Iatrogenic Laryngotracheal Stenosis Research Articles

Closing the Gap: Exploring the Role of Cap Grafts in Tracheocutaneous Fistula Closure.

Exploring the Role of Cap Grafts in tracheocutaneous fistula Closure. A tracheocutaneous fistula (TCF) is an abnormal connection that forms between the trachea (windpipe) and the skin of the neck. If spontaneous closure does not occur, fibrosis of the surrounding tissue may result in a persistent TCF and in some cases, iatrogenic laryngotracheal stenosis at the level of tracheostoma, the so-called A-frame deformity. In all 5 patients, Conchal cartilage was harvested. The new de-epithelialized stoma is measured, and the previously harvested graft is cut to match the defect. Passing through the centre of the tracheal cartilage and into the centre of the auricular cartilage graft, 3-0 PDS, horizontal mattress sutures are placed sequentially around the periphery of the graft, stabilised with Right SCM flap and skin was closed in layers. In each of the five cases, we achieved a resounding success by skilfully closing the fistulas and meticulously restoring the structural integrity. Equally noteworthy, all patients expressed contentment with the cosmetic outcomes at both the donor site and the neck region, deeming it as an acceptable aesthetic result.

Surgical plan selection and efficacy analysis in 32 cases of laryngotracheal stenosis

Objective: To explore the optimization of surgical procedures for laryngotracheal stenosis and its effect analysis. Methods: The data of 32 patients with acquired laryngotracheal stenosis who received surgical treatment from October 2015 to December 2021 were analyzed retrospectively. The age ranged from 19 to 72 years, with an average of (34.0±9.0) years. The medical history ranged from 1 to 32 months (median 3 months). As for etiology, there were 30 cases of iatrogenic laryngotracheal stenosis, including 20 cases of tracheal intubation and 10 cases of tracheotomy (7 cases of percutaneous tracheotomy and 3 cases of traditional tracheotomy). There were 1 case of laryngotracheal trauma and 1 case of airway Penicillium marneffei infection. According to Myer-Cotton grading system, grade Ⅳ stenosis was found in 14 cases, including 12 cases involving trachea and 2 cases involving trachea and subglottic area.There were 18 cases of grade Ⅲ, all of which involved the cervical trachea 5 cases failed in operation in other hospitals. According to stenosis grading, course of disease, primary disease control and the patient's general condition, the surgical plan was determined individually. The operations of end-to-end anastomosis, circumferential tracheal partial resection, T-tube placement and CO2 laser tracheal scar resection were performed respectively. The recovery of airway function and perioperative complications were observed one year after operation. Results: End-to-end anastomosis was performed in 16 cases, and partial circumferential tracheal resection in 2 cases, and tracheal granulation (scar) resection by CO2 laser in 2 cases and T-tube insertion in 12 cases. Eighteen cases which performed end-to-end anastomosis, partial resection of circumferential trachea in and 2 cases which performed laser tracheal scar resection were all recovered airway function at one stage. After 1 year, 19 cases were cured and 1 case was effective. Of 12 patients with T tube implantation, 11 cases were successfully extubated after 6-12 months, 7 cases were cured after 1 year, 2 cases were effective and 3 cases were ineffective. Among the 3 cases of failure, 2 cases were successfully extubated by sleeve resection and end-to-end anastomosis in the second stage, and the other case refused to accept other treatment methods and the T-tube was placed again, and the tube was blocked and the patient survived. During the follow-up period, the total cure rate was 87.5%, the effective rate was 9.4%, and the total extubation rate was 96.9%.The most common complication was subcutaneous emphysema, accounting for 78% (25/32), but no serious mediastinal emphysema or pneumothorax occurred. In the T-tube implantation group, granulation tissue grew in different degrees around the neck wound after operation, and improved or disappeared after 6-9 months. Anterior cervical tracheal fistula occurred in 4 cases of T-tube implantation group after extubation, which were cured by sealing the stoma. There were no complications such as severe bleeding or perioperative death. Conclusion: When there were various factors, the optimization of the surgical plan according to the degree of stenosis, the course of disease, the control of primary disease and the general condition was an important guarantee to improve the curative effect of laryngotracheal stenosis.

Impact of Socioeconomic Demographics and Race on Laryngotracheal Stenosis Etiology and Outcomes.

Certain sociodemographic variables are known to result in health care disparities. This study investigates potential differences in outcomes for patients with laryngotracheal stenosis (LTS) based on racial backgrounds and socioeconomic variables including insurance status and English language-Proficiency. Patients with LTS from 2016 to 2021were identified by relevant ICD codes. Variables including race, age, gender, language preference and insurance status were collected from medical records. Risk factors for LTS including COPD, smoking history, diabetes, GERD, and BMI were obtained. Etiology of LTS was categorized as autoimmune, traumatic, iatrogenic, or idiopathic. Need for temporary tracheostomy and tracheostomy dependence were determined at last follow-up visit. 129 patients were included for review. 70% of Black patients had iatrogenic LTS, whereas 65% of the White patient cohort had autoimmune or idiopathic LTS. Black patients were more strongly associated with temporary tracheostomy and tracheostomy dependence compared to White patients. Public health insurance and co-morbid GERD were associated with tracheostomy dependence for White patients only. This study identified a disproportionate representation of Black patients in the iatrogenic etiology of LTS. Although controlling for risk factors of LTS, this cohort had an increased need for temporary tracheostomy and tracheostomy dependence compared to White and Latinx cohorts. This finding merits further study. 3 Laryngoscope, 133:908-913, 2023.

Laryngotracheal stenosis: Mechanistic review.

BackgroundThe purpose of this review article is to summarize the existing literature surrounding wound healing mechanisms in laryngotracheal stenosis.MethodsA review of general wound healing pathophysiology, followed by a focused review of iatrogenic laryngotracheal stenosis (iLTS) and idiopathic subglottic stenosis (iSGS) as conditions of aberrant wound healing.ResultsiLTS is the scarring of the laryngotracheal complex, coming secondary to injury from prolonged intubation. iSGS is a chronic fibroinflammatory scarring and narrowing of the subglottic airway in the absence of any obvious preceding injury or trauma. They are both thought to result from a prolonged and dysregulated wound healing response that promotes the deposition of pathologic scar in the airway.ConclusionsUnderstanding the mechanisms that underlie wound healing will help identify and intervene on the process early in its development and discover future therapies that target individual wound healing mechanisms limiting the incidence of this recalcitrant disease process.

Phenotypic Epithelial Changes in Laryngotracheal Stenosis.

Characterize and quantify epithelium in multiple etiologies of laryngotracheal stenosis (LTS) to better understand its role in pathogenesis. Controlled in vitro cohort study. Endoscopic brush biopsy samples of both normal (non-scar) and scar were obtained in four patients with idiopathic subglottic stenosis (iSGS) and four patients with iatrogenic LTS (iLTS). mRNA expression of basal, ciliary, and secretory cell markers were evaluated using quantitative PCR. Cricotracheal resection tissue samples (n=5 per group) were also collected, analyzed using quantitative immunohistochemistry, and compared with rapid autopsy tracheal samples. Both iSGS and iLTS-scar epithelium had reduced epithelial thickness compared with non-scar control epithelium (P = .0009 and P = .0011, respectively). Basal cell gene and protein expression for cytokeratin 14 was increased in iSGS-scar epithelium compared with iLTS or controls. Immunohistochemical expression of ciliary tubulin alpha 1, but not gene expression, was reduced in both iSGS and iLTS-scar epithelium compared with controls (P = .0184 and P = .0125, respectively). Both iSGS and iLTS-scar had reductions in Mucin 5AC gene expression (P = .0007 and P = .0035, respectively), an epithelial goblet cell marker, with reductions in secretory cells histologically (P < .0001). Compared with non-scar epithelium, the epithelium within iSGS and iLTS is morphologically abnormal. Although both iSGS and iLTS have reduced epithelial thickness, ciliary cells, and secretory cells, only iSGS had significant increases in pathological basal cell expression. These data suggest that the epithelium in iSGS and iLTS play a common role in the pathogenesis of fibrosis in these two etiologies of laryngotracheal stenosis. Tertiary referral center (2017-2020). NA Laryngoscope, 132:2194-2201, 2022.

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

Iatrogenic laryngotracheal stenosis (iLTS) is the pathologic narrowing of the glottis, subglottis, and/or trachea secondary to intubation or tracheostomy related injury. Patients with type 2 diabetes mellitus (T2DM) are more likely to develop iLTS. To date, the metabolomics and phenotypic expression of cell markers in fibroblasts derived from patients with T2DM and iLTS are largely unknown. Controlled in vitro cohort study. Tertiary referral center (2017-2020). This in vitro study assessed samples from 6 patients with iLTS who underwent surgery at a single institution. Fibroblasts were isolated from biopsy specimens of laryngotracheal scar and normal-appearing trachea and compared with controls obtained from the trachea of rapid autopsy specimens. Patients with iLTS were subcategorized into those with and without T2DM. Metabolic substrates were identified by mass spectrometry, and cell protein expression was measured by flow cytometry. T2DM iLTS-scar fibroblasts had a metabolically distinct profile and clustered tightly on a Pearson correlation heat map as compared with non-T2DM iLTS-scar fibroblasts. Levels of itaconate were elevated in T2DM iLTS-scar fibroblasts. Flow cytometry demonstrated that T2DM iLTS-scar fibroblasts were associated with higher CD90 expression (Thy-1; mean, 95%) when compared with non-T2DM iLTS-scar (mean, 83.6%; P = .0109) or normal tracheal fibroblasts (mean, 81.1%; P = .0042). Scar-derived fibroblasts from patients with T2DM and iLTS have a metabolically distinct profile. These fibroblasts are characterized by an increase in itaconate, a metabolite related to immune-induced scar remodeling, and can be identified by elevated expression of CD90 (Thy-1) in vitro.

Glutamine Inhibition Reduces Iatrogenic Laryngotracheal Stenosis.

Glutamine inhibition has been demonstrated an antifibrotic effect in iatrogenic laryngotracheal stenosis (iLTS) scar fibroblasts in vitro. We hypothesize that broadly active glutamine antagonist, DON will reduce collagen formation and fibrosis-associated gene expression in iLTS mice. Prospective controlled animal study. iLTS in mice were induced by chemomechanical injury of the trachea using a bleomycin-coated wire brush. PBS or DON (1.3 mg/kg) were administered by intraperitoneal injection (i.p.) every other day. Laryngotracheal complexes were harvested at days 7 and 14 after the initiation of DON treatment for the measurement of lamina propria thickness, trichrome stain, immunofluorescence staining of collagen 1, and fibrosis-associated gene expression. The study demonstrated that DON treatment reduced lamina propria thickness (P=.025) and collagen formation in trichrome stain and immunofluorescence staining of collagen 1. In addition, DON decreased fibrosis-associated gene expression in iLTS mice. At day 7, DON inhibited Col1a1 (P < .0001), Col3a1 (P=.0046), Col5a1 (P < .0001), and Tgfβ (P=.023) expression. At day 14, DON reduced Co1a1 (P =.0076) and Tgfβ (P =.023) expression. Broadly active glutamine antagonist, DON, significantly reduces fibrosis in iLTS mice. These results suggest that the concept of glutamine inhibition may be a therapeutic option to reduce fibrosis in the laryngotracheal stenosis. N/A Laryngoscope, 131:E2125-E2130, 2021.

Quantitative Assessment of the Immune Microenvironment in Patients With Iatrogenic Laryngotracheal Stenosis.

Iatrogenic laryngotracheal stenosis (iLTS) is characterized by fibroinflammatory narrowing of the upper airway and is most commonly caused by intubation injury. Evidence suggests a key role for CD4 T cells in its pathogenesis. The objective of this study is to validate emerging multiplex immunofluorescence (mIF) technology for use in the larynx and trachea while quantitatively characterizing the immune cell infiltrate in iLTS. In addition to analyzing previously unstudied immune cell subsets, this study aims to validate previously observed elevations in the immune checkpoint PD-1 and its ligand PD-L1 while exploring their spatial and cellular distributions in the iLTS microenvironment. Controlled ex vivo cohort study. Tertiary care center. mIF staining was performed with formalin-fixed, paraffin-embedded slides from 10 patients with iLTS who underwent cricotracheal resection and 10 control specimens derived from rapid autopsy for CD4, CD8, CD20, FoxP3, PD-1, PD-L1, and cytokeratin. There was greater infiltration of CD4+ T cells, CD8+ T cells, CD20+ B cells, FoxP3+CD4+ Tregs, and FoxP3+CD8+ early effector T cells in the submucosa of iLTS specimens as compared with controls (P < .05 for all). PD-1 was primarily expressed on T cells and PD-L1 predominantly on CD4+ cells and "other" cells. This study leverages the power of mIF to quantify the iLTS immune infiltrate in greater detail. It confirms the highly inflammatory nature of iLTS, with CD4+ cells dominating the immune cell infiltrate; it further characterizes the cellular and spatial distribution of PD-1 and PD-L1; and it identifies novel immunologic targets in iLTS.

Characterization of Fibroblasts in Iatrogenic Laryngotracheal Stenosis and Type II Diabetes Mellitus.

Iatrogenic laryngotracheal stenosis (iLTS) is the pathological narrowing of the glottis, subglottis, and/or trachea due to scar tissue. Patients with type 2 diabetes mellitus (T2DM) are over 8 times more likely to develop iLTS and represent 26% to 53% of all iLTS patients. In this investigation, we compared iLTS scar-derived fibroblasts in patients with and without T2DM. Controlled ex vivo study. iLTS scar fibroblasts were isolated and cultured from subglottic scar biopsies in iLTS patients diagnosed with or without type 2 diabetes (non-T2DM). Fibroblast proliferation, fibrosis-related gene expression, and metabolic utilization of oxidative phosphorylation (OXPHOS) and glycolysis were assessed. Contractility was measured using a collagen-based assay. Metabolically targeted drugs (metformin, phenformin, amobarbital) were tested, and changes in fibrosis-related gene expression, collagen protein, and contractility were evaluated. Compared to non-T2DM, T2DM iLTS scar fibroblasts had increased α-smooth muscle actin (αSMA) expression (8.2× increased, P= .020), increased contractility (mean 71.4 ± 4.3% vs. 51.7 ± 16% Δ area × 90 minute-1 , P= .016), and reduced proliferation (1.9× reduction at 5 days, P< .01). Collagen 1 (COL1) protein was significantly higher in the T2DM group (mean 2.06 ± 0.19 vs. 0.74 ±.44 COL1/total protein [pg/μg], P= .036). T2DM iLTS scar fibroblasts had increased measures of OXPHOS, including basal respiration (mean 86.7 vs. 31.5 pmol/minute/10 μg protein, P= .016) and adenosine triphosphate (ATP) generation (mean 97.5 vs. 25.7 pmol/minute/10 μg protein, P= .047) compared to non-T2DM fibroblasts. Amobarbital reduced cellular contractility; decreased collagen protein; and decreased expression of αSMA, COL1, and fibronectin. Metformin and phenformin did not significantly affect fibrosis-related gene expression. T2DM iLTS scar fibroblasts demonstrate a myofibroblast phenotype and greater contractility compared to non-T2DM. Their bioenergetic preference for OXPHOS drives their increased contractility, which is selectively targeted by amobarbital. NA Laryngoscope, 131:1570-1577, 2021.

M2 Macrophages Promote Collagen Expression and Synthesis in Laryngotracheal Stenosis Fibroblasts.

Macrophages exhibit distinct phenotypes and are dysregulated in a model of iatrogenic laryngotracheal stenosis (iLTS). Increased populations of alternatively activated or M2 macrophages have been demonstrated. However, the role of these macrophages is unknown. The aims of this study are: 1) define the macrophage population in iLTS in the context of classically activated or M1 and M2 macrophage phenotypes, and 2) characterize the effect of monocyte-derived M1 and M2 macrophages on normal airway and LTS-derived fibroblasts (FBs) in vitro. Comparative analysis; in vitro controlled study. Immunohistochemical analysis of human iLTS and control specimens was performed to define the macrophage population. In vitro, M1, and M2 macrophages were polarized using M-CSF + Interferon-gamma and lipopolysaccharide or Interleukin-4, respectively. FBs isolated from laryngotracheal scar (LTS-FBs) and normal tracheal airway (NA-FBs) in eight patients with iLTS were cocultured with polarized macrophages. Fibrosis gene expression, soluble collagen production, and proliferation were assessed. Immunohistochemical analysis revealed increased CD11b + cells (macrophage marker) in laryngotracheal scar specimens (18.3% vs. 8.5%, P = .03) and predominant CD206 (M2) costaining versus CD86 (M1) (51.5% vs. 9.8%, n = 10, P = .001). In vitro, NA-FBs cultured with M2 macrophages demonstrated a 2.41-fold increase in collagen-1 expression (P = .05, n = 8) and an increase in soluble collagen (9.98 vs. 8.875, mean difference: 1.11 95%, confidence interval 0.024-2.192, n = 8, P = .015). Increased populations of CD11b cells are present in iLTS specimens and are predominantly CD206+, indicating an M2 phenotype. In vitro, M2 macrophages promoted collagen expression in airway FBs. Targeting macrophages may represent a therapeutic strategy for attenuating fibrosis in iLTS. NA Laryngoscope, 131:E346-E353, 2021.

Increased Expression of PD-1 and PD-L1 in Patients With Laryngotracheal Stenosis.

Laryngotracheal stenosis (LTS) is a fibrotic condition of the upper airway. Recent evidence suggests dysregulated host immunity plays a role in LTS development and progression. The programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) axis, targeted by paradigm-shifting immunotherapies for cancer treatment, has also recently been implicated in the pathogenesis of fibrotic pulmonary disease. However, a role for the PD-1/PD-L1 axis in the proximal airway fibrosis seen in LTS patients has not been explored. Controlled ex vivo study. Expression of PD-1, PD-L1, CD4, and CD8 were evaluated using immunohistochemical staining of cricotracheal resection specimens from postintubation iatrogenic laryngotracheal stenosis (iLTS), idiopathic subglottic stenosis (iSGS) patients, and normal controls derived from rapid autopsy (n = 8 per group). Fibroblasts derived from iLTS scar were also treated with transforming growth factor beta 1 (TGFβ1) and analyzed for PD-L1 expression by quantitative real-time polymerase chain reaction (n = 6). iLTS specimens exhibited increased expression of PD-1, PD-L1, and CD4 (all P < .0167) compared to controls, whereas iSGS specimens exhibited increased expression of PD-1 and CD4 (P < .0167) compared to controls. PD-1, PD-L1, and CD4 showed periepithelial patterns of expression in both disease cohorts. TGFβ1 treatment of iLTS fibroblasts increased expression of PD-L1 (the cognate ligand for PD-1). Expression of both PD-1 and its ligand PD-L1 are significantly greater in patients with iLTS compared to controls, and PD-1 expression is also elevated in patients with iSGS. Given published evidence implicating the PD-1/PD-L1 axis in pulmonary fibrosis, this suggests a possible role for checkpoint inhibitors targeting the PD-1/PD-L1 axis for the treatment of LTS. N/A Laryngoscope, 131:967-974, 2021.

Inflammatory pathways in the pathogenesis of iatrogenic laryngotracheal stenosis: what do we know?

Iatrogenic laryngotracheal stenosis (LTS) is pathologic airway narrowing due to scar formation following endotracheal intubation or tracheostomy. It is a chronic and recurrent disease that results in significant morbidity or even mortality. Current data suggests that inflammatory pathways play a significant role in mediating the deposition of collagen and extracellular matrix to generate this scar. In particular, the T-helper 2 cell and M2 macrophage axis appears to be activated in both animal models and patients with iatrogenic LTS. Interleukin-6 production in response to hypoxia has also been implicated. In this paper, we review the data supporting the roles of various inflammatory pathways in the pathogenesis of iatrogenic LTS, discuss potential therapeutic approaches targeting these mechanisms, and outline areas for future study.

Inhibition of glutaminase to reverse fibrosis in iatrogenic laryngotracheal stenosis.

Glutamine metabolism is a critical energy source for iatrogenic laryngotracheal stenosis (iLTS) scar fibroblasts, and glutaminase (GLS) is an essential enzyme converting glutamine to glutamate. We hypothesize that the GLS-specific inhibitor BPTES will block glutaminolysis and reduce iLTS scar fibroblast proliferation, collagen deposition, and fibroblast metabolism in vitro. Test-tube Lab Research. Immunohistochemistry of a cricotracheal resection (n = 1) and a normal airway specimen (n = 1) were assessed for GLS expression. GLS expression was assessed in brush biopsies of subglottic/tracheal fibrosis and normal airway from patients with iLTS (n = 6). Fibroblasts were isolated and cultured from biopsies of subglottic/tracheal fibrosis (n = 6). Fibroblast were treated with BPTES and BPTES + dimethyl α-ketoglutarate (DMK), an analogue of the downstream product of GLS. Fibroblast proliferation, gene expression, protein production, and metabolism were assessed in all treatment conditions and compared to control. GLS was overexpressed in brush biopsies of iLTS scar specimens (P = .029) compared to normal controls. In vitro, BPTES inhibited iLTS scar fibroblast proliferation (P = .007), collagen I (Col I) (P < .0001), collagen III (P = .004), and α-smooth muscle actin (P = .0025) gene expression and protein production (P = .031). Metabolic analysis demonstrated that BPTES reduced glycolytic reserve (P = .007) but had no effects on mitochondrial oxidative phosphorylation. DMK rescued BPTES inhibition of Col I gene expression (P = .0018) and protein production (P = .021). GLS is overexpressed in iLTS scar. Blockage of GLS with BPTES significantly inhibits iLTS scar fibroblasts proliferation and function, demonstrating a critical role for GLS in iLTS. Targeting GLS to inhibit glutaminolysis may be a successful strategy to reverse scar formation in the airway. NA Laryngoscope, 2020.

T-Helper 2 Lymphocyte Immunophenotype Is Associated With Iatrogenic Laryngotracheal Stenosis.

This prospective controlled human and murine study assessed the presence of inflammatory cells and cytokines to test the hypothesis that immune cells are associated with fibroproliferation in iatrogenic laryngotracheal stenosis (iLTS). Inflammation was assessed by histology and immunofluorescence (IF), quantitative real-time polymerase chain reaction (qRT-PCR), and flow cytometry of cricotracheal resections of iLTS patients compared to normal controls. An iLTS murine model assessed the temporal relationship between inflammation and fibrosis. iLTS specimens showed increased inflammation versus normal controls (159/high power field [hpf] vs. 119/hpf, P = 0.038), and increased CD3 + T-cells, CD4 + cells, and CD3+/CD4 + T-helper (TH ) cells (all P < 0.05). The inflammatory infiltrate was located immediately adjacent to the epithelial surface in the superficial aspect of the thickened lamina propria. Human flow cytometry and qRT-PCR showed a significant increase in interleukin (IL)-4 gene expression, indicating a TH 2 phenotype. Murine IF revealed a dense CD4 + T-cell inflammatory infiltrate on day 4 to 7 postinjury, which preceded the development of fibrosis. Murine flow cytometry and qRT-PCR studies mirrored the human ones, with increased T-helper cells and IL-4 in iLTS versus normal controls. CD3/CD4 + T-helper lymphocytes and the proinflammatory cytokine IL-4 are associated with iLTS. The association of a TH 2 immunophenotype with iLTS is consistent with findings in other fibroinflammatory disorders. The murine results reveal that the inflammatory infiltrate precedes the development of fibrosis. However, human iLTS specimens with well-developed fibrosis also contain a marked chronic inflammatory infiltrate, suggesting that the continued release of IL-4 by T-helper lymphocytes may continue to propagate iLTS. NA Laryngoscope, 129:177-186, 2019.

Partial laryngotracheal resection and anastomosis, institutional 10 years\u2019 experience

ObjectiveThis study aimed to evaluate the results of partial laryngotracheal resection and anastomosis in the management of iatrogenic laryngotracheal stenosis.Patients and MethodsThis retrospective analytical study was conducted on all patients who had been operated by means of partial laryngotracheal resection and anastomosis in our institute, from 2004 to 2014. The period of follow-up was at least 1 year. The total number of the patients included was 22.ResultsSuccessful decanulation was achieved in 20 (90.9%) cases. The number of complicated cases in our study (with one or more complication) was eight (36.3%). Two cases complained of dyspnea with documented restenosis of the trachea, and one case died from severe hemoptysis at 12 days postoperatively, most probably from trauma of the innominate. Two cases were complicated by surgical emphysema and one case was complicated by hematoma; all of them were managed successfully.ConclusionPartial laryngotracheal resection and anastomosis is a safe and reliable surgical method for the management of grade III and IV iatrogenic laryngotracheal stenosis. This technique achieves best results in male patients when the stenosis is short segment, and not involving the cricoid cartilage.

Targeting metabolic abnormalities to reverse fibrosis in iatrogenic laryngotracheal stenosis.

Management of laryngotracheal stenosis (LTS) remains primarily surgical, with a critical need to identify targets for adjuvant therapy. Laryngotracheal stenosis scar fibroblasts exhibit a profibrotic phenotype with distinct metabolic shifts, including an increased glycolysis/oxidative phosphorylation ratio. This study examines the effects of the glutamine antagonist 6-diazo-5-oxo-l-norleucine (DON) on collagen production, gene expression, proliferation, and metabolism of human LTS-derived fibroblasts in vitro. Paired normal and scar-derived fibroblasts isolated from subglottic and proximal tracheal tissue in patients with iatrogenic laryngotracheal stenosis (iLTS) were cultured. Proliferation rate, gene expression, protein production, and cellular metabolism were assessed in two conditions: 1) fibroblast growth medium, and 2) fibroblast growth medium with 1 × 10-4 M DON. DON treatment reduced cellular proliferation rate (n = 7, P = 0.0150). Expression of genes collagen 1 and collagen 3 both were reduced (n = 7, P = 0.0102, 0.0143, respectively). Soluble collagen production decreased (n = 7, P = 0.0056). As measured by the rate of extracellular acidification, glycolysis and glycolytic capacity decreased (n = 7, P = 0.0082, 0.0003, respectively). adenosine triphosphate (ATP) production and basal respiration decreased (n = 7, P = 0.0045, 0.0258, respectively), determined by measuring the cellular rate of oxygen consumption. The glutamine antagonist DON reverses profibrotic changes by inhibiting both glycolysis and oxidative phosphorylation in iLTS scar fibroblasts. In contrast to untreated iLTS scar fibroblasts, collagen gene expression, protein production, metabolic rate, and proliferation were significantly reduced. These results suggest DON and/or its derivatives as strong candidates for adjuvant therapy in the management of iatrogenic laryngotracheal stenosis. Enzymes involved in glutamine metabolism inhibited by DON offer targets for future investigation. NA. Laryngoscope, 128:E59-E67, 2018.

Interferon-γ Treatment of Human Laryngotracheal Stenosis–Derived Fibroblasts

Laryngotracheal stenosis (LTS) is a fibroproliferative disorder of the glottis, subglottis, and trachea. In models of fibrosis from other organ systems, the CD4+ T-cell response has been shown to regulate extracellular matrix deposition. Specifically, helper T cell 2 (TH2) promotes fibrosis, whereas TH1 and associated cytokines have been shown to be antifibrotic. However, this antifibrotic effect of the TH1 response has not been demonstrated in LTS. To determine whether the TH1 cytokine interferon-γ inhibits the function of LTS-derived fibroblasts in vitro. This in vitro controlled study included 6 patients with iatrogenic LTS undergoing routine surgical subglottic and tracheal dilation at a single institution. Fibroblasts were isolated from biopsy specimens of laryngotracheal scar and normal-appearing trachea. The presence of fibroblasts was confirmed by an immunohistochemical analysis. Laryngotracheal stenosis-derived fibroblasts were treated with interferon-γ and compared with untreated controls (2 sets of untreated, LTS-derived fibroblasts [media did not contain interferon-γ]) and normal airway fibroblasts (fibroblasts isolated from normal trachea). Data were collected from August 2015 through June 2016. Treatment with interferon-γ, 10 ng/mL. Cellular proliferation, fibrosis gene expression (using quantitative reverse transcription polymerase chain reaction analysis), soluble collagen, and cellular histologic features were assessed. Among the 6 patients (6 women; mean [SD] age, 38.3 [17.2] years), LTS-derived fibroblast proliferation was reduced in patients who received interferon-γ treatment compared with untreated controls on days 3 (mean difference, -6515 cells; 95% CI, -10 630 to -2600 cells) to 6 (mean difference, -47 521 cells; 95% CI, -81 285 to -13 757 cells). Interferon-γ treatment reduced collagen types I and III gene expression by 86% and 68%, respectively, and resulted in lower total collagen production (10.94 vs 14.89 μg/mL). In addition, interferon-γ treatment resulted in a 32% reduction in expression of transforming growth factor β in LTS-derived fibroblasts. Interferon-γ reduced proliferation, soluble collagen production, and collagen expression in LTS-derived fibroblasts while also reducing the expression of the profibrotic cytokine transforming growth factor β. These findings suggest that therapeutics aimed at increasing interferon-γ and the TH1 response could attenuate LTS.

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 β, 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.

Laryngotracheal Stenosis: Risk Factors for Tracheostomy Dependence and Dilation Interval

Objective Laryngotracheal stenosis (LTS) is a fibrotic process that narrows the upper airway and has a significant impact on breathing and phonation. Iatrogenic injury from endotracheal and/or tracheostomy tubes is the most common etiology. This study investigates differences in LTS etiologies as they relate to tracheostomy dependence and dilation interval. Study Design Case series with chart review. Setting Single-center tertiary care facility. Subjects and Methods Review of adult patients with LTS was performed between 2004 and 2015. The association of patient demographics, comorbidities, disease etiology, and treatment modalities with patient outcomes was assessed. Multiple logistic regression analysis and Kaplan-Meier analysis were performed to determine factors associated with tracheostomy dependence and time to second procedure, respectively. Results A total of 262 patients met inclusion criteria. Iatrogenic patients presented with greater stenosis ( P = .023), greater length of stenosis ( P = .004), and stenosis farther from the vocal folds ( P < .001) as compared with other etiologies. Iatrogenic patients were more likely to be African American, use tobacco, and have obstructive sleep apnea, type II diabetes, hypertension, chronic obstructive pulmonary disease, or a history of stroke. Iatrogenic LTS (odds ratio [OR] = 3.1, 95% confidence interval [95% CI] = 1.2-8.2), Cotton-Myer grade 3-4 (OR = 2.6, 95% CI = 1.1-6.4), and lack of intraoperative steroids (OR = 2.9, 95% CI = 1.2-6.9) were associated with tracheostomy dependence. Nonsmokers, patients without tracheostomy, and idiopathic LTS patients had a significantly longer time to second dilation procedure. Conclusion Iatrogenic LTS presents with a greater disease burden and higher risk of tracheostomy dependence when compared with other etiologies of LTS. Comorbid conditions promoting microvascular injury-including smoking, COPD, and diabetes-were prevalent in the iatrogenic cohort. Changes in hospital practice patterns to promote earlier tracheostomy in high-risk patients could reduce the incidence of LTS.

An in situ, in vivo murine model for the study of laryngotracheal stenosis.

Laryngotracheal stenosis (LTS) lacks an ideal animal model to study its unique wound-healing pathophysiology and the effect of interventions. To present an in vivo, in situ mouse model of LTS that can be used to investigate its pathophysiology, mechanisms, and interventions for treatment. Prospective controlled animal study performed at an academic animal research facility on 87 C57BL/6 mice. Experimental mice (n = 40) underwent bleomycin-coated wire-brush injury to the larynx and trachea, while mechanical injury controls (n = 32) underwent phosphate-buffered saline-coated wire-brush injury. Normal controls (n = 9) underwent no intervention, and mock surgery controls (n = 6) underwent anterior transcervical tracheal exposure only. Laryngotracheal complexes were harvested at days 7, 14, and 21 after injury. At the respective time points, mice in the chemomechanical and mechanical injury groups were killed, and their laryngotracheal complexes were harvested for histologic analysis. Normal and mock surgery controls were killed and then underwent histologic analysis. The primary outcome measure was lamina propria thickness. The chemomechanical injury group maintained a significant increase in lamina propria thickness through day 21 compared with uninjured controls at day 7 (82.7 vs 41.8 μm; P<.05), day 14 (93.5 vs 26.0 μm; P<.05), and day 21 (91.2 vs 40.8 μm; P<.05). Compared with the mechanical injury group, the chemomechanical injury group demonstrated a significantly increased thickness at 21 days (91.2 vs 33.7 μm; P<.05). Chemomechanical initiation of fibrosis in situ creates a viable mouse model of LTS that incorporates the physiologic circulatory supply and airflow. This small-animal model may be used to investigate the pathogenesis and inflammatory mechanisms of iatrogenic LTS and test therapeutic interventions to reverse or reduce the development of fibrosis.