Annulus Fibrosus Cells Interact With Neuron-Like Cells to Modulate Production of Growth Factors and Cytokines in Symptomatic Disc Degeneration

作者：Moon Hong Joo; Kim Joo Han^*; Lee Hack Sun; Chotai Silky; Kang James D; Suh Jung Keun; Park Youn Kwan

来源：Spine, 2012, 37(1): 2-9.

DOI：10.1097/BRS.0b013e31820cd2d8

• AF cells
• cytokines
• growth factors
• neovascularization
• nerve ingrowth
• SH-SY5Y cell line

Study Design. We hypothesized that AF/neuron interactions during annular injury were involved in neovascularization and nerve ingrowth, the pathologic hallmarks of symptomatic disc degeneration. %26lt;br%26gt;Objective. To identify growth factors and inflammatory cytokines related to AF/neuron interactions using in vitro model. %26lt;br%26gt;Summary of Background Data. Discogenic pain is the chronic intractable pain initiated by tears in the outer annulus fibrosus (AF); this is a unique structure with free nerve endings at outer one-third, located beside dorsal root ganglia. The relationship between AF and neuron cells in annular injury has not been extensively investigated. %26lt;br%26gt;Methods. Human AF cells were cocultured with a retinoic acid (RA)-treated SH-SY5Y human neuroblastoma cell line (neuron-like cells). Conditioned media from cells cultured alone or in coculture were assayed for growth factors and inflammatory cytokines using enzyme-linked immunosorbent assays. The responses of the neuron-like cells, the AF cells, and the cocultured group to IL-1 beta/TNF-alpha were compared using the same outcome measures. %26lt;br%26gt;Results. RA-treated SH-SY5Y cells showed significant neurite outgrowth on the 7th day; this is a typical morphologic finding of neuron-like cells. Neuron-like cells produced vascular endothelial growth factor (VEGF) and IGF-1 under basal conditions and dose-dependently secreted small amounts of IL-8 in response to TNF-alpha. Coculturing enhanced the secretion of VEGF, TGF-beta 1, and beta-NGF, and suppressed the production of IGF-1. VEGF in the coculture group and the AF cells was downregulated by IL-1 beta/TNF-alpha stimulation. IL-1 beta/TNF-alpha stimulation enhanced the production of large amounts of IL-6 and IL-8 from AF cells; IL-1 beta produced a greater response than TNF-alpha. The neuron-like cells did not produce detectable amounts of IL-6 or IL-8. %26lt;br%26gt;Conclusion. These studies suggest that AF cells are involved in an inflammatory reaction and that the interactions between AF and neuron-like cells enhance the production of growth factors responsible for neovascularization and nerve ingrowth. AF injury has the potential to initiate neovascularization/nerve ingrowth and an inflammatory reaction through the interactions of AF and neural tissues.

• 出版日期2012-1-1