LINEAGE TRACING ANALYSIS OF PANCREATIC ACINAR CELL DE­ DIFFERENTIATION AND TRANS-DIFFERENTIATION IN VITRO AND IN VIVO IN THE ABSENCE OF MIST 1
Previous studies suggest that mature pancreatic acinar cells can trans- differentiate into duct and islet cells in vitro; however, the intrinsic factors regulating this process have not been defined. The acinar specific transcription factor MIST1 is required for acinar cell maturation and targeted deletion of Misti (Mist1'A) in mice results in incomplete maturation of acinar cells, and increased susceptibility to pancreatic injury. Previous studies revealed that the majority of Mist1'Aacini assumed a tubular complex phenotype when grown in culture. I hypothesized that Mist1~Aacini undergo trans-differentiation to duct cells in vitro as well as in vivo after induction of cerulein induced pancreatitis. In mouse primary acinar cell cultures, the temporal expression pattern of markers for progenitor cells (PDX1), acinar cells (amylase) and duct cells (CK20) from days 1-11 of culture was examined. Immunofluorescence was performed on cryo- sectioned cultures. Acute pancreatitis was achieved by 7 hourly injections of cerulein (50 pg/kg) and mice were sacrificed 24 h, 48 h, 72 h or 7days later and compared to saline controls. Analysis of the tubular complexes just after formation revealed expression of amylase, demonstrating an acinar cell origin. Mist1'A but not wild type cultures also expressed PDX. By day 7, co-labelling revealed MistTA tubular complexes containing CK20+/amylase+ and PDX1 + cells. To definitively show the originating cell type for the tubular complexes formed in Mist1'Acultures are acinar in origin, molecular lineage tracing analysis was performed in which the R26R LacZ gene was permanently activated in acinar cells. The outcomes demonstrate that deletion of MIST1 enhances the trans-differentiation of acinar cells to other pancreatic cell types, such as duct cells.
acinar cell, MIST1, trans-differentiation, de-differentiation, PDX1, pancreatitis, lineage tracing
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