Abstract
Articular cartilage (AC) pathologies have emerged as a public health problem. Tissue engineering, whose objective is to create new tissues with cells, is a promising therapeutic solution for the repair of AC lesions but still requires research to improve the mechanical properties of the new tissues. The objective of this PhD thesis work was to analyze the impact of mechanical stimuli in the development and maintenance of AC, based on the model of cartilage micropellet, derived from the aggregation of mesenchymal stem cells. For this purpose, a fluidic device able to mechanically stimulate and characterize small and irregularly shaped cartilage micropellets was developed. Six cartilage micropellets in six conical wells can be simultaneously stimulated by compression and characterized through different pressure signals. Associated to a numerical model, the fluidic device has been shown to allow the characterization of the mechanical properties of various microspheres made of alginate, collagen or cross-linked collagen as compared to a conventional characterization method by compression between two planar surfaces. The reliability of the device for the application of mechanical stimuli have been confirmed by analyzing the pressure signals generated. Stimulation of 21-day cartilage micropellets with a square-wave signal with various amplitudes, frequencies and durations have shown that chondrocyte gene expression could be modulated by mechanical stimuli. Moderate levels of deformation of the micropellets were observed without any obvious damage. The mechanical characterization of 21-day micropellets have shown results consistent with the literature. This proof of concept shows the interest of the fluidic device allowing the stimulation and characterization of cartilage micropellets and highlighted possibilities to improve the system and associated numerical analysis methods as well as directions to improve our understanding of cartilage micropellet development under mechanical stimulations.