In the context of shoulder surgical replacement, a new generation of spherical interposition implants has been developed, with the implant being a mobile spacer rubbing against the glenoid cartilage and humeral bone cavity. The aim of the present study was to compare pyrocarbon (PyC) versus cobalt-chromium (CoCr) implants, regarding preservation and regeneration of the surrounding tissues. The effect of the biomaterials on chondrocytes was analysed in vitro. Murine primary chondrocytes were grown on discs made of PyC or CoCr using two culture media to mimic either cartilage-like or bone-like conditions (CLC or BLC). Chondrocytes did grow on PyC and CoCr without alteration in cell viability or manifestation of cytotoxicity. The tissue-like cell membranes grown under BLC were examined for the chondrocyte's ability to mineralise (by alizarin red matrix staining, calcium deposit and alkaline phosphatase activity) and for their mechanical properties (by rheological tests). For the chondrocytes grown under CLC and BLC, extracellular matrix components were analysed by histological staining and immunolabelling. Under CLC, PyC promoted type II collagen expression in chondrocytes, suggesting that they may generate a more cartilage-like matrix than samples grown on both CoCr and plastic control. In BLC, the tissue-like cell membranes grown on PyC were more mineralised and homogenous. The mechanical results corroborated the biological data, since the elastic modulus of the tissue-like cell membranes developed on the PyC surface was higher, indicating more stiffness. Overall, the results suggested that PyC might be a suitable biomaterial for spherical interposition implants.

The mechanotransduction is an important aspect to provide suitable conditions for the cartilage engineering process. Therefore, a new bioreactor is developed to apply different mechanical stresses to cell/organ culture. It allows performing cell culture in situ with appropriate mechanical constraints according to the real-time evolution of the physical parameters with the possibility of microscopic observation. In addition to the two-dimensional mechanical stimulation of a scaffold, the originality of this device is in situ monitoring of the cells and rheological measurements. This study presents the design of the new prototype with the validation of its different functions. First, the mechanical characterization of different nonbiological samples is performed to calibrate the rheological measurement. Then, the monitoring of fluorescent beads in different scaffolds is carried out to estimate the mechanical stress transmitted to the cells. Finally, the ability of the device to handle a cell culture of human chondrocytes seeded in a scaffold is evaluated. The combined functions of the new bioreactor open the possibility to develop new scaffolds with optimal mechanical stress transmission, which is the basis of tissue engineering of cartilage.

No abstract