Hypothesis: Age‑related loss of motor innervation to the thyroarytenoid (TA) muscle creates a chronic unloading state that shifts vocal‑fold fibroblasts toward a pathogenic myofibroblast phenotype, thereby accelerating lamina propria extracellular‑matrix (ECM) breakdown. This mechanotransduction cascade positions TA denervation as the upstream event that drives both sarcopenic atrophy and ECM remodeling, whereas preserved innervation maintains ECM integrity independent of muscle bulk TA atrophy primary driver ECM changes secondary.

To test this, we will (1) induce selective denervation of the TA in young adult sheep via botulinum toxin‑mediated chemoneurotraction or surgical nerve cut, (2) quantify TA cross‑sectional area, fiber‑type distribution, and innervation status using immunohistochemistry and electrophysiology at 4, 8, and 12 weeks, (3) simultaneously measure lamina propria ECM metrics—collagen fibril organization (second‑harmonic generation imaging), elastin content (Verhoeff stain), and hyaluronic acid concentration (ELISA)—and compute effect sizes (Cohen’s d) versus sham‑operated controls, (4) assess fibroblast phenotype by single‑cell RNA‑seq for activation markers (ACTA2, COL1A1, TGFB1) and myofibroblast signature, and (5) rescue a subset with chronic functional electrical stimulation (FES) or neurotrophic factor (GDNF) delivery to re‑establish innervation. If denervation precedes and predicts ECM degradation (significant regression β > 0, p < 0.01, Cohen’s d > 0.8) and FES‑mediated reinnervation normalizes ECM without fully restoring TA mass, the hypothesis is supported; Conversely, if ECM degradation occurs without denervation or persists despite restored innervation, the hypothesis is falsified FES proof-of-concept Open questions.

Mechanistically, we propose that loss of tonic tensile stress reduces integrin‑β1 signaling in fibroblasts, lowering focal adhesion kinase (FAK) activity and permitting Smad2/3‑dependent TGF‑β1 transcription. The secreted TGF‑β1 then autocrinally drives fibroblast‑to‑myofibroblast transition, increasing matrix metalloproteinase‑2/9 secretion and degrading collagen and elastin. This integrates the observed 'wicker basket' collagen disorganization with denervation‑driven mechanotransduction, offering a testable link between muscle innervation status and ECM homeostasis.

Predictive biomarkers—baseline TA innervation density on high‑resolution ultrasound or circulating GDNF levels—could stratify patients likely to respond to FES or reinnervation‑targeted therapies, addressing the current lack of treatment‑response markers.