A study of the histological behavior of a rabbit vocal fold after a hyaluronic acid injection

The vocal fold structure is composed of tissues with many cells surrounded by the extra-cellular matrix. One of the most important components of the extra-cellular matrix is Hyaluronic Acid (HA). The aim of the study was to evaluate the inflammatory response of rabbit vocal folds after a local injection of Restylane HA.

Twelve adult male rabbits randomly received a 0.1 ml injection of Restylane HA in one vocal fold and 0.1 ml of saline in the other vocal fold. The animals were prospectively subdivided into two groups; animals in one group were sacrificed after one week of follow-up and animals in the other group were sacrificed after 3 months. Slides were Hematoxylin-Eosin (HE), Masson Trichromic and Toluidine Blue stained.

Hyaluronic Acid was found microscopically in all specimens in both groups. There was more connective tissue surrounding HA, always associated with a mild inflammatory response. The longer exposure time did not increase the intensity of inflammation. Tissue necrosis and foreign body inflammatory reaction were not observed in both groups.

The study suggests that HA is a good alternative as a filling material in vocal folds when treating glottal insufficiency.