Transdifferentiation of adult exocrine pancreas cells to beta-(like) cells

The majority of cells obtained from cadaveric pancreas donors are exocrine acinar cells that are discarded after clinical islet isolation. If these exocrine cells could be reprogrammed into functional beta cells, theoretically one could be able to obtain about ten times more cells for transplantation from the available donor pancreases. Previously, it was shown that rodent acinar cells exhibit a remarkable plasticity and can transdifferentiate to insulin-positive beta cells following signaling by cytokines activating MAPK and STAT3. In the first part of this thesis, we study the short-term effects of EGF and CNTF treatment on diabetic mice. We report that the cytokines are able to restore normoglycemia and genetic lineage tracing shows that the majority of the new insulipositive cells originate from pre-existing beta cells. The second part of this thesis investigates the effect of the cytokines given at day 35 after beta cell ablation, a condition resembling long-term diabetes. Also under these conditions a functional beta cell mass was restored, sufficient to reinstate normoglycemia for at least 248 days, whereas control mice remained diabetic and eventually died. The main process behind the restoration of normoglycemia was the transdifferentiation of acinar to beta cells, following transient activation of Neurogenin3. An acinar cellspecific knock out of STAT3 resulted in a decrease in acinar to beta cell transdifferentiation and prevented recovery from diabetes, confirming the involvement of STAT3 signaling. Our final aim was to investigate if human exocrine cells possess a similar potential as rodent cells to respond to abovementioned pro-endocrine stimuli by introduction of activated MAPK and STAT3 in vitro. We demonstrate for the first time that human acinar cells can adopt a beta-like phenotype without the need to introduce a combination of pancreatic transcription factors. This acino-insular reprogramming depends on 3-D growth, activated MAPK and STAT3 and transient expression of Neurogenin3. Using genetic lineage tracing we revealed that human acinar cells can not only give rise to duct-like cells but also to cells expressing Neurogenin3 and insulin using our specific pro-endocrine culture conditions.