Features of neuroglia at the epicenter of spinal cord contusion injury and at distant areas in mini-pigs

Aim. To determine the delayed (after 2 months) effect of spinal cord injury (SCI) in the lower thoracic region in the  mini-pigs on the morphologic state of macro- and microglia in nearby and remote caudal areas.

 Materials and methods. Sexually mature female Vietnamese pot-bellied pigs were randomly divided into two groups:  SCI (n = 3) and intact (n = 3). Dosed contusion SCI was modelled at the level of the Th8–Th9 vertebrae, and transverse  cryostat sections of the caudal segment adjacent to the epicenter of injury and the lumbar thickening (L4–S2) were  examined 2 months later. The expression of astrocyte markers (glial fibrillary acidic protein, GFAP) and microglial  markers (ionized calcium-binding adapter molecule 1, Iba1) was assessed as the relative immunopositive area  occupied by cells. When counting the number of oligodendroglial cells (oligodendrocyte transcription factor 2, Olig2),  the presence of nuclei detectable with 4’,6-diamidino-2-phenylindole (DAPI) was taken into account.

Results. After SCI, an increase in the relative areas occupied by GFAP-positive astrocytes and Iba1-positive microglia  and a decrease in Olig2-positive oligodendrocytes were detected in both the lesion area and lumbar thickening. In  both regions, 2 months after SCI, the proportion of astrocytes was not significantly different in the anterior horns  and doubled in the posterior horns. Microglia cells with SCI were 2.5 times more in the anterior horns of both regions  and in the posterior horns of the lumbar thickening, while the presence of microglia increased slightly (1.2 times) in  the posterior horns in the SCI region. The number of oligodendrocytes decreased in the area of the epicenter of SCI  in the anterior and posterior horns by 1.5–1.75 times, and in the lumbar thickening more significantly: the number  decreased by 2.5 times in the anterior horn and 5.5 times in the posterior horn.

 Conclusion. The results of the study revealed a similar pattern of macro- and microglial cell distribution both in the  SCI region and in remote areas. The obtained data testify to the necessity to take into account the state of the areas  of nervous tissue remote from the epicenter of SCI when stimulating neuroregeneration in such patients

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