Recent evidence indicates that low oxygen tension (pO₂) or hypoxia controls the differentiation of several cell types during development. Variations of pO₂ are mediated through the hypoxia-inducible factor (HIF), a crucial mediator of the adaptative response of cells to hypoxia. The aim of this study was to investigate the role of pO₂ in β-cell differentiation.

We analyzed the capacity of β-cell differentiation in the rat embryonic pancreas using two in vitro assays. Pancreata were cultured either in collagen or on a filter at the air/liquid interface with various pO₂. An inhibitor of the prolyl hydroxylases, dimethyloxaloylglycine (DMOG), was used to stabilize HIF1α protein in normoxia.

When cultured in collagen, embryonic pancreatic cells were hypoxic and expressed HIF1α and rare β-cells differentiated. In pancreata cultured on filter (normoxia), HIF1α expression decreased and numerous β-cells developed. During pancreas development, HIF1α levels were elevated at early stages and decreased with time. To determine the effect of pO₂ on β-cell differentiation, pancreata were cultured in collagen at increasing concentrations of O₂. Such conditions repressed HIF1α expression, fostered development of Ngn3-positive endocrine progenitors, and induced β-cell differentiation by O₂ in a dose-dependent manner. By contrast, forced expression of HIF1α in normoxia using DMOG repressed Ngn3 expression and blocked β-cell development. Finally, hypoxia requires hairy and enhancer of split (HES)1 expression to repress β-cell differentiation.

These data demonstrate that β-cell differentiation is controlled by pO₂ through HIF1α. Modifying pO₂ should now be tested in protocols aiming to differentiate β-cells from embryonic stem cells.