The importance of hyaluronic acid in vocal fold biomechanics

TLDR

Hyaluronic acid, a highly hydrated glycosaminoglycan in the vocal fold extracellular matrix, contributes to optimal tissue viscosity and stiffness for phonation and fundamental frequency control, and has been proposed as a bioimplant for repairing ECM defects such as scarring and sulcus vocalis. This study examined the influence of hyaluronic acid on the biomechanical properties of the human vocal fold cover. The authors excised vocal fold tissues from five adult male cadavers, enzymatically removed hyaluronic acid with bovine testicular hyaluronidase, and quantified changes in linear viscoelastic shear properties across 0.01–15 Hz using a parallel‑plate rotational rheometer at 37 °C. Removal of hyaluronic acid reduced the vocal fold cover’s elastic shear modulus by ~35 % and increased its dynamic viscosity by ~70 % at frequencies above 1 Hz, indicating that HA is crucial for the biomechanical behavior of the cover and suggesting its potential as a bioimplant to improve voice production. Otolaryngol Head Neck Surg 2001;124:607‑14.

Abstract

Abstract Objective: This study examined the influence of hyaluronic acid (HA) on the biomechanical properties of the human vocal fold cover (the superficial layer of the lamina propria). Study design: Vocal fold tissues were freshly excised from 5 adult male cadavers and were treated with bovine testicular hyaluronidase to selectively remove HA from the lamina propria extracellular matrix (ECM). Linear viscoelastic shear properties (elastic shear modulus and dynamic viscosity) of the tissue samples before and after enzymatic treatment were quantified as a function of frequency (0.01 to 15 Hz) by a parallel-plate rotational rheometer at 37°C. Results: On removing HA from the vocal fold ECM, the elastic shear modulus (G′ ) or stiffness of the vocal fold cover decreased by an average of around 35%, while the dynamic viscosity (η′) increased by 70% at higher frequencies (>1 Hz). Conclusion: The results suggested that HA plays an important role in determining the biomechanical properties of the vocal fold cover. As a highly hydrated glycosaminoglycan in the vocal fold ECM, it likely contributes to the maintenance of an optimal tissue viscosity that may facilitate phonation, and an optimal tissue stiffness that may be important for vocal fundamental frequency control. Significance: HA has been proposed as a potential bioimplant for the surgical repair of vocal fold ECM defects (eg, vocal fold scarring and sulcus vocalis). Our results suggested that such clinical use may be potentially optimal for voice production from a biomechanical perspective. (Otolaryngol Head Neck Surg 2001;124:607-14.)