Loss of an extensive ciliary connectome induces proteostasis and cell fate switching in a severe motile ciliopathy

Motile cilia have essential cellular functions in development, reproduction, and homeostasis. Genetic causes for motile ciliopathies have been identified, but the consequences on cellular functions beyond impaired motility remain unknown. Variants in CCDC39 and CCDC40 cause severe disease not explained by loss of motility. Using human cells with pathological variants in these genes, Chlamydomonas genetics, cryo-electron microscopy, single cell RNA transcriptomics, and proteomics, we identified perturbations in multiple cilia-independent pathways. Absence of the axonemal CCDC39/CCDC40 heterodimer results in loss of a connectome of over 90 proteins. The undocked connectome activates cell quality control pathways, switches multiciliated cell fate, impairs microtubule architecture, and creates a defective periciliary barrier. Both cilia-dependent and independent defects are likely responsible for the disease severity. Our findings provide a foundation for reconsidering the broad cellular impact of pathologic variants in ciliopathies and suggest new directions for therapies.

Incorporating a Three-Dimensional Printed Airway into a Pediatric Flexible Bronchoscopy Curriculum

Background

Although hands-on simulation plays a valuable role in procedural training, there are limited tools available to teach pediatric flexible bronchoscopy (PFB). Fellowship programs rely on patient encounters, with inherent risk, or high-cost virtual reality simulators that may not be widely available and create education inequalities.

Objective

Our objective was to study the educational value and transferability of a novel, low-cost, three-dimensional-printed pediatric airway model (3D-AM) for PFB training. Our central hypothesis was that the 3D-AM would have high educational value and would be easily transferrable to learners at different teaching hospitals.

Methods

The 3D-AM was designed to teach technical bronchoscopy skills, airway anatomy, airway pathology, and bronchoalveolar lavage (BAL). The curriculum was offered to incoming fellows in pediatric pulmonology, pediatric surgery, and pediatric critical care across three different teaching institutions. After course completion, each participant assessed the simulation model(s) with a 5-point Likert scale across six domains: physical attributes, realism of experience, ability to perform tasks, value, relevance, and global impression. The expert instructors assessed the learners' competency using a modified version of the Bronchoscopy Skills and Tasks Assessment Tool.

Results

A total of 14 incoming fellows participated in the course. The mean scores for the 3D-AM across all six domains and across the three institutions was between 4 and 5, suggesting that learners generally had a favorable impression and a similar experience across different institutions. All learners "agreed" or "strongly agreed" that the course was a valuable use of their time, helped teach technical skills and airway anatomy, and would be useful for extra training during fellowship. Most of the learners correctly identified anatomy, bronchomalacia, and performed a BAL. Wall trauma was observed in 36% of learners.

Conclusion

The utility, low cost, and transferability of this model may create opportunities for PFB training across different institutions despite resource limitations in the United States and abroad.

A multi-disciplinary, comprehensive approach to management of children with heterotaxy

Heterotaxy (HTX) is a rare condition of abnormal thoraco-abdominal organ arrangement across the left-right axis of the body. The pathogenesis of HTX includes a derangement of the complex signaling at the left-right organizer early in embryogenesis involving motile and non-motile cilia. It can be inherited as a single-gene disorder, a phenotypic feature of a known genetic syndrome or without any clear genetic etiology. Most patients with HTX have complex cardiovascular malformations requiring surgical intervention. Surgical risks are relatively high due to several serious comorbidities often seen in patients with HTX. Asplenia or functional hyposplenism significantly increase the risk for sepsis and therefore require antimicrobial prophylaxis and immediate medical attention with fever. Intestinal rotation abnormalities are common among patients with HTX, although volvulus is rare and surgical correction carries substantial risk. While routine screening for intestinal malrotation is not recommended, providers and families should promptly address symptoms concerning for volvulus and biliary atresia, another serious morbidity more common among patients with HTX. Many patients with HTX have chronic lung disease and should be screened for primary ciliary dyskinesia, a condition of respiratory cilia impairment leading to bronchiectasis. Mental health and neurodevelopmental conditions need to be carefully considered among this population of patients living with a substantial medical burden. Optimal care of children with HTX requires a cohesive team of primary care providers and experienced subspecialists collaborating to provide compassionate, standardized and evidence-based care. In this statement, subspecialty experts experienced in HTX care and research collaborated to provide expert- and evidence-based suggestions addressing the numerous medical issues affecting children living with HTX.

Clinical Outcomes of Acute Respiratory Failure Associated With Noninvasive and Invasive Ventilation in a Pediatric ICU

BACKGROUND

It remains unknown if pediatric patients failing initial noninvasive ventilation (NIV) experience worse clinical outcomes than those successfully treated with NIV or those primarily intubated.

METHODS

This was a single-center, retrospective review of patients admitted with acute respiratory failure to the University of Michigan pediatric intensive care or cardiothoracic ICUs and receiving NIV or invasive mechanical ventilation as first-line therapy.

RESULTS

One hundred seventy subjects met inclusion criteria and were enrolled: 65 NIV success, 55 NIV failure, and 50 invasive mechanical ventilation alone. Of those failing NIV, median time to intubation was 1.8 (interquartile range [IQR] < 1-7) h. On multivariable regression, ICU-free days were significantly different between groups (NIV success: 22.9 ± 6.9 d; NIV failure: 13.0 ± 6.6 d; invasive ventilation: 12.5 ± 6.9 d; P < .001 across all groups). Multivariable regression revealed no difference in ventilator-free days between NIV failure and invasive ventilation groups (15.4 ± 10.1 d vs 15.9 ± 9.7 d, P = .71). Of 64 subjects (37.6%) meeting Pediatric Acute Lung Injury Consensus Conference pediatric ARDS criteria, only 14% were successfully treated with NIV. Ventilator-free days were similar between the NIV failure and invasive ventilation groups (11.6 vs 13.2 d, P = .47). On multivariable analysis, ICU-free days were significantly different across pediatric ARDS groups (P < .001): NIV success: 20.8 + 31.7 d; NIV failure: 8.3 + 23.8 d; invasive alone: 8.9 + 23.9 d, yet no significant difference in ventilator-free days between those with NIV failure versus invasive alone (11.6 vs 13.2 d, P = .47).

CONCLUSIONS

We demonstrated that critically ill pediatric subjects unsuccessfully trialed on NIV did not experience increased ICU length of stay or fewer ventilator-free days when compared to those on invasive mechanical ventilation alone, including in the pediatric ARDS subgroup. Our findings are predicated on a median time to intubation of < 2 h in the NIV failure group and the provision of adequate monitoring while on NIV.

Case Report: A Relatively Mild Presentation of Unilateral Congenital Pulmonary Lymphangiectasia

Pulmonary lymphangiectasia (PL) is a rare congenital disorder of pulmonary lymphatic development. Although it was traditionally a fatal disorder of infancy, some cases in later childhood have been reported, suggesting a spectrum of severity. We present an unusual case of unilateral, congenital pulmonary lymphangiectasia. Our patient presented with neonatal respiratory distress, a chronic wet cough and recurrent episodes of bronchitis. Chest CT revealed thickening of the interlobular septae of the right lung. A lung biopsy confirmed the diagnosis of lymphangiectasia. His clinical course is characterized by chronic coughing and recurrent bronchitis but normal growth and development. This case illustrates a relatively mild presentation of unilateral PL, which, along with other reports, suggests variability in the presentation and severity of this disorder. In the absence of imaging and histological examination, mild presentations may go undiagnosed.

Phenotypic features of ciliary dyskinesia among patients with congenital cardiovascular malformations

BACKGROUND

Cilia are cell membrane-bound organelles responsible for airway mucus clearance, establishment of left-right organ asymmetry, cardiogenesis, and many other functions in utero. Phenotypic features suggestive of respiratory ciliary dyskinesia among patients with heterotaxy syndrome, defined as complex cardiovascular malformations (CVM) and situs ambiguus (SA), has not been adequately explored.

OBJECTIVES

We hypothesized that there is a greater incidence of phenotypic features consistent with ciliary dyskinesia among patients with heterotaxy syndrome compared to patients with other CVM and laterality defects without heterotaxy syndrome.

METHODS

Thirty six subjects were identified by medical record search and divided into four groups based on situs status and type of CVM as follows: SA and complex CVM (group 1); SA and simple CVM (group 2); situs solitus and complex CVM (group 3); and situs solitus and simple CVM (group 4). Phenotype was assessed with a clinical questionnaire, nasal nitric oxide (NO) level, and pulmonary function testing. Those with complex CVM underwent additional testing for variants in genes involved in ciliary structure and function.

RESULTS

The mean nasal NO level was significantly lower among all subjects with complex CVM regardless of situs anomalies (groups 1 and 3). There was no significant difference in respiratory symptoms or lung function among the four groups. No bi-allelic genetic mutations were detected among patients with complex CVM.

CONCLUSIONS

This study identified a relatively lower mean nasal NO level, suggestive of relative ciliary dyskinesia, among subjects with complex CVM. Pulmonary function and clinical symptoms did not reflect significant pulmonary disease among those with complex CVM.

A simulation procedure curriculum to increase pediatric resident exposure to procedures rarely performed in clinical practice

BACKGROUND

Pediatrics residents are expected by the Accreditation Council for Graduate Medical Education to competently perform 13 procedures. However, residents are graduating with poor self-perceived competency for these procedures.

OBJECTIVE

We developed a curriculum using simulation training at the beginning of internship and 'refresher' workshops throughout the year in order to increase procedure exposure and improve self-perceived competency.

DESIGN

Procedural workshops were taught during intern orientation and to all pediatrics residents throughout the academic year. Residents provided a quantitative competency self-assessment before and after each workshop; interns provided an additional self-assessment at the end of the intern year.

RESULTS

The curriculum was well-liked and led to more procedural experience. Mean competency self-assessment scores improved immediately after almost every procedure workshop. Mean scores were retained at the end of intern year for most procedures. However, end-of-year mean competency self-assessment and procedural experience on actual patients were similar to interns from a previous year that had not participated in the curriculum.

CONCLUSIONS

A pre-internship procedure workshop coupled with longitudinal workshops is a feasible way to improve intern exposure to pediatric procedural training. However, it was not sufficient to improve mean competency self-assessments compared to a traditional model of bedside procedural training.

Pre-clinical medical student experience in a pediatric pulmonary clinic

OBJECTIVE

Our objective was to evaluate the educational value of introducing pre-clinical medical students to pediatric patients and their families in a subspecialty clinic setting.

METHODS

First- and second-year medical students at the University of Michigan seeking clinical experience outside of the classroom attended an outpatient pediatric pulmonary clinic. Evaluation of the experience consisted of pre- and post-clinic student surveys and post-clinic parent surveys with statements employing a four-point Likert scale as well as open-ended questions.

RESULTS

Twenty-eight first-year students, 6 second-year students, and 33 parents participated in the study. Post-clinic statement scores significantly increased for statements addressing empathic attitudes, confidence communicating with children and families, comfort in the clinical environment, and social awareness. Scores did not change for statements addressing motivation, a sense of team membership, or confidence with career goals. Students achieved their goals of gaining experience interacting with patients, learning about pulmonary diseases, and observing clinic workflow. Parents felt that they contributed to student education and were not inconvenienced.

CONCLUSIONS

Students identified several educational benefits of exposure to a single pediatric pulmonary clinic. Patients and families were not inconvenienced by the participation of a student. Additional studies are warranted to further investigate the value of this model of pre-clinical medical student exposure to subspecialty pediatrics.

Rhinovirus-induced macrophage cytokine expression does not require endocytosis or replication

Rhinovirus (RV) is responsible for the majority of virus-induced asthma exacerbations. We showed previously that RV infection of ovalbumin-sensitized and -challenged BALB/c mice induces production of type 2 cytokines from M2-polarized macrophages. In the present study, we sought to determine the mechanism of RV-induced cytokine expression. We infected bone marrow-derived macrophages (BMMs) from BALB/c mice with RV serotype 1B, a minor group virus that infects mouse cells. Selected cultures were pretreated with IL-4, a type 2 cytokine increased in allergic asthma. RV infection of untreated cells increased messenger RNA and protein expression of the M1 cytokines TNF-α, CXCL1, and IL-6 but failed to induce expression of the M2 cytokines CCL22 and CCL24. Cells pretreated with IL-4 showed decreased expression of M1 cytokines but increased expression of Ym-1, Arg-1 (M2 markers), CCL22, and CCL24. Infection with ultraviolet (UV)-irradiated, replication-deficient RV elicited similar cytokine responses, suggesting that the outcome is replication independent. Consistent with this, viral RNA copy number did not increase in RV-treated BMMs or bronchoalveolar macrophages. RV-induced cytokine expression was not affected when cells were pretreated with cytochalasin D, suggesting that viral endocytosis is not required for the response. Finally, RV-induced cytokine expression and viral attachment were abolished in BMMs from myeloid differentiation factor 88 and Toll-like receptor (TLR)2 KO mice, suggesting a specific requirement of TLR2. We conclude that RV elicits a proinflammatory cytokine response in BMMs through a cell-surface-mediated, TLR2-dependent mechanism that does not require viral endocytosis or replication.

A randomized controlled trial of isotonic versus hypotonic maintenance intravenous fluids in hospitalized children

Background

Isotonic saline has been proposed as a safer alternative to traditional hypotonic solutions for intravenous (IV) maintenance fluids to prevent hyponatremia. However, the optimal tonicity of maintenance intravenous fluids in hospitalized children has not been determined. The objective of this study was to estimate and compare the rates of change in serum sodium ([Na]) for patients administered either hypotonic or isotonic IV fluids for maintenance needs.

Methods

This was a masked controlled trial. Randomization was stratified by admission type: medical patients and post-operative surgical patients, aged 3 months to 18 years, who required IV fluids for at least 8 hours. Patients were randomized to receive either 0.45% or 0.9% saline in 5.0% dextrose. Treating physicians used the study fluid for maintenance; infusion rate and the use of additional fluids were left to their discretion.

Results

Sixteen children were randomized to 0.9% saline and 21 to 0.45% saline. Baseline characteristics, duration (average of 12 hours) and rate of study fluid infusion, and the volume of additional isotonic fluids given were similar for the two groups. [Na] increased significantly in the 0.9% group (+0.20 mmol/L/h [IQR +0.03, +0.4]; P = 0.02) and increased, but not significantly, in the 0.45% group (+0.08 mmol/L/h [IQR -0.15, +0.16]; P = 0.07). The rate of change and absolute change in serum [Na] did not differ significantly between groups.

Conclusions

When administered at the appropriate maintenance rate and accompanied by adequate volume expansion with isotonic fluids, 0.45% saline did not result in a drop in serum sodium during the first 12 hours of fluid therapy in children without severe baseline hyponatremia. Confirmation in a larger study is strongly recommended.

Clinical Trial Registration Number

NCT00457873 (http://www.clinicaltrials.gov/)

An atypical form of erythrokeratodermia variabilis maps to chromosome 7q22

Erythrokeratodermia variabilis 3 (Kamouraska type) or EKV3 is a newly described autosomal recessive disorder observed in patients from the Bas St-Laurent region of Quebec. It has similar skin lesions as observed for EKV, including congenital hyperkeratosis and red patches of variable sizes, shapes, and duration. EKV3 is also characterized by ichthyosis, sensorineural hearing loss, peripheral neuropathy, psychomotor retardation, congenital chronic diarrhea, and an elevation of very long chain fatty acids (VLCFAs). To map the disease locus, we performed candidate gene analysis and a genomewide scan to identify a common homozygous region in affected individuals from three non-consanguineous families. Mutations in connexin 31 (GJB3) and connexin 30.3 (GJB4), implicated in previous reports of EKV, and connexin 26 (GJB2), implicated in palmoplantar keratoderma, were unlikely given the lack of shared homozygous haplotypes in the regions surrounding these genes. The most promising region of common homozygosity observed in a 4,600 single-nucleotide polymorphism genome scan was further characterized by using microsatellites. A 6.8-Mb region on chromosome 7 between D7S2539 and rs727708 was found to be homozygous for the same haplotype in all affected individuals but not in the parents or an unaffected sibling. This region contains connexin 31.3 (GJE1), and although no mutation have been observed in the coding region of this gene, further analyses are required in order to exclude it. Identification of the gene responsible for this disorder will provide insights into the etiology of this multisystemic disorder.