Figure 4. In vitro functionalities of islet-like organoids derived from hESCs.

Responsiveness to 27.5 mM glucose stimulation of hESC-derived ECs and ECCs was analyzed by secretion levels of human insulin (a) and human c-peptide (b). Human insulin secreted in response to secretagogues, such as 30 mM KCl (c) and 100 μM tolbutamide (d) was measured. Secreted insulin and c-peptide levels are represented as the mean ± SEM (n = 3 or 4); *p < 0.05, **p < 0.01, ***p < 0.001. All secretion assays were performed after equilibration in 2.5 mM glucose. (e) Intracellular Ca²⁺ traces from hESC-derived ECCs. Detection of intracellular Ca²⁺ was measured using Fluo-4 AM. Responsive spots within ECCs were independently noted during the overall procedure. A representative spot is indicated by a yellow square in Supplementary Movie 2. (f) Transmission electron microscopy images of hESC-derived ECCs. Insulin-containing granules are indicated by yellow arrows. M, mitochondria. Scale bar, 500 nm.