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.

Frontometaphyseal dysplasia and keloid formation without FLNA mutations.

Frontometaphyseal dysplasia (FMD) is a distinctive sclerosing skeletal dysplasia associated with a number of non-skeletal manifestations including hearing loss, cardiac malformations, and stenosis, particularly of the upper airway and urinary tract. Some, but not all, patients have mutations in FLNA causing the condition. Consonant with the X chromosomal location of FLNA males are generally more severely affected than females. FLNA mutations can be detected in 82% of affected males. We describe seven patients (one male, six females) all of whom have the major clinical and radiological features of FMD, but without detectable mutations in FLNA. The females in our cohort are affected to a similar degree as is usually found in males. In addition, all patients have marked keloid formation at various body sites, including the eye, from an early age. Other features that may indicate a different etiology in these patients are the increased frequency of cleft palate, Robin sequence, tracheal stenosis, and mild intellectual disability, which all occur in three of more patients in the present group. All patients are isolated. We hypothesize that the presently reported patients represent further evidence that phenotypes strongly resembling FMD exist that are not accounted for by mutations in FLNA. Since the frequency of several of the manifestations, their sporadic presentations, and the presence of keloid formation differ from the X-linked form of this condition we propose de novo autosomal dominant acting mutations in a gene functionally related to FLNA, underpin this disorder.

TBX5 pathogenic variant in a patient with congenital heart defect and tracheal stenosis.

Congenital tracheal stenosis is a rare life-threatening disorder caused by narrow O-shaped tracheal ring without smooth muscle. Its underlying genetic cause has not been elucidated. We performed whole exome sequencing in a patient with congenital tracheal stenosis and congenital heart defect, and identified a de novo pathogenic TBX5 variant (NM_181486.4:c.680T>C, p.(Ile227Thr)). The Ile227Thr-TBX5 protein was predicted to have a decreased stability by in silico protein structural analyses, and was shown to have a significantly reduced activity for the NPPA promoter by luciferase assay. The results, together with the expression of mouse Tbx5 in the lung and trachea and the development of tracheal cartilage dysplasia in the lung-specific Tbx5 null mice, imply the relevance of TBX5 pathogenic variants to congenital tracheal stenosis.

Gene expression profiles in COVID-19-associated tracheal stenosis indicate persistent anti-viral response and dysregulated retinol metabolism.

INTRODUCTION: Coronavirus disease 2019 (COVID-19)-associated tracheal stenosis (COATS) may occur as a result of prolonged intubation during COVID-19 infection. We aimed to investigate patterns of gene expression in the tracheal granulation tissue of patients with COATS, leverage gene expression data to identify dysregulated cellular pathways and processes, and discuss potential therapeutic options based on the identified gene expression profiles. METHODS: Adult patients (age ≥ 18 years) presenting to clinics for management of severe, recalcitrant COATS were included in this study. RNA sequencing and differential gene expression analysis was performed with transcriptomic data for normal tracheal tissue being used as a control. The top ten most highly upregulated and downregulated genes were identified. For each of these pathologically dysregulated genes, we identified key cellular pathways and processes they are involved in using Gene Ontology (GO) and KEGG (Kyoto Encyclopedia of Genes and Genomes) applied via Database for Annotation, Visualization, and Integrated Discovery (DAVID). RESULTS: Two women, aged 36 years and 37 years, were included. The profile of dysregulated genes indicated a cellular response consistent with viral infection (CXCL11, PI15, CCL8, DEFB103A, IFI6, ACOD1, and DEFB4A) and hyperproliferation/hypergranulation (MMP3, CASP14 and HAS1), while downregulated pathways included retinol metabolism (ALDH1A2, RBP1, RBP4, CRABP1 and CRABP2). CONCLUSION: Gene expression changes consistent with persistent viral infection and dysregulated retinol metabolism may promote tracheal hypergranulation and hyperproliferation leading to COATS. Given the presence of existing literature highlighting retinoic acid's ability to favorably regulate these genes, improve cell-cell adhesion, and decrease overall disease severity in COVID-19, future studies must evaluate its utility for adjunctive management of COATS in animal models and clinical settings.

IL-11 drives the phenotypic transformation of tracheal epithelial cells and fibroblasts to enhance abnormal repair after tracheal injury.

Tracheal stenosis (TS) is a multifactorial and heterogeneous disease that can easily lead to respiratory failure and even death. Interleukin-11 (IL-11) has recently received increased attention as a fibrogenic factor, but its function in TS is uncertain. This study aimed to investigate the role of IL-11 in TS regulation based on clinical samples from patients with TS and a rat model of TS produced by nylon brush scraping. Using lentiviral vectors expressing shRNA (lentivirus-shRNA) targeting the IL-11 receptor (IL-11Rα), we lowered IL-11Rα levels in the rat trachea. Histological and immunostaining methods were used to evaluate the effects of IL-11Rα knockdown on tracheal injury, molecular phenotype, and fibrosis in TS rats. We show that IL-11 was significantly elevated in circulating serum and granulation tissue in patients with TS. In vitro, TGFß1 dose-dependently stimulated IL-11 secretion from human tracheal epithelial cells (Beas-2b) and primary rat tracheal fibroblasts (PRTF). IL-11 transformed the epithelial cell phenotype to the mesenchymal cell phenotype by activating the ß-catenin pathway. Furthermore, IL-11 activated the atypical ERK signaling pathway, stimulated fibroblasts proliferation, and transformed fibroblasts into alpha-smooth muscle actin (α-SMA) positive myofibroblasts. IL-11-neutralizing antibodies (IL-11NAb) or ERK inhibitors (U0126) inhibited IL-11 activity and downregulated fibrotic responses involving TGFß/SMAD signaling. In vivo, IL-11Rα knockdown rats showed unobstructed tracheal lumen, relatively intact epithelial structure, and significantly reduced granulation tissue proliferation and collagen fiber deposition. Our findings confirm that IL-11 may be a target for future drug prevention and treatment of tracheal stenosis.

Pilot Gene Expression and Histopathologic Analysis of Tracheal Resections in Tracheobronchomalacia.

BACKGROUND: The airway structures and messenger RNA expression of genes that regulate airway inflammation and remodeling may be altered in the trachea of patients with tracheobronchomalacia (TBM). METHODS: Fourteen tracheal specimens obtained from 2005 to 2018 were used in this study. Surgical resection specimens from patients with TBM and tracheal stenosis (TS) were compared with control tracheal specimens obtained from autopsy cases. We investigated the messenger RNA expression of genes encoding fibroblast growth factor (FGF) binding protein 2 (FGFBP2), FGF receptor R3 (FGFR3), interleukin-1ß (IL1ß), tumor growth factor-ß1 (TGFß1), tissue inhibitor of metalloproteinases 1 (TIMP1), and intercellular adhesion molecule 1 (ICAM1) as well as established markers of airway inflammation including interferon-γ (IFNγ) and tumor necrosis factor (TNF). The relative expression of target transcripts was assessed by quantitative real-time polymerase chain reaction. A histologic examination of the same resected airway specimens was performed on formalin-fixed paraffin-embedded tissue sections. RESULTS: FGFBP2 and FGFR3 showed higher expression in TBM compared with TS and control groups (P < .05 and P < .01, respectively). Furthermore, both TGFß1 and TIMP1 were elevated in TBM patients compared with control subjects (P < .05). Conversely ICAM1 was downregulated in TBM versus TS and control subjects (P < .05). IL1ß, IFNγ, and TNF were increased in TBM, although it did not achieve statistical significance. Histologically compared with control airways both TBM and TS demonstrated submucosal fibrotic changes, with TBM additionally demonstrating alterations in elastin fiber quality and density in the posterior membrane. CONCLUSIONS: Significant changes in gene expression are observed in the tracheal walls of patients with TBM and TS compared with control subjects.

Bioinformatics analysis and verification of gene targets for benign tracheal stenosis.

BACKGROUND: Tracheal injury could cause intratracheal scar hyperplasia which in turn causes benign tracheal stenosis (TS). With the increasing use of mechanical ventilation and ventilator, the incidence of TS is increasing. However, the molecular mechanisms of TS have not been elucidated. It is significant to further explore the molecular mechanisms of TS. METHODS: The repeatability of public data was verified. Differently expressed genes (DEGs) and most significant genes were identified between TS and normal samples. Enrichment analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were analyzed. The comparative toxicogenomics database were analyzed. TS patients were recruited and RT-qPCR were performed to verify the most significant genes. RESULTS: There exist strong correlations among samples of TS and normal group. There was a total of 194 DEGs, including 61 downregulated DEGs and 133 upregulated DEGs. GO were significantly enriched in mitotic nuclear division, cell cycle, and cell division. Analysis of KEGG indicated that the top pathways were cell cycle, and p53 pathway. MKI67(OMIM:176741), CCNB1(OMIM:123836), and CCNB2(OMIM:602755) were identified as the most significant genes of TS, and validated by the clinical samples. CONCLUSION: Bioinformatics methods might be useful method to explore the mechanisms of TS. In addition, MKI67, CCNB1, and CCNB2 might be the most significant genes of TS.

Severe upper airway stenosis in a boy with partial monosomy 16p13.3pter and partial trisomy 16q22qter.

We report the case of a boy with a de novo partial monosomy 16p13-pter and partial trisomy 16q22-qter detected by fluorescence in situ hybridization using subtelomeric probes for 16p and 16q. The boy had facial characteristics, skeletal features, congenital heart defects, an imperforate anus, urogenital malformations, pre/postnatal growth retardation, and psychomotor retardation, most of which have been reported both in partial monosomy 16p and partial trisomy 16q. In addition, he suffered from upper airway stenosis due to possible laryngeal stenosis with subglottic webs. The upper airway stenosis could be a rare complication of partial monosomy 16p or partial trisomy 16q, or a nonspecific malformation resulting from chromosomal abnormalities.

Matrix metalloproteinase-1 polymorphism in Taiwanese patients with endobronchial tuberculosis.

Endobronchial tuberculosis (TB) often leads to some degree of tracheobronchial stenosis. Because matrix metalloproteinases (MMPs) play an essential role in tissue remodeling in the airways, we investigated the role of MMP-1 polymorphism in patients with endobronchial TB. One hundred and one cases of pulmonary TB in Taiwanese patients were genotyped for the 1G/2G polymorphism of MMP-1 promoter (-1607 bp). Bronchoscopic examination was performed to determine the presence of endobronchial involvement. Levels of MMP-1 in peripheral blood monocytes and in bronchial biopsies were also determined. 1G genotypes of MMP-1 polymorphism, containing at least one 1G allele, were associated with the presence of endobronchial TB. Using multivariate analysis, 1G genotypes and female gender were independent predictors of the development of endobronchial TB. Endobronchial TB patients with 1G genotypes had a 9.86-fold greater risk of developing tracheobronchial stenosis. IL-1beta increased levels of MMP-1 in peripheral blood monocytes of TB patients with 1G genotypes. MMP-1 activity was also present in the endobronchial TB granuloma from patients with 1G/1G genotype. 1G genotypes of MMP-1 polymorphism were associated with a greater risk of developing tracheobronchial stenosis through up-regulation of MMP-1 activity.

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, TGFß1, 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.

Quantification of Inflammatory Markers in Laryngotracheal Stenosis.

Objectives (1) Develop a novel method for serial assessment of gene and protein expression in laryngotracheal stenosis (LTS). (2) Assess cytokine expression and determine an immunophenotype in LTS. Study Design A matched comparison of endolaryngeal brush biopsy samples from laryngotracheal scar and normal airway. Setting Tertiary care hospital, 2015-2016. Methods Brush biopsy specimens of laryngotracheal scar and normal trachea were obtained from 17 patients with LTS at the time of operating room dilation and were used for protein and RNA extraction. Gene expression of the TH1 cytokine interferon γ (INF-γ), TH2 cytokine interleukin 4 (IL-4), transforming growth factor ß, and collagen 1 (Coll1) was quantified with quantitative real-time polymerase chain reaction. Cytokine analysis was performed with flow cytometry with a cytometric bead array. Results LTS specimens demonstrated a 13.68-fold increase in Coll1 gene expression versus normal ( P < .001, N = 17). Additionally, IL-4 gene expression showed a 3.76-fold increase ( P < .001, N = 17) in LTS scar. When stratified into iatrogenic LTS and idiopathic subglottic stenosis cohorts, INF-γ gene expression was significantly increased in idiopathic subglottic stenosis ( P = .011). Soluble cytokine measurements were below the limit of detection for reliable quantification and thus could not be assessed. Conclusions Brush biopsies from LTS samples can be successfully utilized for RNA extraction and demonstrate the expected increase in Coll1 gene expression associated with LTS. Preliminary gene expression suggests that abnormal collagen production may be mediated by the TH2 cytokine IL-4 and that increased INF-γ expression may represent a key difference between iatrogenic LTS and idiopathic subglottic stenosis. Further analysis of soluble cytokines is needed to confirm these findings.

Congenital tracheobronchial stenosis.

Congenital tracheobronchial stenosis is a rare disease characterized by complete tracheal rings that can affect variable lengths of the tracheobronchial tree. It causes high levels of morbidity and mortality both due to the stenosis itself and to the high incidence of other associated congenital malformations. Successful management of this complex condition requires a highly individualized approach delivered by an experienced multidisciplinary team, which is best delivered within centralized units with the necessary diverse expertise. In such settings, surgical correction by slide tracheoplasty has become increasingly successful over the past 2 decades such that long-term survival now exceeds 88%, with normalization of quality of life scores for patients with non-syndrome-associated congenital tracheal stenosis. Careful assessment and planning of treatment strategies is of paramount importance for both successful management and the provision of patients and carers with accurate and realistic treatment counseling.

Mosaic r(13) resulting in large deletion of chromosome 13q in a newborn female with multiple congenital anomalies.

A newborn female presented with multiple congenital anomalies including facial dysmorphism, agenesis of the corpus callosum, type I laryngeal cleft, tracheal stenosis, bilaterally small kidneys, segmental vertebral anomalies, extranumerary rib, bilateral hip dislocation, digital anomalies, and growth retardation. Newborn aneuploidy detection (NAD) based on interphase fluorescence in situ hybridization (FISH) indicated monosomy 13 in 47 of 200 (23.5%) peripheral blood cells (normal cutoff 8.5% at 95% CI). The follow-up banded metaphase-based analysis of 20 cells revealed a karyotype of 46,XX. The analysis of 30 additional cells revealed one cell to have monosomy 13 and a small ring chromosome. In the abnormal cell line, the ring was positive for whole chromosome paint (wcp) 13 and negative for Rb1 (13q14.3). The ring was detected in 4% of 80 additional metaphases studied by FISH. Therefore, the ring was present in 4% (5/130) of metaphases from peripheral blood. Analysis of buccal cells by FISH indicated the ring was present in 36% of cells. A higher degree of mosaicism (60%) was detected in fibroblast cultures from a skin biopsy. The low-level mosaicism of ring 13 in metaphase cells from peripheral blood would have been missed if the standard 20 GTL-banded metaphases had been analyzed. In this case, a preliminary interphase FISH study had indicated monosomy 13 resulting from a large 13q deletion that included the Rb1 locus. This finding initiated the analysis of additional metaphases by GTL-banding and the analysis of metaphases and interphases by FISH. The clinical presentation of our patient was consistent with reported cases of 13q deletions. In addition, our patient had airway anomalies, including a type I laryngeal cleft and tracheal stenosis, which are previously unreported.

Familial cryptic translocation with del 4q34-->qter and dup 12pter-->p13 in sibs with tracheal stenosis: clinical, classical and molecular cytogenetic studies and CGH analyses from archival placental tissues evidencing tertiary trisomy 4 in one abortion specimen.

We report on two retarded half-sibs of different sex and seemingly normal karyotype who had the same syndrome of minor anomalies, heart defect and a distal tracheal stenosis, and who shared a healthy mother. These findings raised suspicions of a cryptic chromosome translocation. A translocation t(4;12)(q34;p13), balanced in the mother and unbalanced in the sibs with loss of terminal 4q and gain of terminal 12p regions, was verified by FISH using whole chromosome painting, subtelomeric and YAC probes. Clinical features could be explained by partial monosomy 4q and partial trisomy 12p. Tracheal stenosis was interpreted as a consequence of the same developmental disturbance leading to esophageal atresia and tracheo-esophageal fistula. It was attributed to the 4q deletion in which esophageal atresia as also respiratory difficulties and airway obstructions had been described. Paraffin-embedded placental tissues were available from three of the five abortions of the mother allowing DNA extraction and comparative genome hybridization (CGH). Two of the abortion specimens had the same der(4)t(4;12)(q34;p13) unbalanced translocation as identified in the sibs. In the third abortion specimen, suspicious of triploidy because of partial hydatidiform mole, CGH uncovered a tertiary trisomy 4 resulting from a 3:1 segregation of the translocation chromosomes and their homologs during maternal meiosis I. Differences in CGH results using DNA generated directly or after DOP-PCR were explained by DNA fragmentation in paraffin-embedded tissues and unequal amplification. Am. J. Med. Genet. 94:271-280, 2000.

Aortic coarctation, vascular ring, and right aortic arch with aberrant subclavian artery.

Right aortic arch, in all situations, is relatively rare. In association with coarctation and vascular compression, it is extremely rare. We present a patient with a right aortic arch and an aberrant left subclavian artery, in addition to coarctation. This was dealt with through a left thoracotomy by dividing the ligamentum arteriosum and placing a Dacron graft from the ascending aorta to the descending aorta.

Translational genomics of acquired laryngotracheal stenosis.

OBJECTIVES/HYPOTHESIS: Acquired laryngotracheal stenosis (ALTS) results from abnormal mucosal wound healing after laryngeal and/or tracheal injury. Patients with ALTS often present late after significant reduction of the airway lumen and onset of symptoms. Motivated by the need for earlier detection of affected patients, we sought to investigate genetic markers for ALTS that would identify susceptible patients. STUDY DESIGN: Pilot Case-Control Study. METHODS: Seventy-six patients were recruited, 40 patients with ALTS and 36 control patients with airway injury but without ALTS. DNA was isolated from whole blood and formalin-fixed paraffin-embedded specimens from patients. Custom primers were designed and the TaqMan assay employing allele-specific polymerase chain reaction was used to interrogate single nucleotide polymorphisms (SNPs): rs2569190, rs1799750, and rs1800469 located in candidate genes CD14, matrix metalloproteinase-1 (MMP-1), and transforming growth factor-ß1 (TGF-ß1), respectively. A logistic regression model was used to examine the association of candidate gene polymorphisms with the presence or absence of ALTS. RESULTS: All 76 patients were successfully genotyped at the three loci of interest by optimizing the genotyping protocol. MMP-1 SNP rs1799750 was most significantly associated with development of ALTS (P = 0.005). CONCLUSION: Identification of SNPs associated with development of ALTS will provide new experimental targets to study wound healing in human subjects. The association found in the current study between ALTS and SNP rs1799750 is being validated in a larger population examining an expanded set of relevant SNPs. Identifying patients with genetic susceptibility to ALTS and poor wound healing in the upper airway will be useful for management of patients after upper-airway injury.

22q11.2 Microduplication in a patient with 19p13.12-13.13 deletion.

BACKGROUND: The chromosome 22q11.2 region microduplication has been described in patients with variable phenotypes. Here we present a 3-month-old girl with both 22q11.2 microduplication and 19p13.12-13.13 deletion. The presence of both genomic imbalances in one patient has not been previously reported in literature. METHODS: A routine G-banding karyotype analysis was performed using peripheral lymphocytes. Chromosome microarray analysis (CMA) was done using Affymetrix CytoScan™ HD array. RESULTS: The result of karyotyping showed that the patient is 46,XX,t(12;19)(q24.3;p13.1), but CMA detected a 2.8Mb microduplication within the region 22q11.2 (chr22: 18,648,866-21,465,659) and a 1.2Mb deletion on the chromosome 19at band p13.12-p13.13 (chr19: 13,107,938-14,337,347) in her genome, while no abnormalities were identified on 12q24.3. The 3-month-old girl presented with microcephaly, cleft palate, low set and retroverted ears, and facial dysmorphism which consisted of the following: a long narrow face, widely spaced eyes, downslanting palpebral fissures, broad nasal base, short philtrum, thin upper lip, and micro/retrognathia. She also had a congenital right pulmonary artery sling and tracheal stenosis and suffered from significant hypotonia and partial bilateral mixed hearing loss. CONCLUSIONS: We report a case of 22q11.2 duplication syndrome with 19p13.12-13.13 deletion. Synergistic effect from the two genomic imbalances is likely responsible for the complicated clinical features observed in this patient.

Idiopathic subglottic stenosis: a familial predisposition.

Idiopathic subglottic stenosis is a narrowing of the trachea at the level of the cricoid cartilage of unknown etiology. It is a rare condition for which the real incidence has never been established owing to the difficulty of making the diagnosis. Although there is a female preponderance, no familial cases have been reported in the literature. We describe two pairs of sisters as well as a mother and daughter presenting with idiopathic subglottic stenosis. All known causes of tracheal stenosis were excluded, including prolonged intubation, surgery, autoimmune and inflammatory disorders, infection and gastroesophageal reflux disease. These are the first cases reported in the literature that suggest a genetic predisposition for idiopathic subglottic stenosis.