Identifying Phenotypically Distinct Fibroblast Subsets in Type 2 Diabetes-Associated Iatrogenic Laryngotracheal Stenosis

Laser Versus Cold Steel for Endoscopic Management of Subglottic Stenosis

OBJECTIVE

Endoscopic management of subglottic stenosis (SGS) includes a wide range of techniques. This 17-year review compares treatment outcomes between carbon dioxide (CO2) laser and cold steel.

STUDY DESIGN

Retrospective chart review.

SETTING

Single tertiary care center.

METHODS

A chart review was performed for all patients undergoing endoscopic treatment of SGS at Cleveland Clinic between July 12, 2000 and September 1, 2017. Data collected included demographics, stenosis etiology, stenosis severity, comorbidities, treatment modality, and airway procedure history. The primary endpoint was repeated treatment-free survival (RTFS) within 2 years using a Kaplan-Meier analysis and Cox proportional hazard model.

RESULTS

A total of 139 patients (median [interquartile range] aged 48.7 [37.8, 57.0] years; 83.4% female) were included in the analysis, with etiologies including idiopathic (56.8%), granulomatosis with polyangiitis (25.2%), and intubation (16.5%). All patients underwent either cold steel (107 patients) or CO2 laser (32 patients) lysis of stenosis with concurrent dilation. RTFS within 2 years was 50.2% for CO2 laser and 31.9% for cold steel (hazard ratio [HR] and 95% confidence interval [CI]: 1.69, 0.96-2.97, P = .07). In patients with no prior airway procedures, there was no difference in RTFS between laser and cold knife (P = .41). However, in patients with prior airway procedures, RTFS was significantly greater in the laser group, even after adjusting for age, smoking history, and stenosis etiology (50.0% vs 16.8%, adjusted HR and CI: 2.82, 1.14-6.98, P = .025).

CONCLUSION

Endoscopic lysis of SGS with CO2 laser should be considered in revision cases.

Open airway surgery for post-COVID laryngotracheal stenosis

INTRODUCTION

This study reports our experience with open reconstructive surgery in patients with laryngotracheal stenosis (LTS) following prolonged intubation and/or tracheostomy in the context of COVID-19.

METHODS

All patients underwent a preoperative endoscopic airway assessment. Posterior glottic lesions were graded according to the Bogdasarian classification, subglottic-tracheal lesions according to the Cotton-Myers classification and postoperative complications reported by the Clavien-Dindo classification. We report postoperative outcomes and functional results in this patient subset.

RESULTS

We include 14 patients diagnosed to have post COVID LTS, one female and 13 males. This group was compared with a control group, diagnosed with LTS following prolonged intubation. In the COVID group, mean age of patients at the time of the airway surgery was 52.1 ± 16.8 years (range: 13.7-76.3). More than half the patients were multi-morbid with hypertension and obesity being the most common conditions. Eleven patients had multi-site stenoses. Open surgical interventions performed were tracheal resection and anastomosis, laryngotracheal reconstruction and extended cricotracheal resection, and postoperative complications were seen in 12 (85.6%) patients. 70% patients with pre-existing tracheostomy were decannulated. Oral swallowing was not tolerated in one-fifth of the patients and a significant number of them have poor voice quality.

CONCLUSION

Post-COVID pandemic, airway surgeons are seeing an increased number of patients with complex LTS, and we report significant postoperative complications in this patient subset. Decannulation rates, voice and swallowing results are poor in patients with glottic involvement as compared to isolated tracheal stenosis.

Characterizing the T Cell Repertoire in the Proximal Airway in Health and Disease

OBJECTIVES

Recent translational scientific efforts in subglottic stenosis (SGS) support a disease model where epithelial alterations facilitate microbiome displacement, dysregulated immune activation, and localized fibrosis. Given the observed immune cell infiltrate in SGS, we sought to test the hypothesis that SGS cases possessed a low diversity (highly clonal) adaptive immune response when compared with healthy controls.

METHODS

Single cell RNA sequencing (scRNA-seq) of subglottic mucosal scar in iSGS (n = 24), iLTS (n = 8), and healthy controls (n = 7) was performed. T cell receptor (TCR) sequences were extracted, analyzed, and used to construct repertoire structure, compare diversity, interrogate overlap, and define antigenic targets using the Immunarch bioinformatics pipeline.

RESULTS

The proximal airway mucosa in health and disease are equally diverse via Hill framework quantitation (iSGS vs. iLTS vs. Control, p > 0.05). Repertoires do not significantly overlap between individuals (Morisita <0.02). Among iSGS patients, clonality of the TCR repertoire is driven by CD8+ T cells, and iSGS patients possess numerous TCRs targeting viral and intercellular pathogens. High frequency clonotypes do not map to known targets in public datasets.

CONCLUSION

SGS cases do not possess a lower diversity adaptive immune infiltrate when compared with healthy controls. Interestingly, the TCR repertoire in both health and disease contains a restricted number of high frequency clonotypes that do not significantly overlap between individuals. The target of the high frequency clonotypes in health and disease remain unresolved.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:1757-1764, 2024.

Mechanisms of fibrosis in iatrogenic laryngotracheal stenosis: New discoveries and novel targets

Iatrogenic laryngotracheal stenosis (iLTS) is a pathological condition characterized by the narrowing of the laryngeal and tracheal structures due to the formation of abnormal scar tissue. The core of iLTS lies in the fibrosis of the laryngotracheal tissue, and recent research has unveiled novel discoveries regarding the underlying mechanisms of fibrosis. This review provides an overview of the recent advancements in understanding the mechanisms of fibrosis in iLTS. It encompasses various aspects, such as immune system dysregulation, changes in the extracellular matrix (ECM), metabolic alterations, and the role of microbial flora. The review also explores the interplay and relationships between these new mechanisms, establishing a theoretical foundation for the development of multi-target therapies and combination therapies for iLTS.

Characteristics of Idiopathic Subglottic Stenosis in the Elderly

OBJECTIVE

To compare characteristics of patients ≥65 years presenting with idiopathic subglottic stenosis (iSGS) to patients diagnosed at <65 years. We hypothesize that the groups have similar comorbidities and disease courses.

DATA SOURCES

Medical records of patients treated for iSGS at a tertiary care institution from January 2005-September 2022.

REVIEW METHODS

Patient demographics, time from symptom onset to diagnosis, medical history and comorbidities, and treatment modalities/intervals were recorded and analyzed. Characteristics of patients ≥65 and <65 years at presentation were compared using Chi-square analysis for non-numeric values and the Mann-Whitney U-test for numeric values.

RESULTS

One hundred seven patients with iSGS were identified and 16 (15%) were aged ≥65 years (mean age 72.6, 15 female) at presentation. These patients were compared to 91 patients aged <65 years (mean age = 47.6, 90 female). Patients ≥65 years had higher rates of type 2 diabetes mellitus (T2DM) (p = 0.004) and tobacco use (p = 0.004). There were no significant differences in body mass index, gastroesophageal reflux disease, hormone replacement therapy, time from symptom onset to presentation, or length of operative treatment intervals.

CONCLUSION

Patients ≥65 years with iSGS have higher rates of tobacco use, suggesting that alterations in wound healing may play a role in the development of iSGS in this age group. Although rates of T2DM were higher in the elderly group, clinical significance may be limited given the overall higher rate of diabetes mellitus in the elderly population.

LEVEL OF EVIDENCE

4 Laryngoscope, 133:3075-3079, 2023.

Mapping Genetic Susceptibility to Stenosis in the Proximal Airway

OBJECTIVES

Recent translational scientific efforts in subglottic stenosis (SGS) support a disease model where epithelial alterations facilitate microbiome displacement, dysregulated immune activation, and localized fibrosis. Yet despite recent advances, the genetic basis of SGS remains poorly understood. We sought to identify candidate risk genes associated with an SGS phenotype, investigate their biological function, and identify the cell types enriched for their expression.

METHODS

The Online Mendelian Inheritance in Man (OMIM) database was queried for single gene variants associated with an SGS phenotype. The functional intersections and molecular roles of the identified genes were explored using pathway enrichment analysis (PEA) computational methods. Cellular localization of the candidate risk genes was measured via transcriptional quantification in an established single cell RNA sequencing (scRNA-seq) atlas of the proximal airway.

RESULTS

Twenty genes associated with SGS phenotype were identified. PEA resulted in 24 significantly enriched terms including "cellular response to TGF-β," "epithelial-to-mesenchymal transition," and "adherens junctions." Mapping the 20 candidate risk genes to the scRNA-seq atlas found 3 (15%) genes were enriched in epithelial cells, 3 (15%) in fibroblasts, and 3 (15%) in endothelial cells. 11 (55%) genes were expressed ubiquitously among tissue types. Interestingly, immune cells were not significantly enriched for candidate risk genes.

CONCLUSION

We identify and provide biologic context for 20 genes associated with fibrotic disease of the proximal airway and form the foundation for future detailed genetic study.

LEVEL OF EVIDENCE

N/A Laryngoscope, 133:3049-3056, 2023.

Post-COVID-19 airway stenosis treated by tracheal resection and anastomosis: a bicentric experience

Objective

The COVID-19 pandemic was an extraordinary challenge for the global healthcare system not only for the number of patients affected by pulmonary disease, but also for the incidence of long-term sequalae. In this regard, laryngo-tracheal stenosis (LTS) represents one of the most common complications of invasive ventilation.

Methods

A case series of patients who underwent tracheal resection and anastomosis (TRA) for post-COVID-19 LTS was collected from June 2020 to September 2021.

Results

Among 14 patients included, 50% had diabetes and 64.3% were obese. During intensive care unit stay, mean duration of orotracheal intubation (OTI) was 15.2 days and 10 patients (71.4%) underwent tracheostomy, which was maintained in 7 for an average of 31 days. According to the European Laryngological Society classification, 13 patients (92.9%) had a grade IIIa LTS and one a grade IIIa+. All patients underwent Type A TRA, according to the authors’ classification. No major perioperative complications were reported and at the last follow-up all patients were asymptomatic.

Conclusions

With the appropriate indications, TRA represents an effective treatment in post-COVID-19 LTS patients. Short OTI times and careful tracheostomy are required in order to reduce the incidence of airway injury.

Molecular Mechanisms and Physiological Changes behind Benign Tracheal and Subglottic Stenosis in Adults

Laryngotracheal stenosis (LTS) is a complex and heterogeneous disease whose pathogenesis remains unclear. LTS is considered to be the result of aberrant wound-healing process that leads to fibrotic scarring, originating from different aetiology. Although iatrogenic aetiology is the main cause of subglottic or tracheal stenosis, also autoimmune and infectious diseases may be involved in causing LTS. Furthermore, fibrotic obstruction in the anatomic region under the glottis can also be diagnosed without apparent aetiology after a comprehensive workup; in this case, the pathological process is called idiopathic subglottic stenosis (iSGS). So far, the laryngotracheal scar resulting from airway injury due to different diseases was considered as inert tissue requiring surgical removal to restore airway patency. However, this assumption has recently been revised by regarding the tracheal scarring process as a fibroinflammatory event due to immunological alteration, similar to other fibrotic diseases. Recent acquisitions suggest that different factors, such as growth factors, cytokines, altered fibroblast function and genetic susceptibility, can all interact in a complex way leading to aberrant and fibrotic wound healing after an insult that acts as a trigger. However, also physiological derangement due to LTS could play a role in promoting dysregulated response to laryngo-tracheal mucosal injury, through biomechanical stress and mechanotransduction activation. The aim of this narrative review is to present the state-of-the-art knowledge regarding molecular mechanisms, as well as mechanical and physio-pathological features behind LTS.