title: Dynamic morphologic change and differentiation from fetal to mature pancreatic acinar cells in rats.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  Our findings indicate dynamic PdX-1-associated morphologic change from fetal to mature pancreatic acinar cells between 48 and 72 hours after birth.
authors.affiliation: First Department of Pathology, Showa University School of Medicine, Hatanodai, Shinagawa-ku, Tokyo, Japan. tmkooo@med.showa-u.ac.jp
authors.forename: Tomoko
authors.initials: T
authors.lastname: Inagaki
authors.forename: Takuma
authors.initials: T
authors.lastname: Tajiri
authors.forename: Genshu
authors.initials: G
authors.lastname: Tate
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kunimura
authors.forename: Toshio
authors.initials: T
authors.lastname: Morohoshi
mesh_terms: D061354:Acinar Cells / Q000166:cytology*; D000818:Animals; D000831:Animals, Newborn; D002454:Cell Differentiation / Q000235:genetics; D049109:Cell Proliferation; D005260:Female; D018398:Homeodomain Proteins / Q000502:physiology*; D008297:Male; D010179:Pancreas / Q000166:cytology* / Q000196:embryology*; D051381:Rats; D017208:Rats, Wistar; D015534:Trans-Activators / Q000502:physiology*
chemical_list: D018398:Homeodomain Proteins; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein