Fig. 7.

Graphical summary of the role of FGFR3⁺ NP cells in postnatal IVD growth, maintenance and regeneration. FGFR3⁺ cells are mainly found in the outer region of NP. During the early postnatal growth, FGFR3⁺ NP cells proliferate into the inner region along the radius axis of NP, which contributes to the appositional growth of NP. In tail looping and unlooping model, mechanical overloading causes pathological damage of NP. Degenerated NP can undergo intrinsic repair after removing the mechanical pressure. The expansion of FGFR3^·+ NP cells is found to be increased significantly during the recovery stage after overloading