Novel insights into the role of hypoxia-inducible factor-1 in the pathogenesis of human post-intubation tracheal stenosis

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.

Restenosis Following Bronchoscopic Airway Stenting for Complex Tracheal Stenosis

BACKGROUND

Nonsurgical patients with complex postintubation tracheal stenosis (PITS) and tracheostomy-associated tracheal stenosis (PTTS) often require airway stenting. However, the optimal approach is unknown. Identifying patients at higher risk for restenosis after stent removal may allow the treating physician to individualize the vigilance and duration of airway stenting, and help optimize outcomes.

METHODS

This was a single-center retrospective analysis of prospectively collected data on all patients with complex PITS and/or PTTS treated with protocolized bronchoscopic airway stenting over a consecutive 16-year period. The primary outcome analyzed was restenosis rate at 1 year after stent removal. Predictors for restenosis and factors influencing risk for death during stent therapy were also assessed.

RESULTS

Of the 181 subjects treated with silicone airway stenting, 128 were available for analysis of the primary outcome. Restenosis by 1 year after stent removal occurred in 58%. Independent predictors for restenosis were coexisting diabetes [odd ratio (OR)=3.10, 95% confidence interval (CI)=1.04-9.24; P =0.04], morbid obesity (OR=3.13, 95% CI=1.20-8.17; P =0.02), and occurrence of stent-associated complications requiring bronchoscopic management (OR=2.13, 95% CI=1.12-4.03; P =0.02). The overall mortality during the initial stenting period was 14%, and a silicone Y-stent was associated with a higher risk of death (OR=3.58, 95% CI=1.40-9.14; P =0.008).

CONCLUSION

Tracheal restenosis after silicone stent therapy for complex PITS and PTTS is common and more likely to occur in patients with diabetes, morbid obesity, and frequent stent-associated complications. Mortality risk during stent therapy is not negligible, and a Y-stent should be utilized only after careful consideration. These findings may be incorporated into the approach to bronchoscopic airway stenting in these patients.

Construction and Comprehensive Analysis of the ceRNA Network to Reveal Key Genes for Benign Tracheal Stenosis

Objective: To explore the possible biological functions of the differentially expressed genes in patients with benign tracheal stenosis, and to provide a valuable molecular basis for investigating the pathogenesis of benign tracheal stenosis.

Method: Whole transcriptome sequencing was performed on blood samples collected from patients with benign tracheal stenosis and normal controls. Differentially expressed mRNA, lncRNA, and circRNA were analyzed using the DESeq2 package. The protein interaction networks for differentially expressed mRNAs were constructed by STRING. The results of gene co-expression network analysis, Starbase database prediction, and differential gene expression were combined to construct a competing endogenous RNA network. The transcription factors of key genes were predicted using the Network Analyst database and a transcription factor-mRNA regulatory network was constructed. The classical pathways, intermolecular interaction networks, and upstream regulatory components of key genes were analyzed using Ingenuity Pathway Analysis (IPA). Finally, the DGIDB database was used to predict the potential therapeutic drugs to target the identified key genes.

Result: Based on mRNA, lncRNA and circRNA expression data, we found that differentially expressed mRNAs were enriched in oxygen transport, neutrophil activation, immune response, and oxygen binding. Then the pearson correlation between mRNAs of 46 key genes and lncRNAs and cricRNAs were calculated, and the correlation greater than 0.9 were selected to construct the co-expression network of “mRNA-lncRA” and “mRNA-cricRNA.” Moreover, a “lncRNA-miRNA-mRNA” network and a “circRNA-miRNA-mRNA” network were constructed. IPA analysis showed that the 46 key genes were significantly associated with inflammatory activation and acute respiratory distress syndrome. The constructed TF-mRNA regulatory network was composed of 274 nodes and 573 interacting pairs. 251 potential therapeutic drugs were identified from the DGIDB database.

Conclusion: This study analyzed the differential genes associated with benign tracheal stenosis and explored the potential regulatory mechanisms, providing a scientific reference for further studies on the pathogenesis of benign tracheal stenosis.

An Experimental Study on Timing in Tracheal Stenosis Surgery

Background TNF-α, IL-6, and TGF-β are important bio mediators of the inflammatory process. This experimental study has investigated inflammatory biomarkers' efficacy to determine the appropriate period for anastomosis surgery in tracheal stenosis cases.

Methods First, a pilot study was performed to determine the mean stenosis ratio (SR) after the surgical anastomosis. The trial was planned on 44 rats in four groups based on the pilot study's data. Tracheal inflammation and stenosis were created in each rat by using micro scissors. In rats of groups I, II, III, and IV, respectively, tracheal resection and anastomosis surgery were applied on the 2nd, 4th, 6th, 8th weeks after the damage. The animals were euthanized 8 weeks later, followed by histopathological assessment and analysis of TNF-α, IL-6, and TGF-β as biochemical markers.

Results Mean SR of the trachea were measured as 21.9 ± 6.0%, 24.1 ± 10.4%, 25.8 ± 9.1%, and 19.6 ± 9.2% for Groups I to IV, respectively. While Group III had the worst SR, Group IV had the best ratio (p = 0.03). Group II had the highest values for the biochemical markers tested. We observed a statistically significant correlation between only histopathological changes and TNF-α from among the biochemical markers tested (p = 0.02). It was found that high TNF-α levels were in a relationship with higher SR (p = 0.01).

Conclusion Tracheal anastomosis for post-traumatic stenosis is likely to be less successful during the 4th and 6th weeks after injury. High TNF-α levels are potentially predictive of lower surgical success. These results need to be confirmed by human studies.

Expression of histone deacetylase 2 in tracheal stenosis models and its relationship with tracheal granulation tissue proliferation

The current treatments for benign tracheal stenosis are inefficient. The present study examined the expression of histone deacetylase 2 (HDAC2) in different tracheal stenosis models and explored its association with the proliferation of tracheal granulation tissue and its ability to constitute a potential therapy for tracheal stenosis. Animal tracheal stenosis models were established, as indicated by hematoxylin and eosin (H&E) staining. A total of 24 New Zealand White rabbits were randomly divided into control, erythromycin, budesonide and vorinostat groups. Stenotic tracheal tissues were collected on day 11 after drug administration for 10 days. The degree of tracheal stenosis in each group was calculated, and pathological alterations were observed using H&E staining. The mRNA expression of HDAC2, interleukin-8 (IL-8), transforming growth factor-β1 (TGF-β1) and vascular endothelial growth factor (VEGF) was examined via reverse transcription-quantitative PCR. The protein expression of HDAC2 was examined via immunofluorescence, while the expression of type I and type III collagen was assessed using immunohistochemistry. The results of the present study demonstrated that tracheal epithelial hyperplasia in the erythromycin group was improved, the degree of hyperplasia being the lowest among all groups, and tracheal stenosis was reduced compared with the control group. In the vorinostat group, tracheal epithelial tissue hyperplasia was aggravated and stenosis was increased. The HDAC2 mRNA and protein levels were increased and decreased in the erythromycin and vorinostat groups, respectively. In contrast, the IL-8 mRNA expression levels were decreased and increased in the erythromycin and vorinostat groups, respectively. TGF-β1, VEGF, type I and type III collagen expression was decreased in the erythromycin group, while TGF-β1, VEGF and type III collagen expression was increased in the vorinostat group. Compared with the control, the budesonide group did not exhibit any alterations in all of the indicators examined, including TGF-β1, VEGF, IL-8, HDAC2 and collagen. Erythromycin treatment upregulated the expression of HDAC2, inhibited the inflammatory responses and reduced the proliferation of tracheal granulation tissue. In contrast, vorinostat treatment downregulated HDAC2 expression, promoted the inflammatory responses and increased the proliferation of tracheal granulation tissue. These results suggest that regulating HDAC2 may be used as a potential treatment for benign tracheal stenosis.

[Etiopathogenetic factors of wound healing in chronic post-intubation cicatricial stenosis of the larynx and trachea]

Despite the existing modern high-tech methods of examination and a variety of surgical treatment methods, the problem of diagnosis, treatment and rehabilitation of patients with chronic post-intubation cicatricial stenosis of the larynx and trachea still requires further study. Improving the understanding and correction of cellular, molecular genetic and biochemical disorders in a chronic wound is a key condition for increasing the efficiency of diagnosis, individual prognosis of the clinical course and the conduct of adequate therapeutic and preventive measures for post-intubation cicatricial laryngotracheal stenoses. In this regard, it seemed appropriate to analyze the existing etiopathogenetic factors of pathological wound healing in chronic post-intubation cicatricial stenosis of the larynx and trachea. Our attempt to summarize the available literature data demonstrated that laryngotracheal scars are a fibro-proliferative disease caused by aberrant wound healing after a damaging effect on the tissues of the larynx and trachea. The article describes the most pathogenetically significant healing, repair, and scarring factors in post-intubation laryngotracheal stenoses, including transforming growth factor β1, vascular growth factor A, type I and III collagen, and matrix metalloproteinases. An assessment of the features of the diagnostic and prognostic significance of these markers will increase the effectiveness of the treatment of patients with chronic cicatricial stenosis of the larynx and trachea, and will also serve as a prerequisite for the development of strategies for diagnostic, treatment, prophylactic and rehabilitation measures that will improve the quality of medical care and the quality of life of patients with chronic cicatricial stenosis of the larynx and trachea.

Phlorofucofuroeckol A from Ecklonia cava ameliorates TGF-β1-induced fibrotic response of human tracheal fibroblasts via the downregulation of MAPKs and SMAD 2/3 pathways inactivated TGF-β receptor

The objective of this study was to investigate inhibitory effects of a bioactive compound isolated from Ecklonia cava on fibrotic responses to transforming growth factor-β1 (TGF-β1)-stimulated Hs680. Tr human tracheal fibroblasts and the associated mechanisms of action. Post consecutive purification, a potent bioactive compound was identified phlorofucofuroeckol A. Phlorofucofuroeckol A significantly suppressed protein expression levels of collagen type I and α-smooth muscle actin (α-SMA) on TGF-β1-stimulated Hs680. Tr human tracheal fibroblasts. Further mechanistic studies determined that phlorofucofuroeckol A suppressed the phosphorylation of p38, extracellular regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) and SMAD 2/3 in TGF-β1-stimulated Hs680. Tr human tracheal fibroblasts. Moreover, we could show that phlorofucofuroeckol A inhibits binding of TGF-β1 to its TGF-β receptor by molecular docking. Based on the results, we propose that phlorofucofuroeckol A suppresses the MAPKs and SMAD 2/3 pathways and relieves cellular fibrotic activities, thus preventing tracheal fibrosis.

Study on the role of Hsa-miR-31-5p in hypertrophic scar formation and the mechanism

Hypertrophic scar (HS) formation is associated with the fibrosis of fibrocytes caused by excessive extracellular matrix (ECM) synthesis and deposition, the initial event of HS formation. Our high throughput screen of miRNA expression profiles identified hsa-miR31-5p, whose transcription level was most differentially in normal skin fibroblasts (NS) and HS among other miRNAs. The level of hsa-miR31-5p in HS was significantly higher than in NS. In-vitro functional experiments showed hsa-miR31-5p knockdown remarkably suppressed the proliferation of hypertrophic scar fibroblasts (HSFBs) under hypoxia, promoted cell invasion, and inhibited the expression of Collagen I and III and Fibronectin (FN), suggesting that hsa-miR31-5p knockdown effectively reduces HS formation caused by excessive ECM synthesis and deposition in HSFBs under hypoxia. Mechanism study showed that the regulation of HS formation by hsa-miR31-5p was mediated by its target gene, factor-inhibiting HIF-1 (FIH): under hypoxia, hsa-miR31-5p down-regulated FIH and thus increased the level of hypoxia inducible factor-1α (HIF-1α), which subsequently activated the HIF-1α fibrosis regulation pathway in HSFBs, and stimulated the proliferation and ECM synthesis in HSFBs, eventually resulting in fibrosis and scar formation. The data also show that knockdown of hsa-miR31-5p in HSFBs impaired the trend of increased proliferation, reduced invasion and excessive ECM synthesis and deposition caused by HIF-1a activation under hypoxia through upregulating FIH, indicating that knockdown of hsa-miR31-5p effectively inhibits the formation of HS. In conclusion, hsa-miR31 -5p plays an important role in HS formation by inhibiting FIH and regulating the HIF-1α pathway. Therefore, hsa-miR31 -5p may be a novel therapeutic target for HS.

Stent-induced tracheal stenosis can be predicted by IL-8 expression in rabbits

BACKGROUND

Bare metal stents may cause complications like fibrous encapsulation, granulation and tracheal stenosis. We investigated the behaviour of three commercially available stents in vivo (rabbits) and in vitro (coculture of those stents with epithelial and fibroblast cell lines). Also, we investigated whether development of tracheal stenosis could be predicted by any biological marker.

MATERIALS AND METHODS

The tracheae of 30 rabbits were implanted with either nitinol stents, with or without paclitaxel elution, or a cobalt-based stent. An additional ten rabbits underwent mock implantation (controls). Serial peripheral venous blood samples were taken throughout the study, and several cytokines measured. Animals were euthanized on day 90, with immediate tracheal endoscopy and lavage performed, then necropsy.

RESULTS

Rabbits with cobalt-based stent exhibited more inflammation and the highest stenosis incidence, with reduced survival. Both in vivo and in vitro, this stent induced higher IL-8 levels than nitinol stents. Most important, the presence of stent-induced tracheal stenosis was closely associated to increase in IL-8 expression in blood just 1 day after tracheal stent implantation: a 1·19-fold increase vs. baseline had 83% sensitivity, 83% specificity, 77% positive predictive value, 88% negative predictive value and 83% accuracy to predict development of stenosis.

CONCLUSIONS

The cobalt-based stent had the highest incidence of tracheal inflammation and stenosis. On the other hand, the paclitaxel-eluting nitinol stent did not prevent those complications and provoked a marked reaction compared with the bare nitinol stent. Early increase in IL-8 expression in blood after stent implantation could predict development of tracheal stenosis in rabbits.

Inhibitory Effect of β-Elemene on Human Airway Granulation Tissue in vivo and in vitro

BACKGROUND

Recurrent airway granulation hyperplasia and scar formation make airway stenosis a clinical challenge. Therefore, a new approach for the treatment of airway stenosis is necessary.

OBJECTIVE

To explore the inhibitory effect of β-elemene on the proliferation of fibroblasts and airway granulation.

METHODS

In vivo: (1) study of the effect of local β-elemene injection by bronchoscopy. (2) During bronchoscopy, granulation tissues both before and after treatment were obtained. HE staining was performed and the result compared. In vitro: (1) human airway primary fibroblasts were purified and characterized. (2) Fibroblasts were treated with β-elemene and normal saline (NS) and then examined by optical and electron microscopy. (3) Fibroblasts treated with β-elemene or NS were assessed for viability by tetrazolium salt assay. (4) Apoptotic rates were determined by flow cytometry.

RESULTS

In vivo: (1) after local injection of β- elemene, airway granulation tissue was reduced. (2) Granulation tissue was found to have less edema, and fibroblasts turned into mature fiber cells. In vitro: (1) human airway primary fibroblasts were successfully purified and cultured. (2) Compared with the control group, fibroblasts of the experimental group became clumped, the plasma granules were increased, and some fibroblasts lost their nucleus and organelles. (3) Compared with the control group, reduction of cell viability was detected with increased concentrations of β-elemene. (4) With increased concentrations of β-elemene, apoptotic rates of the fibroblasts were raised compared with the control group.

CONCLUSIONS

β-Elemene may induce apoptosis and necrosis of airway primary fibroblasts and inhibit the proliferation of fibroblasts and airway granulation. The results provide a new approach for the treatment of airway stenosis.