Ependymal Cilia: Physiology and Role in Hydrocephalus

Abstract

Cerebrospinal fluid (CSF), a colorless liquid that generally circulates from the lateral ventricles to the third and fourth ventricles, provides essential nutrients for brain homeostasis and growth factors during development. As evidenced by an increasing corpus of research, CSF serves a range of important functions. While it is considered that decreased CSF flow is associated to the development of hydrocephalus, it has recently been postulated that motile cilia, which line the apical surfaces of ependymal cells (ECs), play a role in stimulating CSF circulation by cilia beating. Ependymal cilia protrude from ECs, and their synchronous pulsing transports CSF from the lateral ventricle to the third and fourth ventricles, and then to the subarachnoid cavity for absorption. As a result, we postulated that malfunctioning ependymal cilia could disrupt normal CSF flow, raising the risk of hydrocephalus. This review aims to demonstrate the physiological functions of ependymal cilia, as well as how cilia immobility or disorientation causes problems. We also conclude conceivable ways of treatment of hydrocephalus currently for clinical application and provide theoretical support for regimen improvements by investigating the relationship between ependymal cilia and hydrocephalus development.

Ependymal cells and neurodegenerative disease: outcomes of compromised ependymal barrier function

“… 27 Primary cilia is typically organized in the ‘9 + 0’ axoneme configuration, whereas motile cilia are generally found in the ‘9 + 2’ axoneme configuration. 9 Thus, cilia morphology and function are used to categorize ependymal cells into different subtypes. As previously described, E1 ependymal cells contain multiple motile cilia, E2 ependymal cells contain one motile cilium and one primary cilium, and E3 ependymal cells contain one primary cilium.…”

“… 5 , 6 Ependymal cells are heterogeneous with respect to their cellular dimensions, such that the apical cell membrane can range from 6 × 5 µm to 11 × 8 µm, as observed within the third ventricle, 8 and the cilia can project up to 20 µm into the ventricular cavities. 9 Although less well-defined, the spinal ependymal layer that lines the central canal of the spinal cord consists of three main cell types: E2 ependymal cells, tanycytes and CSF-contacting neurons. 10 Tanycyctes are uniciliated cells with long cellular processes that extend towards the vasculature of the spinal cord parenchyma, whereas CSF-contacting neurons possess mechanosensory properties that resemble retinal bipolar neurons.…”

Behavioral Phenotyping of Bbs6 and Bbs8 Knockout Mice Reveals Major Alterations in Communication and Anxiety

“…In children, this leads to cognitive disorders, including attention, executive, memory, visual, spatial or linguistic dysfunction (e.g., [ 38 ]). Motile cilia, which adorn the ependymal lining of brain ventricles, are master regulators of CSF flow (reviewed in [ 39 , 40 ]). The primary cilium has already been shown to modulate the development and function of ependymal motile cilia, which ultimately contributes to hydrocephalus, often found in ciliary mutant mice.…”

Cfap91-Dependent Stability of the RS2 and RS3 Base Proteins and Adjacent Inner Dynein Arms in Tetrahymena Cilia

“…In most Metazoa, motile cilia play an important role during development and in proper organ/body function. In humans, the movement of cilia assembled by multiciliated epithelial cells lining internal passages, drives the circulation of the cerebrospinal fluid in brain ventricles [ 1 ] and the removal of inhaled bacteria or particles from the airways [ 2 ], in females, supports the transport of oocytes in the oviduct [ 3 ], and in males, counters sperm cell aggregation in the efferent duct while a single flagellum propels sperm cells [ 4 , 5 ]. During early development, the rotatory-like movement of nodal cilia contributes to the establishment of the left–right asymmetry of visceral body organs [ 6 , 7 ].…”