Ependymal cilia decline and AQP4 upregulation in young adult rats with syringomyelia.

Abstract

Background: Syringomyelia was a rare condition characterized by the formation of fluid-filled cysts (syrinx) within the spinal cord, resulting in sensory and motor dysfunction. Currently, there was no satisfactory treatment for syringomyelia. Ependymal cells were integral to water transport and may represent a promising therapeutic target.

Methods: Induction of syringomyelia occurred in 8-week old female rats followed by histological analyses at 3-, 7-, 14-, 30-, 60-, 180-, and 365-days later. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were performed to visualize cilia on rat central canal membrane cells at 30-day post-induction. Syringomyelia was induced via compression at T12-T13 using a sterile cotton ball. Each rat underwent MRI scanning one day before induction and one day prior to sacrifice. In vivo magnetic resonance imaging (MRI) was utilized to measure syrinx enlargement in eight-week-old syringomyelia rats. Histological Analysis and immunofluorescence staining were performed for changes of cilia, neurons, expression of AQP4 and infiltration of immune cells into spinal tissue.

Results: In the current study, the cell junctions between ependymal cells of syringomyelia rats were absent, and the cilia on ependymal cells were reduced significantly on day 30 post syringomyelia. The number of ependymal cells kept increasing lasting for 1-2 months and begin to decrease. Edema and vacuolation in the spinal cord tissue are significant in syringomyelia rats. Furthermore, AQP4 expression was elevated in astrocytes of syringomyelia rats, and IBA1⁺ immune cells infiltrated spinal tissue. Furthermore, neuronal necrosis began in the acute stage of syringomyelia, and reached its peak one month later. Pathological changes in axonal rupture at anterior commissure (connection of the left and right white matter) could be observed in syringomyelia spinal tissue.

Conclusions: These findings underscored the significance of cilia on ependymal cells and the evolving microenvironment post-syringomyelia, providing valuable insights for clinical treatment strategies for this condition.