Abnormal distribution of aquaporin-5 and lymphoid infiltration in salivary glands of primary sjögren's syndrome.

Abstract

Objectives: Patients with Sjögren's syndrome (SS) suffer from impaired saliva secretion due to an autoimmune destruction of salivary glands. Based upon its abnormal distribution in SS salivary glands, a potential role for the water channel protein aquaporin-5 (AQP5) is proposed in the pathogenesis of SS. Methods: The immunohistochemical distribution of AQP5 was compared in minor salivary gland (MSG) biopsies obtained from primary SS with a variety of lymphoid cells infiltration in MSG, and healthy volunteers. Results: Biopsies from normal subjects revealed AQP5 primarily at the apical membrane of the salivary gland acinus. In contrast, biopsies from SS patients with both moderate and severe lymphoid infiltration revealed AQP5 expression diffusely at the cytoplasm of the acinus. Computer-assisted microscopy was performed to quantitatively evaluate AQP5 distribution in the acini. Biopsies of SS patients exhibited lower labeling indices (LI) at the apical membrane compared with biopsies from control subjects. The LI of the acini obtained from SS patients with both moderate and severe lymphoid infiltration showed no difference. Conclusions: Abnormal distribution of AQP5 in salivary gland acini could be responsible for a loss of saliva secretion, and this abnormal distribution is likely to develop during the stage of moderate lymphoid infiltration in salivary gland.