Label-retaining cells in the rat submandibular gland

Area of Science:

• Stem Cell Biology
• Salivary Gland Development and Regeneration
• Histology and Cell Biology

Background:

• Identifying stem cells is crucial for understanding tissue regeneration and development.
• Salivary glands possess regenerative potential, but their resident stem cells remain poorly characterized.
• Label-retaining cells (LRCs) are often used as a proxy for stem or progenitor cells due to their slow-dividing nature.

Purpose of the Study:

• To identify and characterize stem cells within the rat submandibular salivary gland.
• To investigate the location and behavior of putative stem cells during gland regeneration.
• To confirm the stem cell identity of identified cell populations through functional assays.

Main Methods:

• Labeling of developing and regenerating rat submandibular glands with bromodeoxyuridine (BrdU).
• Induction of gland regeneration via duct obstruction.
• Immunohistochemical analysis for keratin18 (K18) and alpha-smooth muscle actin (alphaSMA) markers.
• Gland extirpation experiments using iododeoxyuridine (IdU) and chlorodeoxyuridine (CldU) labeling to assess cell division and fate.

Main Results:

• BrdU-labeled LRCs were found in various parenchymal structures, excluding acini during regeneration.
• A subpopulation of LRCs negative for K18 and alphaSMA (putative stem cells) were located in the intercalated and excretory ducts.
• Extirpation experiments showed that these (K18 and alphaSMA)(neg) LRCs divided asymmetrically, incorporating new labels (CldU) while retaining original labels (IdU).

Conclusions:

• The (K18 and alphaSMA)(neg) LRCs residing in the intercalated and excretory ducts represent salivary gland stem cells.
• These stem cells are capable of asymmetric cell division, contributing to gland regeneration and homeostasis.
• The findings provide a foundation for further research into salivary gland stem cell biology and therapeutic applications.