Histomorphometric study of the soleus muscle under conditions of modeling of spinal cord contusion injury: experimental morphological study

Objective. To conduct a morphometric analysis of the soleus muscle of rats after moderate spinal cord contusion injury.Material and Methods. Experiments were performed on female Wistar rats aged 8–12 months, weighing 270–320 g. Animals of the experimental group (n = 25) underwent laminectomy at the T9 level under general anesthesia and modeling of spinal contusion injury of moderate severity. Intact rats constituted the control group (n = 10). Euthanasia was performed on the 5th, 15th, 30th, 60th, 90th, and 180th days of the experiment. Paraffin sections were stained with hematoxylin-eosin and Masson, the diameters of muscle fibers were determined by computer morphometry, and histograms of their distribution were obtained.Results. In the soleus muscle, the signs of reversible reparative processes prevailed in response to neurotrophic damage. It was evidenced by a local increase in the diversity of myocyte diameters and the loss of polygonality of their profiles, focal destruction of muscle fibers, activation of the connective tissue component, disorganization of some intramuscular nerve conductors, and vascular fibrosis of perimysium. Nevertheless, the histostructure of an intact muscle prevailed in the course of the experiment, which was confirmed by the data of morphometric analysis. All histograms of the distribution of the muscle fiber diameters are unimodal with a mode in the range of 30–41 μm. On the 180th day, the maximum myocyte diameters in the histogram of the left limb muscle belonged to the range of 21–30 μm, which was typical for histograms in the intact group.Conclusion. The nature of the plastic reorganization of the soleus muscle when neurotrophic control is impaired indicates compensatory regeneration of muscle tissue by the type of restitution, which opens up the possibility of predicting the rehabilitation period. It is advisable to take this into account when developing medical and social programs and therapeutic measures, where the most important role is played by superficial neuromuscular and functional electrical stimulation.