Ultrastructure of neurovascular unit in chronic compressive cervical myelopathy rat model / 中华显微外科杂志

ABSTRACT

Objective To observe the ultrastructure of the neurovascular Unit (NVU) in chronic compressive cervical myelopathy rat model at different stages.Methods From March, 2014 to March, 2015, 32 rats were divided into two groups sham control group (n =8) and compressive spinal cord injury group (n =24).The model was established by inserting the compression sheet made of polyurethane at the level of C6.BBB and somatosensory evoked potentials (SEP) were used to evaluate the spinal cord function status of model rat.Transmission Electron Microscopy (TEM) examination of compressive cervical spinal cords was performed separately at the 14th, 21st, 28th and 42nd day after modeling.Results At the 14th, 21st, 28th and 42nd, the BBB score were 17.571 ± 0.870, 15.952 ± 0.870, 15.476 ± 0.602 and 16.190 ± 0.632 were significantly lower than those in the control group (the BBB score of 4 points were 19.600 ± 0.516, 19.500 ± 0.527, 19.600 ± 0.699 and 19.800 ± 0.6232 respectively) (P ＜ 0.05).Latency prolongation and amplitude reduction of somatosensory evoked potentials (SEP) were presented in the compressive spinal cord injury group.At the 14th day, edema around the capillaries was observed, the morphological structure of endothelial cells and basement membrane was normal, the tight junction between endothelial cell was intact, the mitochondria in the axons, oligodendrocytes and astrocyte foot processes were edematous.At the 21st day, extensive edema, even partial necrosis around the capillaries were found, the surrounding structure were arranged loosely, partial loss of endothelial cells and basement membrane, cavitation occurrence in endothelial cells, basal membrane density was significantly lower, mitochondria vacuoles and shrinkage in the cytoplasm, axon myelin loose or broken;at the 28th day, the edematous range surrounding capillaries narrowed, low density of basement membrane and endothelial cells, vacuoles in endothelial cells, loose axon myelin, while some mitochondrias backed to normal.At the 42nd day, capillary integrity, no abnormalities were found in endothelial cells, basement membrane, tight junction and mitochondria, double layers of endothelial cells and basement membrane could be seen, local broken and loose structure were presented in part of the axons;The TEM of the sham control group showed normal ultrastructure of NVU.Conclusion The ultrastructure of NVU in chronic cervical spinal cord compression presented various in the different periods, NVU disruption were found in the early stages (14th-28th days), and compensatory and repair process were developed incompletely later.