Inflammatory pain-related traits of sensory DRG neurons innervating the hip joints.

Abstract

BACKGROUND:

Hip pain is transmitted to the dorsal horn of the spinal cord via the dorsal root ganglion (DRG), which contains two types of neurons with differential sensitivity to neurotrophic factors. If either type predominantly innervates the hip joint, it may represent a good target for hip joint pain treatment.

METHODS:

Inflammation was induced in the left hip joint of rats (n = 10) by using complete Freund's adjuvant. Fluoro-Gold (FG) was applied to the hip joint after 7 days, and T12-L6 DRGs were double-stained for calcitonin gene-related peptide (CGRP) and isolection-IB4 1 week later.

RESULTS:

FG-labeled neurons in the control group were distributed throughout the left DRG from T13 to L5, primarily in L2 to L4, and CGRP-positive neurons were significantly more frequent than IB4-binding neurons. In the inflammatory group, FG-labeled neurons were similarly distributed, primarily at L3 and L4, and CGRP-positive neurons were significantly more frequent than IB4-binding neurons. The percentage of CGRP-positive neurons was significantly greater in the inflammatory group (P < 0.05).

CONCLUSIONS:

Most small neurons innervating the hip joint express CGRP. Furthermore, hip joint inflammation caused an increase in CGRP-positive neurons, but not in IB4-binding neurons. Our results suggest that CGRP-expressing nerve growth factor-dependent neurons are primarily responsible for hip joint pain and may represent therapeutic targets.

• Authors: Takayuki Nakajima, Seiji Ohtori, Junichi Nakamura, Takane Suzuki, Yasuchika Aoki, Atsuya Watanabe, Makoto Takazawa, Kazuhisa Takahashi
• Journal: Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association (J Orthop Sci) Vol. 22 Issue 2 Pg. 325-329 (Mar 2017) ISSN: 1436-2023 [Electronic] Japan
• PMID: 28025021 (Publication Type: Journal Article)
• Copyright: Copyright © 2016 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

Chemical References

• Calcitonin Gene-Related Peptide

Topics

• Animals
• Arthralgia (drug therapy, pathology, physiopathology)
• Arthritis (drug therapy, pathology, physiopathology)
• Biopsy, Needle
• Calcitonin Gene-Related Peptide (metabolism)
• Disease Models, Animal
• Ganglia, Spinal (pathology, physiopathology)
• Hip Joint (innervation, pathology)
• Immunohistochemistry
• Male
• Neurons, Afferent
• Random Allocation
• Rats
• Rats, Sprague-Dawley
• Reference Values
• Sensitivity and Specificity