Objective: Salivary glands are highly differentiated and have little regenerative capacity after reaching maturity or in response to physical or pathological stress. Identification of potential salivary gland stem cells may lead to the regeneration of a functional salivary tissue either in vitro or in vivo. In this report, the expression of known stem cell markers was evaluated in primary salivary cell cultures, and in human (HSY) and rat (PARC5; provided by Quissell, D.O., U. Colorado) salivary cell lines. Methods: Total RNA was extracted from cell homogenates and RT-PCR for CD44, CD105 (Endoglin), FGF8/10 (fibroblast growth factor 8 and 10), DMP1 (dentin matrix protein 1), MEPE (matrix extracellular phosphoglycoprotein), BSP (bone sialoprotein), amylase, and GAPDH (positive control) was determined. Expression of CD44 and CD105 on HSY cell surface was evaluated using flow cytometric (FACS) analysis. Results: mRNA of cell-matrix interaction marker CD44 was present in HSY and PARC5 cells but not in primary cells. CD105 (an angiogenic stem cell marker) was only weakly expressed in HSY cells. Fgf10 was expressed in all three cells, while fgf8 was only detected in primary culture cells. Salivary gland differentiation marker amylase was absent in the primary and cell lines tested. SIBLING matrix proteins, MEPE and BSP and DMP1 expressed by salivary ductal cells were absent in samples tested. FACS analysis demonstrated 100% and 38% of HSY cells expressed CD44 and CD105, respectively. These results were consistent with data from RT-PCR. Conclusion: Current results suggest a differential expression of stem cell markers among salivary cell lines. The elucidation of salivary stem cell markers in normal and transformed cells could provide a basis for tissue engineering for gland replacement or regeneration. Supported by NIDCR grant DE15381 and ADEA Gies Research Award DSTAR.

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