NOTCH1 and osteoarthritis: However, cells in mechanically damaged cartilage migrate to the injured site [4, 5], and cells in early-stage osteoarthritis (OA) express surface markers such as CD105 and CD166 [7] and exhibit stem-cell-related markers such as Notch-1, STRO-1, and vascular cell adhesion molecule-1 (VCAM-1) [1].