Vocal fold injury models in rats: a literature review on techniques and methodology

Abstract

This study reviewed the current literature on technical aspects regarding controlled vocal fold injuries in the rat model. Data from PubMed, Embase, and Scopus database for English language literature was collected to identify methodological steps leading to a controlled surgical injury of the rat vocal fold. Inclusion criteria: full disclosure of anesthesia protocol, positioning of the rat for surgery, vocal fold visualization method, instrumentation for vocal fold injury, vocal fold injury type. Articles with partial contribution were evaluated and separately included due to the limited number of original methodologies. 724 articles were screened, and eleven articles were included in the analysis. Anesthesia: ketamine hydrochloride and xylazine hydrochloride varied in dose from 45 mg/kg and 4.5 mg/kg to 100 mg/kg and 10 mg/kg. Visualization: The preferred method was the 1.9 mm, 25–30 degree endoscopes. The widest diameter endoscope used was 2.7 mm with a 0 or 30 degree angle of view. Instruments for lesion induction range from 18 to 31G needles, microscissors, micro forceps to potassium titanyl phosphate, and blue light lasers. Injury types: vocal fold stripping was the main injury type, followed by vocal fold scarring and charring. One article describes scaffold implantation with injury to the superior aspect of the vocal fold. Rats are good candidates for in vivo larynx and vocal folds research. A more standardized approach should be considered regarding the type of vocal fold injury to ease data comparison.

Effect of Testosterone on the Thyroarytenoid Muscle and Lamina Propria of Female Rat Vocal Folds

“…Our findings suggest that hypertrophy of muscle fibers is the pathophysiological substrate for the increase in TA muscle volume. In the skeletal body musculature, the primary mechanism for gaining muscle mass through androgens is hypertrophy of type I and II fibers, induced by nuclear DNA transcription stimulation 22 …”

“…VFs were dissected, ensuring the inclusion of their entire membranous portion, which has a length of approximately 1.0 mm. The posterior limit was the vocal process of the arytenoid 22,27 …”

“…Rats emit ultrasonic vocalizations that employ laryngeal muscle functions analogous to those in humans 20 and also express receptors for sex hormones within the larynx 21 . Among animal models, the LP of the rat VF is homologous to the human VF in terms of histological structure and composition 22,23 . Concerning sexual dimorphism, male rats also feature a larger TA muscle area and demonstrate vocalization with a lower F0 24 …”

Development and Application of Automated Vocal Fold Tracking Software in a Rat Surgical Model

“…Vocal fold (VF) disorders which impact these functions can have a devastating effect on patients 1–4 . Research in animal models is crucial for understanding the nature of VF dysfunction, and the rat model system is commonly used to study VF dynamics and laryngeal pathology 5–7 …”

“…[1][2][3][4] Research in animal models is crucial for understanding the nature of VF dysfunction, and the rat model system is commonly used to study VF dynamics and laryngeal pathology. [5][6][7] Video laryngoscopy is an important tool for assessing laryngeal function through direct visualization of VF movement. It is frequently used in recurrent laryngeal nerve (RLN) injury and regeneration models both to confirm paralysis following RLN injury and to study the impact of reinnervation on VF function.…”