Asian Spine J.  2017 Feb;11(1):88-92. 10.4184/asj.2017.11.1.88.

Evaluation of Histological Changes in Back Muscle Injuries in Rats over Time

• Abe K
• Inage K
• Sakuma Y
• Orita S
• Yamauchi K
• Suzuki M
• Kubota G
• Oikawa Y
• Sainoh T
• Sato J
• Fujimoto K
• Shiga Y
• Kanamoto H
• Takahashi
• Ohtori S

• KMID: 2391591
• DOI: http://doi.org/10.4184/asj.2017.11.1.88

Abstract

STUDY DESIGN: Animal model study. PURPOSE: The purpose of this study was to evaluate the histological variation in the injured muscle and production of calcitonin gene-related peptide in rats over time. OVERVIEW OF LITERATURE: Vertebral surgery has been reported to cause atrophy of the back muscles, which may result in pain. However, few reports have described the time series histological variation in the injured muscle and changes in the dominant nerve.
METHODS
We used 30 male, 8-week-old Sprague-Dawley rats. The right and left sides of the paravertebral muscle were considered as the injured and uninjured sides, respectively. A 115 g weight was dropped from a height of 1 m on the right paravertebral muscle. Hematoxylin and eosin (H&E) staining of the muscle was performed 1-3 weeks after injury for histological evaluation. Fluoro-Gold (FG) was injected into the paravertebral muscle. The L2 dorsal root ganglia on both sides were resected 1, 2, and 3 weeks after injury, and immunohistochemical staining for calcitonin gene-related peptide was performed.
RESULTS
H&E staining of the paravertebral muscle showed infiltration of inflammatory cells and the presence of granulation tissue in the injured part on the ipsilateral side 1 week after injury. Muscle atrophy occurred 3 weeks after injury, but was repaired via spontaneous replacement of muscle cells/fibers. In contrast, compared with the uninjured side, the percentage of cells double-labeled with FG and calcitonin gene-related peptide in FG-positive cells in the dorsal root ganglia of the injured side was significantly increased at each time point throughout the study period.
CONCLUSIONS
These results suggest that sensitization of the dominant nerve in the dorsal root ganglia, which may be caused by cicatrix formation, can protract injured muscle pain. This information may be helpful in elucidating the underlying mechanism of persistent pain after back muscle injury.

Keyword

Back muscles; Spine; Rats; Calcitonin gene-related peptide; Ganglia, sensory

MeSH Terms

Animals
Atrophy
Back Muscles*
Calcitonin Gene-Related Peptide
Cicatrix
Eosine Yellowish-(YS)
Ganglia, Sensory
Ganglia, Spinal
Granulation Tissue
Hematoxylin
Humans
Male
Models, Animal
Muscular Atrophy
Myalgia
Rats*
Rats, Sprague-Dawley
Spine
Calcitonin Gene-Related Peptide
Eosine Yellowish-(YS)
Hematoxylin