Ultrastructural abnormalities of respiratory cilia: a 25-year experience

An Integrated Analysis of Radial Spoke Head and Outer Dynein Arm Protein Defects and Ciliogenesis Abnormality in Nasal Polyps

Background: Nasal polyp (NP) is a chronic upper airway inflammatory disease that is frequently triggered by defective host-defense. However, the mechanisms underlying the impaired barrier function such as cilia-mediated mucociliary clearance remain poorly understood.

Objective: To assess ciliary ultrastructural and ciliogenesis marker expression and the phenotypes of ciliated cells in NP.

Methods: NP biopsy samples were obtained from 97 NP patients and inferior turbinate from 32 healthy controls. Immunofluorescence staining, quantitative polymerase chain reaction, and single-cell cytospin staining were performed. We classified the patterns of radial spoke head protein (RSPH) 1, 4A (RSPH4A), 9 (RSPH9), and dynein axonemal heavy chain 5 (DNAH5) localization. A semi-quantitative scoring system was developed to assess their expression patterns and associations with ciliogenesis markers [centrosomal protein 110 (CP110) and forkhead box j1 (FOXJ1)].

Results: Median scores of RSPH1, RSPH4A, RSPH9, and DNAH5 were significantly higher in NP than in healthy controls, particularly in eosinophilic NPs. Expression pattern scores of RSPH1, RSPH4A, RSPH9, and DNAH5 correlated positively with each other in both groups. In primary-cell specimens, abnormal expression patterns were significantly more common in NP. The total fluorescence intensity of CP110 and FOXJ1 was significantly higher in NPs and correlated positively with expression pattern scores of RSPH1, RSPH4A, RSPH9, and DNAH5. A trend towards lengthened cilia was observed in NP.

Conclusion: In the chronic airway inflammatory milieu, the up-regulated ciliogenesis correlates with the abnormal expression of ciliary ultrastructural markers (i.e., DNAH5) in NP (particularly eosinophilic NP).

Prevalence of chronic rhinosinusitis in bronchiectasis patients suspected of ciliary dyskinesia

BACKGROUND

Mucociliary clearance is a main defense mechanism of the airway and is impaired in ciliary dyskinesia. The objective of this study was to evaluate the prevalence of chronic rhinosinusitis (CRS) and its characteristics in bronchiectasis patients suspected of harboring ciliary dyskinesia.

METHODS

Bronchiectasis patients referred to a rhinology clinic for nasal brush biopsy (NBB) were included in this study. NBB was performed using a curettage technique whereby ciliated epithelial cells were obtained from the surface of the inferior nasal turbinate. Results of transmission electron microscopy findings, primary ciliary dyskinesia (PCD) gene (35 genes) analyses (Invitae), and sinus computed tomography (CT) scans were reviewed.

RESULTS

Twenty-three patients (age, 54 ± 2.9 years) were referred for NBB between 2015 and 2018. Thirteen patients (56.5%) met the criteria for diagnosis of CRS. Nineteen patients had ciliary ultrastructural defects. The most common finding was compound cilia (n = 11, 47.8%). Five patients (21.7%) had central microtubule defects (CMD) with higher forced expiratory volume in 1 second (FEV₁ ) at the time of referral than those without CMD (CMD⁺ , 91 ± 3.7%; CMD^- , 73.5 ± 5.7%; p = 0.023). Of 15 subjects with a PCD gene panel, 67% (9 of 15) carried at least 1 gene associated with PCD. Only 1 patient reached diagnosis of PCD. Approximately 50% of non-PCD carriers had a smoking history (p < 0.05). Lund-Mackay scores did not significantly differ between PCD and non-PCD carriers (p = 0.72).

CONCLUSION

Nearly half of bronchiectasis patients referred for NBB had concurrent CRS. The presence of ciliary abnormalities was not amplified in bronchiectasis patients with CRS compared to those without CRS. Extrinsic factors may be related to ciliary structural abnormalities in non-PCD gene carriers.

Histologic and Ultrastructural Findings in Dogs With Chronic Respiratory Disease Suspected of Ciliary Dyskinesia

Mucociliary clearance is a main defense mechanism of the respiratory tract, which can be inherently impaired in primary ciliary dyskinesia (PCD) or reversibly altered in secondary ciliary dyskinesia (SCD). Limited diagnostic test availability likely leads to misdiagnosis or underdiagnosis of PCD in animals. This study evaluated the light and transmission electron microscopy (TEM) changes in the respiratory mucosa of 15 dogs with chronic respiratory disease suspected of PCD. Necropsy was performed in 1 case and 2 dogs were used as negative controls. PCD was confirmed in 1 dog, which presented with chronic otitis, bronchopneumonia, hydrocephalus and ultrastructural abnormalities in 84% of the assessed cilia, including absence of dynein arms and microtubular changes. The 14 other cases showed only nonspecific alterations, such as ciliary disorientation, compound cilia, ciliary edema, and axoneme bubbles in a minority of the evaluated cilia and were classified as SCD. Ciliary ultrastructural analysis can confirm a diagnosis of PCD if specific abnormalities exist. TEM remains an important investigational tool in veterinary medicine, as no other specific test for PCD in dogs has been standardized yet.

Long-term outcome of Tunisian children with primary ciliary dyskinesia confirmed by transmission electron microscopy

BACKGROUND

Primary ciliary dyskinesia (PCD) is rare. Its diagnosis requires experienced specialists and expensive infrastructure. Its prognosis is variable.

OBJECTIVE

To study the long-term outcome of PCD in Tunisian children with ciliary ultra-structure defects detected by electron microscope.

METHODS

Covering a period of 20 years (1996-2015), this retrospective study included all patients with definite PCD (outer dynein arms (DA) defects and/or situs inversus) and presumed PCD (other ciliary ultra-structure defects). The clinical data and the investigations made were registered at diagnosis and during the follow-up.

RESULTS

Patients with a definite PCD (G1, n=7) were diagnosed earlier compared to those with a presumed PCD (G2, n=13) (2.5 vs. 9.3 years on average). At diagnosis, bronchiectasis was more frequent in G1 (3/7 vs. 4/13). The inner DA loss was constant in G1 and predominant in G2. The treatment adhesion was more often irregular in G2 (2/7 vs. 8/13). During a mean follow-up of 11 years, G1 showed less severe outcome (clubbing (0 vs. 3), bronchiectasis (3 vs. 11; more expanded in G2), proximal and distal airway obstruction (0/3 vs. 5/7), lobectomy (0 vs. 2), and death (0 vs. 2)).

CONCLUSION

Precocious diagnosis and regular treatment may enhance the PCD prognosis.

Clinical manifestations in primary ciliary dyskinesia: systematic review and meta-analysis

Few original studies have described the prevalence and severity of clinical symptoms of primary ciliary dyskinesia (PCD). This systematic review and meta-analysis aimed to identify all published studies on clinical manifestations of PCD patients, and to describe their prevalence and severity stratified by age and sex.We searched PubMed, Embase and Scopus for studies describing clinical symptoms of ≥10 patients with PCD. We performed meta-analyses and meta-regression to explain heterogeneity.We included 52 studies describing a total of 1970 patients (range 10-168 per study). We found a prevalence of 5% for congenital heart disease. For the rest of reported characteristics, we found considerable heterogeneity (I² range 68-93.8%) when calculating the weighted mean prevalence. Even after taking into account the explanatory factors, the largest part of the between-studies variance in symptom prevalence remained unexplained for all symptoms. Sensitivity analysis including only studies with test-proven diagnosis showed similar results in prevalence and heterogeneity.Large differences in study design, selection of study populations and definition of symptoms could explain the heterogeneity in symptom prevalence. To better characterise the disease, we need larger, multicentre, multidisciplinary, prospective studies that include all age groups, use uniform diagnostics and report on all symptoms.

Automated identification of abnormal respiratory ciliary motion in nasal biopsies

Motile cilia lining the nasal and bronchial passages beat synchronously to clear mucus and foreign matter from the respiratory tract. This mucociliary defense mechanism is essential for pulmonary health, because respiratory ciliary motion defects, such as those in patients with primary ciliary dyskinesia (PCD) or congenital heart disease, can cause severe sinopulmonary disease necessitating organ transplant. The visual examination of nasal or bronchial biopsies is critical for the diagnosis of ciliary motion defects, but these analyses are highly subjective and error-prone. Although ciliary beat frequency can be computed, this metric cannot sensitively characterize ciliary motion defects. Furthermore, PCD can present without any ultrastructural defects, limiting the use of other detection methods, such as electron microscopy. Therefore, an unbiased, computational method for analyzing ciliary motion is clinically compelling. We present a computational pipeline using algorithms from computer vision and machine learning to decompose ciliary motion into quantitative elemental components. Using this framework, we constructed digital signatures for ciliary motion recognition and quantified specific properties of the ciliary motion that allowed high-throughput classification of ciliary motion as normal or abnormal. We achieved >90% classification accuracy in two independent data cohorts composed of patients with congenital heart disease, PCD, or heterotaxy, as well as healthy controls. Clinicians without specialized knowledge in machine learning or computer vision can operate this pipeline as a "black box" toolkit to evaluate ciliary motion.

Diagnosis of primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a genetic disorder of ciliary structure or function. It results in mucus accumulation and bacterial colonization of the respiratory tract which leads to chronic upper and lower airway infections, organ laterality defects, and fertility problems. We review the respiratory signs and symptoms of PCD, as well as the screening tests for and diagnostic investigation of the disease, together with details related to ciliary function, ciliary ultrastructure, and genetic studies. In addition, we describe the difficulties in diagnosing PCD by means of transmission electron microscopy, as well as describing patient follow-up procedures.

Number of nexin links detectable at standard electron microscopy of normal human nasal cilia and at nexin link deficiency

BACKGROUND

Eleven years ago we had described three patients with missing nexin links as a possible cause of primary ciliary dyskinesia (PCD). The assumption was substantiated last year by finding a mutation in these patients.

MATERIALS AND METHODS

We counted the nexin links, inner (IDA) and outer (ODA) dynein arms and microtubuli in each of, if possible, 50 cilia in 41 patients with normal cilia, 4 patients with deficiency of nexin links only and 4 with deficiency of nexin links and IDA.

RESULTS

In the control group the median number of nexin links was 4.5 per cilium, range 3.4-5.3. In the second group the mean numbers of nexin links per cilium were 1.1-1.4, in the third group 0.8-1.2, per patient. The median number of IDA was in the control group 4.2, range 3.3-5.2. In groups 2 and 3 the numbers were 3.0-3.5 and 0.2-1.0, respectively. Numbers of ODA were normal in all groups.

CONCLUSIONS

It is possible to reliable count the number of nexin links in nasal human cilia and to distinguish cases with missing nexin links from normal controls.

Impact of cilia ultrastructural examination on the diagnosis of primary ciliary dyskinesia

Ultrastructural examination of cilia is the "gold standard" for diagnosing primary ciliary dyskinesia. There is little evidence suggesting the most effective method of procuring a ciliary biopsy and scant benchmark data on rates of conclusive biopsies or on the diagnostic impact of such biopsies. To critically assess rates of inconclusive, positive, and negative ciliary biopsies and to identify clinical factors associated with conclusive results, we reviewed ciliary biopsies submitted for electron microscopy from 2006 to 2011, noting whether specimens were adequate for analysis and whether the ciliary structure was normal. The biopsy site, method used, procedurist's specialty, and clinical diagnoses were determined. Biopsy findings were categorized by diagnostic impact. Over 5 years, 187 patients had 211 biopsies. Conclusive results were obtained on 133/211 biopsies (63%); the remainder were insufficient. The rate of inconclusive biopsies did not vary significantly (P > 0.05; Fisher's exact) among sampling methods. Abnormal results were identified in 8/133 (6.0%) of the adequate specimens. Forceps compared to brush biopsies (abnormal in 4/12 versus 4/121 of the adequate specimens, P  =  0.002), along with multiple biopsy samples (taken on same or different days) compared with a single biopsy sample (abnormal in 3/12 versus 1/110 of the adequate specimens, P  =  0.01), were more likely to yield an abnormal result. Only 63% of pediatric ciliary biopsies provide adequate morphology for analysis, the large majority of these samples showing normal ciliary anatomy. The method of obtaining biopsies did not significantly affect result conclusiveness. Understanding the diagnostic impact of ultrastructural analysis is important as new diagnostic algorithms are developed for primary ciliary dyskinesia.

The structural heterogeneity of radial spokes in cilia and flagella is conserved

Radial spokes (RSs) are ubiquitous components of motile cilia and flagella and play an essential role in transmitting signals that regulate the activity of the dynein motors, and thus ciliary and flagellar motility. In some organisms, the 96 nm axonemal repeat unit contains only a pair of spokes, RS1 and RS2, while most organisms have spoke triplets with an additional spoke RS3. The spoke pairs in Chlamydomonas flagella have been well characterized, while spoke triplets have received less attention. Here, we used cryoelectron tomography and subtomogram averaging to visualize the three-dimensional structure of spoke triplets in Strongylocentrotus purpuratus (sea urchin) sperm flagella in unprecedented detail. Only small differences were observed between RS1 and RS2, but the structure of RS3 was surprisingly unique and structurally different from the other two spokes. We observed novel doublet specific features that connect RS2, RS3, and the nexin-dynein regulatory complex, three key ciliary and flagellar structures. The distribution of these doublet specific structures suggests that they could be important for establishing the asymmetry of dynein activity required for the oscillatory movement of cilia and flagella. Surprisingly, a comparison with other organisms demonstrated both that this considerable RS heterogeneity is conserved and that organisms with RS pairs contain the basal part of RS3. This conserved RS heterogeneity may also reflect functional differences between the spokes and their involvement in regulating ciliary and flagellar motility.

Epithelial sodium channels (ENaC) are uniformly distributed on motile cilia in the oviduct and the respiratory airways

Epithelial sodium channels (ENaCs) are located on the apical surface of cells and funnel Na(+) ions from the lumen into the cell. ENaC function also regulates extracellular fluid volume as water flows across membranes accompanying Na(+) ions to maintain osmolarity. To examine the sites of expression and intracellular localization of ENaC, we generated polyclonal antibodies against the extracellular domain of human α-ENaC subunit that we expressed in E. coli. Three-dimensional (3D) confocal microscopy of immunofluorescence using these antibodies for the first time revealed that ENaCs are uniformly distributed on the ciliary surface in all epithelial cells with motile cilia lining the bronchus in human lung and female reproductive tract, all along the fimbrial end of the fallopian tube, the ampulla and rare cells in the uterine glands. Quantitative analysis indicated that cilia increase cell surface area >70-fold and the amount of ENaC on cilia is >1,000-fold higher than on non-ciliated cell surface. These findings indicate that ENaC functions as a regulator of the osmolarity of the periciliary fluid bathing the cilia. In contrast to ENaC, cystic fibrosis transmembrane conductance regulator (CFTR) that channels chloride ions from the cytoplasm to the lumen is located mainly on the apical side, but not on cilia. The cilial localization of ENaC requires reevaluation of the mechanisms of action of CFTR and other modulators of ENaC function. ENaC on motile cilia should be essential for diverse functions of motile cilia, such as germ cell transport, fertilization, implantation, clearance of respiratory airways and cell migration.

Ultrastructural pathology of primary ciliary dyskinesia: report about 125 cases in Germany

Background

Primary ciliary dyskinesia (PCD) is a rare genetically induced disorder of cilia inducing mainly respiratory diseases. Transmission electron microscopy (TEM) analysis of ciliary ultrastructure is classically used for diagnosis. We report our experience of TEM investigations in a large series of patients.

Methods

TEM analysis performed of 742 biopsies from patients with suspected PCD was reviewed retrospectively. Ultrastructural defects were analysized further in 125 cases with changes typical for PCD.

Results

In 18.1% of patients diagnosis of PCD was made because of morphological alterations, in 68.2% secondary changes were seen. In 13.7% material was not feasible for analysis. Mostly defects of dynein arms were detected in PCD (96.8%). In particular defects of the inner arms (51.2%) and combined dynein defects (37.6%) were found. Total loss of dynein arms was dominant. Only in 3.2% deficiencies of central structures were found alone. Associated situs inversus or dextracardia was reported clinically in 21.4%.

Conclusions

TEM analysis is possible in most patients and a useful tool for diagnosis of PCD. Functional and genetic analysis should be done additionally. Registers should be installed to collect all available informations and push further research.

[Primary ciliary dyskinesia: a retrospective review of clinical and paraclinical data]

INTRODUCTION

Primary ciliary dyskinesia (PCD) is an inherited disease responsible for a disruption of normal ciliary function. Its clinical presentation is usually in early childhood with pulmonary and otorhinolaryngologic symptoms. Early diagnosis is essential to avoid the development of bronchiectasis. The aim of the study was to retrospectively review the clinical features of children suspected to have PCD.

RESULTS

A total of 89 children had a bronchoscopy to perform a biopsy analyzed by transmission electron microscopy (TEM) in the childrens' hospital of Rennes between 2000 and 2009. PCD was diagnosed in 17 children, excluded in 51 and results were uncertain in 21 children. Mean age at diagnosis was 6.5 years. In the PCD group, a history of neonatal respiratory distress was found in 40% of cases, 82% had had bronchopneumonia, 37% sinusitis, 82% recurrent otitis and 23% situs inversus. These subjects had defects in ciliary structure, 59% in the dynein arms, 35% in the central complex and 6% having both. Nasal nitric oxide production was consistent with the results of TEM in 16 cases: five PCD, 11 without PCD. In two cases, the results were discordant.

CONCLUSION

This case series highlights the key clinical features of recurrent otitis, sinusitis, and situs inversus, especially when occurring in combination with bronchitic symptoms. Measures of nasal nitric oxide are useful for the diagnosis of PCD and in the case of high levels of NO, PCD is unlikely. Results may not be definitive and TEM analysis of biopsies is still indispensable to ensure the diagnosis and guide genetic counselling.

Primary ciliary dyskinesia: evaluation using cilia beat frequency assessment via spectral analysis of digital microscopy images

Ciliary beat frequency (CBF) measurements provide valuable information for diagnosing of primary ciliary dyskinesia (PCD). We developed a system for measuring CBF, used it in association with electron microscopy to diagnose PCD, and then analyzed characteristics of PCD patients. The CBF measurement system was based on power spectra measured through digital imaging. Twenty-four patients suspected of having PCD (age 1-19 yr) were selected from a group of 75 children and adolescents with pneumopathies of unknown causes. Ten healthy, nonsmoking volunteers (age ≥ 17 yr) served as a control group. Nasal brush samples were collected, and CBF and electron microscopy were performed. PCD was diagnosed in 12 patients: 5 had radial spoke defects, 3 showed absent central microtubule pairs with transposition, 2 had outer dynein arm defects, 1 had a shortened outer dynein arm, and 1 had a normal ultrastructure. Previous studies have reported that the most common cilia defects are in the dynein arm. As expected, the mean CBF was higher in the control group (P < 0.001) and patients with normal ultrastructure (P < 0.002), than in those diagnosed with cilia ultrastructural defects (i.e., PCD patients). An obstructive ventilatory pattern was observed in 70% of the PCD patients who underwent pulmonary function tests. All PCD patients presented bronchial wall thickening on chest computed tomography scans. The protocol and diagnostic techniques employed allowed us to diagnose PCD in 16% of patients in this study.

Diagnostic yield of nasal scrape biopsies in primary ciliary dyskinesia: a multicenter experience

Examination of ciliary ultrastructure remains the cornerstone diagnostic test for primary ciliary dyskinesia (PCD), a disease of abnormal ciliary structure and/or function. Obtaining a biopsy with sufficient interpretable cilia and producing quality transmission electron micrographs (TEM) is challenging. Methods for processing tissues for optimal preservation of axonemal structures are not standardized. This study describes our experience using a standard operating procedure (SOP) for collecting nasal scrape biopsies and processing TEMs in a centralized laboratory. We enrolled patients with suspected PCD at research sites of the Genetic Disorders of Mucociliary Clearance Consortium. Biopsies were performed according to a SOP whereby curettes were used to scrape the inferior surface of the inferior turbinate, with samples placed in fixative. Specimens were shipped to a central laboratory where TEMs were prepared and blindly reviewed. Four hundred forty-eight specimens were obtained from 107 young children (0-5 years), 189 older children (5-18 years), and 152 adults (> 18 years), and 88% were adequate for formal interpretation. The proportion of adequate specimens was higher in adults than in children. Fifty percent of the adequate TEMs showed normal ciliary ultrastructure, 39% showed hallmark ultrastructural changes of PCD, and 11% had indeterminate findings. Among specimens without clearly normal ultrastructure, 72% had defects of the outer and/or inner dynein arms (IDA), while 7% had central apparatus defects with or without IDA defects. In summary, nasal scrape biopsies can be performed in the outpatient setting and yield interpretable samples, when performed by individuals with adequate training and experience according to an SOP.

[What is new in 2010 for electron microscopy in surgical pathology?]

Différentes méthodes complémentaires permettant d’optimiser le diagnostic et le pronostic des lésions observées dans un laboratoire d’anatomopathologie ont permis, ces dernières années, d’améliorer considérablement l’offre de soins aux patients. Ces méthodes correspondent essentiellement aux techniques d’immuno-histochimie et de biologie moléculaire. La place d’une autre technique autrefois largement utilisée en anatomopathologie, la microscopie électronique (ME), est à l’inverse de plus en plus restreinte. La ME est une méthode longue, difficile, onéreuse, nécessitant un personnel hautement qualifié. Elle est de moins en moins implantée dans un laboratoire de pathologie et devient surtout réservée à des centres universitaires et de recherche. Toutefois, la ME reste un outil indispensable pour le pathologiste. En effet, elle permet parfois de confirmer, et plus exceptionnellement de poser, le diagnostic de certaines lésions tissulaires et cellulaires observées en pathologie humaine. La ME est aussi d’un apport très important pour la compréhension de la physiopathologie de certaines maladies humaines émergentes, notamment d’origine infectieuse. Nous abordons dans cette revue les principales indications actuelles de la ME, en insistant sur certains domaines de la pathologie humaine, comme les maladies infectieuses et certaines tumeurs.