Syringomyelia is characterized by the formation of a fluid-filled cyst within the spinal cord(Greitz, 2006; Milhorat, 2000), which is believed to arise from the disruption of cerebrospinal fluid (CSF) circulation(Bertram and Heil, 2017; Giner et al., 2019a). CSF circulation is regulated by the coordinated beating of ependymal cilia, which are anchored to the apical surface of ependymal cells (ECs) through centrioles and protrude into the lumen of brain ventricles and the central canal (CC) (Kumar et al., 2021; Mitchell, 2017). The coordinated beating of ependymal cilia also assembles a dense actin network around the centrioles, which protects them against shear stress(Mahuzier et al., 2018). Disruption of the actin network can lead to the detachment of centrioles and a subsequent decline in cilia. Furthermore, intercellular communication among ECs through gap junctions, with the main component being connexin 43 (Cx43), is critical for the maintenance of cilia(Kovacs, 2017). A study has shown a decline in cilia and CC expansion in Cx43-knockout mice(Zhang et al., 2020).

While descriptive studies have reported on the decline of ependymal cilia in the kaolin-induced syringomyelia model(Hall et al., 1977; Rascher et al., 1987) and autopsy(Milhorat et al., 1995), there is limited knowledge on the dynamic changes in cilia and related pathologies during syringomyelia formation.

In this study, an extradural compression-induced syringomyelia rat model was utilized to explore the status of ependymal cilia and their associated histological changes. The findings suggest that the loss of Cx43 may act as an initiating factor, triggering early cilia decline and leading to a vicious circle between actin network disorganization and later cilia decline, which results in the accumulation of CSF in the CC and the formation of syringomyelia. These findings provide valuable insights into the mechanism of ependymal cilia decline in syringomyelia and offer a novel perspective for future research in this area.