Sandrine Lavenus

Behaviour of mesenchymal stem cells, fibroblasts and osteoblasts on smooth surfaces.

Understanding of the interactions between cells and surfaces is essential in the field of tissue engineering and biomaterials. This study aimed to compare the adhesion, proliferation and differentiation of human mesenchymal stem cells (hMSCs), an osteoblast cell line (MC3T3-E1) and gingival fibroblasts (HGF-1) on tissue culture polystyrene (TCPS), glass and titanium (Ti). The average surface roughness was 5, 0.2 and 40×10(-3) μm for TCPS, glass and Ti, respectively. Immunocytochemistry and image analysis made it possible to quantify the number and morphology of adherent cells as well as the density of the focal points. Regardless of the substrate, both hMSCs and osteoblastic cells were mainly branch-shaped. HGF-1 exhibited a significantly higher number of focal points on Ti than on TCPS and glass. Alizarin red quantification indicated that both hMSCs and osteoblastic cells were more differentiated on TCPS than on Ti and glass. The surface properties of substrates, such as roughness, wettability and chemical composition, modulated the behaviour of the cells. Early events, such as cell adhesion, may influence the differentiation of hMSC and consequently tissue healing around implanted biomaterials.

Cell interaction with nanopatterned surface of implants.

Metals such as titanium and alloys are commonly used for manufacturing orthopedic and dental implants because their surface properties provide a biocompatible interface with peri-implant tissues. Strategies for modifying the nature of this interface frequently involve changes to the surface at the nanometer level, thereby affecting protein adsorption, cell-substrate interactions and tissue development. Recent methods to control these biological interactions at the nanometer scale on the surface of implants are reviewed. Future strategies to control peri-implant tissue healing are also discussed.

Nanotechnology and Dental Implants

The long-term clinical success of dental implants is related to their early osseointegration. This paper reviews the different steps of the interactions between biological fluids, cells, tissues, and surfaces of implants. Immediately following implantation, implants are in contact with proteins and platelets from blood. The differentiation of mesenchymal stem cells will then condition the peri-implant tissue healing. Direct bone-to-implant contact is desired for a biomechanical anchoring of implants to bone rather than fibrous tissue encapsulation. Surfaces properties such as chemistry and roughness play a determinant role in these biological interactions. Physicochemical features in the nanometer range may ultimately control the adsorption of proteins as well as the adhesion and differentiation of cells. Nanotechnologies are increasingly used for surface modifications of dental implants. Another approach to enhance osseointegration is the application of thin calcium phosphate (CaP) coatings. Bioactive CaP nanocrystals deposited on titanium implants are resorbable and stimulate bone apposition and healing. Future nanometer-controlled surfaces may ultimately direct the nature of peri-implant tissues and improve their clinical success rate.

Cell differentiation and osseointegration influenced by nanoscale anodized titanium surfaces.

AIMS We aimed to study the interactions between human mesenchymal stem cells and the bone integration of nanostructured titanium implants. MATERIALS & METHODS Nanopores of 20, 30 and 50 nm were prepared by anodization of titanium at 5, 10 and 20 V in a mixture of fluorhydric and acetic acid. Ti 30 and 50 nanostructures promoted early osteoblastic gene differentiation of the human mesenchymal stem cells without osteogenic supplements. The osseointegration of nanostructured and control titanium implants was compared by implantation in rat tibias for 1 and 3 weeks. RESULTS The nanostructures significantly accelerated bone apposition and bone bonding strength in vivo in correlation with in vitro results. CONCLUSION These findings demonstrate that specific nanostructures controlled the differentiation of cells and, thus, the integration of implants in tissues. These nanoporous titanium surfaces may be of considerable interest for dental and orthopedic implants.

Early adhesion of human mesenchymal stem cells on TiO2 surfaces studied by single-cell force spectroscopy measurements†

Understanding the interactions involved in the adhesion of living cells on surfaces is essential in the field of tissue engineering and biomaterials. In this study, we investigate the early adhesion of living human mesenchymal stem cells (hMSCs) on flat titanium dioxide (TiO2) and on nanoporous crystallized TiO2 surfaces with the use of atomic force microscopy‐based single‐cell force spectroscopy measurements. The choice of the substrate surfaces was motivated by the fact that implants widely used in orthopaedic and dental surgery are made in Ti and its alloys. Nanoporous TiO2 surfaces were produced by anodization of Ti surfaces. In a typical force spectroscopy experiment, one living hMSC, immobilized onto a fibronectine‐functionalized tipless lever is brought in contact with the surface of interest for 30 s before being detached while recording force‐distance curves. Adhesion of hMSCs on nanoporous TiO2 substrates having inner pore diameter of 45 nm was lower by approximately 25% than on TiO2 flat surfaces. Force–distance curves exhibited also force steps that can be related to the pulling of membrane tethers from the cell membrane. The mean force step was equal to 35 pN for a given speed independently of the substrate surface probed. The number of tethers observed was substrate dependent. Our results suggest that the strength of the initial adhesion between hMSCs and flat or nanoporous TiO2 surfaces is driven by the adsorption of proteins deposited from serum in the culture media. Copyright

COMPUTATIONAL MODEL COMBINED WITH IN VITRO EXPERIMENTS TO ANALYSE MECHANOTRANSDUCTION DURING MESENCHYMAL STEM CELL ADHESION

The shape that stem cells reach at the end of adhesion process influences their differentiation. Rearrangement of cytoskeleton and modification of intracellular tension may activate mechanotransduction pathways controlling cell commitment. In the present study, the mechanical signals involved in cell adhesion were computed in in vitro stem cells of different shapes using a single cell model, the so-called Cytoskeleton Divided Medium (CDM) model. In the CDM model, the filamentous cytoskeleton and nucleoskeleton networks were represented as a mechanical system of multiple tensile and compressive interactions between the nodes of a divided medium. The results showed that intracellular tonus, focal adhesion forces as well as nuclear deformation increased with cell spreading. The cell model was also implemented to simulate the adhesion process of a cell that spreads on protein-coated substrate by emitting filopodia and creating new distant focal adhesion points. As a result, the cell model predicted cytoskeleton reorganisation and reinforcement during cell spreading. The present model quantitatively computed the evolution of certain elements of mechanotransduction and may be a powerful tool for understanding cell mechanobiology and designing biomaterials with specific surface properties to control cell adhesion and differentiation.

Chapter 5 – Impact of nanotechnology on dental implants

The long-term clinical success of dental implants is related to their early osseointegration. This chapter reviews the different steps of the interactions between biological fluids, cells, tissues, and surfaces of implants. Immediately following implantation, implants are in contact with proteins and platelets from blood. The differentiation of mesenchymal stem cells will then condition the peri-implant tissue healing. Direct bone to implant contact is desired for a biomechanical anchoring of implants to bone rather than fibrous tissue encapsulation. Surfaces properties such as chemistry and roughness play a determinant role in these biological interactions. Physicochemical features in the nanometer range may ultimately control the adsorption of proteins as well as the adhesion and differentiation of cells. Nanotechnologies are increasingly used for surface modifications of dental implants. Another approach to enhance osseointegration is the application of thin calcium phosphate (CaP) coatings. Bioactive CaP nanocrystals deposited on titanium implants are resorbable and stimulate bone apposition and healing. Future nanometer–controlled surfaces may ultimately direct the nature of peri-implant tissues and improve their clinical success rate.

Chapter 5 – Impact of Nanotechnology on Dental Implants

Publisher Summary This chapter elaborates the impact of nanotechnology on dental implants. Recent studies have shown that nanometer-controlled surfaces have a great effect on early events such as the adsorption of proteins, blood clot formation, and cell behaviors occurring upon implantation of dental implants. These early events have an effective impact on the migration, adhesion, and differentiation of mesenchymal stem cells (MSCs). Studies indicate that nanostructured surfaces may control the differentiation pathways into specific lineages and ultimately direct the nature of peri-implant tissues. This chapter begins with a discussion on nanoscale surface modifications. The chapter then elaborates interactions of surface dental implants with blood. Interactions between surfaces and MSCs are also discussed. The chapter reviews the different steps of the interactions between biological fluids, cells, tissues, and surfaces of implants. Recent nanoscale surface modifications and CaP coating technologies of dental implants are discussed. The sequence of biological events in relation to surface properties is related. Mechanisms of interaction with blood, platelets, hematopoietic, and MSCs on the surface of implants are described. The chapter concludes with a discussion on tissue integration.