IADR Abstract Archives
Unveling Multiple Salivary Stem Cells by In Vivo Lineage Analysis
Objectives: Despite many studies demonstrating potential therapeutic efficacy of stem cell-based therapies to treat hypofunctional salivary glands, the identity and function of tissue stem/progenitor cells in post-natal salivary glands remain elusive. Recently, we conducted in vivo lineage analysis with novel genetic labeling systems and were able to delineate three stem/progenitor populations in the mouse submandibular gland (SMG) that contribute to post-natal development, homeostasis and regeneration. Concomitantly, the expression patterns of various salivary stem cell markers were analyzed to correlate these three cell types to other putative stem cells that have been previously documented by in vitro studies.
Methods: For lineage analysis, three variants of the inducible Cre-loxP system were prepared to selectively label either intercalated duct cells, basal excretory duct cells or myoepithelial cells in the post-natal SMG. After induction of labeling with fluorescent markers, self-renewal and differentiation capability of labeled cells were evaluated during development, homeostasis, and regeneration in the excretory duct-ligation injury model. All analyses were performed on immunofluorescent staining images of frozen sections of the gland. To precisely locate parenchymal cells expressing salivary stem cell markers, SMG frozen sections were immuno-stained for CD49f, CD29, CD24, CD133, c-Kit, Sca-I, P63, Keratin14 in combination with one of tissue differentiation markers (AQP5, K19, SMA).
Results: Intercalated ducts (ID) contain two different progenitor populations; c-Kit+ K14- and c-Kit- K14+ ductal cells. c-Kit+ K14- cells reside in the proximal region of ID close to acinus and remain mostly quiescent after birth, whereas distal c-Kit- K14+ ID cells are continuously cycling to produce granular duct (GD) cells. Following injury, both cell types together made major (>70%) contribution to acinar cell regeneration. Interestingly, c-Kit- K14+ cells exhibited more robust stem cell activity by replenishing c-Kit+ K14- progenitors as well. Third progenitor cell type resides in the basal layer of excretory ducts, producing supra-basal cells.
Conclusions: Our data indicates that the post-natal glandular parenchyma relies on multiple stem/progenitor populations for its development, maintenance and regeneration.
Methods: For lineage analysis, three variants of the inducible Cre-loxP system were prepared to selectively label either intercalated duct cells, basal excretory duct cells or myoepithelial cells in the post-natal SMG. After induction of labeling with fluorescent markers, self-renewal and differentiation capability of labeled cells were evaluated during development, homeostasis, and regeneration in the excretory duct-ligation injury model. All analyses were performed on immunofluorescent staining images of frozen sections of the gland. To precisely locate parenchymal cells expressing salivary stem cell markers, SMG frozen sections were immuno-stained for CD49f, CD29, CD24, CD133, c-Kit, Sca-I, P63, Keratin14 in combination with one of tissue differentiation markers (AQP5, K19, SMA).
Results: Intercalated ducts (ID) contain two different progenitor populations; c-Kit+ K14- and c-Kit- K14+ ductal cells. c-Kit+ K14- cells reside in the proximal region of ID close to acinus and remain mostly quiescent after birth, whereas distal c-Kit- K14+ ID cells are continuously cycling to produce granular duct (GD) cells. Following injury, both cell types together made major (>70%) contribution to acinar cell regeneration. Interestingly, c-Kit- K14+ cells exhibited more robust stem cell activity by replenishing c-Kit+ K14- progenitors as well. Third progenitor cell type resides in the basal layer of excretory ducts, producing supra-basal cells.
Conclusions: Our data indicates that the post-natal glandular parenchyma relies on multiple stem/progenitor populations for its development, maintenance and regeneration.
