Implementation of surface tension force in fluid flow during reactive rotational molding

During Reactive Rotational Molding (RRM), it is very important to predict the fluid flow in order to obtain the piece with homogeneous shape and high quality. This prediction may be possible by simulation the fluid flow during rotational molding. In this study we have used a mixture of isocyanate and polyol as reactive system. The kinetic rheological behaviors of thermoset polyurethane are investigated in anisothermal conditions. Thanks to these, rheokinetik model of polyurethane was identified. Then, to simulate the RRM, we have applied Smoothed Particles Hydrodynamics (SPH) method which is suited method to simulate the fluid flow with free surface such as occurs at RRM. Modelling and simulating reactive system flow depend on different parameters; one of them is the surface tension of reactive fluid. To implement force tension surface, the interface between polymer and air is dynamically tracked by finding the particles on this border. First, the boundary particles are detected by free-surface detection algorithm developed by Barecasco, Terissa and NAA [1, 2] in two and three dimension. Then, analytical and geometrical algorithms have been used for interface reconstructions. The aim of this work is the implementation of surface tension force in the SPH solver applied to RRM. To illustrate that, we used novel and simple geometric algorithm fitting circle and fitting sphere, in two and three dimensional configurations, respectively. The model has been validated using a well-known dam break test case which covered the experimental data

257 A novel polysaccharide-based porous scaffold for cell delivery into the infarcted heart

BackgroundCellular cardiomyoplasty has been proposed as an attractive strategy to repair myocardial damage. One of the crucial point is the optimal delivery strategy. In the present study, we examined the use of an implantable porous scaffold for promoting bone marrow-derived mesenchymal stem cells (MSCs) survival and functions in a rat model of acute myocardial infarction.Methods and ResultsCardiac patch was based on biodegradable polysaccharides porous scaffold. After ligation of the left anterior coronary artery, the fate of 1x106 GFP+ MSC administered either using cellularized scaffold implantation or direct injection was examined at 1 and 2 months. The number of residual GFP+ cells in the sample studied was estimated on the basis of the fluorescence emitted by a defined number of GFP+ cells used for calibration. Cellularized scaffold allowed a more efficient delivery and the difference with direct injection was significant at 2 months, with respectively 2100±1300×103 and 215±85x103 residual GFP+ cells (p<0.03). Cardiac tissue levels of matrix metalloproteinase-2 and -9 mRNA were similar whatever the administration conditions but a slight increase in the local production of vascular endothelial growth factor was observed at 2 months after patch implantation in comparison to direct injection (p<0.05). In animals having received MSC implemented on scaffold, clusters of GFP+ cells, mainly phenotypically consistent with immature MSC cells, were detected in the peri-infarct area. The increased survival using scaffold was not translated in an improved myocardial remodelling and functions with no significant difference in the LVEDD, LVESD, and FS between the 2 groups as in comparison with animals implanted with non cellularized scaffold.ConclusionsThese findings demonstrate that the implantation of cellularized grafts is safe and effective for delivering mesenchymal stem cells into damaged myocardium, and results in a better cellular engraftment compared to direct injection

Modelling of sintering during rotational moulding of the thermoplastic polymers

This paper concerns the study of sintering phenomenon during rotational molding of polypropylene(PP),Polyvinylidenefluoride (PVDF) and Polymethyl methacrylate (PMMA). First, the coalescence (first step of sintering) of two grains has been followed. Bellehumeur’s model has been tested as a model to explain this phenomenon. In order to study the effect of neighboring grains on coalescence of two grains, a third grain has been put in contact with these two grains. For modeling the phenomenon in this case, Bellehumeur’s model has been modified by a geometric parameter called Farz Factor (FF), being this model validated by experimental test. Concerning densification, two different stages have been observed. In the first stage, before welding of the grains and formation of interphases between them, the grains are not stuck yet. The air trapped between the grains escapes through free ways between grains. This first step of densification is directly related to the coalescence where the density of the polymer varies very quickly. A new tridimensional model, based on a Body Centered Tetragonal (BCT) configuration, has been proposed to explain the densification during this first stage. In the second stage, the migration of air is controlled by diffusion

Fucoidan promotes early step of cardiac differentiation from human embryonic stem cells and long term maintenance of beating areas.

International audienceSomatic stem cells require specific niches and 3D scaffolds may provide a way to mimic this microenvironment. Here, we tested a scaffold based on fucoidan, a sulfated polysaccharide known to influence morphogen gradients during embryonic development, to support human Embryonic Stem Cells (hESCs) differentiation towards the cardiac lineage. A macroporous (pore 200 µm) Fucoidan scaffold was selected to support hESCs attachment and proliferation. Using a protocol based on the cardiogenic morphogen BMP2 and TGFb followed by TNFa, an effector of cardiopoietic priming. we examined the cardiac differentiation in the scaffold compared to culture dishes and embryoid bodies (EBs). At day 8, Fucoidan scaffolds supported a significantly higher expression of all 3 genes encoding for transcription factors marking the early step of embryonic cardiac differentiation NKX2.5 (p<0.05), MEF2C (p<0.01) and GATA4 (p<0.01), confirmed by flow cytometry analysis for MEF2C and NKX2.5. Fucoidan scaffolds ability to locally concentrate and slowly release TGF and TNF was confirmed by Luminex technology. We also found that Fucoidan scaffolds supported the late stage of embryonic cardiac differentiation marked by a significantly higher ANF expression (p<0.001), although only rare beating areas were observed. We postulated that absence of mechanical stress in the soft hydrogel impaired sarcomere formation, as confirmed by molecular analysis of the cardiac muscle myosin MYH6 and immunohistological staining of sarcomeric -actinin. Nevertheless, Fucoidan scaffolds contributed to the development of thin filaments connecting beating areas through promotion of smooth muscle cells, thus enabling maintenance of beating areas for up to 6 months. In conclusion, Fucoidan scaffolds appear as a very promising biomaterial to control cardiac differentiation from hESCs that could be combined with mechanical stress to promote sarcomere formation at terminal stages of differentiation

Mesenchymal stem cell delivery into rat infarcted myocardium using a porous polysaccharide-based scaffold: a quantitative comparison with endocardial injection.

International audienceThe use of mesenchymal stem cells (MSCs) for tissue regeneration is often hampered by modest engraftment in host tissue. This study was designed to quantitatively compare MSCs engraftment rates after delivery using a polysaccharide-based porous scaffold or endocardial (EC) injection in a rat myocardial infarction model. Cellular engraftment was measured by quantitative reverse transcription-polymerase chain reaction using MSCs previously transduced with a lentiviral vector that expresses green fluorescent protein (GFP). The use of a scaffold promoted local cellular engraftment and survival. The number of residual GFP(+) cells was greater with the scaffold than after EC injection (9.7% vs. 5.1% at 1 month and 16.3% vs. 6.1% at 2 months, respectively [n=5]). This concurred with a significant increase in mRNA vascular endothelial growth factor level in the scaffold group (p<0.05). Clusters of GFP+ cells were detected in the peri-infarct area, mainly phenotypically consistent with immature MSCs. Functional assessment by echocardiography at 2 months postinfarct also showed a trend toward a lower left ventricular dilatation and a reduced fibrosis in the scaffold group in comparison to direct injection group (n=10). These findings demonstrate that using a porous biodegradable scaffold is a promising method to improve cell delivery and engraftment into damaged myocardium

Apolipoprotein E is an HIV-1-inducible inhibitor of viral production and infectivity in macrophages.

Apolipoprotein E (ApoE) belongs to a class of cellular proteins involved in lipid metabolism. ApoE is a polymorphic protein produced primarily in macrophages and astrocytes. Different isoforms of ApoE have been associated with susceptibility to various diseases including Alzheimer's and cardiovascular diseases. ApoE expression has also been found to affect susceptibility to several viral diseases, including Hepatitis C and E, but its effect on the life cycle of HIV-1 remains obscure. In this study, we initially found that HIV-1 infection selectively up-regulated ApoE in human monocyte-derived macrophages (MDMs). Interestingly, ApoE knockdown in MDMs enhanced the production and infectivity of HIV-1, and was associated with increased localization of viral envelope (Env) proteins to the cell surface. Consistent with this, ApoE over-expression in 293T cells suppressed Env expression and viral infectivity, which was also observed with HIV-2 Env, but not with VSV-G Env. Mechanistic studies revealed that the C-terminal region of ApoE was required for its inhibitory effect on HIV-1 Env expression. Moreover, we found that ApoE and Env co-localized in the cells, and ApoE associated with gp160, the precursor form of Env, and that the suppression of Env expression by ApoE was cancelled by the treatment with lysosomal inhibitors. Overall, our study revealed that ApoE is an HIV-1-inducible inhibitor of viral production and infectivity in macrophages that exerts its anti-HIV-1 activity through association with gp160 Env via the C-terminal region, which results in subsequent degradation of gp160 Env in the lysosomes

Heterozygous and homozygous JAK2(V617F) states modeled by induced pluripotent stem cells from myeloproliferative neoplasm patients.

JAK2(V617F) is the predominant mutation in myeloproliferative neoplasms (MPN). Modeling MPN in a human context might be helpful for the screening of molecules targeting JAK2 and its intracellular signaling. We describe here the derivation of induced pluripotent stem (iPS) cell lines from 2 polycythemia vera patients carrying a heterozygous and a homozygous mutated JAK2(V617F), respectively. In the patient with homozygous JAK2(V617F), additional ASXL1 mutation and chromosome 20 allowed partial delineation of the clonal architecture and assignation of the cellular origin of the derived iPS cell lines. The marked difference in the response to erythropoietin (EPO) between homozygous and heterozygous cell lines correlated with the constitutive activation level of signaling pathways. Strikingly, heterozygous iPS cells showed thrombopoietin (TPO)-independent formation of megakaryocytic colonies, but not EPO-independent erythroid colony formation. JAK2, PI3K and HSP90 inhibitors were able to block spontaneous and EPO-induced growth of erythroid colonies from GPA(+)CD41(+) cells derived from iPS cells. Altogether, this study brings the proof of concept that iPS can be used for studying MPN pathogenesis, clonal architecture, and drug efficacy

Clonal architecture of patient 1 CD34⁺ cells and origin of the iPS cell lines.

<p>(A) The allele burdens (by NGS) of the mutations and the status of chromosome 20 are indicated in CD3⁺, CD34⁺, iPSa and iPSb cell lines. (B) The <i>JAK2 </i>^V617F/V617F<i>ASXL1</i>^{<i>mut/wt</i>} subclone subsequently acquired new genetic abnormalities (<i>FBX015</i> and <i>MATN2</i>) mutations and an additional abnormal chromosome 20. During reprogramming or cell culture, 2 cell lines were generated: iPSa subclone <i>JAK2 </i>^V617F/V617F<i>ASXL1</i>^{<i>mut/wt</i>} and iPSb subclone <i>JAK2 </i>^V617F/V617F<i>ASXL1 </i>^{<i>mut/wt</i>}<i>FBX015 </i>^{<i>mut/wt</i>}<i>MATN2 </i>^{<i>mut/wt</i>} and <i>JAK2 </i>^V617F/V617F<i>ASXL1 </i>^{<i>mut/wt/wt</i>}<i>MATN2 </i>^{<i>mut/wt</i>} with an additional abnormal chromosome 20.</p