Expression and regulation of neurotrophins in the nondegenerate and degenerate human intervertebral disc

Our findings show that both the annulus fibrosus and nucleus pulposus cells of the IVD express the neurotrophins NGF and BDNF, factors that may influence and enhance innervation and pain in the degenerate IVD. Expression of Trk-A and Trk-B by cells of the nondegenerate and degenerate IVD suggests an autocrine role for neurotrophins in regulation of disc cell biology. Furthermore, modulation of neurotrophin expression by IL-1beta and modulation of substance P expression by TNFalpha, coupled with their increased expression in the degenerate IVD, highlights novel roles for these cytokines in regulating nerve ingrowth in the degenerate IVD and associated back pain.