Neurogenin 3+ cells contribute to ß-cell neogenesis and proliferation in injured adult mouse pancreas.

We previously showed that injury by partial duct ligation (PDL) in adult mouse pancreas activates Neurogenin 3 (Ngn3)(+) progenitor cells that can differentiate to ß cells ex vivo. Here we evaluate the role of Ngn3(+) cells in ß cell expansion in situ. PDL not only induced doubling of the ß cell volume but also increased the total number of islets. ß cells proliferated without extended delay (the so-called 'refractory' period), their proliferation potential was highest in small islets, and 86% of the ß cell expansion was attributable to proliferation of pre-existing ß cells. At sufficiently high Ngn3 expression level, upto 14% of all ß cells and 40% of small islet ß cells derived from non-ß cells. Moreover, ß cell proliferation was blunted by a selective ablation of Ngn3(+) cells but not by conditional knockout of Ngn3 in pre-existing ß cells supporting a key role for Ngn3(+) insulin(-) cells in ß cell proliferation and expansion. We conclude that Ngn3(+) cell-dependent proliferation of pre-existing and newly-formed ß cells as well as reprogramming of non-ß cells contribute to in vivo ß cell expansion in the injured pancreas of adult mice.

Differentiating neural crest stem cells induce proliferation of cultured rodent islet beta cells.

AIMS/HYPOTHESIS: Efficient stimulation of cycling activity in cultured beta cells would allow the design of new strategies for cell therapy in diabetes. Neural crest stem cells (NCSCs) play a role in beta cell development and maturation and increase the beta cell number in co-transplants. The mechanism behind NCSC-induced beta cell proliferation and the functional capacity of the new beta cells is not known. METHODS: We developed a new in vitro co-culture system that enables the dissection of the elements that control the cellular interactions that lead to NCSC-dependent increase in islet beta cells. RESULTS: Mouse NCSCs were cultured in vitro, first in medium that stimulated their proliferation, then under conditions that supported their differentiation. When mouse islet cells were cultured together with the NCSCs, more than 35% of the beta cells showed cycle activity. This labelling index is more than tenfold higher than control islets cultured without NCSCs. Beta cells that proliferated under these culture conditions were fully glucose responsive in terms of insulin secretion. NCSCs also induced beta cell proliferation in islets isolated from 1-year-old mice, but not in dissociated islet cells isolated from human donor pancreas tissue. To stimulate beta cell proliferation, NCSCs need to be in intimate contact with the beta cells. CONCLUSIONS/INTERPRETATION: Culture of islet cells in contact with NCSCs induces highly efficient beta cell proliferation. The reported culture system is an excellent platform for further dissection of the minimal set of factors needed to drive this process and explore its potential for translation to diabetes therapy.