Chondrogenic differentiationof mesenchymal stem cells was enhancedby piezostimulation on quartz substrates with US waves; in this case,cell clustering, activation of the Wnt signaling,and up-regulation of the SOX9 chondrogenic marker were observed after 3 days of chronic treatment.85 This approach also needs further developments:new findings in this research field could have a significant impacton the treatment of degenerative joint diseases, such as osteoarthritis. This evidence concerns the gene SOX9 and osteoarthritis.