Isolation and characterization of adult stem cells from human salivary glands

Currently, adult stem cells are attracting significant interest in regenerative medicine and tissue engineering. These cells have been isolated from various tissue sources; however, in most cases, adult stem cells useful for tissue engineering and regeneration are present at a low frequency. High numbers of stem cells with an effective and reliable potential for differentiation are needed for clinical applications. Thus, the identification of new stem cell sources and the establishment of optimized cell culture conditions that allow for the amplification of stem cells are of utmost relevance. In addition, the isolation procedure should ideally be minimally invasive and possibly be performed under local anesthesia. We report here for the first time on the identification of adult stem cells with mesenchymal characteristics in human parotid gland tissue. Cells were isolated from freshly resected specimens of parotid glands using enzymatic digestion and plastic adhesion protocols. Following an initial proliferation period and short-term culture for four passages, immunophenotyping revealed the presence of mesenchymal stem cell markers. In the presence of tissue-specificinduction medium, stem cells could be differentiated into adipogenic, osteogenic, and chondrogenic cell types. Tissue-specific differentiation was confirmed by histochemical and immunocytochemical staining as well as by RT-PCR for defined marker genes. This study is, to the best of our knowledge, the first report on the isolation and differentiation of stem cells from adult human parotid glands. Although isolated from an endodermal tissue source, these stem cells share many characteristics with MSCs. Easy accessibility and a high differentiation potential make salivary gland-derived stem cells a promising source for future applications in regenerative medicine.