Laminin alpha1-chain normally induces intercalated duct progenitors to differentiate to acinar cells through integrin (INT) alpha1ss1 and alpha2ss1 receptors. Maintenance of acinar cells is impaired in Sjögren's syndrome (SS), which is also characterized by low levels of serum and salivary androgens. We hypothesized that androgens normally support salivary gland remodeling by upregulating either laminin alpha1 chain or its cellular alpha1 or alpha2 INT subunit-containing receptors.
Intercalated duct and acinar human salivary gland (HSG) cells and labial salivary gland (LSG) biopsies from healthy controls and patients with SS were cultured without or with sex steroids. Laminin alpha1 chain and INT alpha1 and alpha2 subunits were studied using quantitative reverse-transcription real-time polymerase chain reaction and INT alpha1 and alpha2 subunits using immunofluorescence staining.
INT alpha1-subunit and alpha2-subunit messenger RNA (mRNA) levels were increased in intercalated duct and acinar cells by DHEA and testosterone. In contrast, laminin alpha1-chain mRNA levels were not affected. The upregulating effect of DHEA on INT subunits was also seen at the protein level. DHEA also increased mRNA levels of both INT subunits in healthy but not SS LSG.
Androgens increased INT alpha1 and alpha2 subunits in tubuloepithelial cells and in healthy LSG, but in SS salivary glands this androgen regulation was defective, which is likely to contribute to defective outside-in signaling, acinar atrophy, and ductal cell hyperplasia.