Cell interactions between human progenitor-derived endothelial cells and human mesenchymal stem cells in a three-dimensional macroporous polysaccharide-based scaffold promote osteogenesis.

Several studies have reported the benefits of mesenchymal stem cells (MSCs) for bone tissue engineering. However, vascularization remains one of the main obstacles that must be overcome to reconstruct large bone defects. In vitro prevascularization of the three-dimensional (3-D) constructs using co-cultures of human progenitor-derived endothelial cells (PDECs) with human bone marrow mesenchymal stem cells (HBMSCs) appeared as a potential strategy. However, the crosstalk between the two lineages has been studied in two-dimensional (2-D), but remains unknown in 3-D. The aim of this study is to investigate the cell interactions between PDECs and HBMSCs in a porous matrix composed of polysaccharides. This biodegradable scaffold promotes cell interactions by inducing multicellular aggregates composed of HBMSCs surrounded by PDECs. Cell aggregation contributes to the formation of junctional proteins composed of Connexin43 (Cx43) and VE-cadherin, and an activation of osteoblastic differentiation of HBMSCs stimulated by the presence of PDECs. Inhibition of Cx43 by mimetic peptide 43GAP27 induced a decrease in mRNA levels of Cx43 and all the bone-specific markers. Finally, subcutaneous implantations for 3 and 8 weeks in NOG mice revealed an increase in osteoid formation with the tissue-engineered constructs seeded with HBMSCs/PDECs compared with those loaded with HBMSCs alone. Taking together, these results demonstrate that this 3-D microenvironment favored cell communication, osteogenesis and bone formation.

A new dextran-graft-polybutylmethacrylate copolymer coated on 316L metallic stents enhances endothelial cell coverage.

Amphiphilic copolymers based on the copolymerization of hydrophilic and hydrophobic moieties offer versatility in various biomedical material applications. Here, a new biocompatible copolymer of dextran-graft-polybutylmethacrylate is synthesized for the coating of metallic endovascular stents. Coating of metallic surfaces is performed and analyzed by X-ray photoelectron spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, contact angle measurement, atomic force microscopy and scanning electron microscopy before and after deformation corresponding to stent deployment by a balloon catheter. In the conditions described here, the resulting coating is smooth and uniform with neither cracks nor detachment after stent expansion. Interestingly, surfaces coated with the copolymer greatly improve in vitro adhesion and growth of endothelial cells. This copolymer provides new opportunities for implanted biomaterials.

Electrochemical impedance spectroscopy as a highly sensitive tool for a dynamic interaction study between heparin and antithrombin: a novel antithrombin sensor.

Specific recognition between two biological partners is widely exploited in biosensors nowadays. To explore this avenue, a novel biosensor for antithrombin (AT) detection was constructed. Heparin was used as the affinity ligand. A well-known acrylic monomer (butyl methacrylate) was polymerized and grafted onto the heparin polysaccharide by the use of ceric ammonium nitrate as a redox initiator in aqueous nitric acid medium. Polymers were deposited as a thin layer onto surface of stainless steel electrode (SS316L). The obtained polymers were studied by Fourier transform infrared spectroscopy (FTIR) and analyzed by differential scanning calorimetry (DSC). Moreover, the films were characterized by electrochemical impedance spectroscopy (EIS), contact-angle measurements and AFM. EIS was used to study the biosensor affinity to AT and the relationship between functionalization growth of modified electrode and the response of the sensor. The proposed approach appears to be simple, sensitive and correlated with methods that analyse the detection of antithrombin.

Magnetic resonance imaging tracking of human adipose derived stromal cells within three-dimensional scaffolds for bone tissue engineering.

For bone tissue engineering, human Adipose Derived Stem Cells (hADSCs) are proposed to be associated with a scaffold for promoting bone regeneration. After implantation, cellularised scaffolds require a non-invasive method for monitoring their fate in vivo. The purpose of this study was to use Magnetic Resonance Imaging (MRI)-based tracking of these cells, labelled with magnetic agents for in vivo longitudinal assessment. hADSCs were isolated from adipose tissue and labelled with USPIO-rhodamine (Ultrasmall SuperParamagnetic Iron Oxide). USPIO internalisation, absence of toxicity towards hADSCs, and osteogenic differentiation of the labelled cells were evaluated in standard culture conditions. Labelled cells were then seeded within a 3D porous polysaccharide-based scaffold and imaged in vitro using fluorescence microscopy and MRI. Cellularised scaffolds were implanted subcutaneously in nude mice and MRI analyses were performed from 1 to 28 d after implantation. In vitro, no effect of USPIO labelling on cell viability and osteogenic differentiation was found. USPIO were efficiently internalised by hADSCs and generated a high T2* contrast. In vivo MRI revealed that hADSCs remain detectable until 28 d after implantation and could migrate from the scaffold and colonise the area around it. These data suggested that this scaffold might behave as a cell carrier capable of both holding a cell fraction and delivering cells to the site of implantation. In addition, the present findings evidenced that MRI is a reliable technique to validate cell-seeding procedures in 3D porous scaffolds, and to assess the fate of hADSCs transplanted in vivo.

Synthesis and characterization of a new polysaccharide-graft-polymethacrylate copolymer for three-dimensional hybrid hydrogels.

Hybrid materials constituted by hydrophobic and hydrophilic biocompatible macromolecules are useful for biomedical applications. In this context, a well-known acrylic monomer (methyl methacrylate) was polymerized and grafted onto the polysaccharide dextran by the use of ceric ammonium nitrate as a redox initiator in aqueous nitric acid medium. The effects of concentrations of dextran, acrylic monomer, and ceric ions on the copolymerization yields were investigated in detail. The obtained polymers were studied by solubility measurements, Fourier transform infrared spectrometry, (13)C nuclear magnetic resonance spectroscopy, and viscosimetric analysis. Interestingly, we found conditions to form transparent and homogeneous thin films or 3D structures with hybrid properties. Indeed, the copolymer, but not dextran or PMMA, could be dissolved in water/THF (20/80 v/v). The thermomechanical properties of the resulting copolymer analyzed by differential scanning calorimetry and dynamic mechanical analysis showed the occurrence of a single glass-transition temperature and a marked difference with the two homopolymers. The cytocompatibility of the copolymer with human endothelial cells was evidenced by the normal cell adhesion, proliferation, and morphology after 5 days in culture on these gels. In conclusion, this type of copolymer with hybrid properties of two biocompatible macromolecules could be of great interest as a 3D scaffold or for coating in biomedical applications.