Pathological examination of spontaneous vacuolation of pancreatic acinar cells in mice

Pancreatic acinar cell vacuolation is spontaneously observed in mice; however, the lesion is rare and has not been well documented. Herein, we present a detailed pathological examination of this lesion. Vacuoles in pancreatic acinar cells were present in 2/15 X gene knockout mice with a C57BL/6J mouse background, 4/298 ICR(CD-1) mice, 1/110 B6C3F1 mice, and 3/399 CByB6F1-Tg(HRAS)2Jic mice. The vacuoles were usually observed in a unit of the acinus, and the lesions were spread throughout the pancreas. These vacuoles contained weakly basophilic material that was positive for the periodic acid-Schiff reaction. Immunohistochemically, the vacuoles were positive for calreticulin antibody. Electron microscopy revealed globular dilatation of the rough endoplasmic reticulum (rER). According to these findings, vacuolation of pancreatic acinar cells is caused by the accumulation of misfolded proteins and enlargement of the rER.