Impairment of Connexin 43 may initiate cilia decline in syringomyelia

Ependymal cilia, which are maintained by the Connexin 43 (Cx43) and protected by the actin network, play an essential role in regulating cerebrospinal fluid (CSF) circulation. The decline of ependymal cilia has been reported in syringomyelia, but the underlying mechanism remains unclear. In this study, we used an extradural compression-induced syringomyelia rat model to investigate the changes in cilia and related pathologies during the formation of syringomyelia. We divided rats into control and syringomyelia groups and sacrificed them at three time points, 7, 14, and 28 days postoperative (dpo). Scanning electron microscopy (SEM) and immunofluorescence (IF) were used to illustrate the number and morphology of ependymal cilia. IF was also used to show the status of centrioles, actin network, and Cx43 (the main component of the gap junction). Transmission electron microscopy (TEM) was used to observe the structure of the gap junction. The results showed that most syringomyelia were located at segments (T10-12) rostral to the compression site (T13). SEM images showed that the number of cilia in the central canal (CC) declined in two phases during the development of syringomyelia (early stage, 7 dpo; later stage, 14 and 28 dpo). The number of cilia showed a significant difference between the early and later stages of syringomyelia development. Additionally, TEM showed the absence of gap junction and IF illustrated less Cx43 expression in ependymal cells (ECs) at the compression site in both the early and later stages. Actin network disruption and centrioles reduction at adjacent segments rostral to the compression site were found in the later stage. These findings indicate that the loss of Cx43 at the compression site may be related to cilia detachment at rostral adjacent segments by disrupting intercellular communication in the early stage of syringomyelia development. This early cilia decline then causes actin network disorganization, further aggravating cilia decline by exposing centrioles to CSF shear stress in the later stage. These findings suggest a potential mechanism of ependymal cilia decline in the development of syringomyelia and may provide a novel perspective for future research in this area.