Laryngotracheal Mucosal Surface Expression of Candidate Biomarkers in Idiopathic Subglottic Stenosis

Abstract

Objectives Idiopathic subglottic stenosis (iSGS) is an inflammatory process leading to fibrosis and narrowing of the laryngotracheal airway. There is variability in patient response to surgical intervention, but the mechanisms underlying this variability are unknown. In this pilot study, we measure expression of candidate targets at the mucosal surface of the subglottis in iSGS patients. We aim to identify putative biomarkers for iSGS that provide insights into the molecular basis of disease progression, yield a gene signature for the disease, and/or predict a response to therapy. Study Design In vitro comparative study of human cells. Methods Levels of candidate transcripts and proteins were measured in healthy and stenotic laryngotracheal tissue specimens taken from the mucosal surface in 16 iSGS patients undergoing endoscopic balloon dilation. Pre‐ and post‐operative pulmonary function test and patient reported voice and breathing outcomes were also assessed. Unsupervised clustering was used to define patient subgroups based on expression profile. Results Pulmonary function and voice and breathing outcome metrics demonstrated significant post‐operative improvement. Transcript levels of αSMA, CCL2, COL1A1, COL3A1, FN1, IFNG, and TGFB1 and protein levels of CCL2, IFNG, and IL‐6 were significantly upregulated in stenotic as compared to healthy tissues. Marked heterogeneity was observed in the patterns of expression of candidate markers across individuals and tissue types. Patient subgroups defined by expression profile did not show a statistically significant difference in dilation interval. Conclusion Pro‐inflammatory and pro‐fibrotic pathways are significantly upregulated along the mucosal surface of stenotic laryngotracheal tissues, and CCL2 and IFNG merit further investigation as potential iSGS biomarkers. Level of Evidence 4 Laryngoscope, 131:342–349, 2021

An Updated Review of Subglottic Stenosis: Etiology, Evaluation, and Management

“…The authors identified patterns of hypermethylation found in iSGS patients that may be associated with differential protein expression and suggest the possibility of iSGS subgroups [23]. Liu et al has demonstrated increased levels of CCL2, IFNγ, and IL-6 protein in iSGS specimen, although with marked heterogeneity [24]. Inflammation and cytokines (such as IL-17A) play an important role in stenosis [25].…”

“…Patients who are tracheotomized due to iSGS have the lowest rate of decannulation (63%) [75•]. Recent research has built upon our knowledge of fibrogenesis in iSGS, but studies have yet to identify biomarkers to monitor disease progression and prognosis [24]. The IL-23/IL-17A inflammatory axis appears to be a potential therapeutic target [21].…”

Persistent Inflammation and Nitric Oxide Dysregulation Are Transcriptomic Blueprints of Subglottic Stenosis

“…All C57BL/6 mice were housed in a temperature-controlled specificpathogen-free facility under 12-hour light/dark cycles. Laryngotracheal complex (LTC) transfer was done as previously described (8). Briefly, LTC transplants were performed using donor tracheal segments from 8-week-old, 20-to 25-g female C57BL/6 mice (Jackson Laboratories, Bar Harbor, Maine).…”

“…Over the past decade, researchers and clinicians have started to shed light on the pathogenesis of SGS. In addition to histological evidence of exuberant granulation tissue and accumulation of permanent scar tissue, prior studies have shown an increased in several markers of inflammation and fibrosis, such as Interleukin (IL)-1, transforming growth factor beta (TGF-b), platelet-derived growth factor (PDGF), Interferon gamma (IFNG), as well as prostaglandin (PG)-2 from excised stenotic tissues (4)(5)(6)(7)(8). The importance of the immune system in the development of SGS was further emphasized by findings that immunodeficient mice failed to develop SGS (9), and that human subglottic tissues were significantly enriched for CD8+ resident memory T cells (10) as well as CD4+ T cells with increased expression of PD-1 and PD-L1 (11,12).…”

Characterizing the Macrophage Population in Patients With Idiopathic Subglottic Stenosis

“…Although adjuvant medical therapies have more recently been employed including serial steroid injections, proton pump inhibitors, and inhaled corticosteroids, their efficacy remains inconsistent 5,8 . Heterogeneity in patient response to surgical and medical treatments underscores the need to better understand the pathogenesis of iSGS 5,9 . An improved understanding of the underlying mechanisms driving fibrosis in iSGS could deliver more effective and targeted therapies.…”