Concentration and distribution of hyaluronic acid in human vocal folds

Objective/Hypothesis. To evaluate the concentration and distribution of hyaluronic acid (HA) in human adult vocal folds. Study Design. Experimental study. Methods. Histologic samples of the anterior, middle, and posterior regions of the vocal folds were studied to determine the tissue distribution of HA. The HA was traced with hyaluronan-binding proteins (HAPB) from bovine cartilage. Chemical bonds were detected through the avidin-biotin immunoperoxidase method. A control with the specific Streptomyces hyalurolyticus hyaluronidase was conducted to avoid false-positive results. The concentration levels of HA were determined through a fluorescence-based assay method with the same HAPB and europium-labeled streptavidin. Results: Women presented higher HA concentrations than men in every studied region of the vocal folds and overall HA concentration levels twice as higher. In regard to the distribution of HA, the macula flavae and the vocal fold intermediate and deep layers presented marked staining, with moderate staining around the vessels, on the gland capsules, and the connective tissue surrounding the vocal fold muscular fibers. Conclusions. HA is diffusely distributed along the vocal folds; the profuse amounts of HA observed in the female vocal folds may be related to impact absorption, acting as a protective factor against the characteristic high vibration frequency.