Generation of insulin-producing cells from pluripotent stem cells: from the selection of cell sources to the optimization of protocols

Abstract

The pancreas arises from Pdx1-expressing progenitors in developing foregut endoderm in early embryo. Expression of Ngn3 and NeuroD1 commits the cells to form endocrine pancreas, and to differentiate into subsets of cells that constitute islets of Langerhans. β-cells in the islets transcribe gene-encoding insulin, and subsequently process and secrete insulin, in response to circulating glucose. Dysfunction of β-cells has profound metabolic consequences leading to hyperglycemia and diabetes mellitus. β-cells are destroyed via autoimmune reaction in type 1 diabetes (T1D). Type 2 diabetes (T2D), characterized by impaired β-cell functions and reduced insulin sensitivity, accounts for 90% of all diabetic patients. Islet transplantation is a promising treatment for T1D. Pluripotent stem cells provide an unlimited cell source to generate new β-cells for patients with T1D. Furthermore, derivation of induced pluripotent stem cells (iPSCs) from patients captures "disease-in-a-dish" for autologous cell replacement therapy, disease modeling, and drug screening for both types of diabetes. This review highlights essential steps in pancreas development, and potential stem cell applications in cell regeneration therapy for diabetes mellitus.

Figure 1. Morphology and CXCR4 expression in human ESC cultures treated with different concentrations of activin A after 5 days

10 ng/ml activin A maintains undifferentiated ESCs in the presence of 10% serum. 100ng/ml activin A induces epithelial-to-mesenchymal transition (EMT) only in serum-free (SF) cultures. EMT plays crucial roles in embryonic gastrulation, and gives rise to the mesoderm and endoderm [67]. FACS analysis shows the number of CXCR4-expressing cells in each culture condition.

Figure 2. Schematic representation of pancreatic endocrine β-cell formation from pluripotent stem cells

Hallmarks of transcription factors expressed at different stage are shown in blue, signaling pathway/molecules involved in differentiation are shown in red, and small molecules used are shown in green. It is currently unknown whether IDE1 and IDE2 induce definitive endoderm (DE) differentiation from bipotent mesendoderm cells. Dashed arrows indicate other cell types that are generated apart from cells differentiating towards the β-cell pathway. FGF: fibroblast growth factor. SHH: Sonic Hedgehog. KGF: keratinocyte growth factor. RA: retinoic acid. Ex: exedin. IGF: insulin growth factor. HGF: hepatocyte growth factor. VEGF: vascular endothelial growth factor. PYY: pancreatic polypeptide. GH-cells: ghrelin-producing cells.