Chronic Paraspinal Muscle Injury Model in Rat

Abstract

ObjectiveThe objective of this study is to establish an animal model of chronic paraspinal muscle injury in rat.MethodsFifty four Sprague-Dawley male rats were divided into experimental group (n=30), sham (n=15), and normal group (n=9). Incision was done from T7 to L2 and paraspinal muscles were detached from spine and tied at each level. The paraspinal muscles were exposed and untied at 2 weeks after surgery. Sham operation was done by paraspinal muscles dissection at the same levels and wound closure was done without tying. Kyphotic index and thoracolumbar Cobb's angle were measured at preoperative, 2, 4, 8, and 12 weeks after the first surgery for all groups. The rats were sacrificed at 4, 8, and 12 weeks after the first surgery, and performed histological examinations.Results At 4 weeks after surgery, the kyphotic index decreased, but, Cobb's angle increased significantly in the experimental group (p<0.05), and then that were maintained until the end of the experiment. However, there were no significant differences of the kyphotic index and Cobb's angle between sham and normal groups. In histological examinations, necrosis and fibrosis were observed definitely and persisted until 12 weeks after surgery. There were also presences of regenerated muscle cells which nucleus is at the center of cytoplasm, centronucleated myofibers.ConclusionOur chronic injury model of paraspinal muscles in rats shows necrosis and fibrosis in the muscles for 12 weeks after surgery, which might be useful to study the pathophysiology of the degenerative thoracolumbar kyphosis or degeneration of paraspinal muscles.

Paraspinal muscle pathophysiology associated with low back pain and spine degenerative disorders

“…Finally, Rederstorff et al, 136 using SEPN1 KO mice that have a reduced muscle cellular ability to deal with oxidative stress and maintain calcium homeostasis, reported that exercise‐induced stress resulted in paraspinal muscle atrophy and a progressive hyperkyphosis of the thoracic spine. Similar to the experimental muscle damage model of Cho et al, 112 this suggests that paraspinal muscle weakness can lead to spine deformity. More detailed degenerative changes to spine tissues were not examined.…”

“…The authors reported no effect on the IVD or nucleus pulposus areas, concluding that multifidus disruption does not lead to IVD degeneration within the time frame studied (28 days). In contrast to this, Cho et al 112 found that severe injury (2‐week ischemia) to the paraspinal muscles (multifidus and erector spinae were not specified in their description) of rats led to a thoracolumbar kyphotic deformity that persisted for the remainder of the study (12 weeks); however, the authors did not quantify the degenerative changes in either the muscles or specific spine tissues.…”

“…Due to the many challenges in conducting studies on human LBPD patients (e.g., accessing healthy and pathological spine muscle tissue and conducting longitudinal studies probing cause‐and‐effect), animal experiments can provide a means to study mechanistic cause‐effect relationships between muscle and spine degeneration/dysfunction. Each of experimental (for example, References 111 , 112 , 113 , 114 , 115 ), naturally developing 116 and genetically induced (for example, 117 , 118 , 119 , 120 ) animal models have been utilized to answer important fundamental and clinical questions. As such, the following section will be divided into animal models that are (a) experimentally (surgically) induced and (b) naturally occurring and genetically induced.…”

“…Generally, experimentally induced spine injury studies have been performed in sheep, 113 , 114 , 121 pigs, 122 rabbits, 111 , 115 and rats. 112 , 123 , 124 Therefore, the following section will focus on these animal models.…”

The Relationship Between Degeneration and Asymmetry of the Lumbar Multifidus and Erector Spinae Muscles in Patients with Lumbar Disc Herniation with and Without Root Compression

“…It was also stated in that study that no intervertebral disc degeneration was seen within 28 days [44]. In contrast, Cho et al found that kyphotic deformity was formed in 12 weeks after serious injury to the paraspinal muscles in rats, but degenerative changes in the spine and muscles were not quanti ed [45].…”