A morphological study of the pelvic floor muscle fibers of rats with spinal cord injury / 中华物理医学与康复杂志

ABSTRACT

Objective:To seek better treatments for abnormal pelvic floor muscle tension and pelvic floor dysfunction after spinal cord injury.Methods:The morphology of pelvic floor muscle fibers of rats with spinal cord injury at different levels was observed under the electron microscope. Thirty female adult Sprague-Dawley rats were randomly divided into a suprasacral (SS) cord injury group, a group with spinal cord injury at or below the sacral level (SC) and a normal group (NG), each of 10. The relevant spinal cord injury models were established in the SS and SC groups through spinal cord disconnection. Four weeks later, the pixel area of ATPase-positive fibers was used to quantify the content of type I fibers in the pubococcygeus muscle of each rat through observation under the electron microscope after hematoxylin and eosin staining.Results:The average content of type I muscle fibers in both the SS and SC group was significantly lower than in the normal group. The SC group′s average level was significantly lower than that of the SS group. Under the microscope the stained myofibers were tortuous, deformed in appearance and with proliferated nuclei. Capillary dilation could be seen locally in the SS group 4 weeks after the injury. In the SC group at 4 weeks after the injury the pubococcal fibers were seriously "dissolved" , or disordered, with spherical nuclei and mild hyperplasia. Under the electron microscope, the sarcomeres of the SC group were obviously dissolved, atrophied and broken, though the basic structure persisted, with mild mitochondrial proliferation. The sarcomeres of the SC group were extremely dissolved and broken, completely losing basic structure, with abundant connective tissue proliferation but without obvious mitochondrial proliferation.Conclusions:After suprasacral cord injury, the content of type I muscle fibers in the pubococcygeus muscle of the pelvic floor decreases somewhat, with the basic structure of the muscle fibers remaining intact. However, after spinal cord injury at or below the sacral level, type I muscle fibers decrease significantly in the pubococcygeus muscle of the pelvic floor, and the basic structure is seriously damaged.