Abstract
The view of articular cartilage as a non-regeneration organ has been challenged in recent years. The articular cartilage consists of distinct zones with different cellular and molecular phenotypes, and the superficial zone has been hypothesized to harbour stem cells. Furthermore, the articular cartilage demonstrates a distinct pattern regarding stem cell markers (that is, Notch-1, Stro-1, and vascular cell adhesion molecule-1). These results, in combination with the positive identification of side population cells in articular cartilage, give additional support for the hypothesis that articular cartilage has residing stem cells with a potential regenerative capacity where the controlling mechanism could be future biomarkers or drug targets or both.