A novel rat model of hip pain by intra-articular injection of nerve growth factor-characteristics of sensory innervation and inflammatory arthritis.
OBJECTIVE
To determine the direct effects of intra-articular injection of nerve growth factor (NGF) into normal rat hips and the time course of pain-related mediator appearance.


METHODS
Using 36 numbers of 8-week-old male Sprague-Dawley rats, 30 μl of 1% Fluoro-Gold solution (FG) (Sham-operated group; n = 12), 30 μl of 1% FG with 50 μg/ml NGF (NGF50 group; n = 12), and 30 μl of 1% FG with 100 μg/ml NGF (NGF100 group; n = 12) were injected into the left hip joints. Neurons in the dorsal root ganglion (DRG) labeled with FG, and FG and calcitonin gene-related peptide-immunoreactivity (CGRP-IR) were counted. The synovia in the left hip joint was examined histologically.


RESULTS
The NGF50 and NGF100 groups showed evidence of synovitis without cartilage degeneration compared with the Sham-operated group. At 7 days, the proportions of CGRP-IR FG-labeled to total FG-labeled neurons were 12%, 18%, and 36% in the Sham-operated, NGF50, and NGF100 groups, respectively. At 14 days, the proportions were 13%, 22%, and 35% in the Sham-operated, NGF50, and NGF100 groups, respectively. At 7 and 14 days, the NGF50 and NGF100 groups showed a significantly higher proportion of CGRP-IR FG-labeled neurons than the Sham-operated group.


CONCLUSIONS
Intra-articular administration of NGF into the hip joint produces a novel rat model for hip pain.
a Department of Orthopaedic Surgery , Graduate School of Medicine, Chiba University , Chiba City , Chiba , Japan.
Takanori
T
Omae
a Department of Orthopaedic Surgery , Graduate School of Medicine, Chiba University , Chiba City , Chiba , Japan.
Junichi
J
Nakamura
a Department of Orthopaedic Surgery , Graduate School of Medicine, Chiba University , Chiba City , Chiba , Japan.
Seiji
S
Ohtori
a Department of Orthopaedic Surgery , Graduate School of Medicine, Chiba University , Chiba City , Chiba , Japan.
Sumihisa
S
Orita
a Department of Orthopaedic Surgery , Graduate School of Medicine, Chiba University , Chiba City , Chiba , Japan.
Kazuyo
K
Yamauchi
a Department of Orthopaedic Surgery , Graduate School of Medicine, Chiba University , Chiba City , Chiba , Japan.
Shuichi
S
Miyamoto
a Department of Orthopaedic Surgery , Graduate School of Medicine, Chiba University , Chiba City , Chiba , Japan.
Shigeo
S
Hagiwara
a Department of Orthopaedic Surgery , Graduate School of Medicine, Chiba University , Chiba City , Chiba , Japan.
Shunji
S
Kishida
a Department of Orthopaedic Surgery , Graduate School of Medicine, Chiba University , Chiba City , Chiba , Japan.
Kazuhisa
K
Takahashi
D000818:Animals; D015740:Calcitonin Gene-Related Peptide; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000187:drug effects / Q000503:physiopathology; D006621:Hip Joint / Q000187:drug effects* / Q000503:physiopathology; D007270:Injections, Intra-Articular; D008297:Male; D020932:Nerve Growth Factor; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D015207:Osteoarthritis, Hip / Q000139:chemically induced* / Q000503:physiopathology; D010146:Pain / Q000139:chemically induced* / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley
D020932:Nerve Growth Factor; D015740:Calcitonin Gene-Related Peptide
Experimental study; hip joint; intra-articular injection; nerve growth factor