Roles of vitamin A and macula flava in maintaining vocal folds

Vitamin A plays important roles in development, growth, and regeneration. Vitamin A-storing stellate cells have been identified in several organs. The functional roles of vitamin A in the vocal folds are still unknown, although vitamin A-storing vocal fold stellate cells have been observed in the macula flava of human and rat vocal folds. The purpose of this study was to investigate the roles of vitamin A in vocal folds.

Vitamin A-deficient rats were generated, and the vocal folds were examined histologically. Messenger RNA was extracted from the vocal folds and analyzed by real-time polymerase chain reaction.

Immunohistochemical analysis of normal vocal folds revealed expression of retinoic acid receptor a in vocal fold stellate cells. The cells in the macula flava of vitamin A-deficient rats showed a larger nucleus/cytoplasm ratio than did those of vitamin A-sufficient rats, but messenger RNA expression of major extracellular matrix components in the macula flava of vitamin A-deficient rats did not present a remarkable change except for procollagen type I. Expression of hyaluronic acid, collagen types I and III, and elastin did not show a significant change in vitamin A-deficient rat vocal folds.

These results indicate that vitamin A is not essential to maintaining the extracellular matrix of normal adult vocal folds, although vocal fold stellate cells participate in vitamin A storage.