|Author||Moon, Hong Joo MD *; Kim, Joo Han MD, PhD *; Lee, Hack Sun MD *; Chotai, Silky MD *; Kang, James D. MD, PhD +; Suh, Jung Keun MD, PhD *; Park, Youn-Kwan MD, PhD *|
|Institution||(*)Department of Neurosurgery, College of Medicine, Korea University, Seoul, Korea;|
(+)Department of Orthopedic Surgery, School of Medicine, University of Pittsburgh, PA.
|Title||Annulus Fibrosus Cells Interact With Neuron-Like Cells to Modulate Production of Growth Factors and Cytokines in Symptomatic Disc Degeneration.[Miscellaneous Article]|
|Source||Spine. 37(1):2-9, January 01, 2012.|
|Abstract||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.|
Objective. To identify growth factors and inflammatory cytokines related to AF/neuron interactions using in vitro model.
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.
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.
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.
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