Nguyen Tran

Effect of uniaxial stretching on rat bone mesenchymal stem cell: Orientation and expressions of collagen types I and III and tenascin-C

Bone marrow mesenchymal stem cells (BMSC) have the potential to differentiate into a variety of cell types like osteoblasts, chondroblasts, adipocytes, etc. It is well known that mechanical forces regulate the biological function of cells. The aim of this study was to investigate the effect of uniaxial stretching on the orientation and biological functions of BMSC. Rat BMSCs were harvested from femoral and tibial bone marrow by density gradient centrifugation. Cells from passages 1–6 were characterized by flow cytometry using monoclonal antibodies. The recovered cells were stably positive for the markers CD90 and CD44 and negative for CD34 and CD45. A cyclic 10% uniaxial stretching at 1 Hz was applied on rat BMSC for different time‐courses. The length, width, and orientation of the cells were subsequently determined. Expression of collagen types I and III and tenascin‐C mRNAs was measured by real‐time RT‐PCR, and the synthesis of these receptors was determined by radioimmunoassay. Results showed that uniaxial stretching lengthened and rearranged the cells. Compared with control groups, expression of collagen types I and III mRNAs was up‐regulated after 12‐h of stretching, while significant increase in synthesis of the two collagen protein types was not observed until after 24‐h stretching. The expression of tenascin‐C mRNA was significantly increased after a 24‐h stretching. These data suggest that cyclic stretching promotes the synthesis of collagen types I and III and tenascin‐C by the rat BMSC.

Repairing chronic myocardial infarction with autologous mesenchymal stem cells engineered tissue in rat promotes angiogenesis and limits ventricular remodeling.

BackgroundTissue engineering scaffold constitutes a new strategy of myocardial repair. Here, we studied the contribution of a patch using autologous mesenchymal stem cells (MSCs) seeded on collagen-1 scaffold on the cardiac reconstruction in rat model of chronic myocardial infarction (MI).MethodsPatches were cultured with controlled MSCs (growth, phenotype and potentiality). Twenty coronary ligated rats with tomoscingraphy (SPECT)-authenticated transmural chronic MI were referred into a control group (n = 10) and a treated group (n = 10) which beneficiated an epicardial MSC-patch engraftment. Contribution of MSC-patch was tested 1-mo after using non-invasive SPECT cardiac imaging, invasive hemodynamic assessment and immunohistochemistry.Results3D-collagen environment affected the cell growth but not the cell phenotype and potentiality. MSC-patch integrates well the epicardial side of chronic MI scar. In treated rats, one-month SPECT data have documented an improvement of perfusion in MI segments compared to control (64 ± 4% vs 49 ± 3% p = 0.02) and a reduced infarction. Contractile parameter dp/dtmax and dp/dtmin were improved (p & 0.01). Histology showed an increase of ventricular wall thickness (1.75 ± 0.24 vs 1.35 ± 0.32 mm, p &0.05) and immunochemistry of the repaired tissue displayed enhanced angiogenesis and myofibroblast-like tissue.Conclusion3D-MSC-collagen epicardial patch engraftment contributes to reverse remodeling of chronic MI.

TREM-1 Mediates Inflammatory Injury and Cardiac Remodeling Following Myocardial Infarction

RATIONALE Optimal outcome after myocardial infarction (MI) depends on a coordinated healing response in which both debris removal and repair of the myocardial extracellular matrix play a major role. However, adverse remodeling and excessive inflammation can promote heart failure, positioning leucocytes as central protagonists and potential therapeutic targets in tissue repair and wound healing after MI. OBJECTIVE In this study, we examined the role of triggering receptor expressed on myeloid cells-1(TREM-1) in orchestrating the inflammatory response that follows MI. TREM-1, expressed by neutrophils and mature monocytes, is an amplifier of the innate immune response. METHODS AND RESULTS After infarction, TREM-1 expression is upregulated in ischemic myocardium in mice and humans. Trem-1 genetic invalidation or pharmacological inhibition using a synthetic peptide (LR12) dampens myocardial inflammation, limits neutrophils recruitment and monocyte chemoattractant protein-1 production, thus reducing classical monocytes mobilization to the heart. It also improves left ventricular function and survival in mice (n=20-22 per group). During both permanent and transient myocardial ischemia, Trem-1 blockade also ameliorates cardiac function and limits ventricular remodeling as assessed by fluorodeoxyglucose-positron emission tomographic imaging and conductance catheter studies (n=9-18 per group). The soluble form of TREM-1 (sTREM-1), a marker of TREM-1 activation, is detectable in the plasma of patients having an acute MI (n=1015), and its concentration is an independent predictor of death. CONCLUSIONS These data suggest that TREM-1 could constitute a new therapeutic target during acute MI.

A Poly(lactic-co-glycolic acid) Knitted Scaffold for Tendon Tissue Engineering: An In Vitro and In Vivo Study

We have designed a composite scaffold for potential use in tendon or ligament tissue engineering. The composite scaffold was made of a cellularized alginate gel that encapsulated a knitted structure. Our hypothesis was that the alginate would act as a cell carrier and deliver cells to the injury site while the knitted structure would provide mechanical strength to the composite construct. The mechanical behaviour and the degradation profile of the poly(lactic-co-glycolic acid) knitted scaffolds were evaluated. We found that our scaffolds had an elastic modulus of 750 MPa and that they lost their physical integrity within 7 weeks of in vitro incubation. Autologous rabbit mesenchymal stem cell seeded composite scaffolds were implanted in a 1-cm-long defect created in the rabbit tendon, and the biomechanical properties and the morphology of the regenerated tissues were evaluated after 13 weeks. The regenerated tendons presented higher normalized elastic modulus of (60%) when compared with naturally healed tendons (40%). The histological study showed a higher cell density and vascularization in the regenerated tendons.

Electrospun poly(vinylidene fluoride-trifluoroethylene)/zinc oxide nanocomposite tissue engineering scaffolds with enhanced cell adhesion and blood vessel formation

Piezoelectric materials that generate electrical signals in response to mechanical strain can be used in tissue engineering to stimulate cell proliferation. Poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), a piezoelectric polymer, is widely used in biomaterial applications. We hypothesized that incorporation of zinc oxide (ZnO )nanoparticles into the P(VDF-TrFE) matrix could promote adhesion, migration, and proliferation of cells, as well as blood vessel formation (angiogenesis). In this study, we fabricated and comprehensively characterized a novel electrospun P(VDF-TrFE)/ZnO nanocomposite tissue engineering scaffold. We analyzed the morphological features of the polymeric matrix by scanning electron microscopy, and utilized Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry to examine changes in the crystalline phases of the copolymer due to addition of the nanoparticles. We detected no or minimal adverse effects of the biomaterials with regard to blood compatibility in vitro, biocompatibility, and cytotoxicity, indicating that P(VDF-TrFE)/ZnO nanocomposite scaffolds are suitable for tissue engineering applications. Interestingly, human mesenchymal stem cells (hMSCs) and human umbilical vein endothelial cells cultured on the nanocomposite scaffolds exhibited higher cell viability, adhesion, and proliferation compared to cells cultured on tissue culture plates or neat P(VDF-TrFE) scaffolds. Nanocomposite scaffolds implanted into rats with or without hMSCs did not elicit immunological responses, as assessed by macroscopic analysis and histology. Importantly, nanocomposite scaffolds promoted angiogenesis, which was increased in scaffolds pre-seeded with hMSCs. Overall, our results highlight the potential of these novel P(VDF-TrFE)/ZnO nanocomposites for use in tissue engineering, due to their biocompatibility and ability to promote cell adhesion and angiogenesis.

Pharmacological inhibition of the triggering receptor expressed on myeloid cells‐1 limits reperfusion injury in a porcine model of myocardial infarction

Limitation of ischemia/reperfusion injury is a major therapeutic target after acute myocardial infarction (AMI). Toll‐like receptors are implicated in the inflammatory response that occurs during reperfusion. The triggering receptor expressed on myeloid cells (TREM)‐1 acts as an amplifier of the immune response triggered by toll‐like receptor engagement. We hypothesized that administration of a TREM‐1 inhibitory peptide (LR12) could limit reperfusion injury in a porcine model of AMI.

Mechanical properties evolution of a PLGA-PLCL composite scaffold for ligament tissue engineering under static and cyclic traction-torsion in vitro culture conditions

This study aims to investigate the in vitro degradation of a poly(L-lactic-co-glycolic acid)-poly(L-lactic-co-ϵ-caprolactone) (PLGA-PLCL) composite scaffold’s mechanical properties under static culture condition and 2 h period per day of traction-torsion cyclic culture conditions of simultaneous 10% uniaxial strain and 90° of torsion cycles at 0.33 Hz. Scaffolds were cultured in static conditions, during 28 days, with or without cell seeded or under dynamic conditions during 14 days in a bioreactor. Scaffolds’ biocompatibility and proliferation were investigated with Alamar Blue tests and cell nuclei staining. Scaffolds’ mechanical properties were tested during degradation by uniaxial traction test. The PLGA-PLCL composite scaffold showed a good cytocompatibility and a high degree of colonization in static conditions. Mechanical tests showed a competition between two process of degradation which have been associated to hydrolytic and enzymatic degradation for the reinforce yarn in poly(L-lactic-co-glycolic acid) (PLGA). The enzymatic degradation led to a decrease effect on mechanical properties of cell-seeded scaffolds during the 21st days, but the hydrolytic degradation was preponderant at day 28. In conclusion, the structure of this scaffold is adapted to culture in terms of biocompatibility and cell orientation (microfiber) but must be improved by delaying the degradation of it reinforce structure in PLGA.

Adhesion and colonization of mesenchymal stem cells on polylactide or PLCL fibers dedicated for tissue engineering

Background Tissue engineering covers a broad range of applications dedicated to the repair or the replacement of part or whole tissue such as blood vessels, bones, cartilages, ligaments, etc [1]. Practically, a bio substitute, made with cells cultivated on scaffold, is needed. Mesenchymal stem cells (MSC) are generally the most suitable cells for such application since they are self-renewable with a great potential for differentiation and immuno suppression [2]. However, materials used for bio functional scaffold synthesis have to meet several criteria, such as biocompatibility and biodegradability. Thus, the aim of the study was to screen several biopolymers differing in their composition for their capability to promote adhesion and growth of MSC.

Structural and Mechanical Multi-Scale Characterization of White New Zealand Rabbit Achilles Tendon

Tendons and ligaments are complex multi-scale collageneous structures playing a fundamental role in mouvement. Even if these tissues are extensively studied in the past decades, modeling their non-linear viscoelastic properties is still a tough challenge. In order to reveal the relationship between the multi-scale structures and the macroscopic mechanical properties, we used atomic force microscopy (AFM) and second harmonic generation (SHG) microscopy to study unstreateched microtome slices of rabbit Achilles tendons, and an Adamel Lomargy DY.22 tensile test machine to study the dynamic properties of these tissues. Based on our data, a Zener model was used to describe the dynamic loading and unloading cycles.Copyright