Characterization of polydactyly-derived chondrocyte sheets versus adult chondrocyte sheets for articular cartilage repair

Background We previously conducted a first-in-human clinical study of articular cartilage repair using autologous chondrocyte sheets and confirmed the regeneration of hyaline-like cartilage in all eight patients. However, regenerative medicine with autologous chondrocyte sheets requires the harvesting of tissue from healthy regions, and the quality of this tissue varies between individuals. To overcome such limitations, allogeneic transplantation is a promising treatment method, particularly for articular cartilage repair. In this study, we investigated the characteristics of polydactyly-derived chondrocyte sheets fabricated from the chondrocytes of young polydactyly donors. Methods Polydactyly-derived chondrocyte (PD) sheets were fabricated from the tissue obtained from eight polydactyly donors (average age = 13.4 months). To create these PD sheets, chondrocytes at passage 2 or 3 were seeded on temperature-responsive culture inserts and cultured for 2 weeks. For comparison, adult chondrocyte sheets were fabricated from tissue obtained from 11 patients who underwent total knee arthroplasty (TKA; average age = 74 years). To create these TKA sheets, chondrocytes and synovial cells were cocultured, and the chondrocyte sheets were triple-layered according to the protocol from our previous clinical study. Cell count, cell viability, cell surface markers, cell histology, and humoral factors secreted by the sheets were characterized and compared between the PD sheets and TKA sheets. Results Polydactyly-derived chondrocytes proliferated rapidly to establish a layered structure with sufficient extracellular matrix and formed sheets that could be easily manipulated without tearing. Similar to TKA sheets, PD sheets expressed aggrecan and fibronectin at the protein level and the surface markers CD44, CD81, and CD90, which are characteristic of mesenchymal cells. PD sheets also produced significantly higher levels of transforming growth factor beta-1 and lower levels of matrix metalloproteinase-3 than those produced by TKA sheets, suggesting that young polydactyly-derived chondrocytes have advantages as a potential cell source. Conclusions PD sheets exhibited characteristics thought to be important to chondrocyte sheets as well as proliferative capacity that may facilitate provision of a stable supply in the future.