Objective To define the inflammatory cell infiltrate preceding fibrosis in a laryngotracheal stenosis (LTS) murine model. Study Design Prospective controlled murine study. Setting Tertiary care hospital in a research university. Subjects and Methods Chemomechanical injury mice (n=44) sustained bleomycin-coated wire-brush injury to the laryngotracheal complex while mechanical injury controls (n=42) underwent PBS-coated wire-brush injury. Mock surgery controls (n=34) underwent anterior transcervical tracheal exposure only. Inflammatory and fibrosis protein and gene expression was assessed in each condition. Immunohistochemistry served as a secondary outcome. Results In chemomechanical injury mice, there was an up-regulation of: Collagen I (p<0.0001, p<0.0001), Tgf-β (p=0.0023, p=0.0008), and elastin (p<0.0001, p<0.0001) on Day 7, acute inflammatory gene: Il1β (p=0.0027, p=0.0008) on Day 1, and macrophage gene: CD11b (p=0.0026, p=0.0033) on Day 1 versus mechanical and mock controls respectively. M1 marker iNOS expression decreased (p=0.0014) while M2 marker arg1 (p=0.0002) increased on Day 7 compared to mechanical controls. Flow cytometry demonstrated increased macrophages (p=0.0058, day 4) and M1 macrophages (p=0.0148, day 4, p=0.0343, day 7, p=0.0229, day 10) compared to mock controls. There were similarities between chemomechanical and mechanical injury mice with an increase in M2 macrophages at day 10 (p=0.0196). Conclusions The mouse model demonstrated increased macrophages involved with the development of LTS. Macrophage immunophenotype suggested that dysregulated M2 macrophages have a role in abnormal laryngotracheal wound healing in both species. These results support this animal model as a representation for human disease. Furthermore, this data delineates inflammatory cells and signaling pathways in LTS that may potentially be modulated to lessen fibroblast proliferation and collagen deposition.

Objective/Purpose Laryngotracheal stenosis (LTS) is a chronic fibrotic disease characterized by fibroblast proliferation, collagen deposition, and matrix remodeling in the lamina propria of the larynx and/or trachea. Current medical therapies are limited by a poor understanding of the effector cell’s (fibroblasts) cellular biology and metabolism. The purpose of this study is to compare cellular proliferation, function, and metabolism between normal and LTS-derived fibroblasts in vitro. Methods Human biopsies of normal and iatrogenic LTS tissue (n=7) were obtained and fibroblasts were isolated and cultured in vitro. Cellular proliferation, cellular histology, gene expression and metabolic analyses were performed. Statistical analyses comparing normal and scar-derived fibroblasts were performed. Results LTS fibroblast proliferation rate, cellular surface area, and collagen-1 expression were increased compared to normal fibroblasts. Cellular metabolic analysis of LTS-derived fibroblasts demonstrated reduced oxidative phosphorylation and increased glycolysis/oxidative phosphorylation ratio compared with normal fibroblasts. Conclusion Human iatrogenic LTS-derived fibroblasts demonstrated aberrant behavior when compared with normal fibroblasts. A Warburg-like effect was revealed suggesting human iatrogenic LTS fibroblasts drive their proliferation with aerobic glycolysis. The distinct metabolism suggests metabolic inhibitors could reduce fibroblast hyperplasia and hypertrophy in LTS and fibrosis in general.

Objective To determine if rapamycin inhibits the growth, function, and metabolism of human laryngotracheal stenosis (LTS)–derived fibroblasts. Study Design Controlled in vitro study. Setting Tertiary care hospital in a research university. Subjects and Methods Fibroblasts isolated from biopsies of 5 patients with laryngotracheal stenosis were cultured. Cell proliferation, histology, gene expression, and cellular metabolism of LTS-derived fibroblasts were assessed in 4 conditions: (1) fibroblast growth medium, (2) fibroblast growth medium with dimethylsulfoxide (DMSO), (3) fibroblast growth medium with 10−10 M (low-dose) rapamycin dissolved in DMSO, and (4) fibroblast growth medium with 10−9 M (high-dose) rapamycin dissolved in DMSO. Results The LTS fibroblast count and DNA concentration were reduced after treatment with high-dose rapamycin compared to DMSO (P = .0007) and normal (P = .0007) controls. Collagen I expression decreased after treatment with high-dose rapamycin versus control (P = .0051) and DMSO (P = .0093) controls. Maximal respiration decreased to 68.6 pMoles of oxygen/min/10 mg/protein from 96.9 for DMSO (P = .0002) and 97.0 for normal (P = .0022) controls. Adenosine triphosphate (ATP) production decreased to 66.8 pMoles from 88.1 for DMSO (P = .0006) and 83.3 for normal (P = .0003) controls. Basal respiration decreased to 78.6 pMoles from 108 for DMSO (P = .0002) and 101 for normal (P = .0014) controls. Conclusions Rapamycin demonstrated an anti-fibroblast effect by significantly reducing the proliferation, metabolism, and collagen deposition of human LTS fibroblast in vitro. Rapamycin significantly decreased oxidative phosphorylation of LTS fibroblasts, suggesting at a potential mechanism for the reduced proliferation and differentiation. Furthermore, rapamycin’s anti-fibroblast effects indicate a promising adjuvant therapy for the treatment of laryngotracheal stenosis.