Mast cells, extracellular matrix components, TGFβ isoforms and TGFβ receptor expression in labial salivary glands in systemic sclerosis

Abstract

Objective - To determine whether there was altered elaboration of non- collagenous extracellular matrix proteins or expression of TGFβ isoforms and their receptors in salivary glands of patients with systemic sclerosis (SSc) and Raynaud's phenomenon (RP). Because of the possible role of mast cells in the early stages of SSc their presence was also investigated. Methods - Sections of normal labial salivary glands (n=10) and glands from patients with SSc (n=13) and RP (n=5) were stained immunohistochemically and using acid toluidine blue. Results - SSc glands contained more mast cells than control tissues (p<0.005) and similar numbers to those found in RP specimens. There were no differences in the pattern or amount of non-collagenous matrix proteins detected. Tenascin and elastin were predominantly found surrounding ducts whereas fibronectin had a more general distribution. TGFβ isoforms and receptors were expressed by glandular epithelium, fibroblasts, vascular endothelium and inflammatory cells. Cell counts showed no differences in expression of TGFβ1 or TGFβ receptors between groups. However, the percentage of TGFβ2 positive fibroblasts was significantly higher in SSc glands compared with controls (p<0.004). RP glands showed an intermediate level of expression. By contrast, a lower percentage of RP fibrolasts expressed TGFβ3 compared with controls with SSc glands showing an intermediate level of expression. Conclusions - These results show that (a) there are no changes in glandular expression of tenascin, elastin and fibronectin in SSc and RP and (b) both conditions are associated with an increased salivary gland mast cell population and changes in expression of TGFβ2 and β3 isoforms by glandular fibroblasts.