Generation of β cells from human pluripotent stem cells: are we there yet?

Abstract

In 1998, the landmark paper describing the isolation and culture of human embryonic stem cells (ESCs) was published. Since that time, the main goal of many diabetes researchers has been to derive β cells from ESCs as a renewable cell-based therapy for the treatment of patients with diabetes. In working toward this goal, numerous protocols that attempt to recapitulate normal pancreatic development have been published that result in the formation of pancreatic cell types from human pluripotent cells. This review examines stem cell differentiation methods and places them within the context of pancreatic development. We additionally compare strategies that are currently being used to generate pancreatic cell types and contrast them with approaches that have been used to generate functional cell types in different lineages. In doing this, we aim to identify how new approaches might be used to improve yield and functionality of in vitro-derived pancreatic β cells as an eventual cell-based therapy for type 1 diabetes.

Keywords: diabetes; differentiation; endoderm; pancreas; pluripotent stem cell; β cell.

Figure 1

Schematic depicting key developmental stages and corresponding morphogenetic processes occurring in the embryo during pancreas formation. The lower rows show the relative mouse and human developmental timelines, as well as some of the pivotal genes used to identify these stages.

Figure 2

(A) Timelines of published multistep procedures that have been used to induce differentiation of hESCs toward insulin-secreting cells before cell transplantation. (B) Characteristics of hESC-derived pancreatic cells that have been differentiated toward insulin-secreting cells. ActA, activin A; ALK5i, ALK5 inhibitor; BSA, bovine serum albumin; CDM, chemically defined media; Cyc, cyclopamine; D/F12-B, DMEM/F12 with BSA; EGF, epidermal growth factor; FBS, fetal bovine serum; FCS, fetal calf serum; Hep, heparin; HrgB, heregulin 1b; Nic, nicotinamide; Nog, Noggin; RA, retinoic acid; RPMI-B, RPMI1640 with BSA; SFM, serum-free medium; TBI, TGF-βR1 kinase inhibitor; TT, TTNPB.

Figure 3

Schematic depicting the influence of surrounding tissues on β cell development. (A) At E8.0, the notochord plays an important role in the suppression of Shh in the pancreatic endoderm. (B) At E10.5, the mesenchyme surrounding the pancreas produces FGF10 that signals to the pancreatic epithelium and plays an important role in endocrine progenitor cell proliferation, replication, and differentiation. (C) At E13.5, endocrine cells produce proangiogenic factors, such as angiopoeitin and VEGF-A, in order to attract the developing endothelium. Ang, angiopoeitin; DS, dorsal somite; Ec, ectoderm; En, endoderm; IM, intermediate mesoderm; LPM, lateral plate mesoderm; No, notochord; NT, neural tube; Shh, sonic hedgehog; VS, ventral somite.

Figure 4

Schematic depicting self-organization of PSCs in order to form differentiated tissues. (A) hPSCs can be differentiated into intestinal cell types. As differentiation occurs, spheroids bud from a posterior endoderm monolayer and go on to form lumen-containing organoids with both epithelial and mesenchymal tissue that contain the major cell types of the intestine. (B) mESC cell aggregates self-organize to form spherical vesicles on the edge of the aggregates, which then evaginate to form optic cup–like structures. (C) mESC cell aggregates form ectoderm on the surface that can self-organize to form anterior pituitary–like structures.