Insights of stem cell-based endogenous repair of intervertebral disc degeneration

Figure 1 Cell resources of endogenous repair strategy. A: Stem cell niche, defined as the perichondrium region adjacent to the epiphyseal plate and outer zone of the annulus fibrosus (AF); B-D: Stem/progenitor cells could be isolated from the nucleus pulposus, AF, and cartilaginous endplates or migrate from the stem cell niche toward the nucleus pulposus (B), AF (C), and cartilaginous endplates (D). NP: Nucleus pulposus; EP: Epiphyseal plate; AF: Annulus fibrosus; AFo: Outer zone of the AF; AFi: Inner zone of the AF; CEP: Cartilaginous endplates.