Acinar cell-specific recombination of the R26R reporter allele in Villin-Cre pancreas. (A) Low magnification view of neonatal pancreas from a Villin-Cre; R26R pup stained for β-gal activity (blue) and counterstained with Eosin. (B) High-magnification view showing lack of β-gal activity in islet and large duct. (C) High-magnification view showing an intralobular duct with no β-gal activity and all cells with a clear acinar morphology positive for β-gal. (D) High magnification view showing no β-gal staining in terminal intercalated ducts that are most closely associated with acini. β-Gal activity is lacking in the large blood vessel in the upper right corner. In all panels, β-gal activity is present in all acinar cells. Scale bars: 10 μm. Arrows indicate pancreatic ducts. a, acinus; i, islet; v, blood vessel.

Villin-Cre-based lineage tracing reveals that acinar cells transdifferentiate into ductal cells. Pancreatic epithelium from Villin-Cre;R26R mice was isolated and fixed immediately after plating (A,C,E) or after culture in the presence of TGFα for 5 days (B,D,F). On day 0, most cells (A) contained β-gal activity (blue) and were amylase positive (C) and cytokeratin negative (E), confirming that β-gal expression was confined to acinar cells. A small percentage of cells did not displayβ -gal activity, and most of these cells were positive for the ductal cytokeratins (arrows in C and E). Following 5 days of TGFα treatment, most cells were still β-gal positive (B). No intact amylase-positive cells were observed (D) and β-gal activity was present in cells expressing ductal cytokeratins (F), indicating that the β-gal-expressing acinar cells had transdifferentiated into ductal cells. Scale bars: 100 μm in A,B; 10 μm in C-F.

Ela-CreERT2-based lineage tracing confirms acinar cell origin of metaplastic epithelium. (A,B) Phase-contrast images of X-gal stained Ela-CreERT2; R26R epithelium on initiation of explant culture, demonstrating mosaic expression of β-gal reporter in acinar cells. (C-F) Phase-contrast (C,D) and bright-field (E,F) images of X-gal stained Ela-CreERT2; R26R epithelium on day 4 of culture. β-Gal reporter marks acinar cell origin of metaplastic epithelium.

Activation of nestin expression during TGFα-induced acinar-to-ductal metaplasia. (A) Semi-quantitative RT-PCR demonstrating induction of nestin expression relative to β-actin and GAPDH loading controls. Lane numbers indicate days in culture. (B) Quantification of RT-PCR results from three separate experiments. Values on x-axis indicate days in culture.