Evaluation of the pro-angiogenic effect of nanoscale extracellular vesicles derived from human umbilical cord mesenchymal stem cells.

Mesenchymal stem cells (MSCs) are a common tool in regenerative medicine. The nanoscale extracellular vesicles (nEVs) secreted by these cells were recently brought up to light thanks to their therapeutic potential. In this study, we assessed the in vitro behaviour of human umbilical vein endothelial cells (HUVECs) exposed to nEVs derived from human umbilical cord mesenchymal stem cells (hUC-MSCs). Nanoscale extracellular vesicles were isolated and characterized by NanoSight® and flow cytometry. HUVECs were stimulated with various concentrations of nEVs. To assess nEV interactions with HUVECs, confocal microscopy and angiogenesis assay were performed. The use of nEVs derived from hUC-MSCs was able to produce positive outcomes on HUVECs by acting on their angiogenic potential.

Nacre extract restores the mineralization capacity of subchondral osteoarthritis osteoblasts.

Osteoarthritis (OA) is the most common cause of joint chronic pain and involves the entire joints. Subchondral osteoarthritic osteoblasts present a mineralization defect and, to date, only a few molecules (Vitamin D3 and Bone Morphogenetic Protein2) could improve the mineralization potential of this cell type. In this context, we have tested for the first time the effect of nacre extract on the mineralization capacity of osteoblasts from OA patients. Nacre extract is known to contain osteogenic molecules which have demonstrated their activities notably on the MC3T3 pre-osteoblastic cell line. For this goal, molecules were extracted from nacre (ESM, Ethanol Soluble Matrix) and tested on osteoblasts of the subchondral bone from OA patients undergoing total knee replacement and on MC3T3 cells for comparison. We chose to investigate the mineralization with Alizarin Red staining and with the study of extracellular matrix (ECM) structure and composition. In a complementary way the structure of the ECM secreted during the mineralization phase was investigated using second harmonic generation (SHG). Nacre extract was able to induce the early presence (after 7 days) of precipitated calcium in cells. Raman spectroscopy and electron microscopy showed the presence of nanograins of an early crystalline form of calcium phosphate in OA osteoblasts ECM and hydroxyapatite in MC3T3 ECM. SHG collagen fibers signal was present in both cell types but lower for OA osteoblasts. In conclusion, nacre extract was able to rapidly restore the mineralization capacity of osteoarthritis osteoblasts, therefore confirming the potential of nacre as a source of osteogenic compounds.

Polyelectrolyte multilayer film and human mesenchymal stem cells: an attractive alternative in vascular engineering applications.

Mesenchymal stem cells (MSCs) have tremendous potential as a cell source for regenerative medicine due to their capacity for differentiation into endothelial-like cells when seeded on nonmodified cover glasses. This absence of removable surface, preventing recovery of cell sheet, constitutes a critical obstacle to predict an application in tissue engineering. It remains unknown whether MSCs differentiation could be realized when the cells are cultivated on a scaffold that could be used in vascular engineering. In this study, we propose to differentiate human MSCs into endothelial-like cells on surfaces coated with polyelectrolyte multilayer film (PMF) and fibronectin (control surfaces). We quantified Platelet Endothelial Cell Adhesion Molecule (PECAM) and von Willebrand Factor (vWF) expressions (endothelial cell specific markers) and nitric oxide (NO) production, which is representative of the cell functionality. After only two weeks of differentiation, we showed, on PMF, that MSCs expressed PECAM and vWF, exhibiting a differentiation into endothelial-like cells, which functionality was explored by a significant production of nitrites. These results highlight the importance of PMF to get human MSCs differentiation and suggest that this film of nanometer thickness opens a new route for vascular bioengineering by pre-seeding hMSCs directly into a vascular graft functionalized by a removable coating.

Polyelectrolyte multilayer films: effect of the initial anchoring layer on the cell growth.

In tissue engineering, surface characteristics of a biomaterial are one of most important factors determining the compatibility with the environment. They influence attachment and growth of cells onto the material. In many cases, the surface should to be modified and engineered in the desired direction. The modification of non-adhesive surfaces with polyelectrolyte multilayer films (PMF) was recently depicted as a powerful technique to promote the growth of different cell lines. In this study, we evaluated the possible use of two different PMF as surface modification for the culture of mesenchymal stem cells (MSC). We used two types of PMF which differed by the nature of the initial anchoring layer which was poly(ethylenimine) (PEI) or poly(allylamine hydrochloride) (PAH). This initial polyelectrolytes adsorption was followed by the alternated deposition of poly(sodium 4-styrenesulfonate) (PSS) and (PAH) in order to obtain a PEI-(PSS-PAH)(3) film or a PAH-(PSS-PAH)(3) film. In order to control the behaviour of MSC, the cell viability was evaluated by Alamar Blue assay and the actin cytoskeleton was labelled and visualised in a confocal microscope. The behaviour of cells on the two PMF was compared to cells cultivated on surfaces treated with fibronectin. The results showed that PAH-(PSS-PAH)(3) PMF improve the growth of cells, inducing a higher cell viability compared to PEI-(PSS-PAH)(3) PMF and fibronectin at 2, 3 and 7 days of culture. Moreover, those cells showed a well-organized actin cytoskeleton. In conclusion, PAH-(PSS-PAH)(3) polyelectrolyte multilayer film seems to constitute an excellent material for MSC seeding.