Recurrent laryngeal nerve transection in mice results in translational upper airway dysfunction

Abstract

The recurrent laryngeal nerve (RLN) is responsible for normal vocal‐fold (VF) movement, and is at risk for iatrogenic injury during anterior neck surgical procedures in human patients. Injury, resulting in VF paralysis, may contribute to subsequent swallowing, voice, and respiratory dysfunction. Unfortunately, treatment for RLN injury does little to restore physiologic function of the VFs. Thus, we sought to create a mouse model with translational functional outcomes to further investigate RLN regeneration and potential therapeutic interventions. To do so, we performed ventral neck surgery in 21 C57BL/6J male mice, divided into two groups: Unilateral RLN Transection (n = 11) and Sham Injury (n = 10). Mice underwent behavioral assays to determine upper airway function at multiple time points prior to and following surgery. Transoral endoscopy, videofluoroscopy, ultrasonic vocalizations, and whole‐body plethysmography were used to assess VF motion, swallow function, vocal function, and respiratory function, respectively. Affected outcome metrics, such as VF motion correlation, intervocalization interval, and peak inspiratory flow were identified to increase the translational potential of this model. Additionally, immunohistochemistry was used to investigate neuronal cell death in the nucleus ambiguus. Results revealed that RLN transection created ipsilateral VF paralysis that did not recover by 13 weeks postsurgery. Furthermore, there was evidence of significant vocal and respiratory dysfunction in the RLN transection group, but not the sham injury group. No significant differences in swallow function or neuronal cell death were found between the two groups. In conclusion, our mouse model of RLN injury provides several novel functional outcome measures to increase the translational potential of findings in preclinical animal studies. We will use this model and behavioral assays to assess various treatment options in future studies.

Persistent Feeding and Swallowing Deficits in a Mouse Model of 22q11.2 Deletion Syndrome

“…Mice were subsequently ear punched for identification and group housed (based on sex and litter) without experimental testing until approximately 3 months of age. At that time, 22 mice (11 LgDel: six males and five females; 11 WT: five males and six females) were shipped to the University of Missouri and following a 2-week quarantine period, were processed for fluoroscopic (13)(14)(15) and endoscopic (16)(17)(18)(19) assessments of deglutition-related structure and function. The remaining 10 mice (5 LgDel and 5 WT, all males) were retained at The George Washington University for video surveillance of feeding and grooming activity using automated behavioral analysis (HomeCageScan 3.0; CleverSys Inc., Reston, VA) and Capture Star software (Version 1; CleverSys Inc.).…”

“…Within 1 week after completing VFSS testing, the same 22 mice underwent transoral endoscopy for gross assessment of craniofacial structure and function using our established protocol and custom equipment (16)(17)(18)(19). The night prior to endoscopy, mice were food restricted for 4-6 h to prevent post-prandial retention of food in the pharynx that may interfere with testing.…”

Postnatal Development of the Mouse Larynx: Negative Allometry, Age-Dependent Shape Changes, Morphological Integration, and a Size-Dependent Spectral Feature

“…Developmental biology of the larynx in the mouse and rat is highly relevant to both healthy and disordered human activity, as the rodent larynx is a model for studying laryngeal neuromuscular (e.g., Haney et al, 2020;Montalbano et al, 2019) and connective tissue (e.g., Lungova et al, 2015;Peterson et al, 2013;Welham et al, 2015) maturation and injury. Additional applications of rodent models relevant for human health include chronic electronic a stimulation of the rat thyroarytenoid muscle for voice disorder therapy (McMullen et al, 2011) and characterizing dysphagia in a rat model for Parkinson disease (Russell et al, 2013).…”

A Mouse Model of Dysphagia After Facial Nerve Injury

“…[34][35][36][37] We chose the C57BL/6J mouse strain because it is the most commonly studied laboratory rodent in biomedical research, 38 and more specifically because it is an established model for investigating the neural control of normal swallowing 39,40 and the mechanisms of neurogenic dysphagia secondary to biological aging 40 and iatrogenic laryngeal nerve injury. [41][42][43] In this study, we compared swallowing outcomes in C57BL/6J mice after surgical transection of the MT versus the marginal mandibular branch (MMB) of the facial nerve. Transection injury (neurotmesis) was chosen for experimental replicability over the other two nerve injury types (neurapraxia and axonotmesis).…”

“…Here, we used videofluoroscopy, the clinical gold standard test for dysphagia diagnosis, 31–33 to investigate the effect of facial nerve injury on swallowing in mice, whose neural control of swallowing is remarkably similar to humans 34–37 . We chose the C57BL/6J mouse strain because it is the most commonly studied laboratory rodent in biomedical research, 38 and more specifically because it is an established model for investigating the neural control of normal swallowing 39,40 and the mechanisms of neurogenic dysphagia secondary to biological aging 40 and iatrogenic laryngeal nerve injury 41–43 …”