MIST1, an Inductive Signal for Salivary Amylase in Mesenchymal Stem Cells.

Sjögren's syndrome (SjS) is an autoimmune disease that destroys the salivary glands and results in severe dry mouth. Mesenchymal stem cell (MSC) transplantation has been recently proposed as a promising therapy for restoring cells in multiple degenerative diseases. We have recently utilized advanced proteomics biochemical assays to identify the key molecules involved in the mesenchymal-epithelial transition (MET) of co-cultured mouse bone-marrow-derived MSCs mMSCs with primary salivary gland cells. Among the multiple transcription factors (TFs) that were differentially expressed, two major TFs were selected: muscle, intestine, and stomach expression-1 (MIST1) and transcription factor E2a (TCF3). These factors were assessed in the current study for their ability to drive the expression of acinar cell marker, alpha-salivary amylase 1 (AMY1), and ductal cell marker, cytokeratin19 (CK19), in vitro. Overexpression of MIST1-induced AMY1 expression while it had little effect on CK19 expression. In contrast, TCF3 induced neither of those cellular markers. Furthermore, we have identified that mMSCs express muscarinic-type 3 receptor (M3R) mainly in the cytoplasm and aquaporin 5 (AQP5) in the nucleus. While MIST1 did not alter M3R levels in mMSCs, a TCF3 overexpression downregulated M3R expressions in mMSCs. The mechanisms for such differential regulation of glandular markers by these TFs warrant further investigation.