Sirolimus-eluting airway stent reduces profibrotic Th17 cells and inhibits laryngotracheal stenosis

Localized Knockout of E-Cadherin in Subglottic Mucosa Increases Fibrosis

OBJECTIVE

To assess the effects of localized subglottic knockout of E-cadherin (CDH1-/-) on survival, tracheal luminal thickness, and fibrotic gene expression in a mouse model of subglottic stenosis.

STUDY DESIGN

Case-control in vivo mouse study.

SETTING

Tertiary care academic hospital.

METHODS

Mice with loxP sites flanking E-cadherin underwent extratracheal placement of a fibrin-plasmin gel embedded with either CRE-expressing or control adenovirus. Mice then underwent chemomechanical injury to induce laryngotracheal stenosis, with harvest of subglottis/tracheas 21 days later. Immunofluorescence and Western blotting were used to confirm E-cadherin knockout. Outcomes of interest included Kaplan-Meier survival curves (n = 40), lamina propria thickness on hematoxylin-eosin (H&E) histology (n = 8), and fibrotic gene expression (n = 3).

RESULTS

Immunofluorescence and Western blotting confirmed decreased E-cadherin expression in CDH1-/-. On H&E, lamina propria thickness was greater in CDH1-/- mice (mean difference [95% CI] in μm, 107.2 [74.8-139.7], P < .001). Survival was significantly shorter for knockout mice relative to control (median survival in days, 5.0 vs 8.5; P = .007). Further, fibrotic gene expression of COL1 (mean difference [95% CI] in log-fold change, 11.5 [1.9-21.0]; P = .03), COL3 (31.0 [11.5-50.5]; P = .01), COL5 (6.8 [3.1-10.4]; P = .007), and FN1 (6.9 [1.3-12.6]; P = .03) was significantly greater relative to control.

CONCLUSION

CDH1-/- results in greater fibrosis and increased mortality, further supporting the role of epithelial barrier dysfunction in the pathogenesis of subglottic stenosis. Therapies that restore epithelial integrity may therefore represent a rational pharmacologic target.

Dynamic single-cell transcriptomic reveals the cellular heterogeneity and a novel fibroblast subpopulation in laryngotracheal stenosis

BACKGROUND

Laryngotracheal stenosis (LTS), a pathological narrowing of the upper airway caused by excessive extracellular matrix (ECM) deposition, often leads to dyspnea and even respiratory failure. However, systematic studies addressing the specific subpopulations and their contribution to LTS development still remain underexplored.

RESULTS

We collected laryngotracheal tissue at multiple time points of LTS rat model, established by injuring their laryngotracheal lining, and performed dynamic single-cell RNA sequencing (scRNA-seq) to elucidate the transcriptomic atlas of LTS development. The results showed, from the inflammatory state to the repair/fibrotic state, infiltration of immune cells such as monocyte macrophages decreased and fibroblast increased. We delineated the markers and functional status of different fibroblasts subsets and identified that fibrotic fibroblasts may originate from multiple fibroblast subpopulations, including a new subpopulation characterized by the expression of chondrogenic markers such as Ucma and Col2a1, we designated this subcluster as chondrocyte injury-related fibroblasts (CIRF). Furthermore, we categorized monocytes/macrophages into several subtypes and identified that SPP1 high macrophages represented the largest macrophage subpopulation in LTS, providing evidence to clarify the importance of SPP1 macrophages in fibrosis disease. Our findings also revealed the interactions among these cells to explore the molecular mechanism associated with LTS pathogenesis.

CONCLUSIONS

Our study, for the first time, conducted dynamic scRNA-seq on LTS, revealing the cellular heterogeneity and providing a valuable resource for exploring the intricate molecular landscape of LTS. We propose CIRF may represent a tissue-specific fibroblast lineage in LTS and potentially originate from cells in the perichondrium of the trachea and transform into fibrotic fibroblasts. Integration of our study with those of other respiratory fibrotic diseases will allow for a comprehensive understanding of airway remodeling in respiratory diseases and exploring potential new therapeutic targets for their treatment.

Third Proceedings of The North American Airway Collaborative (NoAAC): Consensus Statement on Trial Design for Airway Stenosis

Importance

Airway stenosis is a rare but debilitating disorder that significantly degrades the quality of life in affected patients. Treatments are primarily surgical, and disease management lacks established medical therapies. The North American Airway Collaborative held its third symposium at The Johns Hopkins Hospital in Baltimore, Maryland, on April 15, 2024, focused on strategies to advance the care of these patients. The proceedings summarize the discussion of trial design in airway stenosis and the resulting North American Airway Collaborative consensus regarding clinical end points for rigorous study of novel therapies.

Observations

The lectures and panels centered on the translation of a growing body of preclinical data into therapeutic targets. Additionally, detailed discussion explored design of clinical trials to evaluate safety and efficacy of novel therapeutics. The need for a consensus regarding clinically meaningful end points in airway stenosis was identified to facilitate the comparison of outcomes across institutions and future multi-institutional trials.

Conclusions and Relevance

The group achieved consensus regarding change in peak expiratory flow as the primary clinical end point in airway stenosis. Additional clinical measures, such as disease recurrence (identified as time to recurrent intervention), anatomical characterization of subglottic scar via axial computed tomography imaging, and patient-reported outcome measures (Clinical COPD Questionnaire [CCQ], Voice Handicap Index-10 [VHI-10], Eating Assessment Tool-10 [EAT-10], and 12-Item Short-Form Health Survey, version 2 [SF-12]) were identified as essential secondary outcomes.

Polytrauma impairs fracture healing accompanied by increased persistence of innate inflammatory stimuli and reduced adaptive response

The field of bone regeneration has primarily focused on investigating fracture healing and nonunion in isolated musculoskeletal injuries. Compared to isolated fractures, which frequently heal well, fractures in patients with multiple bodily injuries (polytrauma) may exhibit impaired healing. While some papers have reported the overall cytokine response to polytrauma conditions, significant gaps in our understanding remain in how fractures heal differently in polytrauma patients. We aimed to characterize fracture healing and the temporal local and systemic immune responses to polytrauma in a murine model of polytrauma composed of a femur fracture combined with isolated chest trauma. We collected serum, bone marrow from the uninjured limb, femur fracture tissue, and lung tissue over 3 weeks to study the local and systemic immune responses and cytokine expression after injury. Immune cell distribution was assessed by flow cytometry. Fracture healing was characterized using microcomputed tomography (microCT), histological staining, immunohistochemistry, mechanical testing, and small angle X-ray scattering. We detected more innate immune cells in the polytrauma group, both locally at the fracture site and systemically, compared to other groups. The percentage of B and T cells was dramatically reduced in the polytrauma group 6 h after injury and remained low throughout the study duration. Fracture healing in the polytrauma group was impaired, evidenced by the formation of a poorly mineralized and dysregulated fracture callus. Our data confirm the early, dysregulated inflammatory state in polytrauma that correlates with disorganized and impaired fracture healing.

Airway stenosis: classification, pathogenesis, and clinical management

Airway stenosis (AS) is a fibroinflammatory disease characterized by abnormal activation of fibroblasts and excessive synthesis of extracellular matrix, which has puzzled many doctors despite its relatively low prevalence. Traditional treatment such as endoscopic surgery, open surgery, and adjuvant therapy have many disadvantages and are limited in the treatment of patients with recurrent AS. Therefore, it is urgent to reveal the pathogenesis of AS and accelerate its clinical transformation. Based on the discovered pathogenesis, including fibrosis, inflammation, epithelial-mesenchymal transition, metabolic reprogramming, microbiome, genetic susceptibility, and other mechanisms, researchers have developed a series of treatments, such as drug therapy, gene therapy, stem cell therapy, growth factor therapy, protein therapy, and photodynamic therapy. This review introduces the classification of AS, explores the existing pathogenesis and preclinical treatments developed based on the pathogenesis, and finally summarizes the current clinical management. In addition, the prospect of exploring the interaction between different types of cells and between microorganisms and cells to identify the intersection of multiple mechanisms based on single-cell RNA sequencing, 16S rRNA gene sequencing and shotgun metagenomic sequencing is worth looking forward to.

3D printed drug-eluting stents: Toward personalized therapy for airway stenosis

Airway stents are life-saving medical devices used to treat malignant or benign central airway stenoses. Unfortunately, these devices, typically manufactured from silicone alone and/or nitinol, can result in serious complications, such as stent migration, bacterial colonization, and tissue granulation, eventually forcing stent removal. Customized airway stents exhibit reduced migration and they can be tailored to address other complications by releasing drugs, such as the antibiotic levofloxacin and the antifibrotic drug nintedanib. Herein, the incorporation of these molecules in customized, bioresorbable 3D printed airway stents was investigated. Nintedanib (1.5 wt%) and levofloxacin (2.0 wt%) were incorporated in the polymer-based resin, which was used to 3D print tracheal stents with adequate mechanical and drug release properties. The drug-loaded stents were then deployed into rabbit tracheas and found to deliver the drugs locally with minimal systemic exposure. Drug activities were demonstrated by inhibition of bacterial colonization and reduced interleukin 8 (IL8) local expression. Although the application of these tracheal stents requires further exploration in larger animal models, this work paves the way for the rapid manufacturing of personalized medical devices with therapeutic functions.

Macrophage STING signaling promotes fibrosis in benign airway stenosis via an IL6-STAT3 pathway

Acute and chronic inflammation are important pathologies of benign airway stenosis (BAS) fibrosis, which is a frequent complication of critically ill patients. cGAS-STING signalling has an important role in inflammation and fibrosis, yet the function of STING in BAS remains unclear. Here we demonstrate using scRNA sequencing that cGAS‒STING signalling is involved in BAS, which is accompanied by increased dsDNA, expression and activation of STING. STING inhibition or deficiency effectively alleviates tracheal fibrosis of BAS mice by decreasing both acute and chronic inflammation. Macrophage depletion also effectively ameliorates BAS. Mechanistically, dsDNA from damaged epithelial cells activates the cGAS-STING pathway of macrophages and induces IL-6 to activate STAT3 and promote fibrosis. In summary, the present results suggest that cGAS-STING signalling induces acute inflammation and amplifies the chronic inflammation and tracheal fibrosis associated with benign airway stenosis, highlighting the mechanism and potential drug target of BAS.

Advances in studies on tracheal stent design addressing the related complications

Tracheal stents can be used to quickly reconstruct the airway and relieve symptoms of dyspnea in patients with tracheal stenosis. However, existing tracheal stents lead to complications such as granulation tissue formation, difficulty in removal, persistent growth of malignant tumors, stent migration, and mucus plugging. In this article, we reviewed the main methods used to reduce complications associated with tracheal stent design. Drug-eluting stents can inhibit granulation tissue formation and prevent infection and local chemotherapy. The biodegradable stent can support the trachea for some time, maintain tracheal patency, and degrade gradually, which avoids removing or replacing the stent. Radioactive stents loaded with I125 have good potential for inhibiting the persistent growth of malignant tumors. Three-dimensional printing technology enables the manufacturing of patient-specific stents, which increases the degree of matching between the complex tracheal anatomy and the stent, thus providing a new solution for stent migration caused by structural mismatch. Minimizing the barrier of the stent to mucociliary clearance, providing an anti-fouling coating, and culturing respiratory epithelial cells on the surface of the stent are the main methods used to reduce mucus plugging. We also proposed future research directions for tracheal stents to guide the design and manufacture of ideal tracheal stents.

Oral Everolimus Following Dilation in Idiopathic Subglottic Stenosis: A Phase 1 Nonrandomized Clinical Trial

Importance

Current medical therapies in idiopathic subglottic stenosis (iSGS) are insufficient in preventing the development and progression of scar tissue. An inhibitor of mammalian target of rapamycin, everolimus is an immunosuppressive medication shown to be effective in reducing fibrosis across a variety of fibroproliferative disorders, including preclinical models of iSGS.

Objective

To evaluate the effect of oral everolimus on postoperative recurrence of stenosis in iSGS.

Design, Setting, and Participants

This open-label, single-arm, phase 1, nonrandomized clinical trial analyzed 7 perimenopausal participants diagnosed with iSGS and followed-up at a tertiary care academic center for 6 months after dilation surgery. The trial was conducted from November 1, 2022, through May 15, 2024.

Intervention

Participants took a 1.5-mg daily oral dose of everolimus for 42 days after surgery.

Main outcomes and measures

The primary outcome measure was safety as determined by adverse events. Secondary outcome measures included change in peak expiratory flow from baseline through 180 days after surgery; change in the luminal area, measured by computed tomographic (CT) scan, from the 14th and the 180th day; and changes in quality-of-life scores.

Results

Of the 8 perimenopausal participants, 7 (median age, 50 years [IQR, 45.0-52.5 years]) completed the study. Compared with baseline at all time points, there was an increase in peak expiratory flow. The median difference in liters per minute was 125 (95% CI, 90-270) on day 7 after surgery; 150 (95% CI, 110-290) on day 14; 138 (95% CI, 116-280) on day 28; 160 (95% CI, 100-270) on day 42; 155 (95% CI, 110-270) on day 60; 140 (95% CI, 100-270) on day 90; and 100 (95% CI, 20-240) on day 180. A decrease in the CT luminal area was observed from the day-14 measure to the day-180 measure (median stenosis, 7.2%; IQR, 1.9%-15.4%). During the trial, 1 participant (14.3%) each developed oral ulcers, a urinary tract infection, and a skin infection.

Conclusions and Relevance

In this interventional nonrandomized clinical trial of iSGS, adjuvant everolimus was well-tolerated with minor adverse events. Participants sustained postdilation peak expiratory flow for 13 weeks. These results support proceeding to a phase 2 trial to study drug efficacy and a more detailed investigation of adverse effects.

Trial Registration

ClinicalTrials.gov Identifier: NCT05153668.

Study on the complications after implantation of different types of metal stents in rabbit trachea

OBJECTIVE

To observe the complications and inflammatory responses caused by the different types of metal stents in the trachea of rabbits.

METHOD

79 rabbits were randomly divided into 4 groups and were implanted with the customized nickel-titanium alloy metal stents(fully covered metal stent: group A, bare metal stent: group B, segmented covered metal stent: group C and control group: group D). The complications (tracheal deformation, granulation tissue hyperplasia, scar hyperplasia and secretion retention) of different types of metal stents were compared by observing the anatomical and pathological specimens of dead rabbits; And the expression of inflammatory factors of different types of metal stents were compared by detecting the tissue of tracheas of dead rabbits.

RESULTS

(1)There were significant differences in the above four complications among groups A, B and C(p < 0.01). The incidences of tracheal deformation, scar hyperplasia and secretion retention in group A were significantly higher than that in group B(p < 0.0167), however, the incidence of granulation tissue hyperplasia in group A was significantly lower than that in group B(p < 0.0167). The incidence of scar hyperplasia in group A was significantly lower than that in group C(p < 0.0167) and there were no significant differences in other complications between these two groups(p > 0.0167). The incidences of tracheal deformation, scar hyperplasia and secretion retention in group B were significantly lower than that in group C(p < 0.0167), however, the incidence of granulation tissue hyperplasia in group B was significantly higher than that in group C(p < 0.0167). (2)The concentration of IL-1β in group A was higher than that in group B (p < 0.05 and foldchange>1.2).

CONCLUSION

(1)There are significant differences in complications between the fully covered metal stent, bare metal stent and segmented covered metal stent; the incidences of complications between the segmented covered metal stent and fully covered metal stent are similar. (2)Changes in different inflammatory factors can be observed between the fully covered and bare metal stent.

An Ovine Model Yields Histology and Gene Expression Changes Consistent with Laryngotracheal Stenosis

OBJECTIVES

Animal models for laryngotracheal stenosis (LTS) are critical to understand underlying mechanisms and study new therapies. Current animal models for LTS are limited by small airway sizes compared to human. The objective of this study was to develop and validate a novel, large animal ovine model for LTS.

METHODS

Sheep underwent either bleomycin-coated polypropylene brush injury to the subglottis (n = 6) or airway stent placement (n = 2) via suspension microlaryngoscopy. Laryngotracheal complexes were harvested 4 weeks following injury or stent placement. For the airway injury group, biopsies (n = 3 at each site) were collected of tracheal scar and distal normal regions, and analyzed for fibrotic gene expression. Lamina propria (LP) thickness was compared between injured and normal areas of trachea.

RESULTS

No mortality occurred in sheep undergoing airway injury or stent placement. There was no migration of tracheal stents. After protocol optimization, LP thickness was significantly increased in injured trachea (Sheep #3: 529.0 vs. 850.8 um; Sheep #4: 933.0 vs. 1693.2 um; Sheep #5: 743.7 vs. 1378.4 um; Sheep #6: 305.7 vs. 2257.6 um). A significant 62-fold, 20-fold, 16-fold, 16-fold, and 9-fold change of COL1, COL3, COL5, FN1, and TGFB1 was observed in injured scar specimen relative to unaffected airway, respectively.

CONCLUSION

An ovine LTS model produces histologic and transcriptional changes consistent with fibrosis seen in human LTS. Airway stent placement in this model is safe and feasible. This large airway model is a reliable and reproducible method to assess the efficacy of novel LTS therapies prior to clinical translation.

LEVEL OF EVIDENCE

N/A Laryngoscope, 134:4239-4245, 2024.

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.