Antifibrotic Role of Nintedanib in Tracheal Stenosis After a Tracheal Wound

Endoscopic treatment of benign tracheal stenosis: a single-centre study

BACKGROUND

Benign tracheal stenosis is relatively rare but remains a significant chronic disease due to its drastic symptoms including dyspnoea and inspiratory stridor, and consequent negative effect on quality of life. Traditionally, the surgical approach by resection of the stenotic tracheal segment has been the therapy of choice. However, endoscopic techniques have arisen and may offer a safe and less invasive alternative.

OBJECTIVES

The aim of the retrospective study was to evaluate procedure-related safety and outcome of endoscopic treatment of benign tracheal stenosis at a single centre.

METHODS

The study included all patients at our institution who between 2013 and 2022 had received endoscopic treatment of benign tracheal stenosis by rigid tracheoscopy, radial incision by electric papillotomy needle and dilation (endoscopic tracheoplasty) followed by triamcinolone acetonide as a local submucosal injection and additionally, from 2020, budesonide inhalation.

RESULTS

A total of 22 patients were treated in a total of 38 interventions, each resulting in immediate improvement of symptoms. There were no peri-interventional complications or mortality. Of the 38 interventions, 11 received no triamcinolone acetonide administration, resulting in a 54.5% recurrence rate after an average of 21.1 (±18.0) months, while 27 had local triamcinolone acetonide, with a 37% recurrence rate. Since 2020, we additionally initiated post-interventional budesonide inhalation as recurrence prophylaxis for newly admitted patients and patients with recurrences(n = 8), of whom only one (12.5%) has to date experienced a recurrence.

CONCLUSION

Our results indicate that endoscopic tracheoplasty offers a safe and successful, minimally invasive alternative to open surgery for patients with benign tracheal stenosis. We recommend local administration of triamcinolone into the mucosa as an additional treatment to decrease the risk of recurrence. However, given the uncontrolled study design and low sample size, safety and effectiveness cannot be conclusively demonstrated. Nonetheless, our findings suggest promising avenues for further investigation. Further studies on the additional benefit of inhaled corticosteroids are warranted.

Drug delivery systems for wound healing treatment of upper airway injury

INTRODUCTION

Endotracheal intubation is a common procedure to maintain an open airway with risks for traumatic injury. Pathological changes resulting from intubation can cause upper airway complications, including vocal fold scarring, laryngotracheal stenosis, and granulomas and present with symptoms such as dysphonia, dysphagia, and dyspnea. Current intubation-related laryngotracheal injury treatment approaches lack standardized guidelines, relying on individual clinician experience, and surgical and medical interventions have limitations and carry risks.

AREAS COVERED

The clinical and preclinical therapeutics for wound healing in the upper airway are described. This review discusses the current developments on local drug delivery systems in the upper airway utilizing particle-based delivery systems, including nanoparticles and microparticles, and bulk-based delivery systems, encompassing hydrogels and polymer-based approaches.

EXPERT OPINION

Complex laryngotracheal diseases pose challenges for effective treatment, struggling due to the intricate anatomy, limited access, and recurrence. Symptomatic management often requires invasive surgical procedures or medications that are unable to achieve lasting effects. Recent advances in nanotechnology and biocompatible materials provide potential solutions, enabling precise drug delivery, personalization, and extended treatment efficacy. Combining these technologies could lead to groundbreaking treatments for upper airways diseases, significantly improving patients' quality of life. Research and innovation in this field are crucial for further advancements.

Recombinant Slit2 attenuates tracheal fibroblast activation in benign central airway obstruction by inhibiting the TGF-β1/Smad3 signaling pathway

Airway fibrosis is among the pathological manifestations of benign central airway obstruction noted in the absence of effective treatments and requires new drug targets to be developed. Slit guidance ligand 2-roundabout guidance receptor 1 (Slit2-Robo1) is involved in fibrosis and organ development. However, its significance in airway fibrosis has not yet been reported. The study explored how the recombinant protein Slit2 functions in transforming growth factor-β1 (TGF-β1)-mediated airway fibrosis in vivo and in vitro. In this study, Slit2 expression initially increased in the tracheal granulation tissues of patients with tracheobronchial stenosis but decreased in the fibrotic tissue. In primary rat tracheal fibroblasts (RTFs), recombinant Slit2 inhibited the expression of extracellular matrices such as Timp1, α-SMA, and COL1A2, whereas recombinant TGF-β1 promoted the expression of Robo1, α-SMA, and COL1A2. Slit2 and TGF-β1 played a mutual inhibitory role in RTFs. Slit2 supplementation and Robo1 downregulation inhibited excessive extracellular matrix (ECM) deposition induced by TGF-β1 in RTFs via the TGF-β1/Smad3 pathway. Ultimately, exogenous Slit2 and Robo1 knockdown-mediated attenuation of airway fibrosis were validated in a trauma-induced rat airway obstruction model. These findings demonstrate that recombinant Slit2 alleviated pathologic tracheobronchial healing by attenuating excessive ECM deposition. Slit2-Robo1 is an attractive target for further exploring the mechanisms and treatment of benign central airway obstruction.

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.

Inhalation of Carboxymethyl Chitosan Alleviates Posttraumatic Tracheal Fibrosis

OBJECTIVES

The present study was performed to determine whether the inhalation of carboxymethyl (CM)-chitosan can alleviate tracheal fibrosis in a rabbit model.

METHODS

We designed a rabbit model of tracheal stenosis involving electrocoagulation with a spherical electrode. Twenty New Zealand white rabbits were randomly divided into experimental and control groups (10 animals each). Tracheal damage was successfully established by electrocoagulation in all animals. The experimental group was given CM-chitosan (inhalation for 28 days), while the control group inhaled saline. The effects of CM-chitosan inhalation on tracheal fibrosis were analyzed. Laryngoscopy was performed to evaluate and grade tracheal granulation, while tracheal fibrosis was evaluated by histological examination. The effects of CM-chitosan inhalation on the tracheal mucosa were examined by scanning electron microscopy (SEM), and hydroxyproline content in tracheal scar tissue was determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Laryngoscopy showed that the tracheal cross-sectional area was smaller in the experimental than control group. The amounts of loose connective tissue and damaged cartilage, as well as the severity of collagen and fibrosis, decreased following inhalation of CM-chitosan. According to the ELISA, the experimental group had low levels of hydroxyproline in the tracheal scar tissue.

CONCLUSION

The findings presented here showed that inhalation of CM-chitosan mitigated posttraumatic tracheal fibrosis in a rabbit model, thus suggesting a potential new treatment for tracheal stenosis.

GATA6 triggers fibroblast activation and tracheal fibrosis through the Wnt/β-catenin pathway

Tracheal fibrosis is a key abnormal repair process leading to fatal stenosis, characterized by excessive fibroblast activation and extracellular matrix (ECM) deposition. GATA6, a zinc finger-containing transcription factor, is involved in fibroblast activation, while its role in tracheal fibrosis remains obscure. The present study investigated the potential role of GATA6 as a novel regulator of tracheal fibrosis. It was found that GATA6 and α-smooth muscle actin (α-SMA) were obviously increased in tracheal fibrotic granulations and in TGFβ1-treated primary tracheal fibroblasts. GATA6 silencing inhibited TGFβ1-stimulated fibroblast proliferation and ECM synthesis, promoted cell apoptosis, and inactivated Wnt/β-catenin pathway, whereas GATA6 overexpression showed the reverse effects. SKL2001, an agonist of Wnt/β-catenin signaling, restored collagen1a1 and α-SMA expression which was suppressed by GATA6 silencing. Furthermore, in vivo, knockdown of GATA6 ameliorated tracheal fibrosis, as manifested by reduced tracheal stenosis and ECM deposition. GATA6 inhibition in rat tracheas also impaired granulation proliferation, increased apoptosis, and inactivated Wnt/β-catenin pathway. In conclusion, our findings indicate that GATA6 triggers fibroblast activation, cell proliferation, and apoptosis resistance in tracheal fibrosis via the Wnt/β-catenin signaling pathway. Targeting GATA6 may represent a promising therapeutic approach for tracheal fibrosis.

GDF15 alleviates the progression of benign tracheobronchial stenosis by inhibiting epithelial-mesenchymal transition and inactivating fibroblasts

Benign tracheobronchial stenosis (BTS) is a fatal and incurable disease. Epithelial repair and matrix reconstruction play an important role in the wound repair process. If the interstitial context is not restored and stabilized in time, it can lead to pathological fibrosis. Here we attempted to identify cytokines that are involved in promoting wound repair. Growth differentiation factor 15 (GDF15) is a cytokine secreted by tracheal epithelial cells, which is indispensable for the growth of epithelial cells and inhibits the overgrowth of fibroblasts. GDF15 can counteract transforming growth factor-β (TGFβ1) stimulation of epithelial-mesenchymal transition (EMT) in tracheal epithelial cells and inhibit fibroblast activation via the TGFβ1-SMAD2/3 pathway. In a rat model of tracheal stenosis, GDF15 supplementation alleviated the degree of tracheal stenosis. These results suggest that GDF15 prevents fibroblast hyperactivation and promotes epithelial repair in injured trachea. GDF15 may be a potential therapy to improve benign tracheobronchial stenosis.

Knockdown of SOX9 alleviates tracheal fibrosis through the Wnt/β-catenin signaling pathway

Trachealfibrosis is an important cause of tracheal stenosis without effective treatments, and new drug targets need to be developed. The role of SOX9 in the injury and repair of the trachea is unknown; this study aims to investigate the role of SOX9 in the regulation of tracheal fibrosis based on clinical samples from patients with tracheal injury and a model of tracheal fibrosis produced by tracheal brushing in rats. The results showed that the expressions of SOX9 and mesenchymal and ECM-related indicators were increased in the injury and fibrosis of the trachea in patients and rats. Serum SOX9 levels exhibited a sensitivity of 83.87% and specificity of 90% in distinguishing patients with tracheal fibrosis from healthy volunteers when the cut‑off value was 13.24 ng/ml. Knockdown SOX9 can markedly inhibit granulation tissue proliferation, reduce inflammation and ECM deposition, promote epithelial regeneration and granulation tissue apoptosis, and attenuate the tracheal fibrosis after injury. Additionally, RNA sequencing showed that the proliferation, migration, and ECM deposition of tracheal granulation tissue were related to the activation of Wnt pathway, activation of the β-catenin, and p-GSK3β after injury can be inhibited by the knockdown of SOX9. In summary, SOX9 is upregulated in tracheas fibrosis and may be a novel factor to promote tracheal fibrosis progression. Inhibiting SOX9 may be used to prevent and treat tracheal fibrosis in the future. KEY MESSAGE : The expression of SOX9 is upregulated the process of injury and repair of the tracheal fibrosis. Knocking down SOX9 can attenuate tracheal fibrosis after injury by inhibiting inflammation response, granulation tissue proliferation, ECM deposition, and promoting granulation tissue apoptosis. The Wnt/β-catenin-SOX9 axis is activated during tracheal injury and fibrosis, and inhibition of SOX9 can partially alleviate tracheal fibrosis. SOX9 may act as a new diagnostic and therapeutic target in patients with tracheal fibrosis in the future.

Radiotherapy-induced oxidative stress and fibrosis in breast cancer are suppressed by vactosertib, a novel, orally bioavailable TGF-β/ALK5 inhibitor

Radio-resistance resulting from radiotherapy-induced fibrosis is a major clinical obstacle in breast cancer treatment because it typically leads to cancer recurrence, treatment failure, and patient death. Transforming growth factor-β (TGF-β) is a key signal messenger in fibrosis, which plays an important role in radiation-induced fibrosis and cancer stem cell (CSC) development, may be mediated through the generation of oxidative stress. This study was conducted to confirm the efficacy of vactosertib, a TGF-β/ALK5 inhibitor, as a potent inhibitor in radiation-induced oxidative stress generation, fibrosis and CSC development. We used a 4T1-Luc allograft BALB/c syngeneic mouse model and 4T1-Luc and MDA-MB-231 cells for histological analysis, qRT-PCR, western blotting, ROS analysis, mammosphere formation analysis, monolayer fluorescence imaging analysis. Radiotherapy induces TGF-β signaling, oxidative stress markers (4-HNE, NOX2, NOX4, PRDX1, NRF2, HO-1, NQO-1), fibrosis markers (PAI-1, α-SMA, FIBRONECTIN, COL1A1), and CSC properties. However, combination therapy with vactosertib not only inhibits these radiation-induced markers and properties by blocking TGF-β signaling, but also enhances the anticancer effect of radiation by reducing the volume of breast cancer. Therefore, these data suggest that vactosertib can effectively reduce radiation fibrosis and resistance in breast cancer treatment by inhibiting radiation-induced TGF-β signaling and oxidative stress, fibrosis, and CSC.

Clinical, Histological, and Profibrotic Extracellular Matrix Protein Changes in a Model of Tracheal Stenosis Induced by Cervical Tracheal Autotransplantation

BACKGROUND

Tracheal stenosis (TS) is a complication of prolonged intubation, tracheotomy, and tracheal surgery that compromises the vascular supply. Animal models are essential for studying its pathophysiology and the effect of interventions.

OBJECTIVE

To establish a TS model in rats secondary to tracheal autotransplantation with a graft submerged in bleomycin (Atx-Bleo). Additionally, to evaluate the clinical and histological changes, as well as the expression of newly formed collagen (NFC), isoforms of transforming growth factor beta (TGFβ), fibronectin (FN), elastin (ELN), integrin β1 (ITGβ1), and matrix metalloproteinase 1 (MMP1) in TS.

METHODS

Twenty Wistar rats were divided into three groups: group I (n = 20) control; group II (n = 10) end-to-end anastomosis of the trachea (tracheoplasty); and group III (n = 10) Atx-Bleo. The animals were evaluated clinically, tomographically, macroscopically, morphometrically, and microscopically. NFC deposition, and the expression of profibrotic and antifibrotic proteins were evaluated in tracheal scars.

RESULTS

All animals survived the surgical procedure and the study period. Compared with the other study groups, the Atx-Bleo group developed TS and fibrosis, exhibited higher expression of NFC, TGFβ1, TGFβ2, FN, ELN, and ITGβ1, and mild expression of TGFβ3 and MMP1 (p < 0.005; analysis of variance, Dunnett and Tukey tests).

CONCLUSION

Atx-Bleo in TS model rats produces tomographic and histological changes, and induces the upregulation of profibrotic proteins (TGFβ1, TGFβ2, collagen, FN, ELN, ITGβ1) and downregulation of antifibrotic proteins (TGFβ3, MMP1). Therefore, this model may be used to test new pharmacological treatments for reversing or preventing TS, and conduct basic studies regarding its pathophysiology.

Molecular Mechanisms and Physiological Changes behind Benign Tracheal and Subglottic Stenosis in Adults

Laryngotracheal stenosis (LTS) is a complex and heterogeneous disease whose pathogenesis remains unclear. LTS is considered to be the result of aberrant wound-healing process that leads to fibrotic scarring, originating from different aetiology. Although iatrogenic aetiology is the main cause of subglottic or tracheal stenosis, also autoimmune and infectious diseases may be involved in causing LTS. Furthermore, fibrotic obstruction in the anatomic region under the glottis can also be diagnosed without apparent aetiology after a comprehensive workup; in this case, the pathological process is called idiopathic subglottic stenosis (iSGS). So far, the laryngotracheal scar resulting from airway injury due to different diseases was considered as inert tissue requiring surgical removal to restore airway patency. However, this assumption has recently been revised by regarding the tracheal scarring process as a fibroinflammatory event due to immunological alteration, similar to other fibrotic diseases. Recent acquisitions suggest that different factors, such as growth factors, cytokines, altered fibroblast function and genetic susceptibility, can all interact in a complex way leading to aberrant and fibrotic wound healing after an insult that acts as a trigger. However, also physiological derangement due to LTS could play a role in promoting dysregulated response to laryngo-tracheal mucosal injury, through biomechanical stress and mechanotransduction activation. The aim of this narrative review is to present the state-of-the-art knowledge regarding molecular mechanisms, as well as mechanical and physio-pathological features behind LTS.