Comparative analysis reveals similarities between cultured submandibular salivary gland cells and liver progenitor cells

Mouse submandibular salivary gland cells and liver progenitor cells from long-term in vitro cultures with a high proliferation potential were side-by-side compared by methods of immunocytochemistry, quantitative real-time PCR, flow cytometry, and transcriptome analysis. The two cell types were found to be similar in expressing cell markers such as EpCAM, CD29, c-Kit, Sca-1, and c-Met. In addition, both cell types expressed cytokeratins 8, 18, and 19, alpha-fetoprotein, and (weakly) albumin. Unlike the liver cells, however, the salivary gland cells in culture showed high-level expression of cytokeratin 14 and CD49f, which was indicative of their origin from salivary gland ducts. Quantitative real-time PCR and deep-sequencing transcriptome analysis revealed similarities in the expression pattern of transcription factors between the two cell types. In this respect, however, the cultured salivary gland cells proved to be closer to exocrine cells of the pancreas than to the liver progenitor cells. Thus, ductal cells of postnatal submandibular salivary glands in culture show phenotypic convergence with progenitor cells of endodermal origin, suggesting that these glands may serve as a potential cell source for cellular therapy of hepatic and pancreatic disorders. The results of this study provide a deeper insight into the molecular features of salivary gland cells and may help optimize procedures for stimulating their differentiation in a specified direction.