Paranasal sinus mucosal regeneration: The effect of topical retinoic acid

Background: Paranasal sinus mucosa may suffer morphological and functional alterations as a result of surgical trauma. Mucosal stripping typically yields regenerated mucosa characterized by fibrosis, inflammatory infiltrate, and dysmorphic or absent cilia. The aim of this study was to determine the effect of topical retinoic acid (vitamin A) on regeneration of paranasal sinus mucosa. Methods: Both maxillary sinuses of 12 New Zealand white rabbits were surgically opened and stripped of mucosa. Six rabbits received 0.01% topical retinoic acid gel treatment to the stripped left maxillary sinus (low concentration group). The remaining six rabbits received 0.025% topical retinoic acid gel to the stripped left maxillary sinus (high concentration group). The stripped right maxillary sinus of all 12 rabbits served as the operated, untreated control to reflect the normal healing process. Six other animals served as unoperated controls. The sinus mucosa was examined by light microscopy after 14 days. Results: Untreated regenerated mucosa showed expected changes of submucosal gland loss, basal lamina and lamina propria fibrosis, cellular atypia, and loss of cilia. Topical retinoic acid treatment appeared to result in better mucosal regeneration marked by less cellular atypia and fibrosis. Although the regenerated mucosa was still grossly abnormal, the degree of ciliary loss and cellular derangement was reduced. The lower-concentration retinoic acid group had more favorable morphology than the higher-concentration retinoic acid group, and both were improved when compared with no treatment. Conclusions: In a rabbit model, topical vitamin A in the form of retinoic acid gel appears to enhance regeneration of ciliated paranasal sinus mucosa. This preliminary study suggests that topical retinoids may have applicability in promoting sinus wound healing.