Adipose-derived stem cells in articular cartilage regeneration: current concepts and optimization strategies.

Knee osteoarthritis (KOA) is the most common progressive joint disorder associated with disability in the world. As a chronic disease, KOA has multifactorial etiology. However, the poor self-healing ability of the articular cartilage due to its intrinsic tissue hypovascularity and hypocellularity seems to be directly incriminated in the physio-pathological mechanism of KOA. While conventional therapies result in unfavorable clinical outcomes, regenerative cell therapies have shown great promise in articular cartilage regeneration. Adipose-derived stem cells (ASCs) appear to be an ideal alternative to bone-marrow derived stem cells (BMSCs) and autologous chondrocytes, due to their lower immunogenicity, richer source and easier acquisition. Since the first case report in 2011, ASCs have demonstrated safety and efficacy for articular cartilage regeneration in several phase I/II clinical trials. However, different levels of abnormality were found in the regenerated cartilage for most of the patients. A large portion of recent publications investigated different optimization strategies to improve the therapeutic function of ASCs, including cell source selection, preconditioning and co-delivery. Herein, we give an update on the latest research progress on ASCs, with a focus on the most promising optimization strategies for ASC-based therapy.