Nasal ciliary function and ultrastructure in Down syndrome

Down syndrome is associated with altered frequency and functioning of tracheal multiciliated cells, and response to influenza virus infection

Individuals with Down syndrome (DS) clinically manifest severe respiratory illnesses; however, there is a paucity of data on how DS influences homeostatic physiology of lung airway, and its reactive responses to pulmonary pathogens. We generated well-differentiated ciliated airway epithelia using tracheas from wild-type and Dp(16)1/Yey mice in vitro, and discovered that Dp(16)1/Yey epithelia have significantly lower abundance of ciliated cells, an altered ciliary beating profile, and reduced mucociliary transport. Interestingly, both sets of differentiated epithelia released similar quantities of viral particles after infection with influenza A virus (IAV). However, RNA-sequencing and proteomic analyses revealed an immune hyperreactive phenotype particularly for monocyte-recruiting chemokines in Dp(16)1/Yey epithelia. Importantly, when we challenged mice in vivo with IAV, we observed immune hyper-responsiveness in Dp(16)1/Yey mice, evidenced by higher quantities of lung airway infiltrated monocytes, and elevated levels of pro-inflammatory cytokines in bronchoalveolar lavage fluid. Our findings illuminate mechanisms underlying DS-mediated pathophysiological changes in airway epithelium.

A Multimodal Imaging-Supported Down Syndrome Mouse Model of RSV Infection

Individuals with Down syndrome (DS) are more prone to develop severe respiratory tract infections. Although a RSV infection has a high clinical impact and severe outcome in individuals with DS, no vaccine nor effective therapeutics are available. Any research into infection pathophysiology or prophylactic and therapeutic antiviral strategies in the specific context of DS would greatly benefit this patient population, but currently such relevant animal models are lacking. This study aimed to develop and characterize the first mouse model of RSV infection in a DS-specific context. Ts65Dn mice and wild type littermates were inoculated with a bioluminescence imaging-enabled recombinant human RSV to longitudinally track viral replication in host cells throughout infection progression. This resulted in an active infection in the upper airways and lungs with similar viral load in Ts65Dn mice and euploid mice. Flow cytometric analysis of leukocytes in lungs and spleen demonstrated immune alterations with lower CD8+ T cells and B-cells in Ts65Dn mice. Overall, our study presents a novel DS-specific mouse model of hRSV infection and shows that potential in using the Ts65Dn preclinical model to study immune-specific responses of RSV in the context of DS and supports the need for models representing the pathological development.

Down Syndrome for the Otolaryngologist: A Review

Importance

There are many features of Down syndrome that prompt referral to an otolaryngologist. As the lifetime prevalence and life expectancy of individuals with Down syndrome increase, it is increasingly likely that otolaryngologists will have the opportunity to care for patients with Down syndrome.

Observations

A confluence of characteristics common to Down syndrome may be associated with issues in the head and neck, from infancy through adulthood. Hearing concerns range from narrow ear canals and cerumen impactions to eustachian tube dysfunction, middle ear effusion, cochlear malformations, and conductive, sensorineural, and/or mixed hearing loss. Immune deficiency, hypertrophy of Waldeyer ring, and hypoplastic sinuses may complicate and develop into chronic rhinosinusitis. Speech delay, obstructive sleep apnea, dysphagia, and airway anomalies are also common among this patient population. Because these concerns may necessitate otolaryngologic surgery, it is vital for otolaryngologists to familiarize themselves with anesthetic concerns, including cervical spine instability, in patients with Down syndrome. Comorbid cardiac disease, hypothyroidism, and obesity may also affect these patients and otolaryngologic care.

Conclusions and Relevance

Individuals with Down syndrome may visit otolaryngology practices at all ages. Otolaryngologists that familiarize themselves with the head and neck manifestations that are common among patients with Down syndrome and know when to order screening tests will be able to provide comprehensive care.

Down Syndrome: A Review of Key Perioperative Implications

Down syndrome (DS) is the most common chromosomal abnormality in humans that is compatible with life. This syndrome occurs when there is an extra copy of the 21st chromosome. Down syndrome is associated with numerous comorbidities that can pose challenges for the perioperative nurse caring for a patient with DS undergoing surgery. These challenges can affect the patient assessment, communication with the patient, and patient safety (eg, preventing complications). As the life expectancy of people with DS has increased, so too have the chances that perioperative nurses will care for a patient with this disorder. This article reviews the pathophysiology of DS, discusses common comorbidities that may directly affect perioperative care, and reviews an exemplar case study that demonstrates how personnel with knowledge of DS can positively influence surgical team decision making for these patients in the perioperative setting.

Lung disease manifestations in Down syndrome

Down syndrome (DS) is one of the most prevalent chromosomal abnormalities worldwide, affecting 1 in 700 live births. Although multiple organ systems are affected by the chromosomal defects, respiratory failure and lung disease are the leading causes of morbidity and mortality observed in DS. Manifestations of DS in the respiratory system encompass the entire lung starting from the nasopharynx to the trachea/upper airways to the lower airways and alveolar spaces, as well as vascular and lymphatic defects. Most of our knowledge on respiratory illness in persons with DS arises from pediatric studies; however, many of these disorders present early in infancy, supporting developmental mechanisms. In this review, we will focus on the different lung phenotypes in DS, as well as the genetic and molecular pathways that may be contributing to these complications during development.

Airway Ciliary Beating Affected by the Pcp4 Dose-Dependent [Ca2+]i Increase in Down Syndrome Mice, Ts1Rhr

In Ts1Rhr, a Down syndrome model mouse, the airway ciliary beatings are impaired; that is, decreases in ciliary beat frequency (CBF) and ciliary bend angle (CBA, an index of ciliary beat amplitude)). A resumption to two copies of the Pcp4 gene on the Ts1Rhr trisomic segment (Ts1Rhr:Pcp4^+/+/-) rescues the decreases in CBF and CBA that occur in Ts1Rhr. In airway cilia, upon stimulation with procaterol (a β₂-agonist), the CBF increase is slower over the time course than the CBA increase because of cAMP degradation by Ca²⁺/calmodulin-dependent phosphodiesterase 1 (PDE1) existing in the metabolon regulating CBF. In Ts1Rhr, procaterol-stimulated CBF increase was much slower over the time course than in the wild-type mouse (Wt) or Ts1Rhr:Pcp4^+/+/-. However, in the presence of 8MmIBMX (8-methoxymethyl isobutylmethyl xanthine, an inhibitor of PDE1) or calmidazolium (an inhibitor of calmodulin), in both Wt and Ts1Rhr, procaterol stimulates CBF and CBA increases over a similar time course. Measurements of cAMP revealed that the cAMP contents were lower in Ts1Rhr than in Wt or in Ts1Rhr:Pcp4^+/+/-, suggesting the activation of PDE1A that is present in Ts1Rhr airway cilia. Measurements of the intracellular Ca²⁺ concentration ([Ca²⁺]_i) in airway ciliary cells revealed that temperature (increasing from 25 to 37 °C) or 4αPDD (a selective transient receptor potential vanilloid 4 (TRPV4) agonist) stimulates a larger [Ca²⁺]_i increase in Ts1Rhr than in Wt or Ts1Rhr:Pcp4^+/+/-. In airway ciliary cells of Ts1Rhr, Pcp4-dose dependent activation of TRPV4 appears to induce an increase in the basal [Ca²⁺]_i. In early embryonic day mice, a basal [Ca²⁺]_i increased by PCP4 expressed may affect axonemal regulatory complexes regulated by the Ca²⁺-signal in Ts1Rhr, leading to a decrease in the basal CBF and CBA of airway cilia.

Trisomy 21 Represses Cilia Formation and Function

Trisomy 21 (T21) is the most prevalent human chromosomal disorder, causing a range of cardiovascular, musculoskeletal, and neurological abnormalities. However, the cellular processes disrupted by T21 are poorly understood. Consistent with the clinical overlap between T21 and ciliopathies, we discovered that T21 disrupts cilia formation and signaling. Cilia defects arise from increased expression of Pericentrin, a centrosome scaffold and trafficking protein encoded on chromosome 21. Elevated Pericentrin is necessary and sufficient for T21 cilia defects. Pericentrin accumulates at centrosomes and dramatically in the cytoplasm surrounding centrosomes. Centrosome Pericentrin recruits more γ-tubulin and enhances microtubules, whereas cytoplasmic Pericentrin assembles into large foci that do not efficiently traffic. Moreover, the Pericentrin-associated cilia assembly factor IFT20 and the ciliary signaling molecule Smoothened do not efficiently traffic to centrosomes and cilia. Thus, increased centrosome protein dosage produces ciliopathy-like outcomes in T21 cells by decreasing trafficking between the cytoplasm, centrosomes, and cilia.

The evaluation and management of respiratory disease in children with Down syndrome (DS)

Children with Down syndrome (DS) have wide range of respiratory problems. Although underlying abnormalities in the respiratory system are important causes of morbidity and mortality in children with DS, particularly in the young, abnormalities in other organ systems may also impact respiratory function. A comprehensive evaluation of the child with DS and respiratory disease may prevent short-term morbidity and mortality, and reduce the incidence of complications in the long term. This review provides an overview of the various causes of respiratory disease, and insight into some of the newer therapies available to treat obstructive sleep apnea, in this population.

What people with Down Syndrome can teach us about cardiopulmonary disease

Down syndrome is the most common chromosomal abnormality among live-born infants. Through full or partial trisomy of chromosome 21, Down syndrome is associated with cognitive impairment, congenital malformations (particularly cardiovascular) and dysmorphic features. Immune disturbances in Down syndrome account for an enormous disease burden ranging from quality-of-life issues (autoimmune alopecia) to more serious health issues (autoimmune thyroiditis) and life-threatening issues (leukaemia, respiratory tract infections and pulmonary hypertension). Cardiovascular and pulmonary diseases account for ∼75% of the mortality seen in persons with Down syndrome. This review summarises the cardiovascular, respiratory and immune challenges faced by individuals with Down syndrome, and the genetic underpinnings of their pathobiology. We strongly advocate increased comparative studies of cardiopulmonary disease in persons with and without Down syndrome, as we believe these will lead to new strategies to prevent and treat diseases affecting millions of people worldwide.

An overview of respiratory problems in children with Down's syndrome

Respiratory disease is a common cause of morbidity and mortality in children with Down's syndrome (DS). Causes range from those problems common to many children with DS, such as a narrow airway or impaired immunity, to rare structural lesions, such as tracheal bronchus. Additionally, other organ systems or extrinsic factors may play a role. A thorough understanding of the range of potential problems will aid in the evaluation and management of children with DS and respiratory symptoms.

[Anesthesiological considerations for patients with trisomy 21 (Down syndrome)]

The most common chromosomal abnormality is trisomy 21 which is also known as Down syndrome and occurs in approximately 1 in 800 births. The majority of the resulting disabling conditions cannot be cured and affect people of all ages, ethnicity and economic levels. Life expectancy has increased with advances in medical care in the same way as in the rest of the population. One of the major tasks for health care professionals is to help these differently abled children and their families function in the most effective way possible as they learn to accept the limitations imposed by a persistent disability. Signs and symptoms of trisomy 21 are very variable based on the trias of mental retardation to a variable degree, hand anomalies and cardiac complications. Other abnormalities are atlantoaxial instability (AAI), tracheal stenosis, a predisposition to respiratory complications, chronic hypothyroidism, microgenia and macroglossia. These conditions are relevant to anesthetic procedures and patients with Down syndrome and their families have specific expectations and attitudes towards medical and anesthetic treatment.

A scanning electron microscopic study of nasal respiratory epithelium in pregnant rats

Pregnancy is a very important period in mammals. Various morphological and functional changes can be observed. Some studies examining nasal epithelial structure deal with changes found in pregnancy. In this study, a total of 16 adult female Sprague Dawley rats (8 control and 8 pregnant) were used. They were anesthetized with ketamine and sacrificed via cardiac perfusion with 2.5%-glutaraldehyde solution (in 0.1 M sodium phosphate buffer, pH 7.4). The heads of the rats were bisected midsagittally and one half was completely passed through the routine histological procedures for SEM examination. On the apical surfaces of ciliated cells of pregnant rat respiratory epithelium disoriented cilia and cilia with dilated blebs at their free ends were observed. In addition, some masses of mucus due to hypersecretion were striking. Goblet cells appeared swollen and their apical surfaces showed microvilli varying considerably in length and number.

Nasal health in Down syndrome: a cross-sectional study

OBJECTIVE

To investigate peripheral nasal pathology as a contributor to olfactory impairment in DS.

STUDY DESIGN

Twenty DS and 16 non-DS subjects were recruited. Nasal history and symptoms were assessed by self-report or informant. Olfactory threshold, odor identification, and nasal endoscopy were assessed on each subject.

RESULTS

DS subjects were impaired on olfactory threshold (P<0.0001) and odor identification (P<0.001). Although DS subjects tended toward upper-respiratory infections, sleep-disordered breathing, and nasal itching, differences were not significant (P=0.07, 0.06, and 0.058, respectively). There were no significant differences on self-reported nasal history or symptoms. Endoscopy showed equivalent health in DS and control subjects.

CONCLUSION

This DS population shows olfactory impairment. However, nasal health is comparable in DS subjects and controls. Nasal dysfunction is unlikely to contribute to olfactory impairment in DS.

SIGNIFICANCE

Olfactory deficits in DS appear to be secondary to central, rather than rhinologic, pathology.

EBM RATING

B-2b.

Chronic rhinosinusitis in congenital craniofacial malformations

OBJECTIVES

To review developmental abnormalities and iatrogenic alterations in sinus anatomy that may predispose patients with congenital craniofacial malformations to chronic rhinosinusitis.

STUDY DESIGN

Retrospective study.

METHODS

Seven patients with craniofacial malformations who were surgically treated by the senior author were included in the study. All were diagnosed with chronic rhinosinusitis refractory to medical management. Four patients had undergone previous corrective craniofacial surgery, and three of these patients developed iatrogenic sinus disease. Demographic data, diagnoses and anatomical abnormalities were included.

RESULTS

Abnormal sinus anatomy was present in all patients, most commonly skull base abnormalities and dehiscent lamina papyracea. All patients underwent successful endoscopic surgical management (n = 7) for their chronic rhinosinusitis. Two patients had adjuvant external procedures. There were no complications and no recurrences after a mean follow up time of 15 months.

CONCLUSIONS

Otolaryngologists should be aware of the possibility of chronic rhinosinusitis in patients with craniofacial malformations. Careful preoperative evaluation of radiographic studies should be performed as most of these patients will have abnormal sinus anatomy. In addition, patients who undergo surgery to correct their craniofacial malformations are susceptible to altered sinus anatomy that may predispose them to the development of iatrogenic chronic rhinosinusitis.