Quantifying vocal fold wound-healing biomechanical property changes

Localized delivery of therapeutics impact laryngeal mechanics, local inflammatory response, and respiratory microbiome following upper airway intubation injury in swine

BACKGROUND

Laryngeal injury associated with traumatic or prolonged intubation may lead to voice, swallow, and airway complications. The interplay between inflammation and microbial population shifts induced by intubation may relate to clinical outcomes. The objective of this study was to investigate laryngeal mechanics, tissue inflammatory response, and local microbiome changes with laryngotracheal injury and localized delivery of therapeutics via drug-eluting endotracheal tube.

METHODS

A simulated traumatic intubation injury was created in Yorkshire crossbreed swine under direct laryngoscopy. Endotracheal tubes electrospun with roxadustat or valacyclovir- loaded polycaprolactone (PCL) fibers were placed in the injured airway for 3, 7, or 14 days (n = 3 per group/time and ETT type). Vocal fold stiffness was then evaluated with normal indentation and laryngeal tissue sections were histologically examined. Immunohistochemistry and inflammatory marker profiling were conducted to evaluate the inflammatory response associated with injury and ETT placement. Additionally, ETT biofilm formation was visualized using scanning electron microscopy and micro-computed tomography, while changes in the airway microbiome were profiled through 16S rRNA sequencing.

RESULTS

Laryngeal tissue with roxadustat ETT placement had increasing localized stiffness outcomes over time and histological assessment indicated minimal epithelial ulceration and fibrosis, while inflammation remained severe across all timepoints. In contrast, vocal fold tissue with valacyclovir ETT placement showed no significant changes in stiffness over time; histological analysis presented a reduction in epithelial ulceration and inflammation scores along with increased fibrosis observed at 14 days. Immunohistochemistry revealed a decline in M1 and M2 macrophage markers over time for both ETT types. Among the cytokines, IL-8 levels differed significantly between the roxadustat and valacyclovir ETT groups, while no other cytokines showed statistically significant differences. Additionally, increased biofilm formation was observed in the coated ETTs with notable alterations in microbiota distinctive to each ETT type and across time.

CONCLUSION

The injured and intubated airway resulted in increased laryngeal stiffness. Local inflammation and the type of therapeutic administered impacted the bacterial composition within the upper respiratory microbiome, which in turn mediated local tissue healing and recovery.

Vocal Fold Injury Produces Similar Biomechanical Outcomes in Male and Female Rabbits

OBJECTIVE

Sex differences in response to trauma and physiologic stressors have been identified in numerous organ systems but have not yet been defined in the larynx. The objective of this study was to develop an endoscopic vocal fold injury model in rabbits and to compare structural and functional outcomes between male and female subjects.

STUDY DESIGN

Basic science study.

METHODS

Two male and two female rabbits underwent unilateral endoscopic cordectomy. Animals were intubated with a size 3-0 neonatal endotracheal tube, and laryngoscopy was performed with a 4 mm Hopkins rod telescope. While visualizing, a 2 mm cupped forceps grasped and resected the mid-membranous portion of the right true vocal fold. Larynges were then harvested after 8weeks. Excised larynx phonation with high-speed videography and kymography was used to assess vibrational quality. Tissue elastic (Young's) modulus was measured by indentation.

RESULTS

Injured larynges phonated with fundamental frequencies between 237-415 Hz. In both males and females, the scarred vocal fold exhibited an increased Young's modulus compared to the contralateral nonoperated vocal fold. There were no notable differences in glottal closure pattern or vocal fold oscillation symmetry between sexes.

CONCLUSION

We have demonstrated a model for vocal fold scarring in rabbits. Vibrational and structural outcomes were similar between the examined male and female larynges.

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.

Drug delivery systems for wound healing treatment of upper airway injury

INTRODUCTION

Endotracheal intubation is a common procedure to maintain an open airway with risks for traumatic injury. Pathological changes resulting from intubation can cause upper airway complications, including vocal fold scarring, laryngotracheal stenosis, and granulomas and present with symptoms such as dysphonia, dysphagia, and dyspnea. Current intubation-related laryngotracheal injury treatment approaches lack standardized guidelines, relying on individual clinician experience, and surgical and medical interventions have limitations and carry risks.

AREAS COVERED

The clinical and preclinical therapeutics for wound healing in the upper airway are described. This review discusses the current developments on local drug delivery systems in the upper airway utilizing particle-based delivery systems, including nanoparticles and microparticles, and bulk-based delivery systems, encompassing hydrogels and polymer-based approaches.

EXPERT OPINION

Complex laryngotracheal diseases pose challenges for effective treatment, struggling due to the intricate anatomy, limited access, and recurrence. Symptomatic management often requires invasive surgical procedures or medications that are unable to achieve lasting effects. Recent advances in nanotechnology and biocompatible materials provide potential solutions, enabling precise drug delivery, personalization, and extended treatment efficacy. Combining these technologies could lead to groundbreaking treatments for upper airways diseases, significantly improving patients' quality of life. Research and innovation in this field are crucial for further advancements.

Endotracheal tubes with dexamethasone eluting electrospun coating improve tissue mechanical function after upper airway injury

Corticosteroid-eluting endotracheal tubes (ETTs) were developed and employed in a swine laryngotracheal injury model to maintain airway patency and provide localized drug delivery to inhibit fibrotic scarring. Polycaprolactone (PCL) fibers with or without dexamethasone were electrospun onto the ETT surface PCL-only coated ETTs and placed in native airways of 18 Yorkshire swine. Regular and dexamethasone-PCL coated ETTs were placed in airways of another 18 swine injured by inner laryngeal mucosal abrasion. All groups were evaluated after 3, 7 and 14 days (n = 3/treatment/time). Larynges were bisected and localized stiffness determined by normal indentation, then sequentially matched with histological assessment. In the native airway, tissue stiffness with PCL-only ETT placement increased significantly from 3 to 7 days (p = 0.0016) and 3 to 14 days (p < 0.0001) while dexamethasone-PCL ETT placement resulted in stiffness decreasing from 7 to 14 days (p = 0.031). In the injured airway, localized stiffness at 14 days was significantly greater after regular ETT placement (23.1 ± 0.725 N/m) versus dexamethasone-PCL ETTs (17.10 ± 0.930 N/m, p < 0.0001). Dexamethasone-loaded ETTs were found to reduce laryngotracheal tissue stiffening after simulated intubation injury compared to regular ETTs, supported by a trend of reduced collagen in the basement membrane in injured swine over time. Findings suggest localized corticosteroid delivery allows for tissue stiffness control and potential use as an approach for prevention and treatment of scarring caused by intubation injury.

Clinical study of injectable collagen scaffold with autologous fat cells for repair of severe vocal fold injury

Cell retention and survival after transplantation remains a major problem for long-term efficiency in therapy of severe vocal fold injury with autologous cells. In this study, injectable collagen scaffold was used to deliver autologous fat cells (AFCs) for repairing of severe vocal fold injury. We found injectable collagen scaffold could enhance the retention and survival of green fluorescent protein (GFP) labeled fat cells in the transplantation sites in rats. Based on these data, a randomized controlled clinical trial was conducted to evaluate the safety and efficiency of transplantation of collagen scaffold with AFCs for severe vocal fold injury. Ten patients with vocal fold paralysis were randomly assigned to control (AFCs only) and intervention (AFCs + collagen) groups. AFCs with or without collagen scaffold were injected into vocal folds of patients under general anesthesia, respectively. The safety and efficacy were regularly assessed during 24 months post-surgery. No obvious complications occurred in all patients during the follow-up. The collagen scaffold maintained the stability of implants after injection and reconstructed the vocal fold structure. The improvement of voice quality of patients was observed through voice quality evaluation with the voice handicap index (VHI) questionnaire, as well as acoustic analysis of maximum phonation time, jitter, and shimmer. The VHI score of patients in AFCs + collagen group improved significantly than those in AFCs group at 6, 12 and 24 months post-surgery. It demonstrates the injectable collagen scaffold is safe and efficient for delivering AFCs for vocal fold injury.