Figure 1. Mutant Kras blocks acinar regeneration and promotes ADM/PanIN formation.

(A–H) H&E staining of regeneration time course in Pdx1-Cre^Early (A–D) and Pdx1-Cre^Early;LSL-Kras^G12D (E–H) mice. (E and M) Asterisks indicate spontaneous PanIN lesions in PBS-treated Pdx1-Cre^Early;LSL-Kras^G12D animals. Insets in B and F show morphologically similar duct-like cells 2 days after induction of acute pancreatitis. (I–P) Amylase (red)/CK19 (green) immunofluorescent labeling. Note CK19 expression in spontaneous PanIN lesions in Pdx1-Cre^Early;LSL-Kras^G12D mice (asterisk, M). (J and N) Amylase is downregulated and CK19 is weakly expressed in transient duct-like cells in Pdx1-Cre^Early mice (inset, J) while strongly expressed in duct-like cells in Pdx1-Cre^Early;LSL-Kras^G12D mice (inset, N). Rare amylase-positive cells are found in metaplastic epithelium (arrowheads, O). (Q–T) Amylase (red), CK19 (blue), YFP (green) immunofluorescent labeling in Elastase-Cre^ERT;LSL-Kras^G12D;R26R-EYFP mice. Without caerulein treatment, YFP expression is restricted to amylase-positive cells and restricted from CK19-positive cells. Arrowheads indicate autofluorescent erythrocytes (Q). Double-CK19/YFP–positive cells (cyan, indicating blue/green overlap) persist following caerulein treatment (R–T). Original magnification, ×400 (A–P; insets). Scale bars: 50 μm (Q–T).