Fig. 2

a–d Phase-contrast images of differentiated IPCs obtained from WJ-MSCs after induction by differentiation protocols: upon differentiation, cells lose their fibroblastic morphology and tend to aggregate forming clusters, which tend to detach and grow in suspension media, in contrast to their control WJ-MSCs which retain fibroblast-like morphology. Magnification, 20×; scale bar = 20 μm. e–h Phase-contrast images of generated IPCs stained by Dithizone (DTZ): e uninduced WJ-MSCs as a control showing negative DTZ staining; f IPCs generated by protocol A showing positive crimson red staining by DTZ; g uninduced WJ-MSCs as a control showing negative DTZ staining; h IPCs generated by protocol B showing positive crimson red staining by DTZ. Magnification 40×; scale bar = 20 μm. i In-vitro GSIS assay for differentiated IPCs derived from protocol A (without exendin-4) and protocol B (with exendin-4); insulin release in response to either 5.5 mM or 16.7 mM glucose concentrations was measured after 1 hour of incubation. It is noteworthy that control uninduced undifferentiated WJ-MSCs did not show any detectable levels of secreted insulin in response to either 5.5 mM or 16.7 mM glucose concentrations. Results presented as mean ± standard error of mean, obtained from three independent experiments. *Means are significantly different from secreted insulin levels in response to 5.5 mM glucose at p < 0.05. GSIS glucose-stimulated insulin secretion, HG high glucose, LG low glucose