Stem Cells used for Tissue Engineering of Articular Cartilage: Literature Review

Adult articular cartilage (AC) has a limited self-healing capacity. Cartilage defects lead to osteoarthritis (OA) characterized by severe pain and impaired mobility. Currently, there are no approved treatments for OA that successfully reverse or heal structural defects permanently. Although techniques such as microfracture, arthroplasty and subchondral drilling have been effective at treating small to intermediate sized AC defects over the short term, a long-term solution for OA is still necessary. In recent years, research has focused on tissue engineering of articular cartilage (TEAC) as a potential treatment option for OA. TEAC therapies utilizing chondrocytes such as autologous chondrocyte implantation (ACI) are promising but are limited by their complexity, high cost and inability to promote the formation of healthy hyaline AC. Due to the limitations of ACI, stem cells have been investigated as an alternative cell source for TEAC. To engineer AC, stem cells are allowed to differentiate on/in a scaffold in a bioreactor that controls chemical, physical and biological cues to support the chondrogenic potential of the stem cells. The use of stem cells provides numerous advantages as treatment costs can be lowered, the number of required surgeries can be reduced and high-quality AC can be formed. Mesenchymal stem cells (MSC) in particular are advantageous in that they are easily available and can be extracted from a diverse range of tissues including, bone marrow, adipose, and synovium. Each type of MSC have their own advantages and disadvantages but generally each of them possess high chondrogenic potential and immunosuppressive capacities. Induced pluripotent stem cells (iPSC) have also been recognized as a promising cell type for TEAC due to their unlimited proliferation and self-renewal capacities. Ultimately, each cell source has potential for use in TEAC therapies but further studies comparing cell sources are required before a gold standard can be determined. This review summarizes the pros and cons for potential use of each stem cell source in TEAC. The review is not meant to be comprehensive of the current literature.