Mesenchymal stem cell sheet encapsulated cartilage debris provides great potential for cartilage defects repair in osteoarthritis.

The restoration of the degenerated articular cartilage in patients with osteoarthritis (OA) is still a challenge for researchers and clinicians. Drug interventions and surgical treatments have been widely attempted for cartilage regeneration in OA. However, the results were largely unsatisfactory. Autologous chondrocyte implantation (ACI) or matrix-induced autologous chondrocyte implantation (MACI) offers potential for the regeneration of cartilage over the long-term. However, due to the limitations and disadvantages of ACI, alternative therapies for cartilage regeneration are in need. The availability of large quantities of mesenchymal stem cells (MSCs) and the multilineage differentiation, especially their chondrogenic differentiation property, have made MSCs the most promising cell source for cartilage regeneration. In addition, MSCs have been shown the ability to undergo site-specific differentiation. MSCs can be obtained as MSC sheets using the temperature-responsive culture dish method. The MSC sheet can provide amounts of cells and extracellular matrix, which might provide the continuity between the implant and host cartilage, thus improving integrative cartilage repair. Moreover, OA is associated with progressive and often severe inflammation. MSCs not only have the ability to contribute structurally to tissue repair, but also possess potent immunomodulatory and anti-inflammatory effects. Taken together, these properties make MSC sheet promising candidate for cartilage repair in OA. We hypothesize that MSC sheet encapsulated cartilage debris can efficiently promote cartilage repair in OA patients. Chondrocytes can be obtained and cultured from small cartilage debris in vitro. Therefore, the chondrocytes may grow from the debris in cartilage defect and improve cartilage regeneration. MSC sheet provide amounts of cells, ECM and protein for cartilage regeneration and integration, and may play some roles of periosteum. The operation of MSC sheet encapsulated cartilage debris for cartilage repair is simple and practical. Moreover, the cell sheet/cartilage debris constructs can be easily shaped based on the size and shape of cartilage defects. The new method might have great potential in treating cartilage defects clinically, especially for OA patients.