-Original-

Dynamic Morphologic Change and Differentiation from Fetal to Mature Pancreatic Acinar Cells in Rats

Tomoko Inagaki¹, Takuma Tajiri², Genshu Tate², Toshiaki Kunimura³ and Toshio Morohoshi¹

¹First Department of Pathology, Showa University School of Medicine
²Department of Pathology, Showa University Fujigaoka Hospital
³Department of Pathology, Showa University Northern Yokohama Hospital

Background/Aims: Because of the notion that pancreatic and duodenal homeobox 1 (PdX-1)-positive cells are pancreatic stem cells that contribute to the differentiation and proliferation of exocrine cells, we examined PdX-1-associated changes in the morphology of rat pancreatic acinar cells that occur between the late fetal and early neonatal periods.
Methods: Light and electron microscopy and PdX-1 and MIB-5 immunohistochemistry were used to examine pancreatic tissues obtained from fetal rats 22 days postconception (dpc), from newborn rats 48 and 72 hours after natural birth, and from rats 7 days after natural birth.
Results: At 22 dpc, the cytoplasm of the acinar cells was large and eosinophilic due to accumulation of dense and numerous zymogen granules. Zymogen granules, rough endoplasmic reticulum, and other organelles were distributed throughout the cytoplasm. At 48 hours, i.e., just after feeding, the cytoplasm appeared smaller, less eosinophilic, and vacuolated. Electron microscopic examination showed cleaved nuclei and fewer zymogen granules. Expression of both PdX-1 and MIB-5 was increased at 48 hours. At 72 hours, acinar cell cytoplasm was decreased in size. At 7 days, the acinar cells were larger, biphasic distribution of zymogen granules was seen on the eosinophilic apical side, and rough endoplasmic reticulum and other ergastoplasms were seen on the basophilic basal side, typical of mature pancreatic acinar cells. Expression of PdX-1 and MIB-5 was markedly decreased in acinar cells.
Conclusion: Our findings indicate dynamic PdX-1-associated morphologic change from fetal to mature pancreatic acinar cells between 48 and 72 hours after birth.

J Nippon Med Sch 2012; 79: 335-342

Keywords
pancreatic and duodenal homeobox 1, reconstruction, acinar cell, differentiation

Correspondence to
Tomoko Inagaki, First Department of Pathology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-0064, Japan
tmkooo@med.showa-u.ac.jp

Received, December 26, 2011
Accepted, February 10, 2012