Fig. 2

Scheme illustrating main cell phenotypes already identified in inner and outer healthy AF, surrounding the NP (represented in blue), with respective hematoxylin-eosin images below obtained during immunohistochemistry assays. The vertebral body scheme is to represent the complex changeover between these AF regions, whose cell populations are hard to distinguish since there are scarcely any definitive or exclusive markers. (A) Outer AF with fibroblast like-cells and rich in collagen type I. (B) Inner AF with chondrocyte-like cells, also called fibrochondrocytes, rich in collagen type II