Isolation, tissue localization, and cellular characterization of progenitors derived from adult human salivary glands

Progenitors that can transdifferentiate into cells with hepatic or pancreatic phenotypes can be isolated from experimentally injured salivary glands of rodents. In this study, we isolated progenitors from "uninjured" adult human salivary glands by fluorescence-activated cell sorting using anti-CD49f and anti-Thy-1 antibodies. The sorted cells that were contained in the CD49f+/Thy-1+ fraction showed good proliferation on type I collagen. Single purified progenitor cells in plate culture expressed intracellular laminin, CD49f, Thy-1, and NGF receptor p75 (p75(NGFR)). Immunohistological analysis revealed the expression of Thy-1 and p75(NGFR) in stromal cells in the periductal area of the salivary gland. Under overconfluent conditions in plate culture, cell clusters containing insulin and glucagon-positive cells were occasionally formed. In order to produce differentiated cell clusters with uniform quality, we used a spherical culture system. Autonomous differentiation of cells in clusters into insulin-positive cells was induced in the spherical culture system. We measured C-peptide to estimate the endogenously produced insulin content. The C-peptide content of the spheroid bodies was low (3.5 ng/mg of protein), and they simultaneously expressed the early islet differentiation factor Nkx6.1, proendocrine gene neurogenin3, and ductal cell marker cytokeratin19. The progenitors existing in the interstitium of the salivary gland were able to transdifferentiate into cells with a pancreatic endocrine phenotype.