A preliminary integrated morphologic and transcriptomic analysis of denervation remodeling in rat laryngeal and hindlimb muscles

Abstract

The translational relevance of the rat laryngeal model has been questioned due to key interspecies differences in laryngeal muscle fiber-type and MyHC composition from humans, notably the absence of type I fibers in the thyroarytenoid muscle. This difference fueled the view that fiber-type composition alone dictates outcomes of denervation injury. To preliminarily assess whether organ context (larynx vs. hindlimb), rather than fiber type (type I vs. type II) or subtype (IIB vs. IIA vs. IIX), influences structural and transcriptional responses to denervation and to explore the translational relevance of the rat model for future investigation. Unilateral left recurrent laryngeal nerve and tibial nerve transections were performed in male and female Sprague Dawley rats. Five weeks following injury, muscle fiber size was quantified by minimum Feret diameter (mFD) in three laryngeal muscles (medial thyroarytenoid (MTA), lateral thyroarytenoid (LTA), and posterior cricoarytenoid (PCA) and two hindlimb muscles (gastrocnemius, soleus). Bulk RNA-seq was performed on each muscle type and pathway enrichment was used to define the molecular response. Structurally, laryngeal muscles demonstrated significantly less atrophy compared to fiber-matched hindlimb muscles. This structural resilience was mirrored at the molecular level. Denervated hindlimb muscles exhibited a robust transcriptional response, characterized by pathways related to inflammation, extracellular matrix remodeling, and oxidative stress, hallmarks of a classic injury response. In contrast, an attenuated and selective transcriptional response was observed in the laryngeal muscles: the TP53 stress-response network was activated in the PCA, modest changes in mitochondrial pathways were observed in the MTA, and no significantly enriched pathways were observed in the LTA. Within the larynx itself, type IIB fibers were more susceptible to atrophy than putative type IIX/IIX-like fibers, suggesting an alternative fiber-subtype influence. These preliminary findings suggest organ context is a primary determinant of denervation-associated remodeling, with fiber subtype serving as a secondary modifier. Collectively, these data provide translational insight into laryngeal atrophy and support the rat larynx as a mechanistic model of organ-specific protective and remodeling responses to denervation, rather than as a strict fiber-type analog.