Decoding Intervertebral Disc Cell Populations: Challenges in Isolation and Phenotype Definition.

Degenerative disc disease (DDD) is the main cause of back pain, one of the most impactful musculoskeletal disorders. In the last decades, significant advances have emerged in the field of intervertebral disc (IVD) biology. Despite cumulative knowledge on cell heterogeneity, there is a lack of understanding about the molecular signature of different IVD cell populations and their potential as therapeutic targets. This is not only due to progress in single-cell analysis being recent, but also to difficulties and lack of standardization in the isolation of distinct IVD cell populations based on the phenotypic markers used. Herein, we review the literature on IVD resident cells and the main challenges faced in the source, isolation, and culture of IVD cell subsets that are yet to be overcome. The profiling of IVD subpopulations and their cellular dynamics with development, aging, and disease progression will certainly advance the knowledge on IVD homeostasis and associated diseases, while contributing to the development of game-changing, personalized targeted therapies.