Glucocorticoid signalling affects pancreatic development through both direct and indirect effects

Area of Science:

• Endocrinology
• Developmental Biology
• Pancreatic Biology

Background:

• Glucocorticoids influence beta cell development, with known direct effects on pancreatic precursors.
• Indirect effects of glucocorticoids on pancreatic development are largely unexplored.
• The glucocorticoid receptor (GR) mediates glucocorticoid actions.

Purpose of the Study:

• To investigate the role of the glucocorticoid receptor (GR) in pancreatic development, focusing on indirect effects.
• To determine the impact of GR absence on pancreatic tissue organization, cell survival, and beta cell mass expansion.

Main Methods:

• Studied pancreatic phenotype of GR(null/null) mice at embryonic days E15.5 and E18 using immunohistochemistry and beta cell fraction measurements.
• Grafted E15.5 GR(null/null) mutant pancreata into a GR-expressing environment to differentiate direct vs. indirect effects.
• Analyzed pancreatic tissue structure, cell types, apoptosis, and beta cell fraction.

Main Results:

• GR(null/null) fetuses at E18 exhibited smaller pancreata, disorganization, and increased apoptosis, despite normal cell type presence.
• Early-stage (E15.5) GR(null/null) pancreata were phenotypically normal, but grafting into a GR-expressing environment rescued apoptosis.
• Reduced GR levels (heterozygous mutants) led to increased beta cell fraction, highlighting the importance of GR dosage.

Conclusions:

• Pancreatic tissue organization and survival are influenced by indirect effects mediated by the glucocorticoid receptor (GR).
• GR is not essential for early pancreatic development but is critical for modulating beta cell mass expansion in later fetal stages.
• Accurate glucocorticoid receptor (GR) dosage is vital for regulating beta cell mass expansion.