A study of the photoelectrical signal from human nasal cilia under several conditions

Light-sheet laser speckle imaging for cilia motility assessment

Mucociliary clearance is an important innate defense mechanism predominantly mediated by ciliated cells in the upper respiratory tract. Ciliary motility on the respiratory epithelium surface and mucus pathogen trapping assist in maintaining healthy airways. Optical imaging methods have been used to obtain several indicators for assessing ciliary movement. Light-sheet laser speckle imaging (LSH-LSI) is a label-free and non-invasive optical technique for three-dimensional and quantitative mapping of velocities of microscopic scatterers. Here, we propose to use an inverted LSH-LSI platform to study cilia motility. We have experimentally confirmed that LSH-LSI can reliably measure the ciliary beating frequency and has the potential to provide many additional quantitative indicators for characterizing the ciliary beating pattern without labeling. For example, the asymmetry between the power stroke and the recovery stroke is apparent in the local velocity waveform. PIV (particle imaging velocimetry) analysis of laser speckle data could determine the cilia motion directions in different phases.

Analysis of ependymal ciliary beat pattern and beat frequency using high speed imaging: comparison with the photomultiplier and photodiode methods

Background

The aim of this study was to compare beat frequency measurements of ependymal cilia made by digital high speed imaging to those obtained using the photomultiplier and modified photodiode techniques. Using high speed video analysis the relationship of the power and recover strokes was also determined.

Methods

Ciliated strips of ependyma attached to slices from the brain of Wistar rats were incubated at 30°C and observed using a ×50 water immersion lens. Ciliary beat frequency was measured using each of the three techniques: the high speed video, photodiode and photomultiplier. Readings were repeated after 30 minutes incubation at 37°C. Ependymal cilia were observed in slow motion and the precise movement of cilia during the recovery stroke relative to the path travelled during the power stroke was measured.

Results

The mean (95% confidence intervals) beat frequencies determined by the high speed video, photomultiplier and photodiode at 30°C were 27.7 (26.6 to 28.8), 25.5 (24.4 to 26.6) and 20.8 (20.4 to 21.3) Hz, respectively. The mean (95% confidence intervals) beat frequencies determined by the high speed video, photomultiplier and photodiode at 37°C were 36.4 (34 to 39.5), 38.4 (36.8 to 39.9) and 18.8 (16.9 to 20.5) Hz. The inter and intra observer reliability for measurement of ciliary beat frequency was 3.8% and 1%, respectively. Ependymal cilia were observed to move in a planar fashion during the power and recovery strokes with a maximum deviation to the right of the midline of 12.1(11.8 to 13.0)° during the power stroke and 12.6(11.6 to 13.6)° to the left of the midline during the recovery stroke.

Conclusion

The photodiode technique greatly underestimates ciliary beat frequency and should not be used to measure ependymal ciliary beat frequency at the temperatures studied. Ciliary beat frequency from the high speed video and photomultiplier techniques cannot be used interchangeably. Ependymal cilia had minimal deviation to the right side during their power stroke and to the left during the recovery stroke.

Comparison of ciliary wave disorders measured by image analysis and electron microscopy

CONCLUSION

We have developed a simple, reliable method for the simultaneous determination of the ciliary wave disorder (CWD) and ciliary beat frequency (CBF) of actively beating cilia.

OBJECTIVE

The CBF and the directions of beating cilia are two important components of mucociliary transport. Although lots of studies have been performed on the measurement of the CBF, there have been few studies on the direction of cilia, with the exception of those using electron microscopy (EM). EM takes too long to determine the directions of cilia, and it cannot determine the direction of actively beating cilia. The aim of this study was to develop an image analysis (IA) system to conveniently determine the wave directions of multiple actively beating cilia as well as the CBF.

MATERIAL AND METHODS

Sphenoid sinus mucosae obtained from 10 patients undergoing pituitary tumor removal via a trans-septal trans-sphenoidal approach were divided into two 4 x 4 mm2-sized pieces. One piece was studied using IA, the other with EM. Using IA, ciliary wave directions were determined from 5 20 x 20 microm2 regions of interest and the mean of 5 consecutive values was regarded as the CWD of each sample. The CBF was also measured. CWD was also measured using EM.

RESULTS

The average number of cilia analyzed by EM was 102.50 (range 48-136). The mean CWDs determined using IA and EM were 28.25+/-4.84 degrees and 23.59+/-8.16 degrees, respectively. There was a significant correlation between the CWDs determined using these two methods (Spearman's correlation coefficient =0.648; p =0.043). The mean CBF of sphenoid mucosa was 10.50+/-2.20 Hz.

Directional disorder of ciliary metachronal waves using two-dimensional correlation map

The interrelationship of cilia and the order of wave directions are important factors that determine the effectiveness of cilia to transport materials in mucociliary systems of the respiratory tract. The interrelationship of cilia and the directional disorder of ciliary metachronal wave were analyzed using digital microscopic images. The degree of synchronization between ciliary beats was determined by the correlation factor between two different spots. To find out the uniphase directions of beating cilia, principal axes of inertia were applied to the two-dimensional correlation map calculated from sequential ciliary images. The standard deviation of determined wave directions in a region of interest (ROI) was defined as a measure of metachronal wave disorder. The pooled mean of metachronal wave disorder was 23.4 +/- 8.79 degrees in ROIs of 8 microm x 8 microm and 25.4 +/- 6.46 degrees in 32 microm x 24 microm from the sphenoid sinus mucosa of five normal subjects. Our result shows that there is a considerable variation in metachronal wave directions of cilia beating on the epithelium.

Distribution mapping of ciliary beat frequencies of respiratory epithelium cells using image processing

Through their rapid periodic actions, the cilia of the human respiratory tract play an important role in clearing inhaled noxious particles. An automated method is developed, based on an image-processing technique, to measure and analyse objectively and quantitatively, ciliary beat frequency (CBF). Microscopic ciliary images are transformed into digitised grey images through an image grabber inside a PC, and signals are extracted from these, based on an image-subtraction algorithm, and are processed through power spectrum analysis using a fast Fourier transform (FFT). By means of the FFT power spectrum, maximum peak frequencies are detected as CBFs in each partitioned block for the entire digitised field. Using these CBFs, distribution maps are composed in various resolutions, showing visually the spatial distribution of CBFs through cells and in a single cell. To measure CBF variations quantitatively, phenylephrine hydrochloride is used, and the changes in CBF influenced by its concentration and duration are observed.

Extraction of cilium beat parameters by the combined application of photoelectric measurements and computer simulation

Photoelectric signals were created and used to investigate the features of the signals as a function of the ciliary beat parameters. Moreover, correlation between the simulated and the measured signals permitted measurement of the cilium beat parameters. The simulations of the signals were based on generation of a series of time-frozen top-view frames of an active ciliary area and determination of the amount of light passing through an observation area in each of these frames. All the factors that might contribute to the shape of the signals, namely, partial ciliary transmittance of light, three-dimensional ciliary beat (composed of recovery, effective, and pause parts), phase distribution on the ciliary surface, and the large number of cilia that contribute to the photoelectric signal, were taken into account in generation of the signals. Changes in the ciliary parameters influenced the shape of the photoelectric signals, and the different phases of the beat could not be directly and unequivocally identified in the signals. The degree of temporal asymmetry of the beat and the portion of the cycle occupied by the pause significantly influenced the shapes of both the lower and the upper parts of the signal and the slopes of the signal. Increases in the angle of the arc swept by the cilium during the effective stroke smoothed the signals and increased the duration of the upper part of the signal. The angle of the arc projected by the cilium onto the cell surface during the recovery stroke had minor effects on the signal's shape. Characteristics of the metachronal wave also influenced the signal's shape markedly. Decreases in ciliary spacing smoothed the signals, whereas ciliary length had a minor influence on the simulated photoelectric signals. Comparison of the simulated and the measured signals showed that the beat parameters of the best-fitting simulated signals converged to values that agree well with the accepted range of beat parameters in mucociliary systems.

Effects of prostaglandins D2 and E2 on ciliary beat frequency of human upper respiratory cilia in vitro

Diminished mucociliary transport can occur in a type-I (Ig-E mediated) allergic reaction. We determined the effects of the allergy mediators prostaglandin D2 (PGD2) and prostaglandin E2 (PGE2) on the ciliary beat frequency (CBF) of human upper respiratory cilia in vitro. Human adenoid tissue was used as the source for ciliated epithelium. CBF was measured by a computerized photo-electric method. PGD2 (10(-8)-10(-5) M, n = 7) showed no statistically significant effect on CBF. PGE2 (10(-9)-10(-6) M, n = 10) caused a significant dose-dependent stimulation, with a maximum of 37% (ANOVA, p < 0.001). Thus prostaglandins D2 and E2 do not exert a direct negative influence on ciliary activity, which could account for a decrease in mucociliary transport. The stimulating effect of PGE2 may be relevant in promoting mucociliary clearance in vivo.

Normal ciliary beat frequency after ciliogenesis in nasal epithelial cells cultured sequentially as monolayer and in suspension

Ciliary beat frequency (CBF) was measured at room temperature in nasal epithelial cells from 10 control individuals at multiple time points during sequential monolayer-suspension culture. CBF was 8.4 +/- 1.6 Hz in the biopsy and decreased in monolayer culture to approximately 6 Hz. During monolayer culture the interindividual variability was increased (3.0 Hz), but not the intercellular and intracellular variability. Immediately after ciliogenesis in suspension culture, CBF was approximately 8 Hz, with a low interindividual variability. After 3 weeks in suspension culture CBF was 8.6 +/- 0.9 Hz. There was no difference in intercellular and intracellular variability of CBF in the different culture conditions. Ciliogenesis in the sequential monolayer-suspension culture results in quantitative normal ciliary activity, with low variability. The most important parameter of ciliary activity that changes during ciliary deterioration and ciliogenesis is the CBF itself.