Inhibiting nerve growth factor or its receptors downregulates calcitonin gene-related peptide expression in rat lumbar dorsal root ganglia innervating injured intervertebral discs

Authors


  • None of the authors have any conflict of interest or disclosures to report in relation to this work.

  • All protocols for animal procedures were reviewed and approved by the ethics committees of our institution (Ethics Committees, Graduate School of Medicine, Chiba University), and followed the National Institutes of Health Guidelines for the Care and Use of Laboratory Animals (1996 revision).

Abstract

Nerve growth factor (NGF) and its dual structurally unrelated receptors, tropomyosin-related kinase A (TrkA) or p75 neurotrophin receptor (p75NTR), cause the pathogenesis of discogenic pain. To investigate the sensory innervation of injured rat lumbar intervertebral disc (IVD), we examined the expression of neuropeptides such as calcitonin gene-related peptide (CGRP) at dorsal root ganglia (DRG) by inhibiting NGF or its dual receptors. Sprague–Dawley rats with multiply punctured L5–L6 IVD were used. Six experimental groups were prepared: naïve, sham control, and four agent-treated groups with punctured IVD (vehicle, anti-NGF antibody, anti-TrkA antibody, and anti-p75NTR antibody). Retrograde neurotracer Fluoro-Gold (FG) was applied together except for the naïve group. Their lumbar DRG were harvested and immunolabeled for CGRP. FG-labeled DRG neurons were most prevalent at L1 and L2 DRG, and the proportion of FG-labeled CGRP-immunoreactive DRG neurons in the vehicle group was significantly elevated (p < 0.05) compared with the sham group, while those of antibody-treated groups, especially in the anti-p75NTR group, significantly decreased compared with the vehicle group (p < 0.05). Direct intradiscal application of antibody to NGF or its receptors suppressed CGRP expression, and p75NTR antagonism induced the most profound suppression. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1614–1620, 2010

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