title: The importance of hyaluronic acid in vocal fold biomechanics.
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).
  
  
  METHODS
  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 degrees 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 (eta') increased by 70% at higher frequencies (>1 Hz).
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Audiology and Speech Sciences, Purdue University, 1353 Heavilon Hall, West Lafayette, IN 47907-1353, USA. rchan@purdue.edu
authors.forename: R W
authors.initials: RW
authors.lastname: Chan
authors.forename: S D
authors.initials: SD
authors.lastname: Gray
authors.forename: I R
authors.initials: IR
authors.lastname: Titze
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004548:Elasticity; D006801:Humans; D006820:Hyaluronic Acid / Q000502:physiology*; D008297:Male; D014783:Viscosity; D014827:Vocal Cords / Q000502:physiology*
chemical_list: D006820:Hyaluronic Acid