Fig. 5
Representative histologic sections (H&E staining) of discs (L4/5) from rats in the C, T and M groups. The NP-AF border is approximately indicated by the solid oval green line. (A) A clear boundary (green solid line) between the NP and AF and a wider area of the NP were found in the C group. (B) In the T group, the area of the normal NP (green solid line) was reduced because of the expanded AF and structurally confused boundary. (C) In the M group, the normal NP structure was absent, and the boundary between the NP and the AF was indistinct. Locally enlarged images of selected regions of interest in A, B, and C are displayed in detail. (D) The NP in the C group presented a mix of large, vacuolated (notochordal) cells (red arrow). The junctional zone of NP-AF (E) and the original NP region (F) in the T and M groups presented a decreased number of notochordal cells and were increasingly occupied by proliferating fibroblasts (yellow arrow) and chondrocyte-like cells (black arrow). The degree of NP fibrosis was more severe in the M group. Abbreviations: C, control; T, traditional; M, modified; NP, nucleus pulposus; AF, annulus fibrosus. **P < 0.01, ***P < 0.001. Scale bars = 500 µm.
