Development of the Endocrine Pancreas in the Beagle Dog: From Fetal to Adult Life.

Our objectives were to describe, in Beagle dogs, the ontogenesis of beta (insulin-producing) and alpha (glucagon-producing) cells from fetal to early postnatal life and adulthood. In addition, to have some insight into interspecies comparison, Beagle dog pancreases were compared to pancreases from a Labrador and Chow Chow. At midgestation, the epithelium was dense, beta cells scarce, and alpha cells numerous and concentrated in the center of the pancreatic bud. From 36 to 45 days post conception (pc), beta cell numbers increased and the epithelium expanded and branched out. At 55 days pc, large beta cell aggregates were seen. At weaning, the islets were similar to those in adults, with limited alpha cells intermingled with numerous beta cells. Quantification of the Alpha to Beta cells ratio has shown a gradual increase of beta cells proportion throughout development. Similar findings were obtained in the two other breeds. In conclusion, in the fetal Beagle dog beta cells emerge from the pancreatic bud at midgestation, but the endocrine structure is mature only in early postnatal life. The ontogenesis of the endocrine pancreas demonstrated in dogs resembles that reported in rats and mice. In contrast, human beta cells appear earlier, at the beginning of the second trimester of gestation. Our study provides a detailed morphological description of pancreatic development in dogs but supplies no information on alpha- or beta-cell function during fetal life. The morphological data reported here provide a foundation for building physiological studies. Anat Rec, 300:1429-1438, 2017. (c) 2017 Wiley Periodicals, Inc.