Figure 1.

Structure of the IVD and pathogenesis of IVD degeneration. During the aging process, calcification occurs in the bone-cartilage junction of CEP. The calcified zone is impermeable thereby, reducing nutrient transport and inhibiting IVD cell metabolism. The NP cells, originally under adverse condition, are the first to be affected. Altered aggrecan composition and reduced type II collagen weakens the structural integrity of NP. Myxomatous degeneration in AF can disrupt its highly organized collagen fiber arrangement. These processes increase the potential IVD structural damage. IVD; intervertebral disc, NP; nucleus pulposus, AF; annulus fibrosus, CEP; cartilage endplate.