Modulated Fibrosis and Mechanosensing of Fibroblasts by SB525334 in Pediatric Subglottic Stenosis.

OBJECTIVE: Subglottic stenosis (SGS) may result from prolonged intubation where fibrotic scar tissue narrows the airway. The scar forms by differentiated myofibroblasts secreting excessive extracellular matrix (ECM). TGF-ß1 is widely accepted as a regulator of fibrosis; however, it is unclear how biomechanical pathways co-regulate fibrosis. Therefore, we phenotyped fibroblasts from pediatric patients with SGS to explore how key signaling pathways, TGF-ß and Hippo, impact scarring and assess the impact of inhibiting these pathways with potential therapeutic small molecules SB525334 and DRD1 agonist dihydrexidine hydrochloride (DHX). METHODS: Laryngeal fibroblasts isolated from subglottic as well as distal control biopsies of patients with evolving and maturing subglottic stenosis were assessed by α-smooth muscle actin immunostaining and gene expression for α-SMA, FN, HGF, and CTGF markers. TGF-ß and Hippo signaling pathways were modulated during TGF-ß1-induced fibrosis using the inhibitor SB525334 or DHX and analyzed by RT-qPCR for differential gene expression and atomic force microscopy for ECM stiffness. RESULTS: SGS fibroblasts exhibited higher α-SMA staining and greater inflammatory cytokine and fibrotic marker expression upon TGF-ß1 stimulation (p < 0.05). SB525334 restored levels to baseline by reducing SMAD2/3 nuclear translocation (p < 0.0001) and pro-fibrotic gene expression (p < 0.05). ECM stiffness of stenotic fibroblasts was greater than healthy fibroblasts and was restored to baseline by Hippo pathway modulation using SB525334 and DHX (p < 0.01). CONCLUSION: We demonstrate that distinct fibroblast phenotypes from diseased and healthy regions of pediatric SGS patients respond differently to TGF-ß1 stimulation, and SB525334 has the superior potential for subglottic stenosis treatment by simultaneously modulating TGF-ß and Hippo signaling pathways. LEVEL OF EVIDENCE: NA Laryngoscope, 134:287-296, 2024.

Amelioration of Subglottic Stenosis by Antimicrobial Peptide Eluting Endotracheal Tubes.

Introduction: Pediatric subglottic stenosis (SGS) results from prolonged intubation where scar tissue leads to airway narrowing that requires invasive surgery. We have recently discovered that modulating the laryngotracheal microbiome can prevent SGS. Herein, we show how our patent-pending antimicrobial peptide-eluting endotracheal tube (AMP-ET) effectively modulates the local airway microbiota resulting in reduced inflammation and stenosis resolution. Materials and Methods: We fabricated mouse-sized ETs coated with a polymeric AMP-eluting layer, quantified AMP release over 10 days, and validated bactericidal activity for both planktonic and biofilm-resident bacteria against Staphylococcus aureus and Pseudomonas aeruginosa. Ex vivo testing: we inserted AMP-ETs and ET controls into excised laryngotracheal complexes (LTCs) of C57BL/6 mice and assessed biofilm formation after 24 h. In vivo testing: AMP-ETs and ET controls were inserted in sham or SGS-induced LTCs, which were then implanted subcutaneously in receptor mice, and assessed for immune response and SGS severity after 7 days. Results: We achieved reproducible, linear AMP release at 1.16 µg/day resulting in strong bacterial inhibition in vitro and ex vivo. In vivo, SGS-induced LTCs exhibited a thickened scar tissue typical of stenosis, while the use of AMP-ETs abrogated stenosis. Notably, SGS airways exhibited high infiltration of T cells and macrophages, which was reversed with AMP-ET treatment. This suggests that by modulating the microbiome, AMP-ETs reduce macrophage activation and antigen specific T cell responses resolving stenosis progression. Conclusion: We developed an AMP-ET platform that reduces T cell and macrophage responses and reduces SGS in vivo via airway microbiome modulation. Supplementary Information: The online version contains supplementary material available at 10.1007/s12195-023-00769-9.

A 7-Year-Old With Persistent Fever and Cough.

A previously healthy, fully immunized 7-year-old girl presented with a 7-week history of daily fevers and a worsening cough with persistently elevated inflammatory markers. Before admission, she had an unrevealing outpatient workup by infectious disease, rheumatology, pulmonology, and otorhinolaryngology for her fever and other symptoms. Multiple courses of antibiotics had no effect, but brief courses of steroids seemed to modestly alleviate her symptoms. At an outside hospital, a computed tomography neck and chest scan revealed mediastinal lymphadenopathy. She was subsequently transferred to the authors' institution. Her examination was notable for a febrile, tired-appearing girl in respiratory distress with a muffled voice and inspiratory stridor. Her laboratory tests revealed leukocytosis with left shift, microcytic anemia, and hypoalbuminemia, as well as elevated inflammatory markers, ferritin, and fecal calprotectin. Her peripheral smear, uric acid, and lactate dehydrogenase were all within normal limits. Infectious study results, including blood and urine cultures, cytomegalovirus serologies, and Bartonella serologies were negative. On the second read of her outside computed tomography imaging, her lymphadenopathy was felt to be nonpathologic. Based on a recommendation by rheumatology, an ophthalmologic examination was obtained, which revealed bilateral anterior uveitis; however, rheumatologic laboratory test results returned negative. Her fevers continued, and inflammatory markers remained elevated despite antibiotics. On day 6 of hospitalization, she developed worsening respiratory distress, necessitating intubation and transfer to the ICU. Repeat laryngoscopy and bronchoscopy revealed severe purulent tracheitis; however, throat cultures remained sterile. Her clinical deterioration without identification of an offending organism prompted additional evaluation for a systemic etiology.

Drug delivery to the pediatric upper airway.

Pediatric upper airway disorders are frequently life-threatening and require precise assessment and intervention. Targeting these pathologies remains a challenge for clinicians due to the high complexity of pediatric upper airway anatomy and numerous potential etiologies; the most common treatments include systemic delivery of high dose steroids and antibiotics or complex and invasive surgeries. Furthermore, the majority of innovative airway management technologies are only designed and tested for adults, limiting their widespread implementation in the pediatric population. Here, we provide a comprehensive review of the most recent challenges of managing common pediatric upper airway disorders, describe the limitations of current clinical treatments, and elaborate on how to circumvent those limitations via local controlled drug delivery. Furthermore, we propose future advancements in the field of drug-eluting technologies to improve pediatric upper airway management outcomes.

Volumetric MRI analysis pre- and post-Transoral robotic surgery for obstructive sleep apnea.

OBJECTIVES/HYPOTHESIS: To quantitatively measure volumetric changes in upper airway soft tissue structures using magnetic resonance imaging (MRI) pre- and post transoral robotic surgery for obstructive sleep apnea (OSA-TORS). STUDY DESIGN: Prospective, nonrandomized, institutional board-approved study. METHODS: Apneics undergoing OSA-TORS, which included bilateral posterior hemiglossectomy with limited pharyngectomy and uvulopalatopharyngoplasty, had upper airway MRIs pre- and postoperatively. Changes (percent and absolute values) in upper airway and surrounding soft tissue volumes were calculated. We assessed whether there were significant volumetric changes and if changes correlated with apnea-hypopnea index (AHI) changes. RESULTS: Nineteen MRIs and 18 polysomnograms were analyzed pre- and postoperation. Total airway volume increased by 19.4% (P = 0.030). Soft palate and tongue volumes decreased by 18.3% (P = 0.002) and 5.8% (P = 0.013), respectively. Retropalatal and total lateral wall volumes decreased by 49.8% (P = 0.0001) and 17.9% (P = 0.008), respectively. Changes in other structures were not significant. Eleven patients had surgical success, with a mean AHI decrease of 52.9; six were nonsuccesses with a mean AHI decrease of 4.5 (P =0.006). Decreased retropalatal lateral wall volume correlated with decreased AHI. CONCLUSION: Airway, tongue, soft palate, and lateral wall volumes change significantly after OSA-TORS. Changes in the volume of the lateral walls correlated with changes in AHI. Volumetric upper airway MRI may be a helpful tool to better understand reasons for surgical success. LEVEL OF EVIDENCE: 4.

Quantitative airway analysis during drug-induced sleep endoscopy for evaluation of sleep apnea.

OBJECTIVES/HYPOTHESIS: To quantitatively measure changes in airway caliber at multiple anatomical levels during drug-induced sleep endoscopy (DISE) for evaluation of sleep apnea. We hypothesize that patients undergoing DISE will show: 1) collapse at multiple upper airway regions (retropalatal, retroglossal, and retroepiglottic), with greater collapse in the retropalatal region; and 2) greater anterior-posterior dimensional narrowing than the lateral. STUDY DESIGN: Case series. METHODS: Patients underwent DISE employing propofol as part of a nonrandomized prospective trial assessing candidacy for transoral robotic surgery intervention for sleep apnea. Images of the retropalatal, retroglossal, and retroepiglottic regions were captured during an initial period of light sedation and again in a period of deep sedation. Images were analyzed using software to measure the percent change in regional airway measurements as a result of DISE. RESULTS: Thirty-seven sleep endoscopy videos were analyzed from patients with obstructive sleep apnea (apnea-hypopnea index: 42.9 ± 27.0 events/hour). Analyzable images were in the retropalatal (n = 24), retroglossal (n = 27), and retroepiglottic (n = 29) regions. The patients demonstrated mean reductions in airway area in the retropalatal (84.1 ± 18.7%), retroglossal (39.3 ± 37.5%), and retroepiglottic region (44.6 ± 42.8%). No statistically significant differences were found between lateral and anterior-posterior airway dimensional changes. CONCLUSIONS: Patients undergoing DISE had significant reductions in airway area at multiple regions under deep sedation with propofol. We conclude that collapse in the retropalatal region is greater than the hypopharyngeal region. This method can be used to quantitatively measure DISE upper airway changes, which could potentially be used as a means for understanding surgical outcomes in patients with sleep apnea.