Rabbit model of tracheal stenosis using cylindrical diffuser

Establishment of a survival rabbit model for laryngotracheal stenosis: A prospective randomized study

Objective

To develop a reproducible survival rabbit model for laryngotracheal stenosis (LTS).

Methods

Seventy New Zealand white (NZW) rabbits were randomly divided into experimental groups (n = 30) and a control group (n = 40). In experimental groups, a nylon brush was inserted retrograde from the tracheotomy through the subglottis and rotated until a full layer circumferential mucosal injury to cartilage exposure, assisted by fiberoptic laryngoscopy (FOL) visualization. Experimental group 1 (n = 10), rotated 10 times; group 2 (n = 20), rotated 20 times. The control group underwent tracheotomy only without nylon brush scraping. The rabbits underwent FOL at 1st, 4th, 8th, and 12th week postinjury respectively to observe the formation of LTS. They were euthanized and the larynxes and tracheas were subjected to gross and histopathological examination at 12 weeks postinjury.

Results

The control group all survived, while five cases in experimental groups died from LTS and/or mucous plug. Histological observation showed that the control group had intact laryngotracheal mucosal epithelium without any stenosis; the experimental groups showed proliferation of fibroblasts and thickening of collagen fibers. The mean stenosis in control group was 9.31 ± 0.98%, while that in experimental group 1 was 32.78 ± 7.07% and 58.25 ± 8.96% in experimental group 2. The difference between the three groups was statistically significant (χ 2 = 47.98, p < .05).

Conclusions

We successfully developed a reproducible survival rabbit model for LTS using a nylon brush through FOL visualization combined with tracheostomy. This model can provide a mature and stable animal model for the exploration of wound-healing pathophysiology and the effect of interventions.

Level of evidence

NA.

Laxative Effects of Phlorotannins Derived from Ecklonia cava on Loperamide-Induced Constipation in SD Rats

This study investigated the laxative effects of phlorotannins (Pt) derived from Ecklonia cava (E. cave) on chronic constipation by evaluating alterations in stool parameters, gastrointestinal motility, histopathological structure, mucin secretion, gastrointestinal hormones, muscarinic cholinergic regulation, and fecal microbiota in SD rats with loperamide (Lop)-induced constipation subjected to Pt treatment. Stool-related parameters (including stool number, weight, and water contents), gastrointestinal motility, and length of intestine were significantly enhanced in the Lop+Pt-treated group as compared to the Lop+Vehicle-treated group. A similar recovery was detected in the histopathological and cytological structure of the mid-colon of Lop+Pt-treated rats, although the level of mucin secretion remained constant. Moreover, rats with Lop-induced constipation subjected to Pt treatment showed significant improvements in water channel expression, gastrointestinal hormone secretions, and expression of muscarinic acetylcholine receptors M2/M3 (mAChRs M2/M3) and their mediators of muscarinic cholinergic regulation. Furthermore, the Lop+Pt-treated group showed a significant recovery of Bifidobacteriaceae, Muribaculaceae, Clostridiaceae, and Eubacteriaceae families in fecal microbiota. Taken together, these results provide the first evidence that exposure of SD rats with Lop-induced constipation to Pt improves the constipation phenotype through the regulation of membrane water channel expression, GI hormones, the mAChR signaling pathway, and fecal microbiota.

Dieckol induces cell cycle arrest by down-regulating CDK2/cyclin E in response to p21/p53 activation in human tracheal fibroblasts

The phlorotannin derivative dieckol isolated from Ecklonia cava has been shown to exhibit anti-inflammatory, anti-bacterial, anti-oxidative anti-adipogenic and anti-stenosis activity. However, the role of dieckol in cyclin-dependent kinase 2 (CDK2)/cyclin E signalling, which regulates fibrosis development, has not yet been determined. In this study, we report that dieckol-suppressed cell proliferation through the cell cycle arrest of Hs680.Tr human tracheal fibroblasts. Following consecutive purification, dieckol was identified as a potent bioactive compound. The results showed that dieckol had significant anti-proliferative activity against Hs680.Tr human tracheal fibroblastsWestern blotting analysis also found that dieckol dose-dependently induced the cell cycle arrest of Hs680.Tr fibroblasts in the G0/G1 phase, accompanied by the downregulation of CDK2 and cyclin E and the upregulation of p21 and p53. As attested by molecular docking study, the dieckol interacted with the core interface residues in transforming growth factor-β receptor with high affinity. These findings suggest that dieckol from E. cava inhibits the cell proliferation of Hs680.Tr, potentially through p21- and p53-mediated G0/G1 cell cycle arrest.

Phlorotannins ameliorate extracellular matrix production in human vocal fold fibroblasts and prevent vocal fold fibrosis via aerosol inhalation in a laser-induced fibrosis model

Vocal fold fibrosis is an abnormal condition characterized by unfavorable changes in the organization of the extracellular matrix in vocal fold lamina propria. To prevent and treat vocal fold fibrosis, a number of synthetic drugs, such as mitomycin C and the glucocorticoid family, are used after surgery, but these are known to have some side effects. Therefore, using both in vitro and in vivo studies, this study investigated whether phlorotannins extracted from Ecklonia cava have the potential to prevent vocal fold fibrosis with minimal side effects. The results show that phlorotannins suppressed both the expression of the fibrotic phenotypic marker and cell migration by inhibiting the activation of the mitogen-activated protein kinase (MAPK) and Smad2/3 signaling pathways in human vocal fold fibroblasts stimulated by transforming growth factor-β. Additionally, phlorotannins exhibited antifibrotic efficacy without an excessive inflammatory response in a laser-induced fibrosis rabbit model when delivered as an aerosol via inhalation. Based on these results, phlorotannins should be considered a promising candidate for use in the prevention of vocal fold fibrosis.

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.

Concentric photothermal coagulation with basket-integrated optical device for treatment of tracheal stenosis

A basket-integrated optical device is developed to consistently treat tubular tissue by centering an optical diffuser in the lumen. Four nitinol arms in conjunction with the optical diffusing applicator are deployed to induce homogeneous circumferential light emission and concentric photothermal coagulation on tracheal tissue. A 1470-nm laser light is employed for the tissue testing at various irradiation conditions and evaluated in terms of thermal gradient and temperature evolution. Preliminary experiments on liver tissue demonstrate the concentric development of the radial thermal coagulation in the tissue (eccentric ratio = ~5.5%). The interstitial tissue temperature increases with the total amount of energy delivery (around 65°C). Ex vivo trachea testing yields up to 16.5% tissue shrinkage due to dehydration as well as uniform ablation of the cilia and goblet cells in a mucosa layer under 7-W irradiation for 10 s. The proposed optical device may be a feasible therapeutic method to entail the circumferential coagulation in the tubular tissues in a reliable manner.

Reproducing severe acute subglottic stenosis in a rabbit model

OBJECTIVES

The objectives of this study were to develop an animal model with consistent, severe subglottic stenosis (SGS), and to develop the timeline needed for intervention to limit rabbit mortality.

METHODS

Subglottic stenosis was created endoscopically using either a nylon or polypropylene brush in sixteen New Zealand White rabbits. The subglottic cross-sectional area was measured endoscopically using a right-angled probe and an open source image analysis software The cross-sectional areas of the stenotic and native airways were compared to calculate the subglottic stenosis percentage and Myer-Cotton grade classification.

RESULTS

The average diameter of the native subglottis was 4.7 mm (SD 0.4). The mean subglottic stenosis percentage was 73% (SD 32) for all rabbits. The three rabbits injured with the nylon brush had 30, 52, and 76% stenosis. Nine of the 12 surviving rabbits (75%) injured with the polypropylene brush had a >86% subglottic stenosis. Four rabbits in the polypropylene brush cohort died from procedural complications.

CONCLUSION

This study demonstrates a reliable model using a polypropylene brush to create severe acute subglottic stenosis. Cartilage exposure after creating the injury was associated with more severe stenosis. Mortality rate may have been reduced if endoscopic balloon dilation was performed electively seven days after injury, rather than emergently nine days after injury.

LEVEL OF EVIDENCE

4.

Spatial effect of conical angle on optical-thermal distribution for circumferential photocoagulation

A uniformly diffusing applicator can be advantageous for laser treatment of tubular tissue. The current study investigated various conical angles for diffuser tips as a critical factor for achieving radially uniform light emission. A customized goniometer was employed to characterize the spatial uniformity of the light propagation. An ex vivo model was developed to quantitatively compare the temperature development and irreversible tissue coagulation. The 10-mm diffuser tip with angle at 25° achieved a uniform longitudinal intensity profile (i.e., 0.90 ± 0.07) as well as a consistent thermal denaturation on the tissue. The proposed conical angle can be instrumental in determining the uniformity of light distribution for the photothermal treatment of tubular tissue.