The Effect of Arthritic Induction on Skeletal Muscle and Tendons in the Rat

Choi, Yusun; Cho, Yongwoo

Abstract

BACKGROUND
The purpose of this study was to investigate the changes in the gastrocnemius muscle and patellar ligament of Sprague-Dawley rat after knee joint arthritis induction. METHODS: Arthritis was induced in the rats by an injection of 0.1 ml carrageenan into the knee joint of the left hind limb after anesthesia with sevoflurane. The rats were killed 72 hours after the arthritic induction. The gastrocnemius muscle and patellar ligament were then removed from the hind limb, their diameters and circles measured, and the morphological changes examined under both light and electron microscopies. RESULTS: In the arthritis-induced group, the diameters and circles of the gastrocnemius muscle and patellar ligament were larger than those of the controls. The muscle cell groups were divided by the intercellular gap, and some tended to become round. The intercellular gaps of some groups were irregular, with several cell groups showing an increased size by cellular fusion and swollen perimysium of muscle cells. Under electron microscopy, many vacuoles, dense bodies and dilated cisternae of the rough endoplasmic reticulum, were seen in the sarcoplasm of the gastrocnemius muscle of the rats. The tendon was divided into small groups by the intratendon gap, and the margin of the tendon also divided by small furrows. The tendon fibers showed a waved arrangement, with a short or waved intracellular gap and the tendon muscle cells divided by penetration into the junction between the muscle and tendon. CONCLUSIONS: The effects of carrageenan induced arthritis on the skeletal muscles and tendons in rats result not only in an increased diameter and circle, but also in changes in the morphology.