Fig. 2

Isolation and culture of NPSCs. The MRI T2-weighted signal of targeted discs (red arrows) was in high intensity in the heathy rabbit (a). The punctured discs (red arrows) showed decreasing signal intensity at week 2 (b), and this signal intensity worsened gradually at week 4 (b). The degenerated discs were obtained 2 weeks after intervention, and the NP tissue (red arrow) could be seen in the middle of the discs (d). NPSCs isolated from early degenerated discs formed colonies after in vitro culture for 10 days as indicated by crystal violet staining (e). The morphology of cells in the colonies varied, with some of them being cobblestone-like and others being spindle-like (f). As a control, cells isolated from healthy rabbit discs formed more colonies (h), but shared similar morphology (i, j). Scale bars, 100 mm. MRI magnetic resonance imaging, NP nucleus pulposus, NPSCs nucleus pulposus-derived stem cells