Expression of CD47 in the pancreatic β-cells of people with recent-onset type 1 diabetes varies according to disease endotype

Aims: We are studying the dialogue between beta-cells and the immune system in type 1 diabetes and have identified a cell surface receptor, signal regulatory protein-alpha (SIRP alpha) as an important component in the regulation of beta-cell survival. SIRP alpha interacts with another protein. CD47, to mediate signalling. In the present work. we have studied the expression and role of CD47 in human islet cells in type 1 diabetes. Methods: Clonal EndoC-beta H1 cells were employed for functional studies. Cells were exposed to pro-inflammatory cytokines and their viability monitored by flow cytometry after staining with propidium iodide. Targeted knockdown of CD47 or SIRP alpha was achieved with small interference RNA molecules and the expression of relevant proteins studied by Western blotting or immunocytochemistry. Human pancreas sections were selected from the Exeter Archival Diabetes Biobank and used to examine the expression of CD47 by immunofluorescence labelling. Image analysis was employed to quantify expression. Results: CD47 is abundantly expressed in both alpha and beta cells in human pancreas. In type 1 diabetes, the levels of CD47 are increased in a cells across all age groups, whereas the expression in beta-cells varies according to disease endotype. Knockdown of either CD47 or SIMI in EndoC-beta H1 cells resulted in a loss of viability. Conclusions: We conclude that the CD47 plays a previously unrecognised role in the regulation of beta-cell viability. This system is dysregulated in type 1 diabetes suggesting that it may be targeted therapeutically to slow disease progression.