Annulus fibrosus (AF) injuries are common in degenerative disc disease (DDD) and can lead to substantial deterioration of the intervertebral disc. However, repair or regeneration of AF remains challenging. Recently, we have found that there exists a subpopulation of cells, which form colonies in vitro and could self-renew, in AF tissue. These cells express typical surface antigen molecules of mesenchymal stem cells, including CD29, CD44, and CD166. They also express common stem cell markers such as Oct-4, nucleostemin, and SSEA-4. In addition, they can be induced to differentiate into adipocytes, osteocytes, and chondrocytes. Being AF tissue-specific, such AF-derived stem cells may potentially be an ideal candidate for DDD treatments using stem cell-based cell therapies or tissue engineering approaches.
Keywords: Annulus fibrosus; Annulus fibrosus-derived stem cells; Colony-forming; Degenerative disc disease; Differentiation; Stemness.