In vitro generation of insulin-secreting cells from human pancreatic exocrine cells

Cellular stress drives pancreatic plasticity

Controversy has long surrounded research on pancreatic beta cell regeneration. Some groups have used nonphysiological experimental methodologies to build support for the existence of pancreatic progenitor cells within the adult pancreas that constantly replenish the beta cell pool; others argue strongly against this mode of regeneration. Recent research has reinvigorated enthusiasm for the harnessing of pancreatic plasticity for therapeutic application--for example, the transdifferentiation of human pancreatic exocrine cells into insulin-secreting beta-like cells in vitro; the conversion of mouse pancreatic acinar cells to beta-like cells in vivo via cytokine treatment; and the potential redifferentiation of dedifferentiated mouse beta cells in vivo. Here, we highlight key findings in this provocative field and provide a perspective on possible exploitation of human pancreatic plasticity for therapeutic beta cell regeneration.

Preferential gene expression and epigenetic memory of induced pluripotent stem cells derived from mouse pancreas

Induced pluripotent stem cells (iPSCs) have been established from various somatic cell types. Accumulating evidence suggests that iPSCs from different cell sources have distinct molecular and functional properties. Here, we establish iPSC derived from mouse pancreas (Panc-iPSC) and compared their properties with those of iPSC derived from tail-tip fibroblast (TTF-iPSC). The metabolic profile differs between Panc-iPSC and TTF-iPSC, indicating distinct cell properties in these iPSCs. Expression of Pdx1, a marker of pancreas differentiation, is increased through formation of embryoid body (EB) in Panc-iPSC, but the level is similar to that in TTF-iPSC. In contrast, EBs derived from Panc-iPSC express liver-specific albumin (Alb) and alpha-fetoprotein (Afp) genes much more strongly than those from TTF-iPSC. Epigenetic analysis shows a different histone modification pattern between Panc-iPSC and TTF-iPSC. Promoter regions of Alb and Afp genes in Panc-iPSC are suggested to have a more open chromatin structure than those in TTF-iPSC, which also is seen in primary cultured pancreatic cells. Our data suggest that Panc-iPSC possesses distinct differentiation capacity from that of TTF-PSC, which may be influenced by epigenetic memory.

Current status of regeneration of pancreatic β-cells

Newly generated insulin‐secreting cells for use in cell therapy for insulin‐deficient diabetes mellitus require properties similar to those of native pancreatic β‐cells. Pancreatic β‐cells are highly specialized cells that produce a large amount of insulin, and secrete insulin in a regulated manner in response to glucose and other stimuli. It is not yet explained how the β‐cells acquire this complex function during normal differentiation. So far, in vitro generation of insulin‐secreting cells from embryonic stem cells, induced‐pluripotent stem cells and adult stem/progenitor‐like cells has been reported. However, most of these cells are functionally immature and show poor glucose‐responsive insulin secretion compared to that of native pancreatic β‐cells (or islets). Strategies to generate functional β‐cells or a whole organ in vivo have also recently been proposed. Establishing a protocol to generate fully functional insulin‐secreting cells that closely resemble native β‐cells is a critical matter in regenerative medicine for diabetes. Understanding the physiological processes of differentiation, proliferation and regeneration of pancreatic β‐cells might open the path to cell therapy to cure patients with absolute insulin deficiency.