2 meoe2

Male C57BL/6 mice were used at 8–12 weeks of age for all experiments. The isolation and purification of mouse islets were performed by collagenase P and Ficoll as we previously described^{17 (link)}
. Eighty to 100 mouse islets were used per experimental well. For co-culture experiment, 1 × 10⁵ hUC-MSCs were seeded into the lower chamber of a 24-well transwell plate (CorningBioCoat, Corning, NY, USA) containing co-culture medium. After hUC-MSCs became attached, the medium was changed immediately and the freshly isolated islets were placed into the upper chamber (indirect contact co-culture). To test the direct contact co-culture, islets were seeded into wells having hUC-MSCs without transwell. Before the hypoxia operation, the specific inhibitor 2-methoxyestradiol^{18 (link)}
(2-MeOE2 or 2ME2, 100 μM, S1233, Selleck, Shanghai, China) and the activator dimethyloxalylglycine¹⁹
(DMOG, 100 μM, S7483, Selleck, Shanghai, China) were, respectively, added to the different conditions of islets culture medium to suppress or activate HIF-1α. At the same time, in the presence of hUC-MSCs and without hUC-MSCs, the islets of different groups were placed in normoxia (20% O₂, 37°C, 5% CO₂) and hypoxia (1% O₂, 37°C, 5% CO₂) co-cultured for 48 h. The following functional-related parameters were evaluated.