High-Level Expression of Matrix-Associated Transforming Growth Factor-β 1 in Benign Airway Stenosis

POSTN Regulates Fibroblast Proliferation and Migration in Laryngotracheal Stenosis Through the TGF-β/RHOA Pathway

OBJECTIVES

To investigate the role of periostin (POSTN) and the transforming growth factor β (TGF-β) pathway in the formation of laryngotracheal stenosis (LTS) scar fibrosis and to explore the specific signaling mechanism of POSTN-regulated TGF-β pathway in tracheal fibroblasts.

METHODS

Bioinformatics analysis was performed on scar data sets from the GEO database to preliminarily analyze the involvement of POSTN and TGF-β pathways in fibrosis diseases. Expression of POSTN and TGF-β pathway-related molecules was analyzed in LTS scar tissue at the mRNA and protein levels. The effect of POSTN on the biological behavior of tracheal fibroblasts was studied using plasmid DNA overexpression and siRNA silencing techniques to regulate POSTN expression and observe the activation of TGF-β1 and the regulation of cell proliferation and migration via the TGF-β/RHOA pathway.

RESULTS

The bioinformatics analysis revealed that POSTN and the TGF-β pathway are significantly involved in fibrosis diseases. High expression of POSTN and TGF-β/RHOA pathway-related molecules (TGFβ1, RHOA, CTGF, and COL1) was observed in LTS tissue at both mRNA and protein levels. In tracheal fibroblasts, overexpression or silencing of POSTN led to the activation of TGF-β1 and regulation of cell proliferation and migration through the TGF-β/RHOA pathway.

CONCLUSION

POSTN is a key molecule in scar formation in LTS, and it regulates the TGF-β/RHOA pathway to mediate the formation of cicatricial LTS by acting on TGF-β1. This study provides insights into the molecular mechanisms underlying LTS and suggests potential therapeutic targets for the treatment of this condition.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:4078-4087, 2024.

Electrospun composite-coated endotracheal tubes with controlled siRNA and drug delivery to lubricate and minimize upper airway injury

Endotracheal Tubes (ETTs) maintain and secure a patent airway; however, prolonged intubation often results in unintended injury to the mucosal epithelium and inflammatory sequelae which complicate recovery. ETT design and materials used have yet to adapt to address intubation associated complications. In this study, a composite coating of electrospun polycaprolactone (PCL) fibers embedded in a four-arm polyethylene glycol acrylate matrix (4APEGA) is developed to transform the ETT from a mechanical device to a dual-purpose device capable of delivering multiple therapeutics while preserving coating integrity. Further, the composite coating system (PCL-4APEGA) is capable of sustained delivery of dexamethasone from the PCL phase and small interfering RNA (siRNA) containing polyplexes from the 4APEGA phase. The siRNA is released rapidly and targets smad3 for immediate reduction in pro-fibrotic transforming growth factor-beta 1 (TGFϐ1) signaling in the upper airway mucosa as well as suppressing long-term sequelae in inflammation from prolonged intubation. A bioreactor was used to study mucosal adhesion to the composite PCL-4APEGA coated ETTs and investigate continued mucus secretory function in ex vivo epithelial samples. The addition of the 4APEGA coating and siRNA delivery to the dexamethasone delivery was then evaluated in a swine model of intubation injury and observed to restore mechanical function of the vocal folds and maintain epithelial thickness when observed over 14 days of intubation. This study demonstrated that increase in surface lubrication paired with surface stiffness reduction significantly decreased fibrotic behavior while reducing epithelial adhesion and abrasion.

Identifying Molecular Pathophysiology and Potential Therapeutic Options in Iatrogenic Tracheal Stenosis

INTRODUCTION

While most patients with iatrogenic tracheal stenosis (ITS) respond to endoscopic ablative procedures, approximately 15% experience a recalcitrant, recurring disease course that is resistant to conventional management. We aimed to explore genetic profiles of patients with recalcitrant ITS to understand underlying pathophysiology and identify novel therapeutic options.

METHODS

We collected 11 samples of granulation tissue from patients with ITS and performed RNA sequencing. We identified the top 10 most highly up- and down-regulated genes and cellular processes that these genes corresponded to. For the most highly dysregulated genes, we identified potential therapeutic options that favorably regulate their expression.

RESULTS

The dysregulations in gene expression corresponded to hyperkeratinization (upregulation of genes involved in keratin production and keratinocyte differentiation) and cellular proliferation (downregulation of cell cycle regulating and pro-apoptotic genes). Genes involved in retinoic acid (RA) metabolism and signaling were dysregulated in a pattern suggesting local cellular RA deficiency. Consequently, RA also emerged as the most promising potential therapeutic option for ITS, as it favorably regulated seven of the ten most highly dysregulated genes.

CONCLUSION

This is the first study to characterize the role of hyperkeratinization and dysregulations in RA metabolism and signaling in the disease pathophysiology. Given the ability of RA to favorably regulate key genes involved in ITS, future studies must explore its efficacy as a potential therapeutic option for patients with recalcitrant ITS.

miR-34c-5p inhibited fibroblast proliferation, differentiation and epithelial-mesenchymal transition in benign airway stenosis via MDMX/p53 pathway

Benign airway stenosis (BAS) means airway stenosis or obstruction that results from a variety of non-malignant factors, including tuberculosis, trauma, benign tumors, etc. In consideration of the currently limited research on microRNAs in BAS, this study aimed to explore the role and mechanism of miR-34c-5p in BAS. The expression of miR-34c-5p in BAS granulation tissues showed a significant down-regulation compared with the normal control group. Moreover, miR-34c-5p mimics suppressed the proliferation and differentiation of human bronchial fibroblasts (HBFs) and the epithelial-mesenchymal transition (EMT) of human bronchial epithelial cells (HBE). Conversely, miR-34c-5p inhibitors aggravated those effects. A dual-luciferase reporter assay confirmed that miR-34c-5p can target MDMX rather than Notch1. The over-expression of MDMX can reverse the inhibiting effect of miR-34c-5p on HBFs proliferation, differentiation and EMT. Furthermore, the expressions of tumor protein (p53) and PTEN were down-regulated following the over-expression of MDMX. In addition, the expressions of PI3K and AKT showed an up-regulation. In conclusion, miR-34c-5p was down-regulated in BAS and may inhibit fibroblast proliferation differentiation and EMT in BAS via the MDMX/p53 signaling axis. These findings expand the understanding of the role of miR-34c-5p and will help develop new treatment strategies for BAS.

Biocompatibility and sub-chronic toxicity studies of phlorotannin/polycaprolactone coated trachea tube for advancing medical device applications

The phlorotannin-polycaprolactone-coated endotracheal tube (PP tube) has been developed with the aim of preventing tracheal stenosis that can result from endotracheal intubation, a factor that can lead to a serious airway obstruction. Its preventive efficacy has been assessed through both in vitro and in vivo investigations. However, there is a lack of studies concerning its biocompatibility and sub-chronic toxicity in animal models, a crucial factor to ensure the safety of its usage as a functional endotracheal tube. Thus, this study aimed to evaluate the biocompatibility and sub-chronic (13 weeks) toxicity of the PP tube through L929 cell line and diverse in vivo models. The cytotoxicity testing was performed using the extracts of PP tube on L929 cells for 72 h. Furthermore, other tests conducted on animal models, including ICR mice (acute systemic toxicity), New Zealand white rabbit (intradermal reactivity and pyrogen tests), guinea pig (maximization sensitization), and Sprague Dawley rats (sub-chronic toxicity). In both biocompatibility and sub-chronic toxicity analyses, no significant adverse effects are observed in the groups exposed to the PP tube, when compared to control group. Altogether, the findings suggested that the PP tube exhibits relative non-toxic and safety, supporting its suitability for clinical usage. However, extended periods of intubation may produce mild irritant responses, highlighting the clinical caution of limiting intubation duration to less than 13 weeks.

Differential expression of miRNAs revealed by small RNA sequencing in traumatic tracheal stenosis

Introduction: Traumatic tracheal stenosis (TTS) is a major cause of complex difficult airways, without clinically definitive efficacious drugs available. The aim of this study was to provide a general view of interactions between micro and messenger ribonucleic acids (miRNAs and mRNAs) and many potential mechanisms in TTS via small RNA sequencing. Methods: In this study, the identification of miRNAs was completed using small RNA sequencing and samples from four TTS patients and four normal control cases. By using bioinformatics tools, such as miRanda and RNAhybrid, for identifying the candidate target genes of miRNAs with differential expression in each sample, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes were employed for enriching the predicted target genes of miRNAs with differential expression based on the correspondence between miRNAs and their target genes. We detected the expression of the candidate miRNAs using quantitative real-time polymerase chain reaction (qRT-PCR). Results: Twenty-four miRNAs with significant differential expression were identified, including 13 upregulated and 11 downregulated ones. Bioinformation technology was adopted to predict 2,496 target genes. These miRNA-target genes were shown to be primarily enriched in cells and organelles with catalytic activity and binding function, such as binding proteins, small molecules, and nucleotides. Finally, they were observed to process into TTS through the intercellular and signal regulation of related inflammatory signaling and fibrosis signaling pathways. QRT-PCR confirmed the upregulation of miR21-5p and miR214-3p and the downregulation of miR141-3p and miR29b-3p, which was expected to become a high-specific miRNA for TTS. Conclusion: Among all the miRNAs detected, 24 miRNAs demonstrated differential expression between the TTS and normal control groups. A total of 2,496 target genes were predicted by bioinformation technology and enriched in inflammatory and fibrotic signaling pathways. These results provide new ideas for further studies and the selection of targets for TTS in the future.

Mechanisms of fibrosis in iatrogenic laryngotracheal stenosis: New discoveries and novel targets

Iatrogenic laryngotracheal stenosis (iLTS) is a pathological condition characterized by the narrowing of the laryngeal and tracheal structures due to the formation of abnormal scar tissue. The core of iLTS lies in the fibrosis of the laryngotracheal tissue, and recent research has unveiled novel discoveries regarding the underlying mechanisms of fibrosis. This review provides an overview of the recent advancements in understanding the mechanisms of fibrosis in iLTS. It encompasses various aspects, such as immune system dysregulation, changes in the extracellular matrix (ECM), metabolic alterations, and the role of microbial flora. The review also explores the interplay and relationships between these new mechanisms, establishing a theoretical foundation for the development of multi-target therapies and combination therapies for iLTS.

Triamcinolone acetonide induces the autophagy of Ag85B-treated WI-38 cells via SIRT1/FOXO3 pathway

BACKGROUND

Tracheobronchial stenosis due to tuberculosis (TSTB) seriously threatens the health of tuberculosis patients. The inflammation and autophagy of fibroblasts affect the development of TSTB. Triamcinolone acetonide (TA) can regulate the autophagy of fibroblasts. Nevertheless, the impact of TA on TSTB and underlying mechanism has remained unclear.

OBJECTIVE

To study the impact of TA on TSTB and underlying mechanism.

MATERIAL AND METHODS

In order to simulate the TSTB-like model in vitro, WI-38 cells were exposed to Ag85B protein. In addition, the cell counting kit (CCK)-8 assay was applied to assess the function of TA in Ag85B-treated WI-38 cells. Quantitative real-time polymerase chain reaction was applied to detect the mRNA level of sirtuin 1 (SIRT1) and forkhead box O3 (FOXO3a), and autophagy-related proteins were evaluated by Western blot analysis. Vascular endothelial growth factor (VEGF) level was investigated by immunohistochemical staining. Enzyme-linked immunosorbent serologic assay was applied to detect the secretion of inflammatory cytokines. Furthermore, hematoxylin and eosin staining was applied to observe tissue injuries.

RESULTS

Ag85B affected WI-38 cell viability in a limited manner, while TA notably suppressed Ag85B-treated WI-38 cell viability. TA induced the apoptosis of Ag85B-treated WI-38 cells in a dose-dependent manner. In addition, Ag85B-treated WI-38 cells demonstrated the upregulation of interleukin (IL)-6, tumor necrosis factor-α (TNF-α), interferon gamma (IFN-γ), and fibrotic proteins (transforming growth factor-beta [TGF-β] and vascular endothelial growth factor [VEGF]), which can be significantly destroyed by the TA. Meanwhile, TA reversed Ag85-induced inhibition of cell autophagy by mediation of p62, LC3, and Beclin1. Furthermore, silencing of SIRT1/FOXO3a pathway could reverse the effect of TA on the autophagy of Ag85B-treated cells.

CONCLUSION

TA significantly induced the autophagy of fibroblasts in Ag85B-treated cells by mediation of SIRT1/FOXO3 pathway. This study established a new theoretical basis for exploring strategies against TSTB.

Plumbagin attenuates traumatic tracheal stenosis in rats and inhibits lung fibroblast proliferation and differentiation via TGF-β1/Smad and Akt/mTOR pathways

Traumatic tracheal stenosis (TS) is a serious respiratory disease characterized by hyperplasia of airway granulation. Plumbagin (PLB) is a natural naphthoquinone component with anti-fibrotic properties. This research aimed to explore the roles of PLB in alleviating TS and the underlying mechanisms. For in vitro studies, lung fibroblasts (IMR-90 cells), with/without PLB treatment or TGF-β1 induction, were used. The viability and proliferation of IMR-90 cells were examined by CCK-8 and EdU incorporation assays. The differentiation of IMR-90 cells was assessed by detecting the mRNA and protein expression levels of collagen (COL)-1 and alpha-smooth muscle actin (α-SMA). Besides, immunofluorescence assay was conducted to evaluate the localization of α-SMA in TGF-β1-induced IMR-90 cells. Moreover, the combination of PLB with/without TβRI (SB-431,542), PI3K/Akt (Ly294002) or mTOR (rapamycin) inhibitor was pretreated on IMR-90 cells after TGF-β1 induction. For in vivo studies, a rat model of TS was established. The pathological features and severity of TS were determined by hematoxylin and eosin staining. The protein levels of TGF-β1/Smad and Akt/mTOR pathways were detected for both in vitro and in vivo models. PLB effectively inhibited the proliferation and differentiation of TGF-β1-induced IMR-90 cells, and suppressed TGF-β1/Smad and Akt/mTOR signaling pathways both in vivo and in vitro. Furthermore, PLB reduced the degree of TS in rats. Taken together, our results indicate that PLB regulates lung fibroblast activity and attenuates TS in rats by inhibiting TGF-β1/Smad and Akt/mTOR signaling pathways. In conclusion, this study implies that PLB may serve as a promising therapeutic compound for TS.

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

OBJECTIVES

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.

STUDY DESIGN

Controlled ex vivo study.

METHODS

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).

RESULTS

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).

CONCLUSION

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.

LEVEL OF EVIDENCE

N/A Laryngoscope, 131:967-974, 2021.

Respiratory acidosis during bronchoscopy-guided percutaneous dilatational tracheostomy: impact of ventilator settings and endotracheal tube size

Background

The current study investigates the effect of bronchoscopy-guided percutaneous dilatational tracheostomy (PDT) on the evolution of respiratory acidosis depending on endotracheal tube (ET) sizes. In addition, the impact of increasing tidal volumes during the intervention was investigated.

Methods

Two groups of ICU-patients undergoing bronchoscopy-guided PDT with varying tidal volumes and tube sizes were consecutively investigated: 6 ml/kg (N = 29, mean age 57.4 ± 14.5 years) and 12 ml/kg predicted body weight (N = 34, mean age 59.5 ± 12.8 years).

Results

The mean intervention time during all procedures was 10 ± 3 min. The combination of low tidal volumes and ETs of 7.5 mm internal diameter resulted in the most profound increase in PaCO₂ (32.2 ± 11.6 mmHg) and decrease in pH-value (− 0.18 ± 0.05). In contrast, the combination of high tidal volumes and ETs of 8.5 mm internal diameter resulted in the least profound increase in PaCO₂ (8.8 ± 9.0 mmHg) and decrease of pH (− 0.05 ± 0.04). The intervention-related increase in PaCO₂ was significantly lower when using higher tidal volumes for larger ET: internal diameter 7.5, 8.0 and 8.5: P > 0.05, =0.006 and = 0.002, respectively. Transcutaneous PCO₂ monitoring revealed steadily worsening hypercapnia during the intervention with a high correlation of 0.87 and a low bias of 0.7 ± 9.4 mmHg according to the Bland-Altman analysis when compared to PaCO₂ measurements.

Conclusions

Profound respiratory acidosis following bronchoscopy-guided PDT evolves in a rapid and dynamic process. Increasing the tidal volume from 6 to 12 ml/kg PBW was capable of attenuating the evolution of respiratory acidosis, but this effect was only evident when using larger ETs.

Trial registration

DRKS00011004. Registered 20th September 2016.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0824-5) contains supplementary material, which is available to authorized users.

Antifibrotic effect of mitomycin-C on human vocal cord fibroblasts

OBJECTIVE

Acquired laryngotracheal stenosis is a potentially life-threatening situation and a very difficult and challenging problem in laryngology. Therefore, new trends and innovative approaches based on antifibrotic drugs and minimally invasive regimens are being developed to attenuate laryngotracheal fibrosis and scarring. The purpose of this study was to examine the efficacy of mitomycin-C (MMC) to reverse the transforming growth factor (TGF)-β-induced differentiation of MRC-5 fibroblast and human primary vocal cord fibroblasts to reveal the possible applicability of MMC to laryngotracheal fibrotic conditions.

METHODS

Human primary fibroblast cells were isolated from vocal cord specimens of patients undergoing total laryngectomy. The established primary vocal cord fibroblast cell cultures as well as the MRC-5 human fibroblast cells were treated with 5 ng/mL TGF-β alone and then with 0.5 µg/mL MMC for 24 hours. Differentiation of fibroblasts was characterized by α-smooth muscle actin (α-SMA) immunhistochemistry, Western blot analysis, and real-time polymerase chain reaction. Cell motility was assessed by wound-healing assay.

RESULTS

Elevated α-SMA mRNA and protein expression as well as increased cell motility were observed upon TGF-β exposures. However, after MMC treatments the TGF-β-induced fibroblasts exhibited a significant decrease in α-SMA expression and wound-healing activity. Therefore, TGF-β-stimulated fibroblast-myofibroblast transformation was reversed at least in part by MMC treatment. Histopathological examinations of tissue specimens of a laryngotracheal stenosis patient supported these findings.

CONCLUSION

Antifibrotic effects of MMC were demonstrated on the human MRC-5 cell line and on primary vocal cord fibroblast cultures. These results verify that MMC can be used with success to reverse upper airway stenosis by reverting the myofibroblast phenotype.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E255-E262, 2019.

Pathologic Fibroblasts in Idiopathic Subglottic Stenosis Amplify Local Inflammatory Signals

OBJECTIVE

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).

STUDY DESIGN

Basic science.

SETTING

Laboratory.

SUBJECTS AND METHODS

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.

RESULTS

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).

CONCLUSION

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.

β-Elemene inhibits the proliferation of primary human airway granulation fibroblasts by down-regulating canonical Wnt/β-catenin pathway

Benign airway stenosis is a clinical challenge because of recurrent granulation tissues. Our previous study proved that a Chinese drug, β-elemene, could effectively inhibit the growth of fibroblasts cultured from hyperplastic human airway granulation tissues, which could slow down the progression of this disease. The purpose of the present study is to find out the mechanism for this effect. We cultured fibroblasts from normal human airway tissues and human airway granulation tissues. These cells were cultured with 160 μg/ml normal saline (NS), different doses of β-elemene, or 10 ng/ml canonical Wnt/β-catenin pathway inhibitor (Dickkopf-1, DKK-1). The proliferation rate of cells and the expression of six molecules involved in canonical Wnt/β-catenin pathway, Wnt3a, glycogen synthase kinase-3β (GSK-3β), β-catenin, α-smooth muscle actin (α-SMA), transforming growth factor-β (TGF-β), and Collagen I (Col-I), were measured. At last, we used canonical Wnt/β-catenin pathway activator (LiCl) to further ascertain the mechanism of β-elemene. Canonical Wnt/β-catenin pathway is activated in human airway granulation fibroblasts. β-Elemene didn't affect normal human airway fibroblasts; however, it had a dose-responsive inhibitive effect on the proliferation and expression of Wnt3a, non-active GSK-3β, β-catenin, α-SMA, TGF-β, and Col-I of human airway granulation fibroblasts. More importantly, it had the same effect on the expression and nuclear translocation of active β-catenin. All these effects were similar to 10 ng/ml DKK-1 and could be attenuated by 10 mM LiCl. Thus, β-elemene inhibits the proliferation of primary human airway granulation fibroblasts by down-regulating canonical Wnt/β-catenin pathway. This pathway is possibly a promising target to treat benign tracheobronchial stenosis.

Airway Management and Bronchoscopic Treatment of Subglottic and Tracheal Stenosis Using Holmium Laser with Balloon Dilatation

Tracheal and subglottic stenosis are chronic inflammatory processes which can occur as a result of several possible aetiologies, most commonly as a result of prolonged intubation. All consecutive cases of subglottic and tracheal stenosis, secondary to prolonged intubation treated endoscopically over a period of 2 years were reviewed. The surgical approach consisted of radial incision and ablation using Holmium YAG laser, balloon dilatation and topical instillation of mitomycin C through flexible fiberoptic bronchoscope. Ventilation throughout was maintained through LMA. Laser fiber delivered through working channel of bronchoscope. CRA balloon passed through adopter of LMA. Every patient followed for 1 year with 1, 3, 6 months and 1 year interval. Serial balloon dilatation and mitomycin C instillation done in patients during follow up visit. Thirteen patients who underwent airway intervention during study period were studied for clinical outcome. Average follow up was 1 year. Etiology for airway stenosis in all patients of study group was intubation injury. Average frequency of balloon dilatation required was three. Average tracheal lumen achieved at the end of 1 year in our study group was 70%. Symptomatic improvement observed in all patients. Average PEFR achieved was up to 60% of predicted value. Benign subglottic and tracheal stenosis can be safely and effectively managed with flexible bronchoscopy, holmium YAG lasar ablation, balloon dilatation and Mitomycin-C after securing the airway with LMA for general anaesthesia and optimal ventilation.

EW-7197 eluting nano-fiber covered self-expandable metallic stent to prevent granulation tissue formation in a canine urethral model

PURPOSE

To evaluate an EW-7197-eluting nanofiber-covered stent (NFCS) for suppressing granulation tissue formation after stent placement in a canine urethral model.

MATERIALS AND METHODS

All experiments were approved by the committee of animal research. A total of 12 NFCSs were placed in the proximal and distal urethras of six dogs. Dogs were divided into two groups with 3 dogs each. The control stent (CS) group received NFCSs and the drug stent (DS) group received EW-7197 (1000 μg)-eluting NFCSs. All dogs were sacrificed 8 weeks after stent placement Histologic findings of the stented urethra were compared using the Mann-Whitney U test.

RESULTS

Stent placement was technically successful in all dogs without procedure-related complications. On urethrographic analysis, the mean luminal diameter was significantly larger in the DS group than in the CS group at 4 and 8 weeks after stent placement (all p < 0.001). On histological examination, mean thicknesses of the papillary projection, thickness of submucosal fibrosis, number of epithelial layers, and degree of collagen deposition were significantly lower in the DS group than in the CS group (all p < 0.001), whereas the mean degree of inflammatory cell infiltration was not significantly different (p > 0.05).

CONCLUSION

The EW-7197-eluting NFCS is effective and safe for suppressing granulation tissue formation after stent placement in a canine urethral model.

The Potential Role of Bile Acids in Acquired Laryngotracheal Stenosis

OBJECTIVE

Gastroesophageal reflux is thought to be a risk factor for laryngotracheal stenosis. Bile acids are a component of gastric refluxate and have previously been implicated in the development of fibrosis in other airway subsites. There is clear evidence that bile acids reflux into the upper airway. We therefore investigated the potential role of bile acids in the pathophysiology of laryngotracheal fibrosis and stenosis, specifically investigating the highly conserved process of epithelial-mesenchymal transition (EMT).

STUDY DESIGN

Translational research study.

METHODS

Human primary tracheal epithelial cells (PTECs) were challenged with the four most common digestive bile acids (cholic, chenodeoxycholic, deoxycholic, and lithocholic). EMT markers transforming growth factor (TGF)-β1, Matrix metalloproteinase (MMP)-9, and procollagen proteins were measured in the supernatant at 48 hours via enzyme-linked immunosorbent assay. Real-time polymerase chain reaction was also used to measure E-cadherin and fibronectin expression.

RESULTS

Significantly greater concentrations of TGF-β1 and MMP-9 were measured in the culture supernatants of cells treated with each bile acid at 10 µmol/L. Lithocholic acid and deoxycholic acid induced significantly increased expression of procollagen protein. Upregulation of fibronectin and downregulation of E-cadherin were observed with all bile acids, except for deoxycholic acid.

CONCLUSION

This is the first proof of principle demonstration that physiologically relevant bile acid challenge induces EMT mechanisms in PTECs. This implies a potential role for bile acids in laryngotracheal scarring and airway remodeling of potential translational significance in laryngotracheal stenosis.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:2029-2033, 2018.

Inflammatory protein expression in human subglottic stenosis tissue mirrors that in a murine model

OBJECTIVES

We undertook to describe the genetic and protein composition of subglottic stenosis (SGS) by measuring an array of protein expression and messenger RNA levels within human SGS tissue. We also sought to compare this human array to cytokine expression from a murine model of SGS in order to confirm the effective translational nature of our animal model.

METHODS

Human granulation tissue from 10 patients with early symptomatic SGS was compared to control bronchus. The expression levels of 24 different cytokines were measured by a Luminex protein assay and real-time polymerase chain reaction.

RESULTS

The protein expression in human SGS mirrors that seen in murine SGS. Transforming growth factor β1, interleukin 1β, and matrix metalloproteinase 9 were markedly elevated in both human and mouse SGS tissues. The protein array showed a statistically significant elevation in the proinflammatory cytokines tumor necrosis factor α, interleukin 1, granulocyte macrophage colony-stimulating factor, and interferon γ.

CONCLUSIONS

This is the first study, to our knowledge, to measure an array of protein expression within human SGS tissue. The expression profile suggests that symptomatic tracheal granulation tissue is mostly within the early inflammatory phase of wound healing and has only begun fibrotic and angiogenic remodeling. This study validates our murine model of SGS, and also helps to define the exact pathways of tissue injury, in the hope of leading to new treatments for this difficult condition.

Bacterial biofilms and increased bacterial counts are associated with airway stenosis

OBJECTIVES

Most airway stenoses are acquired secondary to the use of prolonged endotracheal intubation. Antibiotics have been shown to decrease local inflammation and granulation tissue formation in the trachea. However, antibiotic therapy is not 100% effective in preventing or treating granulation tissue formation. Development of bacterial biofilms may explain this finding. This study evaluates the difference between tracheal stenotic segments and normal trachea in terms of (1) presence of bacterial biofilms, (2) quantitative bacterial counts, and (3) inflammatory markers.

STUDY DESIGN

Cross-sectional study.

SETTING

Tertiary care academic medical center.

SUBJECTS

A total of 12 patients were included in the study. Tissue from stenotic segments from 6 patients with airway stenosis undergoing open airway procedures were compared with tracheal tissue from 6 patients without airway stenosis undergoing tracheostomy.

METHODS

Scanning electron microscopy for biofilm detection, quantitative polymerase chain reaction for quantitative analysis of bacterial count, and immunohistochemistry were performed for inflammatory markers transforming growth factor β1 (TGF-β1) and SMAD3.

RESULTS

Compared with the patients without airway stenosis, patients in the airway stenosis group showed presence of bacterial biofilms, a significantly higher expression of 16S rRNA gene copies per microgram of tissue (187.5 vs 7.33, P = .01), and higher expression of TGF-β1 (91% vs 8%, P < .001) and SMAD3 (83.5% vs 17.8%, P < .001).

CONCLUSION

Bacterial biofilms, increased bacterial counts, and higher expression of TGF-β1 and SMAD3 are associated with airway stenosis.

Endoscopic treatment of tracheal stenosis

For all cases of tracheal obstructions surgery should be considered first. Interventional endoscopic procedures can provide immediate relief. Intraluminally growing tumors can be resected with laser, argon-plasma coagulation, an electrosurgical knife or cryo-probe. Photodynamic therapy of smaller tracheal tumors can be curative. Narrowing from intramural tumor growth or wall destruction requires internal splinting with an airway stent. Scar strictures can be dilated with balloons but the biotrauma may stimulate new scarring. In benign strictures and malacias, tracheal stents should only be placed if all other methods are exhausted. Complications including stent migration, mucostasis, halitosis and granulation tissue development must be considered. Most important for a good outcome is a multidisciplinary approach.

Utility of rigid bronchoscopic dilatation and mitomycin C application in the management of postintubation tracheal stenosis: case series and systematic review of literature

BACKGROUND

Postintubation tracheal stenosis (PITS) is a common problem encountered by interventional pulmonologists. The aim of this study was to evaluate the utility of mitomycin C (MMC) as an adjunctive treatment to rigid bronchoscopic dilatation in patients with PITS.

METHODS

Prospective analysis of data from the interventional pulmonology unit of a large tertiary care teaching center in North India. Patients with a diagnosis of PITS undergoing rigid bronchoscopic dilatation and MMC (0.4 mg/mL) application were included. The primary outcome was the occurrence of restenosis.

RESULTS

Seven patients underwent rigid bronchoscopic dilatation, followed by the application of MMC at 4 quadrants of the stenosis. Controlled radial expansion balloon bronchoplasty was also performed, if necessary, in addition to mechanical dilatation using the barrel of the rigid bronchoscope. Restenosis occurred in all 7 patients (100%) and the mean duration to the detection of restenosis was 27 days. The restenosis was symptomatic in 6 out of 7 (85.7%) patients.

CONCLUSIONS

Rigid bronchoscopic dilatation and a single application of MMC is not an effective treatment in the management of PITS.

Pulse Steroid Therapy Inhibits Murine Subglottic Granulation

Objective

Using a functional model of airway granulation tissue in subglottic stenosis, we investigated changes in inflammatory markers within granulation tissue in response to intraperitoneal dexamethasone injections. Changes in inflammatory markers will allow us to identify potential targets for immunological therapy.

Study Design

Institutional Animal Care and Use Committee–approved animal study.

Setting

Philadelphia Veterans Administration Medical Center animal research facility.

Subjects and Methods

Laryngotracheal complexes of donor mice underwent direct airway injury and were transplanted into subcutaneous tissue of 19 recipient mice in 2 groups: steroid treated and untreated, with sample sizes of 10 and 9, respectively. The steroid-treated arm received intraperitoneal injection of dexamethasone for 3 weeks. Laryngotracheal complexes were then harvested, and granulation formation was measured. The messenger RNA (mRNA) expression of transforming growth factor (TGF)–β1 and interleukin (IL)–1 was quantified.

Results

At 3 weeks posttransplantation, there were statistically significant differences in observable granulation formation as well as mRNA expression of TGF-β1 and IL-1β in all groups within the steroid treated arm as compared with the untreated arm.

Conclusions

Systemic steroids have been used to prevent formation of granulation tissue and subglottic stenosis. However, the study of the immunologic markers and the corresponding changes with steroid treatment has not been well studied in animal models. Using a previously described novel murine model, we begin to delineate inflammatory markers that can be applied for potential therapeutic targets.

The effectiveness of erythromycin in reducing stent-related tissue hyperplasia: an experimental study with a rat esophageal model

BACKGROUND

Erythromycin is not only a potent antibiotic; it also has effects of reduction of inflammation and suppression of protein synthesis.

PURPOSE

To evaluate the impact of erythromycin on tissue hyperplasia after stent placement in a rat esophageal model.

MATERIAL AND METHODS

A total of 21 rats were included. After placement of self-expanding stents in the mid esophagus, the rats were divided into two experimental groups and one control group. The rats in the experimental groups received daily intraperitoneal injections of erythromycin for 5 weeks; 4 mg/kg (group A, n = 7) and 8 mg/kg (group B, n = 7). Those in the control group (n = 7) received 1 mL of saline intraperitoneally. After sacrifice, histologic analysis was done for thickness of the papillary projection, granulation tissue area, percentage of granulation tissue area, and degree of inflammatory cell infiltration. The statistical significance of differences between groups was assessed by Mann-Whitney U test.

RESULTS

Tissue hyperplasia as reflected in thickness of papillary projection, granulation tissue area, and percentage of granulation tissue area, was higher in the control group than in the experimental groups, although there was no statistical significance (P = 1.00, 0.332, and 0.263, respectively). However, degree of inflammatory cell infiltration was significantly lower in the experimental groups than the control group (P = 0.025), and the higher dosage of erythromycin reduced inflammatory cell infiltration significantly (P = 0.037).

CONCLUSION

Intraperitoneal administration of erythromycin is very effective in reducing inflammation after stent placement in a rat esophageal model but has no significant effect on granulation tissue formation.

The roles of transforming growth factor-β₁ and vascular endothelial growth factor in the tracheal granulation formation

BACKGROUND

Acquired tracheal stenosis is common in patients with a long-term tracheostomy and granulation is one of the most commonly observed lesions in benign airway stenosis. The aim of this study was to investigate the mechanisms of tracheal granulation formation and find the potential therapeutic targets to prevent the granulation formation.

RESULTS

In granulation tissue obtained from patients during interventional bronchoscopy for the relief of airway obstruction, increased expression of transforming growth factor (TGF)-β₁ and vascular endothelial growth factor (VEGF), as well as increased numbers of fibroblasts, was found by immunohistochemical staining. TGF-β₁ expression was detected in both the epithelial and submucosal layers. The highest levels of VEGF and vimentin expression occurred in the submucosal layers. In comparison with the control, significantly increased numbers of small vessels were observed in the submucosal layers of the granulation tissue. In vitro, TGF-β₁ stimulated production of VEGF by cultured fibroblasts at both the mRNA and protein level. VEGF siRNA treatment resulted in a significant decrease of TGF-β₁-induced VEGF production. SIS3, a selective Smad3 inhibitor, and UO126 both inhibited p44/42 MAP kinase phosphorylation and attenuated subsequent VEGF production by fibroblasts. A low concentration of erythromycin (1 μg/ml), but not dexamethasone (100 μM), inhibited TGF-β₁-induced VEGF production.

CONCLUSION

This study provides important information that facilitates an understanding, at least in part, of the mechanisms of granulation formation. Targeting these mediators and cells may help to prevent the formation of granulation tissue in long-term tracheostomy or prolonged endotracheal intubation patients.

Interventional bronchoscopy from bench to bedside: new techniques for central and peripheral airway obstruction

This article discusses how basic scientific concepts, based on a greater understanding of airway physiology, support the development and dissemination of multidimensional classification systems for tracheal stenosis, expiratory central airway collapse, and innovative interventional bronchoscopic procedures for patients with asthma and chronic obstructive pulmonary disease.

IN-1233, an ALK-5 inhibitor: prevention of granulation tissue formation after bare metallic stent placement in a rat urethral model

PURPOSE

To evaluate the efficacy of an activin receptor-like kinase-5 inhibitor, IN-1233, for the prevention of tissue hyperplasia after bare stent placement in a rat urethral model.

MATERIALS AND METHODS

Procedures were performed in accordance with the National Institutes of Health guidelines for humane handling of animals; approval of the committee of animal research was obtained. In 20 Sprague-Dawley male rats (weight range, 300-350 g), a self-expanding metallic bare stent was inserted in the urethra by using fluoroscopic guidance. One group of 10 rats (group A) was treated with IN-1233, the other group of 10 rats (group B) received no treatment. Retrograde urethrography was performed 4 and 8 weeks after stent placement. All rats were sacrificed at 8 weeks for histologic analysis.

RESULTS

Stent placement was technically successful in all rats. The average stent diameter was significantly larger in group A compared with group B at follow-up retrograde urethrography performed 4 (P = .006) and 8 (P < .001) weeks after stent placement. At histologic analysis, the percentage of granulation tissue area (P < .001), thickness of submucosal fibrosis (P < .001), and number of epithelial layers (P < .001) were significantly decreased in group A compared with group B. Inflammatory cell infiltration (P < .001) was significantly increased in group A compared with group B.

CONCLUSION

IN-1233 is effective for the prevention of granulation tissue formation after bare metallic stent placement in a rat urethral model.

Postintubation injuries and open surgical tracheostomy: should we always perform isthmectomy?

OBJECTIVE

To evaluate the influence of the surgical team (general surgery or thoracic surgery) and the surgical technique (with or without isthmectomy) on the incidence of postintubation injuries in the airways of tracheostomized patients.

METHODS

Between January 1st and August 31st, 2007, 164 patients admitted to the adult intensive care unit and tracheally intubated for more than 24 h were studied prospectively at the Sumaré State Hospital, located at the city of Sumare, Brazil. When tracheostomy was necessary, these patients were randomly assigned to thoracic or general surgery teams. All of the patients were submitted to fiberoptic tracheoscopy for decannulation or late evaluation of the airway.

RESULTS

Of the 164 patients in the study, 90 (54.88%) died (due to causes unrelated to the procedure), 67 (40.85%) completed follow-up, and 7 (4.27%) were lost to follow-up. Of the 67 patients who completed follow-up, 32 had undergone tracheostomy (21 by the general surgery team and 11 by the thoracic surgery team), and 22 had been submitted to isthmectomy (11 by the general surgery team and 11 by the thoracic surgery team). There was no difference between the surgical teams in terms of the incidence of stomal complications. However, there was a significant difference when the surgical techniques (with or without isthmectomy) were compared.

CONCLUSIONS

Not performing isthmectomy in parallel with tracheostomy leads the surgeon to open the tracheal stoma more distally than expected. In such cases, there were more stomal complications.

Liquid (188)Re-filled balloon dilation for the treatment of refractory benign airway strictures: preliminary experience

PURPOSE

To present the preliminary results of beta irradiation with use of liquid rhenium 188 ((188)Re)-filled balloon dilation in the treatment of refractory benign airway strictures.

MATERIALS AND METHODS

Ten sessions of beta irradiation by using liquid (188)Re-filled balloon dilation were prospectively performed in nine patients with refractory bronchial strictures between 2003 and 2006. Indications for treatment were dyspnea caused by repeat stricture or no response to previous treatment (ie, balloon dilation and/or temporary stent placement or laser therapy) in seven patients and dyspnea caused by exuberant granulation tissue formation at the distal end of the placed stent in two. To assess the treatment efficacy, the authors calculated and compared the mean intervals of interventional treatments before and after dilation with (188)Re and mercaptoacetyltriglycine (MAG(3))-filled balloons.

RESULTS

Liquid (188)Re-filled balloon dilation was successfully performed in all nine patients, with no procedure-related complications. Immediately after the procedure, all patients showed resolution of their dyspnea. Five patients remained asymptomatic at 5-25-month follow-up. Four patients experienced dyspnea caused by recurrent stricture 1-10 months after dilation. The mean intervals between interventional treatments increased significantly from 3.1 months +/- 2.1 before (188)Re-MAG(3)-filled balloon dilation to 10.8 months +/- 8.8 after (188)Re-MAG(3)-filled balloon dilation in all nine patients (Wilcoxon signed rank test, P = .025).

CONCLUSIONS

beta irradiation with liquid (188)Re-filled balloon dilation can be safely used for refractory benign airway strictures. A large study with longer follow-up is needed to draw a definite conclusion.

Anti-transforming growth factor beta as a treatment for laryngotracheal stenosis in a canine model

OBJECTIVES/HYPOTHESIS

Laryngotracheal stenosis (LTS) represents a significant treatment dilemma faced by otolaryngologists. Recent topical use of Mitomycin C as an adjunctive treatment has proved helpful but does not completely prevent stenosis. Current literature suggests that transforming growth factor beta (TGFB) plays a significant role in the development of subglottic stenosis. We modified an existing canine model to test antitransforming growth factor beta (anti-TGFB) as a possible treatment for laryngotracheal stenosis.

STUDY DESIGN

Pilot study in a modified canine model.

METHODS

Eight mixed-breed dogs underwent cautery injury to the subglottic region creating subsequent laryngotracheal stenosis. Four dogs were treated with saline injection into the injury site and four dogs were treated with a combination of intravenous (5 mg/kg on day 0 and 5 of the experiment) and local injection of anti-TGFB (50 micrograms).

RESULTS

In the canine model of induced subglottic airway injury, a combination of intralesional and intravenous anti-TGFB results in a reduction in tracheal stenosis (P < .05) and an increase in survival time (P < .03) when compared to the saline control subjects.

CONCLUSIONS

Anti-TGFB appears to be a useful adjunct in the treatment of LTS. Further study regarding the optimal dosing, route of administration, and timing of delivery is needed to understand the role of anti-TGFB in the treatment for laryngotracheal stenosis.