Translational genomics of acquired laryngotracheal stenosis

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.

Balloon dilatation is superior to CO2 laser excision in the treatment of subglottic stenosis

INTRODUCTION

Endoscopic treatment of subglottic stenosis (SGS) is regarded as a safe procedure with rare complications and less morbidity than open surgery yet related with a high risk of recurrence. The abundance of techniques and adjuvant therapies complicates a comparison of the different surgical approaches. The primary aim of this study was to investigate disease recurrence after CO₂ laser excisions and balloon dilatation in patients with SGS and to identify potential confounding factors.

MATERIALS AND METHODS

In a tertiary referral center, two cohorts of previously undiagnosed patients treated for SGS were retrospectively reviewed and followed for 3 years. The CO₂ laser cohort (CLC) was recruited between 2006 and 2011, and the balloon dilatation cohort (BDC) between 2014 and 2019. Kaplan‒Meier and multivariable Cox regression analyzed time to repeated surgery and estimated hazard ratios (HRs) for different variables.

RESULTS

Nineteen patients were included in the CLC, and 31 in the BDC. The 1-year cumulative recurrence risk was 63.2% for the CLC compared with 12.9% for the BDC (HR 33.0, 95% CI 6.57-166, p < 0.001), and the 3-year recurrence risk was 73.7% for the CLC compared with 51.6% for the BDC (HR 8.02, 95% CI 2.39-26.9, p < 0.001). Recurrence was independently associated with overweight (HR 3.45, 95% CI 1.16-10.19, p = 0.025), obesity (HR 7.11, 95% CI 2.19-23.04, p = 0.001), and younger age at diagnosis (HR 8.18, 95% CI 1.43-46.82, p = 0.018).

CONCLUSION

CO₂ laser treatment is associated with an elevated risk for recurrence of SGS compared with balloon dilatation. Other risk factors include overweight, obesity, and a younger age at diagnosis.

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.

[Chronic respiratory failure correction in cicatricial laryngeal and tracheal stenosis using helium-oxygen mixture]

The article provides a review of the literature on the development of chronic respiratory failure in patients with chronic cicatricial stenosis of the larynx and cervical trachea. The authors provide data on the etiology, pathogenetic features of the course of cicatricial stenosis of the larynx and trachea, the reasons for the development of chronic respiratory failure, the effect of hypoxemia on general metabolic processes in the body and on regeneration processes, as well as on methods of their correction and improvement of the postoperative period. The methods of respiratory impact on chronic respiratory failure in these patients are considered, based on the experience of a number of researchers and technical advances in recent years.

IL-6: An endogenous activator of MMP-9 in preterm birth

Preterm birth or PTB (<37 weeks) is a heterogeneous phenotype with numerous biological pathways. The lack of explanation due to complex pathways, inconsistent observations indicates the need for employing the role of genetic determinants to anticipate the danger of PTB. In this present study, we investigated the possible gene-gene interaction of five SNPs with PTB and its association with total MMP-9 levels. A total of 510 recruitments (250 terms and preterm each) were made and were genotyped by Restriction Fragment length polymorphism (RFLP). Generalized Multifactor Dimensionality Reduction (GMDR) method was carried out for determining gene-gene interaction. ANOVA and t-test were used to identify the association of IL-6 polymorphism with PTB alone and correspondingly with PTB and low birth weight infants (i.e. < 2500 kg). The combination of IL-6 and MMP-9 and MMP-1, MMP-8 and MMP-9 polymorphism was selected through GMDR analysis concerning mothers with preterm and term birth (accuracy 0.5921 and 0.8030 with Cross-Validation Consistency (CVC) 10/10 respectively). Increased expression of MMP-9 was reported in cases in those mothers carrying IL-6 G allele, which was profoundly associated with PTB independently. IL-6 polymorphisms showed synergistic effects in terms of increased total MMP-9 levels in the present study.

[Etiopathogenetic factors of wound healing in chronic post-intubation cicatricial stenosis of the larynx and trachea]

Despite the existing modern high-tech methods of examination and a variety of surgical treatment methods, the problem of diagnosis, treatment and rehabilitation of patients with chronic post-intubation cicatricial stenosis of the larynx and trachea still requires further study. Improving the understanding and correction of cellular, molecular genetic and biochemical disorders in a chronic wound is a key condition for increasing the efficiency of diagnosis, individual prognosis of the clinical course and the conduct of adequate therapeutic and preventive measures for post-intubation cicatricial laryngotracheal stenoses. In this regard, it seemed appropriate to analyze the existing etiopathogenetic factors of pathological wound healing in chronic post-intubation cicatricial stenosis of the larynx and trachea. Our attempt to summarize the available literature data demonstrated that laryngotracheal scars are a fibro-proliferative disease caused by aberrant wound healing after a damaging effect on the tissues of the larynx and trachea. The article describes the most pathogenetically significant healing, repair, and scarring factors in post-intubation laryngotracheal stenoses, including transforming growth factor β1, vascular growth factor A, type I and III collagen, and matrix metalloproteinases. An assessment of the features of the diagnostic and prognostic significance of these markers will increase the effectiveness of the treatment of patients with chronic cicatricial stenosis of the larynx and trachea, and will also serve as a prerequisite for the development of strategies for diagnostic, treatment, prophylactic and rehabilitation measures that will improve the quality of medical care and the quality of life of patients with chronic cicatricial stenosis of the larynx and trachea.

The Incidence of Laryngotracheal Stenosis in Neonates With a History of Ventilator-Associated Pneumonia

OBJECTIVES/HYPOTHESIS

Neonatal patients requiring prolonged intubation are susceptible to both infection and laryngotracheal stenosis (LTS). This study investigated the effect of ventilator-associated pneumonia (VAP) on the development of LTS in neonates.

STUDY DESIGN

Retrospective case-control study.

METHODS

The incidence of LTS in neonates with VAP was compared with the incidence of LTS in matched intubated controls without VAP. Patients were treated at a tertiary-care medical center from 2004 to 2014. Eligible patient records were assessed for the development of LTS. Demographics, medical comorbidities, infection characteristics, and treatment variables were compared using unpaired t test or χ² test. Statistical significance was set a priori at P < .05.

RESULTS

When comparing the VAP patients with matched non-VAP controls, we found no significant differences in the incidence of LTS (VAP vs. non-VAP, 8.3% vs. 6.7%; P = .73). In subgroup analysis of the VAP cohort, LTS and non-LTS patients demonstrated similar VAP organisms on broncho-alveolar lavage (Klebsiella pneumoniae, Pseudomonas aeroginosa, Escherichia coli, methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae, and Enterobacter). Additionally, within the VAP cohort, LTS and non-LTS patients showed similar gestational age (LTS vs. non-LTS, 31.3 days vs. 28.1 days; P = .22), birth weight (LTS vs. non-LTS, 1.6 kg vs. 1.2 kg; P = .33), and similar intubation duration (LTS vs. non-LTS, 37.8 days vs. 27.5 days; P = .52).

CONCLUSIONS

In this neonatal cohort, VAP was not associated with an increased incidence of LTS. Given severity of the burden of LTS on the healthcare system, multi-institutional longitudinal investigation into contributing risk factors for neonatal LTS is warranted.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:2252-2255, 2020.

Laryngotracheal stenosis in burn patients requiring mechanical ventilation

Objective

To identify the incidence of laryngotracheal stenosis (LTS) in burn patients requiring mechanical ventilation at a regional academic burn center.

Methods

A retrospective review of all burn patients requiring endotracheal intubation or tracheostomy for airway management between 2003 and 2009 was performed. A group of trauma patients requiring similar airway instrumentation during the same period of time was used as a control.

Results

None of the trauma patients and 2 of the burn patients developed LTS. Both presented with stridor and were diagnosed within 2–5 weeks after extubation. One patient underwent successful carbon dioxide laser radial incision and dilation and continues to do well. The other patient failed endoscopic treatment and required T-tube placement. The incidence of LTS in burn patients requiring mechanical ventilation was 2.98% overall and 4.76% among those with inhalational injury.

Conclusions

Patients become symptomatic within weeks of the initial injury. Treatment is challenging and multiple surgical procedures are often required. A larger study is necessary to determine if the incidence is higher among burn patients.

Determining Candidate Single Nucleotide Polymorphisms in Acquired Laryngotracheal Stenosis

OBJECTIVES/HYPOTHESIS

Despite wide adoption of strategies to prevent injury from prolonged intubation and tracheotomy, acquired laryngotracheal stenosis (ALTS) has not disappeared. ALTS' persistence may be due to patient factors that confer unique susceptibility for some. We sought to identify genetic markers in genes associated with wound healing that could be associated with ALTS.

STUDY DESIGN

Case-control study.

METHODS

One hundred thirty-eight patients were recruited, 53 patients with ALTS and 85 control patients who underwent intubation or tracheotomy without evidence of ALTS. The patients' DNA was isolated from whole blood. Custom primers were designed, and the TaqMan assay employing allele-specific polymerase chain reaction was used to interrogate single nucleotide polymorphisms (SNPs) rs1799750, rs522616, rs2276109, rs2569190, rs1800469, and rs1024611 of candidate wound healing genes MMP1, MMP3, MMP12, CD14, TGFβ1, and MCP1, respectively. A logistic regression model was used to examine the association of candidate gene polymorphisms with the presence or absence of ALTS.

RESULTS

All 138 patients were successfully genotyped. No significant association was found between candidate SNPs and development of ALTS in the overall group. However, subgroup analysis within each ethnicity identified SNPs that are associated with ALTS depending upon the ethnic background.

CONCLUSIONS

Patient factors such as variations in wound healing due to functional SNPs may shed light on the development of ALTS. There may be a difference in susceptibility to developing ALTS in different ethnic backgrounds. These preliminary findings need to be corroborated in larger population studies.

LEVEL OF EVIDENCE

3b. Laryngoscope, 128:E111-E116, 2018.

Fibroblasts in Hypoxic Conditions Mimic Laryngotracheal Stenosis

Objective To elucidate the role of hypoxia and inflammatory pathways in the pathogenesis of iatrogenic laryngotracheal stenosis (iLTS). Study Design (1) Examination of mucosal surface gene expression in human iLTS. (2) In vitro comparison of normal and scar laryngotracheal fibroblasts under normoxic and hypoxic conditions. Setting Tertiary care hospital in a research university (2012-2016). Subjects and Methods Brush biopsies were obtained from normal laryngotracheal tissue and scar in iLTS patients; gene expression was compared. Fibroblasts were isolated from normal and scarred trachea and grown in vitro in either a 1% O₂ or normoxic environment. Cell growth and gene and protein expression were compared. Statistical analysis utilized a multilevel mixed effects model. Results Expression of IL-6 (fold change = 2.8, P < .01), myofibroblast marker αSMA (fold change = 3.0, P = .01), and MMP13 (fold change = 5.4, P = .02) was significantly increased in scar biopsy samples as compared to normal. Under hypoxic conditions in vitro, normal laryngotracheal fibroblasts proliferated significantly faster (n = 8, P < .01 each day). Expression of IL-6 (n = 8, fold change = 2.6, P < .01) increased significantly after 12 hours under hypoxia. Expression of αSMA (n = 8, fold change= 2.0, P = .03), COL1 (n = 8, fold change = 1.1, P = .03), and MMP13 (n = 8, fold change = 1.6, P = .01) increased significantly after 48 hours under hypoxia. Scar fibroblasts also proliferated significantly faster under hypoxic conditions but did not display the same expression profile. Conclusion Human iLTS scar has a myofibroblast phenotype. Under hypoxic conditions in vitro, normal laryngotracheal fibroblasts can transdifferentiate into a similar phenotype. These changes may be mediated by IL-6, a fibrosis-related cytokine.

Cicatricial posterior glottic stenosis. Our experience

INTRODUCTION AND OBJECTIVES

Presentation of the results obtained in the treatment of cicatricial posterior glottic stenosis.

METHODS

A retrospective study of 34 patients diagnosed and treated for cicatricial posterior glottic stenosis in our ENT Department.

RESULTS

In our series, 85.36% of our patients were decannulated. Of these, 80% of the patients with glottic stenosis were decannulated, while 92.9% of the patients with other associated laryngotracheal stenosis were paradoxically decannulated. Of all the patients, 70% required more than 1 surgical procedure, although most of these interventions were to resolve minor issues following our protocol. The number of subsequent interventions was determined by the location of the stenosis, with there being more interventions when the posterior glottic stenosis was associated with another type of laryngotracheal stenosis (p=.001).

CONCLUSIONS

The surgical results for treating cicatricial posterior glottic stenosis are quite positive. However, unlike other types of posterior glottic stenosis (such as neurogenic abductor paralysis), it requires a greater number of interventions to achieve definitive decannulation. Endoscopic procedures play an important role and represent our main tool.