The exocrine pancreas, which comprises more than 95% of the pancreas mass, consists of lobules formed by tubuloacinar glands that are built by two cell types: acinar cells and ductal cells. A third, centroacinar cells type has been identified in murine studies, but their existence and functional role is under debate. Acinar cells are large pyramidal secretory epithelial cells, with apical-basal polarization, that surround the lumen of the acinus. Acinar cells have prominent endoplasmic reticulum and Golgi networks, and their cytoplasm contains a large number of secretory zymogen granules, filled with various digestive enzymes, that are clustered in the vicinity of the apical surface. At the surface of the lumen, acinar cells are attached to each other by apical tight junctions, while their basal surfaces are associated with the basal lamina. For overview, please refer to Liggitt and Dintzis, “Pancreas”, 241-250. For review, please refer to Tritschler et al. 2017.
Pancreatic acinar cells originate from definitive endoderm cells that form during gastrulation, and then undergo patterning along anterior/posterior, dorsal/ventral, and median/lateral axes, producing, among other embryonal cell types, endoderm cells of dorsal and ventral foregut, which, after transitioning through an intermediary duodeno-pancreatic endoderm cell state for dorsal foregut endoderm and possibly a hepato-pancreatic or pancreato-biliary intermediary state for ventral foregut endoderm, give rise to multipotent pancreatic progenitor cells (MPCs) that form dorsal and ventral pancreatic buds (Yu et al. 2019, reviewed in Jennings et al. 2015). Developing pancreas undergoes branching morphogenesis, which results in the apical-basal polarity that is critical for establishing the acinar-ductal functional unit (Darrigrand et al. 2024). Both dorsal and ventral MPCs located at the tips of the developing, branching pancreas, start committing to the acinar cell fate from Carnegie stage 19 (45-47 days post conception) of human embryonic development and around embryonic day E12 during mouse development, initially becoming distinct tip progenitors, and then pro-acinar and acinar cells (Yu et al. 2019, reviewed in Jennings et al. 2015).
