Live Imaging of the Ependymal Cilia in the Lateral Ventricles of the Mouse Brain

Summary

Using high-resolution differential interference contrast (DIC) microscopy, an ex vivo observation of the beating of motile ependymal cilia located within the mouse brain ventricles is demonstrated by live-imaging. The technique allows a recording of the unique ciliary beating frequency and beating angle as well as their intracellular calcium oscillation pacing properties.

Abstract

Multiciliated ependymal cells line the ventricles in the adult brain. Abnormal function or structure of ependymal cilia is associated with various neurological deficits. The current ex vivo live imaging of motile ependymal cilia technique allows for a detailed study of ciliary dynamics following several steps. These steps include: mice euthanasia with carbon dioxide according to protocols of The University of Toledo’s Institutional Animal Care and Use Committee (IACUC); craniectomy followed by brain removal and sagittal brain dissection with a vibratome or sharp blade to obtain very thin sections through the brain lateral ventricles, where the ependymal cilia can be visualized. Incubation of the brain’s slices in a customized glass-bottom plate containing Dulbecco’s Modified Eagle’s Medium (DMEM)/High-Glucose at 37 °C in the presence of 95%/5% O₂/CO₂ mixture is essential to keep the tissue alive during the experiment. A video of the cilia beating is then recorded using a high-resolution differential interference contrast microscope. The video is then analyzed frame by frame to calculate the ciliary beating frequency. This allows distinct classification of the ependymal cells into three categories or types based on their ciliary beating frequency and angle. Furthermore, this technique allows the use of high-speed fluorescence imaging analysis to characterize the unique intracellular calcium oscillation properties of ependymal cells as well as the effect of pharmacological agents on the calcium oscillations and the ciliary beating frequency. In addition, this technique is suitable for immunofluorescence imaging for ciliary structure and ciliary protein localization studies. This is particularly important in disease diagnosis and phenotype studies. The main limitation of the technique is attributed to the decrease in live motile cilia movement as the brain tissue starts to die.

Introduction

Cilia are sensory microtubule-based organelles that extend from the cell surface to the extracellular environment. Depending on their microtubule organization, cilia can be categorized into two types - “9+0” or “9+2”. Functionally, based on their motility, these can be classed as motile or non-motile cilia ¹. Primary cilia is a term commonly used to denote “9+0” non-motile cilia. These have nine parallel doublet microtubules (denoted by ‘9’) and a central pair of microtubules is absent within the central sheath (denoted by ‘0’). However, some “9+0” cilia, such as nodal cilia, which regu....

Protocol

The procedures for animal use were approved by the Institutional Animal Care and Use Committee (IACUC) of The University of Toledo in accordance with the guidelines of the Institutional Animal Care and Use Committee at the National Institutes of Health and the Guide for the Care and Use of Laboratory Animals.

1. Brain Extraction, Sectioning and Tissue Preparation

1. Sacrifice wild-type mouse strain C57BL/6 by deeply euthanizing with CO₂ asphyxiation for 5 min. Assure death by cervical dislocation.
2. Clean the mouse head with 70% ethanol.
3. Perform craniectomy using sterile scissors and forceps by first pu....

Results

Measuring ependymal cilia function in live mouse brain

The method described in this protocol is used to monitor ependymal cilia function and structure in the fresh tissue dissected from the mouse brain as well as to monitor and study cilia beating frequency. The steps followed to accomplish a complete experiment are depicted in a schematic flowchart (Figure 1). It is highly recommended that the experiment is conducted within a short time frame in order to keep the motile cilia.......

Discussion

Described here is a protocol for the preparation of mouse brain tissue for both live-imaging and fluorescence microscopy that provides a rapid and sensitive close observation of the ependymal cilia within the brain ventricles. This technique is not restricted to the lateral ventricle only; it could be utilized to observe the cilia in other brain ventricles. This imaging technique provides a live stream that resembles the movement of the CSF by ciliary beating in an ex vivo setting. Moreover, it enables analysis .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
DMEM/HIGH GLUCOSE	Cellgro Mediatech Inc.	10-013-CV
Fetal bovine serum (FBS)	Hyclone	SH30088-03
Penicillin/Streptomycin	Thermo Scientific	SV30010
Phosphate buffered saline	Thermo Scientific	SH30256-01
Paraformaldehyde	Electron Microscopy Sciences	15710-SP
Sucrose	Sigma-Aldrich	S-2395
Triton-X	Sigma-Aldrich	T9284
Fluo-2	TEF Labs	#0200
DMSO
B27	Gibco	17504044
VECTASHIELD HardSet Mounting Medium with DAPI	Vector Labs	H-1500
Anti-acetylated a-tubulin antibody	Sigma-Aldrich	T7451	clone 6-11B1
FITC Anti-mouse antibody	Vector Labs	FI-2000
Cell Culture plate	VWR Vista Vision	30-2041
Cover Slip (18 x 18)	VWR Vista Vision	16004.326
Vibratome	Leica Biosystems	Leica VT1200S
Cryostat	Leica Biosystems	Leica CM1860
Inverted Fluorescence Microscope	Nikon	Nikon TE2000	60X oil
Microscope cover glass 24 x 60 mm2	VWR Vista Vision	16004-312
Mounting Medium with DAPI	Vector Laboratories	H-1500
DAPI filter cube	Chroma Technology