measured by crystal violet, scratch, and Boyden chamber assays, respectively. Self-renewal potential was assessed by clonogenic assay and spheroid formation in MammoCultTM medium. RESULTS: High expression of Notch-3 receptor was associated with lower pathological stage (p 0.05) and absence of lymphovascular invasion (p 0.05) in the cystectomy specimens. Notch-1 expression did not correlate with pathologic variables. WB revealed expression of Notch-1 and -3 in epithelial bladder cancer cell lines only. Silencing of Notch-1 or Notch-3 in the selected epithelial cell lines promoted EMT at the mRNA and protein levels. Accordingly, phenotypic changes were seen in the form of enhanced migration and invasion but unaltered proliferation. In addition, colony and spheroid formation was increased after specific Notch-3 silencing. The simultaneous knock down of Notch-1 and -3 showed no additive effect. CONCLUSIONS: Our results provide evidence that Notch-1 and Notch-3 are involved in invasion and progression of BCA by maintaining an epithelial phenotype and inhibiting EMT and self-renewal potential. This is the opposite of what we have seen previously with Notch-2. Beside verification of our observations in metastatic xenograft models, further investigation is needed to elucidate the molecular mechanisms of these alterations.