Early human pancreas development and the influence of glucagon-like peptide-1

Abstract

Understanding how the pancreas develops is valuable information in the quest to develop regenerative therapies to treat diabetes mellitus. Much of our understanding of this process arises from developmental studies in mouse and other species. However, in order to achieve successful in vitro stem cell differentiation to functional beta cells, a detailed understanding of human pancreas development is needed. The work presented in this thesis aims to understand the earliest events of human pancreas development. Furthermore, this thesis aims to define a novel endocrine axis in human development.This thesis focused on three main areas: defining the earliest events of human pancreas development, from its inception through to endocrine commitment; defining the transcriptome of human distal foregut derivatives to identify novel gene regulators of organogenesis; investigating the role of glucagon-like peptide-1 (GLP-1) in human development and specifically, pancreas development.By immunohistochemistry pancreas was first observed at 29 - 31 days post conception as dorsal and ventral thickenings in the foregut endoderm, at which stage the pancreatic epithelial cells expressed nuclear PDX1, GATA4 and FOXA2 in the presumptive dorsal and ventral buds. In contrast to data in mouse, a single-phase of endocrine differentiation was observed, from 8 weeks post conception (wpc). Further disparities in timing between species were identified.Using laser capture microdissection and RNA-sequencing of human pancreas, liver and extrahepatic biliary duct at 30 - 35 dpc, hundreds of differentially expressed genes were identified in recently divergent tissues, with the greatest difference evident between liver and pancreas. Bioinformatic analysis identified novel gene expression in the developing pancreas including SIM1 and HOXA2, as well as differential expression of an un-annotated region upstream of PTF1A that may represent a novel developmental regulator. Using explant culture of human fetal pancreas and gastrointestinal (GI) tract, GLP-1 was first secreted at 8 wpc, with levels increasing during development. Incubating pancreas explants with a GLP-1 analogue stimulated beta cell differentiation, suggesting a crucial role for GLP-1 in human pancreas development.Taken together, these data define first the first time, early pancreas development and identify potential novel regulators of organogenesis. Furthermore the data describe a novel endocrine axis in human development. These data enhance our understanding of human development, and are anticipated to provide a reference point for researchers looking to differentiate stem cells into functioning human beta cells.

Date of Award	31 Dec 2014
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Neil Hanley (Supervisor) & Karen Piper Hanley (Supervisor)