Interleukin‐1β induces angiogenesis and innervation in human intervertebral disc degeneration

Degenerative disorders of the intervertebral discs (IVDs) are generally characterized by enhanced matrix degradation, angiogenesis, innervation, and increased expression of catabolic cytokines. In this study, we investigated the effects of inflammatory cytokines, IL‐1β, and TNF‐α, on the expression of an angiogenic factor, vascular endothelial growth factor (VEGF), and neurotrophic factors, nerve growth factor (NGF) and brain‐derived neurotrophic factor (BDNF), in human IVD degeneration. IL‐1β and TNF‐α stimulated the gene expression of VEGF, NGF, and BDNF in nucleus pulposus (NP) cells isolated from patient tissues. Immunohistochemical results demonstrated a positive correlation between IL‐1β and VEGF/NGF/BDNF expression in human IVD tissues. RNA expression analysis of patient tissues also identified positive correlations between VEGF and platelet endothelial cell adhesion molecule‐1 (PECAM‐1) and between NGF/BDNF and protein gene product 9.5 (PGP9.5). Our findings suggest that IL‐1β is generated during IVD degeneration, which stimulates the expression of VEGF, NGF, and BDNF, resulting in angiogenesis and innervation. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:265–269, 2011