Airway Scarring Research Articles

Middle Ear Fibrosis Contributes to Hearing Loss in Patients With Myhre Syndrome.

Myhre syndrome (MS) is a rare genetic condition that presents with multiple genetic anomalies including cleft lip and palate and Eustachian tube dysfunction. These patients are at a high risk for airway scarring from intubation and mucosal inflammation. Hearing loss (conductive or mixed, of varying severity) is a common comorbidity in these patients, the exact etiology of which is still unclear. We present the cases of 2 unrelated children with MS who suffered progressive mixed hearing loss from fibrosis and obliteration of the middle ear spaces. Both patients had multiple sets of ear tubes that demonstrated early extrusion. The older patient underwent bone conduction implantation at age 11 which resulted in dramatic improvement of speech recognition and interactive skills. The other younger patient demonstrates a similar trajectory but has not yet undergone implantation. Otolaryngologists should take a cautious approach to surgery of the eardrum and middle ear to avoid unnecessary induction of fibrosis in this susceptible patient population. These cases highlight a newly described etiology for hearing loss and suggest a benefit to bone conduction implantation.

Similarity Network Analysis of the Adaptive Immune Response in the Proximal Airway.

Recent immunologic study of the adaptive immune repertoire in the subglottic airway demonstrated high-frequency T cell clones that do not overlap between individuals. However, the anatomic distribution and antigenic target of the T cell repertoire in the proximal airway mucosa remain unresolved. Single-cell RNA sequencing of matched scar and unaffected mucosa from idiopathic subglottic stenosis patients (iSGS, n = 32) was performed and compared with airway mucosa from healthy controls (n = 10). T cell receptor (TCR) sequences were interrogated via similarity network analysis to explore antigenic targets using the published algorithm: Grouping of Lymphocyte Interactions by Paratope Hotspots (GLIPH2). The mucosal T cell repertoire in healthy control airways consisted of highly expressed T cell clones conserved across anatomic subsites (trachea, bronchi, bronchioles, and lung). In iSGS, high-frequency clones were equally represented in both scar and adjacent non-scar tissue. Significant differences in repertoire structure between iSGS scar and unaffected mucosa was observed, driven by unique low-frequency clones. GLIPH2 results suggest low-frequency clones share targets between multiple iSGS patients. Healthy airway mucosa has a highly conserved T cell repertoire across multiple anatomic subsites. Similarly, iSGS patients have highly expressed T cell clones present in both scar and unaffected mucosa. iSGS airway scar possesses an abundance of less highly expanded clones with predicted antigen targets shared between patients. Interrogation of these shared motifs suggests abundant adaptive immunity to viral targets in iSGS airway scar. These results provide insight into disease pathogenesis and illuminate new treatment strategies in iSGS. NA Laryngoscope, 134:3245-3252, 2024.

Localizing Hormone Receptor Expression to Cellular Compartments in Idiopathic Subglottic Stenosis.

Idiopathic subglottic stenosis (iSGS) is an unexplained progressive fibrosis of the upper airway. iSGS almost exclusively affects women; as a result, female hormones (estrogen and progesterone) have been proposed to participate in the pathogenesis of iSGS. Our aim was to localize cell-specific gene expression of estrogen receptors (ESR1 and ESR2) and progesterone receptor (PGR) using an established iSGS single-cell RNA sequencing (scRNAseq) cell atlas. Ex vivo molecular study of airway scar and healthy mucosa from iSGS patients. An established scRNAseq atlas consisting of 25,974 individually sequenced cells from subglottic scar (n = 7) or matched unaffected mucosa (n = 3) in iSGS patients was interrogated for RNA expression of ESR1, ESR2, and PGR. Results were quantified and compared across cell subsets, then visualized using Uniform Manifold Approximation and Projection (UMAP). Confirmatory protein assessment of endocrine receptors in fibroblasts from iSGS patients (n = 5) was performed via flow cytometry. The proximal airway mucosa in iSGS patients demonstrates differential expression of endocrine receptors (ESR1, ESR2, PGR). Within airway scar, endocrine receptors are primarily expressed by fibroblasts, immune cells, and endothelial cells. Fibroblasts show strong ESR1 and PGR expression, while immune cells possess RNA for both ESR1 and ESR2. Endothelial cells predominantly express ESR2. Epithelial cells in unaffected mucosa express all three receptors, which are all reduced in airway scar. scRNAseq data localized endocrine receptor expression to specific cell subsets. These results provide the foundation for future work interrogating how hormone-dependent mechanisms promote, sustain, or participate in iSGS disease pathogenesis. NA; Basic science Laryngoscope, 133:3506-3511, 2023.

The Impact of Tonsillectomy on the Adult Singing Voice: Acoustic and Aerodynamic Measures

Singers undergoing tonsillectomy are understandably concerned about possible sequelae to their voice. The surgical risks of laryngeal damage from intubation and upper airway scarring are valid reasons for singers to carefully consider their options for treatment of tonsil-related symptoms. No prior studies have statistically assessed objective voice outcomes in a group of adult singers undergoing tonsillectomy. This study determined the impact of tonsillectomy on the adult singing voice by determining if there were statistically significant changes in preoperative versus postoperative acoustic, aerodynamic, and Voice-Related Quality of Life (VRQOL) measures. Prospective cohort study. Tertiary Referral Academic Hospital SUBJECTS: Thirty singers undergoing tonsillectomy from 2012 to 2019. Acoustic recordings were obtained with Computerized Speech Lab (CSL) (Pentax CSL 4500) and analyzed with the Multidimensional Voice Program (MDVP) (Pentax MDVP) and Pratt Acoustic Analysis Software. Estimates of aerodynamic vocal efficiency were obtained and analyzed using the Phonatory Aerodynamic System (Pentax PAS 6600). Preoperative VRQOL scores were recorded, and singers were instructed to refrain from singing for 3 weeks following tonsillectomy. Repeat acoustic and aerodynamic measures as well as VRQOL scores were obtained at the first postoperative visit. Average postoperative acoustic (jitter, shimmer, HNR) and aerodynamic (sound pressure level divided by subglottal pressure) parameters related to laryngeal phonatory function did not differ significantly from preoperative measures. The only statistically significant change in postoperative measures of resonance was a decrease in the 3rd formant (F3) for the /a/ vowel. Average postoperative VRQOL scores (79.8, SD18.7) improved significantly from preoperative VRQOL scores (89, SD12.2) (P=0.007). Tonsillectomy does not appear to alter laryngeal voice production in adult singers as measured by standard acoustic and aerodynamic parameters. The observed decrease in F3 for the /a/ vowel is hypothetically related to increasing the pharyngeal cross-sectional area by removing tonsillar tissue, but this would not be expected to appreciably impact the perceptual characteristics of the vowel. Singers' self-assessment (VRQOL) improved after tonsillectomy.

The Proximal Airway Is a Reservoir for Adaptive Immunologic Memory in Idiopathic Subglottic Stenosis.

Characterization of the localized adaptive immune response in the airway scar of patients with idiopathic subglottic stenosis (iSGS). Basic Science. Utilizing 36 patients with subglottic stenosis (25 idiopathic subglottic stenosis [iSGS], 10 iatrogenic post-intubation stenosis [iLTS], and one granulomatosis with polyangiitis [GPA]) we applied immunohistochemical and immunologic techniques coupled with RNA sequencing. iSGS, iLTS, and GPA demonstrate a significant immune infiltrate in the subglottic scar consisting of adaptive cell subsets (T cells along with dendritic cells). Interrogation of T cell subtypes showed significantly more CD69+ CD103+ CD8+ tissue resident memory T cells (TRM ) in the iSGS airway scar than iLTS specimens (iSGS vs. iLTS; 50% vs. 28%, P = .0065). Additionally, subglottic CD8+ clones possessed T-cell receptor (TCR) sequences with known antigen specificity for viral and intracellular pathogens. The human subglottis is significantly enriched for CD8+ tissue resident memory T cells in iSGS, which possess TCR sequences proven to recognize viral and intracellular pathogens. These results inform our understanding of iSGS, provide a direction for future discovery, and demonstrate immunologic function in the human proximal airway. Laryngoscope, 131:610-617, 2021.

The role of inflammatory cytokines in the development of idiopathic subglottic stenosis.

Idiopathic subglottic stenosis (iSGS) is a debilitating extrathoracic obstruction involving the lower laryngeal and upper tracheal airway. It arises without a known antecedent injury or associated disease process. iSGS is a fibrotic disease marked histologically by excessive accumulation of fibrous connective tissue components of the extracellular matrix (ECM, i.e., collagen and fibronectin) in inflamed tissue, which leads to airway obstruction and clinical dyspnea. Diverse diseases in divergent organ systems are associated with fibrosis, suggesting common pathogenic pathways. One of the most common is sustained host inflammation. Recent investigations focusing on the inflammatory response associated with iSGS have sought to characterize the immunophenotype and cytokine profile of the airway scar in iSGS. While the role of the immune response as inciting event in iSGS remains unresolved, the centrality of an active immune response to the observed subglottic tissue remodeling is becoming more defined.

Pathologic Fibroblasts in Idiopathic Subglottic Stenosis Amplify Local Inflammatory Signals

To characterize the phenotype and function of fibroblasts derived from airway scar in idiopathic subglottic stenosis (iSGS) and to explore scar fibroblast response to interleukin 17A (IL-17A). Basic science. Laboratory. Primary fibroblast cell lines from iSGS subjects, idiopathic pulmonary fibrosis subjects, and normal control airways were utilized for analysis. Protein, molecular, and flow cytometric techniques were applied in vitro to assess the phenotype and functional response of disease fibroblasts to IL-17A. Mechanistically, IL-17A drives iSGS scar fibroblast proliferation ( P < .01), synergizes with transforming growth factor ß1 to promote extracellular matrix production (collagen and fibronectin; P = .04), and directly stimulates scar fibroblasts to produce chemokines (chemokine ligand 2) and cytokines (IL-6 and granulocyte-macrophage colony-stimulating factor) critical to the recruitment and differentiation of myeloid cells ( P < .01). Glucocorticoids abrogated IL-17A-dependent iSGS scar fibroblast production of granulocyte-macrophage colony-stimulating factor ( P = .02). IL-17A directly drives iSGS scar fibroblast proliferation, synergizes with transforming growth factor ß1 to promote extracellular matrix production, and amplifies local inflammatory signaling. Glucocorticoids appear to partially abrogate fibroblast-dependent inflammatory signaling. These results offer mechanistic support for future translational study of clinical reagents for manipulation of the IL-17A pathway in iSGS patients.

Scarring Airway Stenosis in Chinese Adults: Characteristics and Interventional Bronchoscopy Treatment.

Background:Scarring airway stenosis is commonly seen in China as compared to other developed countries, due to the high prevalence of tuberculosis. Nowadays, interventional bronchoscopy treatment has been widely used to treat this disease in China. This study demonstrated the characteristics of scarring airway stenosis in Chinese adults and retrospectively evaluated the efficacy of interventional bronchoscopy treatment of this disease.Methods:Patients with scarring airway stenosis from 18 tertiary hospitals were enrolled between January 2013 and June 2016. The causes, site, and length of scarring airway stenosis were analyzed, and the efficacy of the interventional bronchoscopy treatment was evaluated.Results:The final study cohort consisted of 392 patients. Endotracheobronchial tuberculosis (EBTB) was the most common cause of scarring airway stenosis (305/392, 77.8%) in Chinese adults with a high rate of incidence in young women. The left main bronchus was most susceptible to EBTB, and most posttuberculosis airway scarring stenosis length was 1.1–2.0 cm. The average clinical success rate of interventional bronchoscopy treatment for scarring airway stenosis in Chinese patients is 60.5%. The stent was inserted in 8.7% scarring airway stenosis in China.Conclusions:Scarring airway stenosis exhibits specific characteristics in Chinese patients. Interventional bronchoscopy is a useful and safe treatment method for the disease.

Serum proteomic analysis of cicatricial airway stenosis

To establish serum protein fingerprint profile in patients with cicatricial airway stenosis and compared with healthy control. Serum samples of 17 cicatricial airway stenosis patients and 17 healthy persons were analyzed by SELDI-TOF-MS to select the differently expressed proteins through Biomarker Wizard software. Compared with healthy control, 49 protein biomarkers were identified. Among them, 25 proteins were up-regulated, 24 proteins were down-regulated. These proteins were confirmed by searching database. There are obvious differentially expressed proteins in patients with cicatricial airway stenosis and controls, which may related with the development of airway scar.

The pilot study of the effect of paclitaxel by local application on scar formation after airway injury in rabbits

To investigate the effect of local application of paclitaxel on airway scar formation after airway injury in rabbits. Forty New Zealand rabbits were randomly divided into four groups, negative control group (n = 10), saline control group (n = 10), group I (n = 10), group II (n = 10). All rabbits received tracheotomy. In negative control group, the specimens were harvested for histological examination and immunohistochemical analysis immediately after tracheotomy;in other three groups, rabbits received airway injury after tracheotomy. In group I and group II, 0.4 mg/ml and 1.0 mg/ml paclitaxel was applied locally in injured airway segment for 3 minutes after airway injury. The normal saline was used in control group for 3 minutes. The animals were killed in 21 days after operation. The specimens were harvested for histological examination and immunohistochemical analysis. Transmission electron microscopy was employed to observe the ultrastructure of paclitaxel-induced apoptotic cells. The degree of stenosis in group I and group II were significantly decreased compared to those in saline control group [saline control group (59 ± 13)%, group I (27 ± 8)%, group II (22 ± 7)%]. Histological examination showed fibroblast cells and inflammatory cells in group I and group II were significantly fewer than in saline control group. The TGF-β1 positive cells and VEGF positive cells in group I and group II were significantly decreased compared to those in saline control group (P < 0.05). Paclitaxel-induced cell apoptosis and injured cell organs were observed by transmission electron microscopy. Local application of paclitaxel inhibits airway scar formation after airway injury in rabbit model, and the inhibition is dose dependent. Paclitaxel may have a therapeutic potential for the treatment of airway stenosis caused by endotracheal intubation, tracheotomy or implantation of airway stents.

Role of Vascular Endothelial Growth Factor a in Children with Acquired Airway Stenosis

Vascular endothelial growth factor A (VEGF-A) is important in the angiogenic response for wound healing. This study investigated whether VEGF-A may play a role in the pathogenesis of acquired airway stenosis. Eight lesions from 5 pediatric patients with subglottic stenosis after airway reconstruction (N = 4) or prolonged intubation (N = 1) and normal laryngeal tissue from 5 autopsy patients were included. Formalin-fixed sections of subglottic tissue from each patient were examined by in situ hybridization for the presence of messenger RNA (mRNA) for VEGF-A, vascular endothelial growth factor receptor 1 (VEGFR-1), and vascular endothelial growth factor receptor 2 (VEGFR-2). Strong expression of VEGF-A mRNA was noted in hyperplastic squamous epithelium overlying granulation tissue. Strong expression of VEGFR-1 and VEGFR-2 was noted in the endothelial cells within granulation tissue. No strong labeling of VEGF-A mRNA or its receptors was noted in 2 specimens with mature scar tissue or in the control specimens. The angiogenic growth factor VEGF-A is strongly expressed in hyperplastic epithelium overlying granulation tissue in airway stenosis. Also, VEGFR-1 and VEGFR-2 mRNAs are strongly expressed in the endothelial cells of granulation tissue. This finding suggests an important role of VEGF-A in the pathogenesis of airway scar formation and stenosis.

Is Obliterative Bronchiolitis in Lung Transplantation Associated With Microvascular Damage to Small Airways?

Acute rejection, a vascular-based disorder, has been identified as the major risk factor for obliterative bronchiolitis (OB), an airway-based pathology. This study investigated the hypothesis that changes to the microvascular blood supply of small airways were associated with the development of OB, thus providing a possible link between an acute vascular insult (acute rejection) and chronic airway changes (OB). Microvasculature of 695 small airways (99 patients) was assessed in post-mortem lung allograft specimens using monoclonal antibodies for von Willebrand factor and CD31. Group A consisted of 343 small airways from 58 patients with no evidence of OB. The remaining 41 patients had histological evidence of OB in some of their small airways and grouped as B, C, and D with some patients contributing to all three groups ie, their lung specimen had some small airways which were completely obliterated with OB, some airways which were partially obliterated and some small airways without any histological evidence of OB development. Thus group B consisted of 145 small airways (34 patients) without OB. Group C consisted of 171 small airways with partial luminal obstruction (36 patients). Group D consisted of 36 small airways (14 patients) with complete luminal obliteration. Airway circumference (mean +/- standard deviation) was 2.36 +/- 0.37, 2.41 +/- 0.51, 2.49 +/- 0.51, and 2.57 +/- 0.79 mm, respectively (p = 0.40). Mean number of blood vessels per unit length of airway circumference was 4.12 +/- 1.1, 1.58 +/- 0.61, 2.42 +/- 1.06, and 4.42 +/- 1.46 vessels/mm, respectively (p < 0.001). Blood vessels with circumference greater than 0.2 mm were present in 100%, 64%, 39%, and 7% of small airways, respectively (p < 0.001). Univariate and multivariate analyses (donor and recipient age, sex, and cytomegalovirus status, recipient pretransplant diagnosis, ischemic times, acute rejection and infective episodes, postoperative survival days, recipient group [A to D], blood vessels per unit length, and airway circumference) confirmed that reduction in blood vessels per unit length was associated with the development of OB and was time-independent. Obliterative bronchiolitis was preceded by a decrease in microvascular supply to the small airways (group B). The subsequent onset of airway scarring (groups C and D) was associated with an increased number of significantly smaller vessels, suggestive of neovascularization.

Photodynamic Therapy (PDT) can induce airway scarring and stenosis

PURPOSE: PDT is the most extensively studied endobronchial treatment for early lung cancer in patients who are not candidates for surgical resection. Potential advantages of this localized therapeutical modality relative to other techniques include tumor selectivity and complete healing of the bronchial mucosa after illumination. However, some observations suggest that complete healing is not always present, and we reviewed our own experience with this treatment.

Photodynamic therapy, Nd-YAG laser and electrocautery for treating early-stage intraluminal cancer: which to choose?

The degree of healing and damage of the bronchial wall after photodynamic therapy, Nd-YAG laser and electrocautery for intraluminal early-stage cancer have been analysed. Review of the bronchoscopy reports and follow-up histology specimens of twenty-nine patients treated bronchoscopically with curative intent for their intraluminal tumor have been performed. Seventeen patients had been treated with bronchoscopic electrocautery (BE) only, six with photodynamic therapy (PDT) and six with Nd-YAG laser. Bronchial wall scarring seen during follow-up bronchoscopy was scored and subepithelial fibrosis were histologically evaluated using Alcian blue staining, Azan staining and polarised light. After BE, prominent airway scarring was seen in five patients (29%), with significant stenosis (>50% lumen) in one of these cases. Prominent scarring and significant stenosis were found in four (67%), after PDT. In five (83%) after Nd-YAG laser prominent scarring was found, one patient had significant stenosis. In three cases, two after BE and one after PDT, subepithelial tissue in the follow-up biopsies was insufficient for proper histologic examination. In the remaining biopsy specimen only one (7%) showed a moderate or excessive amount of fibroblasts after BE, whereas for PDT and Nd-YAG this was found in three (60%) and four patients (67%), respectively. Excessive matrix was found in none of the biopsies after BE, in two (40%) after PDT and in three (50%) after Nd-YAG laser. Compact collagen formations were seen in two (12%) biopsies after BE, in two (40 and 33%) after PDT and Nd-YAG, respectively. Compared to electrocautery, more airway scarring and more subepithelial fibrosis were seen after treatment with PDT and Nd-YAG laser. These findings, especially regarding PDT, is in contrast to the assumption that PDT is selective and may be important in the choice of treatment for patients with early stage cancer.

The measurement of reticular basement membrane and submucosal collagen in the asthmatic airway

An increase in types III and V collagen below the bronchial epithelium of the airway is known to be responsible for apparent thickening of the reticular basement membrane (RBM) and is recognized as a characteristic feature of asthma. Wide variations exist in reported ranges of the thickness of the RBM in both asthmatic and control airways. The description of collagen deposition has been confined to the RBM with no previous reports of increased collagen deeper within the bronchial wall (i.e. submucosa), although inflammation is known to extend to deeper levels. The objective of this study was to compare different methods used to measure RBM thickness and to examine collagen deposition in deeper asthmatic bronchial submucosa. We examined bronchial mucosal biopsies from 15 asthmatic and 13 normal healthy controls to measure RBM thickness by light and electron microscopic methods on resin sections and to estimate the extent of collagen deposition in the submucosa by immunochemical staining with monoclonal antibodies to collagen subtypes on paraffin sections. Simple staining with toluidine blue on resin sections coupled with light microscopic evaluation was as accurate and less expensive than electron microscopic methods in the measurement of the thickness of RBM (mean +/- SD, light microscopy: asthma vs control, 6.01 +/- 2.09 vs 3.19 +/- 0.55 microns, P < 0.001; electron microscopy: asthma vs control, 6.09 +/- 2.19 vs 2.85 +/- 0.86 microns, P < 0.01). Using monoclonal antibodies to collagen subtypes and image analysis methods, we identified increased collagen in the submucosa in asthma (type III collagen, asthma vs control: 62 +/- 7 vs 51 +/- 9%, P < 0.05, type V collagen, asthma vs control: 60 +/- 6 vs 52 +/- 9%, P < 0.05). This study has demonstrated that the RBM may be reliably measured by light microscopic methods. This study shows for the first time that the submucosa of the asthmatic airway contains significantly more collagen than normal controls, giving rise to the possibility that airway scar formation may have greater functional implications than has been previously believed from consideration of the RBM alone.

The anterior cricoid split procedure for the management of subglottic stenosis in infants and children

Severe acquired subglottic stenosis occurs most commonly in infants and children who require long-term ventilatory support with indwelling endotracheal tubes for underlying respiratory disease. A variety of operative and endoscopic procedures have been advocated for this problem including endoscopic fulguration, cryotherapy, direct incision or excision, and several types of extensive direct laryngotracheoplasties. The failure rate with these procedures is high. We have treated 22 patients including 12 neonates and 10 older children with acquired airway injury and obstruction with a simple cricoid split. In 15 patients the airway obstruction was completely relieved and these youngsters were extubated without difficulty. An additional 3 patients failed initial extubation which was subsequently successful, however, after repeat intubation for a short period of time. Endoscopic follow-up shows complete healing of the incised area. In 2 neonates the procedure was unsuccessful, and tracheotomy was needed. One of these had additional severe airway injury in the distal tracheobronchial tree secondary to selective bronchial intubation in the newborn period. Two older children also required tracheotomy because of severe airway scarring unrelieved by this procedure. The cricoid split is a simple and successful way of dealing with subglottic stenosis, especially in the newborn premature infant. A significant advantage is that it disturbs the anatomy very little, allowing for more extensive laryngotracheoplasty in the future should it fail.