ISSN: 2161-1149 (Printed)
The poor reparative potential of articular cartilage is largely attributed to its avascular and aneural status combined with low cellularity; chondrocytes only occupy 10% of the tissue volume. Consequently, there have been a number of strategies developed to augment repair most notably through microfracture and Autologous Chondrocyte Implanation (ACI). However, both of these techniques have limitations. In the case of microfracture, the repair tissue is often fibrocartilaginous and in ACI, the number of cells that can be generated that maintain chondrogenicity is limited thus restricting the size of defect that can be treated. Consequently, there has been increasing interest in the use of Mesenchymal Stem Cells (MSCs) for the treatment of cartilage defects. Here, we discuss the isolation and characterization of a tissue-specific stem cell population from articular cartilage and the potential for its use in intrinsic and extrinsic repair of articular cartilage lesions. Significantly, unlike MSCs isolated from bone marrow, upon differentiation into the chondrogenic lineage, these cells fail to terminally differentiate i.e. are not endochondral, failing to synthesize both collagen type X and alkaline phosphatase. Senescence of chondrocytes following injury or as part of aging is hypothesized to be integral to degenerative disease and correlates with significant telomere erosion within chondrocytes. Articular cartilage-derived stem cells exhibit detectable telomerase activity and exhibit reduced erosion of telomeres; therefore, we hypothesize maintenance of this population is critical to tissue homeostasis.