CD146/MCAM distinguishes stem cell subpopulations with distinct migration and regenerative potential in degenerative intervertebral discs.

OBJECTIVE: This study aimed to characterize the mesenchymal stem cell (MSC) subpopulation migrating towards a degenerated intervertebral disc (IVD) and to assess its regenerative potential.

DESIGN: Based on initial screening for migration towards chemokine ligand 5 (CCL5), the migration potential of CD146+ and CD146- MSCs was evaluated in vitro and in a degenerated organ culture model (degeneration by high-frequency loading in a bioreactor). Discogenic differentiation potential of CD146+ and CD146- MSCs was investigated by in vitro pellet culture assay with supplementation of growth and differentiation factor-6 (GDF6). Furthermore, trypsin degenerated IVDs were treated by either homing or injection of CD146+ or CD146- MSCs and synthesis activity of glycosaminoglycan was evaluated by Sulphur 35 incorporation after 35 days of culture.

RESULTS: Surface expression of CD146 led to a higher number of migrated MSCs both in vitro and in organ culture. CD146+ and CD146-pellets responded with a similar up-regulation of anabolic markers. A higher production of sGAG/DNA was observed for CD146+ pellets, while in organ cultures, sGAG synthesis rate was higher for IVDs treated with CD146- MSCs by either homing or injection.

CONCLUSIONS: The CD146+ MSC subpopulation holds greater migration potential towards degenerative IVDs, while the CD146-cells induced a stronger regenerative response in the resident IVD cells. These findings were independent of the application route (injection vs. migration). From a translational point of view, our data suggests that CD146+ MSCs may be suitable for re-population, while CD146- MSCs may represent the primary choice for stimulation of endogenous IVD cells.