Myofibroblast persistence and collagen type I accumulation in the human stenotic trachea

Antimicrobial and Antiproliferative Coatings for Stents in Veterinary Medicine-State of the Art and Perspectives

Microbial colonization in veterinary stents poses a significant and concerning issue in veterinary medicine. Over time, these pathogens, particularly bacteria, can colonize the stent surfaces, leading to various complications. Two weeks following the stent insertion procedure, the colonization becomes observable, with the aggressiveness of bacterial growth directly correlating with the duration of stent placement. Such microbial colonization can result in infections and inflammations, compromising the stent's efficacy and, subsequently, the animal patient's overall well-being. Managing and mitigating the impact of these pathogens on veterinary stents is a crucial challenge that veterinarians and researchers are actively addressing to ensure the successful treatment and recovery of their animal patients. In addition, irritation of the tissue in the form of an inserted stent can lead to overgrowth of granulation tissue, leading to the closure of the stent lumen, as is most often the case in the trachea. Such serious complications after stent placement require improvements in the procedures used to date. In this review, antibacterial or antibiofilm strategies for several stents used in veterinary medicine have been discussed based on the current literature and the perspectives have been drawn. Various coating strategies such as coating with hydrogel, antibiotic, or other antimicrobial agents have been reviewed.

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.

The Effects of Rapamycin on the Proliferation, Migration, and Apoptosis of Human Tracheal Fibroblasts (HTrF) and Human Tracheal Epithelial Cells (HTEpiC)

Background: Restenosis after airway stenting needs to be addressed urgently. Rapamycin has been proven to inhibit restenosis elsewhere. This study aimed at observing its effects on the respiratory tract. Methods: CCK-8, wound healing, Transwell and apoptosis assays were performed to detect the effects of rapamycin on the survival, migration, and apoptosis, respectively, of human tracheal fibroblasts (HTrF) and human tracheal epithelial cells (HTEpiC). Results: The effective concentrations of paclitaxel, mitomycin C and rapamycin on HTrF were 10⁻⁷–10⁻⁴ mol/L, 10⁻⁶–10⁻⁴ mol/L, and 10⁻⁵–10⁻⁴ mol/L, respectively. At the effective concentrations, the inhibition rates of paclitaxel on HTEpiC were (43.03 ± 1.12)%, (49.49 ± 0.86)%, (55.22 ± 1.43)%, and (93.19 ± 0.45)%; the inhibition rates of mitomycin C on HTEpiC were (88.11 ± 0.69)%, (93.82 ± 0.96)%, and (94.94 ± 0.54)%; the inhibition rates of rapamycin on HTEpiC were (10.19 ± 0.35)% and (94.55 ± 0.71)%. At the concentration of (1–4) × 10⁻⁵ mol/L, the inhibition rate of rapamycin on HTrF was more than 50%, and that on HTEpiC was less than 20% (p < 0.05). Conclusions: Compared to paclitaxel and mitomycin C, rapamycin had the least effect on HTEpiC while effectively inhibiting HTrF. The optimum concentration range was (1–4) × 10⁻⁵ mol/L.

Local Delivery of Mometasone Furoate from an Eluting Endotracheal Tube Reduces Airway Morbidity Following Long-Term Animal Intubation

BACKGROUND

upper airway complications are common sequelae of endotracheal tube (ETT) intubation, and systemic corticosteroids are considered a mainstay treatment for this problem. Drug-eluting ETT may present an attractive option for topical steroid delivery while avoiding systemic side effects and improving the therapeutic outcome. The objective of the present study is to evaluate the reduction of tube-related tracheal morbidity via a self-designed steroid-eluting ETT with controlled sustained release properties in an animal model.

METHODS

steroid-eluting ETTs were coated by poly(lactic-co-glycolic acid) -electrospun nanofibers loaded with mometasone furoate (MF) as a model drug. Animals were randomly assigned into three equal groups: non-intubated, blank-ETT, and loaded-ETT. The intubation interval was 1 week. Specimens were analyzed by histology, specific fibrosis staining, and scanning electron microscopy (SEM).

RESULTS

the blank-ETT group exhibited a significant increase in tracheal mucosal thickness compared to the loaded-ETT and control groups. Average tracheal mucosal thickness was 112 ± 34, 242 ± 49, and 113 ± 43 μm in the control, blank-ETT, and loaded-ETT groups, respectively. The blank-ETT group exhibited a significant increase in tracheal fibrosis compared to the loaded-ETT and control groups. Relative fibrosis values were 0.07 ± 0.05, 0.154 ± 0.1, and 0.0984 ± 0.084% for the control, blank-ETT, and loaded-ETT groups, respectively. While SEM imaging showed normal surface structures in the control group, intubated blank-ETT rats showed severe surface structural damage, whereas only mild damage was observed in the loaded-ETT group.

CONCLUSIONS

local sustained release of MF via a self-designed drug-eluting ETT is a potential therapeutic approach which may significantly reduce tube-related upper airway morbidity.

Early medical therapy for acute laryngeal injury (ALgI) following endotracheal intubation: a protocol for a prospective single-centre randomised controlled trial

INTRODUCTION

Respiratory failure requiring endotracheal intubation accounts for a significant proportion of intensive care unit (ICU) admissions. Little attention has been paid to the laryngeal consequences of endotracheal intubation. Acute laryngeal injury (ALgI) after intubation occurs at the mucosal interface of the endotracheal tube and posterior larynx and although not immediately manifest at extubation, can progress to mature fibrosis, restricted glottic mobility and clinically significant ventilatory impairment. A recent prospective observational study has shown that >50% of patients intubated >24 hours in an ICU develop ALgI. Strikingly, patients with AlgI manifest significantly worse subjective breathing at 12 weeks. Current ALgI treatments are largely surgical yet offer a marginal improvement in symptoms. In this study, we will examine the ability of a postextubation medical regime (azithromycin and inhaled budesonide) to improve breathing 12 weeks after ALgI. METHODS AND ANALYSIS: A prospective, single-centre, double-blinded, randomised, control trial will be conducted at Vanderbilt Medical Center. Participants will be recruited from adult patients in ICUs. Participants will undergo a bedside flexible nasolaryngoscopy for the identification of ALgI within 72 hours postextubation. In addition, participants will be asked to complete peak expiratory flow measurements immediately postintubation. Patients found to have ALgI will be randomised to the placebo control or medical therapy group (azithromycin 250 mg and budesonide 0.5 mg for 14 days). Repeat peak expiratory flow, examination of the larynx and patient-reported Clinical COPD (chronic obstructive pulmonary disease) Questionnaire, Voice Handicap Index and 12-Item Short Form Health Survey questionnaires will be conducted at 12 weeks postextubation. Consented patients will also have patient-specific, disease-specific and procedure-specific covariates abstracted from their medical record.

ETHICS AND DISSEMINATION

The Institutional Review Board (IRB) Committee of the Vanderbilt University Medical Center has approved this protocol (IRB #171066). The findings of the trial will be disseminated through peer-reviewed journals, national and international conferences.

TRIAL REGISTRATION NUMBER

NCT03250975.

Erythromycin combined with corticosteroid reduced inflammation and modified trauma-induced tracheal stenosis in a rabbit model

Background:

Patients with endotracheal intubation or tracheostomy are subject to benign tracheal stenosis (TS), for which current therapies are unsatisfactory. We conducted a preliminary investigation of drugs and drug combinations for the prevention and treatment of TS in a rabbit model.

Methods:

Fifty-four rabbits were apportioned into nine groups according to treatment: sham-operated control; untreated TS model; amikacin; budesonide; erythromycin; penicillin; amikacin + budesonide; erythromycin + budesonide; and penicillin + budesonide. TS was induced by abrasion during surgery. The drugs were applied for 7 days before and 10 days after the surgery. Rabbits were killed on the eleventh day. Tracheal specimens were processed for determining alterations in the thicknesses of tracheal epithelium and lamina propria via hematoxylin and eosin. The tracheal mRNA (assessed by real-time quantitative polymerase chain reaction) expressions of the following fibrotic-related factors were determined: transforming growth factor-β1 (TGF- β1), collagen type I (COL1A1), collagen type III (COL3A1), and interleukin-17 (IL-17). The protein levels of TGF-β1, COL1A1, and COL3A1 were determined through immunohistochemistry and integrated optical densities.

Results:

Compared with all other groups, the untreated TS model had significantly thicker tracheal epithelium and lamina propria, and higher mRNA and protein levels of all targeted fibrotic factors. The mRNA and protein levels of the targeted fibrotic factors in all the drug-treated groups were lower than those of the untreated TS model, and differences were most significant in the erythromycin + budesonide group.

Conclusions:

Erythromycin combined with budesonide may reduce inflammation and modify fibrosis progression in TS after tracheal injury.

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.

Effect of tamoxifen on fibrosis, collagen content and transforming growth factor-β1, -β2 and -β3 expression in common bile duct anastomosis of pigs

End-to-end anastomosis in the treatment for bile duct injury during laparoscopic cholecystectomy has been associated with stricture formation. The aim of this study was to experimentally investigate the effect of oral tamoxifen (tmx) treatment on fibrosis, collagen content and transforming growth factor-β1, -β2 and -β3 expression in common bile duct anastomosis of pigs. Twenty-six pigs were divided into three groups [sham (n = 8), control (n = 9) and tmx (n = 9)]. The common bile ducts were transected and anastomosed in the control and tmx groups. Tmx (40 mg/day) was administered orally to the tmx group, and the animals were euthanized after 60 days. Fibrosis was analysed by Masson's trichrome staining. Picrosirius red was used to quantify the total collagen content and collagen type I/III ratio. mRNA expression of transforming growth factor (TGF)-β1, -β2 and -β3 was quantified using real-time polymerase chain reaction (qRT-PCR). The control and study groups exhibited higher fibrosis than the sham group, and the study group showed lower fibrosis than the control group (P = 0.011). The control and tmx groups had higher total collagen content than the sham group (P = 0.003). The collagen type I/III ratio was higher in the control group than in the sham and tmx groups (P = 0.015). There were no significant differences in the mRNA expression of TGF-β1, -β2 and -β3 among the groups (P > 0.05). Tmx decreased fibrosis and prevented the change in collagen type I/III ratio caused by the procedure.

Paclitaxel Drug-eluting Tracheal Stent Could Reduce Granulation Tissue Formation in a Canine Model

Background:

Currently available silicone and metallic stents for tracheal stenosis are associated with many problems. Granulation proliferation is one of the main complications. The present study aimed to evaluate the efficacy of paclitaxel drug-eluting tracheal stent in reducing granulation tissue formation in a canine model, as well as the pharmacokinetic features and safety profiles of the coated drug.

Methods:

Eight beagles were randomly divided into a control group (bare-metal stent group, n = 4) and an experimental group (paclitaxel-eluting stent group, n = 4). The observation period was 5 months. One beagle in both groups was sacrificed at the end of the 1^st and 3^rd months, respectively. The last two beagles in both groups were sacrificed at the end of 5^th month. The proliferation of granulation tissue and changes in tracheal mucosa were compared between the two groups. Blood routine and liver and kidney function were monitored to evaluate the safety of the paclitaxel-eluting stent. The elution method and high-performance liquid chromatography were used to characterize the rate of in vivo release of paclitaxel from the stent.

Results:

Compared with the control group, the proliferation of granulation tissue in the experimental group was significantly reduced. The drug release of paclitaxel-eluting stent was the fastest in the 1^st month after implantation (up to 70.9%). Then, the release slowed down gradually. By the 5^th month, the release reached up to 98.5%. During the observation period, a high concentration of the drug in the trachea (in the stented and adjacent unstented areas) and lung tissue was not noted, and the blood test showed no side effect.

Conclusions:

The paclitaxel-eluting stent could safely reduce the granulation tissue formation after stent implantation in vivo, suggesting that the paclitaxel-eluting tracheal stent might be considered for potential use in humans in the future.

Myofibroblast differentiation: main features, biomedical relevance, and the role of reactive oxygen species

SIGNIFICANCE

Myofibroblasts are prototypical fibrotic cells, which are involved in a number of more or less pathological conditions, from foreign body reactions to scarring, from liver, kidney, or lung fibrosis to neoplastic phenomena. The differentiation of precursor cells (not only of fibroblastic nature) is characterized by a complex interplay between soluble factors (growth factors such as transforming growth factor β1, reactive oxygen species [ROS]) and material properties (matrix stiffness).

RECENT ADVANCES

The last 15 years have seen very significant advances in the identification of appropriate differentiation markers, in the understanding of the differentiation mechanism, and above all, the involvement of ROS as causative and persistence factors.

CRITICAL ISSUES

The specific mechanisms of action of ROS remain largely unknown, although evidence suggests that both intracellular and extracellular phenomena play a role.

FUTURE DIRECTIONS

Approaches based on antioxidant (ROS-scavenging) principles and on the potentiation of nitric oxide signaling hold much promise in view of a pharmacological therapy of fibrotic phenomena. However, how to make the active principles available at the target sites is yet a largely neglected issue.