Résumé
Articular cartilage is a connective tissue, composed of chondrocytes, which represent a smallvolumetric fraction of about 2%, and an extracellular matrix, rich in collagens and proteoglycans[1]. The main biological function of articular cartilage is to permit frictionless movements of theconnected bones while facilitating force transmission. Cartilage therefore exhibits a sufficientrigidity to resist mechanical loading and absorbs a part of the contact energy between the relatedbones. However, articular cartilage is a non-vascularized tissue with limited self-healing and repaircapacities. With aging and disease, articular cartilage fails to respond to biomechanical stimuliresulting in impaired capacity of regeneration. Better understanding the processes ofmechanotransduction and cartilage growth will speed up the improvement of tissue engineeringapproachesIn the present study, we used the in vitro model of cartilage micropellets obtained from thedifferentiation of mesenchymal stem cells (MSC) into chondrocytes by 3D-culture in presence ofTGFβ3 inducing factor [2]. These cartilage micropellets were submitted to mechanical loading (i.e.,compression tests by using a home-made compression device) and biochemical analysis (i.e., RTqPCRand immunocytochemistry) after respectively 7, 14, 21, 29 and 35 days of cell differentiation.This cross analysis showed that generated micropellets exhibit properties which are close to those ofhuman native articular cartilage in terms of mechanical properties and gene expression. Inparticular, the elasticity modulus falls into the range of values obtained by using AFM on nondegradedarticular cartilage at nanometer scale (i.e., actually 150 kPa vs 83 kPa in [3]). Moreover,temporal evolution of the mechanical properties was correlated with gene expression levels of typeII collagen and LINK protein. The present results confirm that MSC-derived cartilage micropelletsare relevant in vitro models devoted to mechanobiological and biomechanical studies of cartilagegrowth.