Dissipation Can Act as a Mechanobiological Signal in Cartilage Differentiation

Knee cartilage is a soft tissue having viscoelastic properties. Under cyclic loadings, viscoelastic materials dissipate mechanical loadings through heat generation. In knee cartilage, this heat might not be convected because of the tissue avascularity, resulting thus to a local temperature increase. As cells are sensitive to temperature, these thermo-mechanical phenomena of energy dissipation could influence their metabolism. The goal of this study is to evaluate the effect of thermogenesis on chondrogenic differentiation. First, we focused our work in quantifying the heat generated in cartilage as a result to deformation. On a cellular level, the effect of thermal alterations on cell metabolism was assessed looking at the gene expression of transcription factors involved in chondrogenesis. Hence, human chondro-progenitor cells were cultured at 33°C and 37°C for 48 h and 96 h. An up-regulation in mRNA expression levels of Sox9 and its co-activator PGC- 1α has been observed. These results point to a thermal contribution to chondrogenic gene expression.