Fig. 2.

Signal pathway implicated in disk intervertebral disk degeneration. Abbreviations: ADAMTS, A Disintegrin And Metalloproteinase with Thrombospondin Motifs; AF, annulus fibrosus; BDNF, brain-derived neurotrophic factor; BMP, bone morphogenetic protein; CGRP, calcitonin gene-related peptide; DRG, dorsal root ganglion; FGF-2, fibroblast growth factor-2; HIF, hypoxia-inducible factor; IGF, MAPK, mitogen-activated protein kinase; MMP, matrix metalloproteinase; NF-κβ, nuclear factor kappa β; NGF, nerve growth factor; NP, nucleus pulposus; PDGF, platelet-derived growth factor; PKC, protein kinase C; SP, substance P; TGF, transforming growth factor; TNF α, tumor necrosis factor-α.