Carbon monoxide enhances calcium transients and glucose-stimulated insulin secretion from pancreatic β-cells by activating Phospholipase C signal pathway in diabetic mice

PDX1+ cell budding morphogenesis in a stem cell-derived islet spheroid system

Remarkable advances in protocol development have been achieved to manufacture insulin-secreting islets from human pluripotent stem cells (hPSCs). Distinct from current approaches, we devised a tunable strategy to generate islet spheroids enriched for major islet cell types by incorporating PDX1+ cell budding morphogenesis into staged differentiation. In this process that appears to mimic normal islet morphogenesis, the differentiating islet spheroids organize with endocrine cells that are intermingled or arranged in a core-mantle architecture, accompanied with functional heterogeneity. Through in vitro modelling of human pancreas development, we illustrate the importance of PDX1 and the requirement for EphB3/4 signaling in eliciting cell budding morphogenesis. Using this new approach, we model Mitchell-Riley syndrome with RFX6 knockout hPSCs illustrating unexpected morphogenesis defects in the differentiation towards islet cells. The tunable differentiation system and stem cell-derived islet models described in this work may facilitate addressing fundamental questions in islet biology and probing human pancreas diseases.

Protocol development to further differentiate and transition stem cell-derived pancreatic progenitors from a monolayer into endocrine cells in suspension culture

The generation of functional β-cells from human pluripotent stem cells (hPSCs) for cell replacement therapy and disease modeling of diabetes is being investigated by many groups. We have developed a protocol to harvest and aggregate hPSC-derived pancreatic progenitors generated using a commercially available kit into near uniform spheroids and to further differentiate the cells toward an endocrine cell fate in suspension culture. Using a static suspension culture platform, we could generate a high percentage of insulin-expressing, glucose-responsive cells. We identified FGF7 as a soluble factor promoting aggregate survival with no inhibitory effect on endocrine gene expression. Notch inhibition of pancreatic progenitor cells during aggregation improved endocrine cell induction in vitro and improved graft function following implantation and further differentiation in mice. Thus we provide an approach to promote endocrine formation from kit-derived pancreatic progenitors, either through extended culture or post implant.

Differentiation of stem cell-derived pancreatic progenitors into insulin-secreting islet clusters in a multiwell-based static 3D culture system

Orbital shaker-based suspension culture systems have been in widespread use for differentiating human pluripotent stem cell (hPSC)-derived pancreatic progenitors toward islet-like clusters during endocrine induction stages. However, reproducibility between experiments is hampered by variable degrees of cell loss in shaking cultures, which contributes to variable differentiation efficiencies. Here, we describe a 96-well-based static suspension culture method for differentiation of pancreatic progenitors into hPSC-islets. Compared with shaking culture, this static 3D culture system induces similar islet gene expression profiles during differentiation processes but significantly reduces cell loss and improves cell viability of endocrine clusters. This static culture method results in more reproducible and efficient generation of glucose-responsive, insulin-secreting hPSC-islets. The successful differentiation and well-to-well consistency in 96-well plates also provides a proof of principle that the static 3D culture system can serve as a platform for small-scale compound screening experiments as well as facilitating further protocol development.

Carbon monoxide and β-cell function: Implications for type 2 diabetes mellitus

Carbon monoxide (CO), a member of the multifunctional gasotransmitters family produced by heme oxygenases (i.e., HO-1 and HO-2), has received significant attention because of its involvement in carbohydrate metabolism. Experimental evidence indicates that both HO-2- and HO-1-derived CO stimulate insulin secretion, but the latter mainly acts as a compensatory response in pre-diabetes conditions. CO protects pancreatic β-cell against cytokine- and hypoxia-induced apoptosis and promotes β-cell regeneration. CO cross-talks with nitric oxide (NO) and hydrogen sulfide (H₂S), other important gasotransmitters in carbohydrate metabolism, in regulating β-cell function and insulin secretion. These data speak in favor of the potential therapeutic application of CO in type 2 diabetes mellitus (T2DM) and preventing the progression of pre-diabetes to diabetes. Either CO (as both gaseous form and CO-releasing molecule) or pharmacological formulations made of natural HO inducers (i.e., bioactive components originating from plant-based foods) are potential candidates for developing CO-based therapeutics in T2DM. Future studies are needed to assess the safety/efficacy and potential therapeutic applications of CO in T2DM.