Expression of the <i>PyMT-IRES-Luc</i> transgene in the pancreata of <i>RIP7-rtTA; tet-o-PyMT-IRES-Luc</i> bitransgenic mice resulted in β-cell hyperplasia.

<p>(A) Transgene expression in <i>RIP7-rtTA; tet-o-PyMT-IRES-Luc</i> bitransgenic mice monitored by <i>in vivo</i> bioluminescent imaging. Control <i>RIP7</i>-rtTA and <i>tet-o-PyMT-IRES-Luc</i> mono-transgenic mice, and <i>RIP7-rtTA; tet-o-PyMT-IRES-Luc</i> bitransgenic mice that were and were not on a doxycycline diet for 4 months were subjected to bioluminescence. Significant luciferase activity was detected in the area over the pancreas only in the bitransgenic mouse on doxycycline (induced). The images are representative of more than 10 mice from each group. (B) Total area of islets in <i>RIP7-rtTA; tet-o-PyMT-IRES-Luc</i> bitransgenic mice that were not on doxycycline (un-induced) compared with islet area in animals that received doxycycline at 4 weeks of age for 4 months (induced). The area of the islets was determined from histological slides of insulin-stained pancreatic sections, using Leica Application Suite 3.1.0. (C) Representative stained slides of enlarged, insulin-positive islets from <i>RIP7-rtTA; tet-o-PyMT-IRES-Luc</i> bitransgenic mice that received doxycycline. Immunohistochemical staining for insulin, glucagon, somatostatin, and Ki67 in pancreatic sections from <i>RIP7-rtTA; tet-o-PyMT-IRES-Luc</i> bitransgenic mice that were not on doxycycline (un-induced, left panels) and from those that received doxycycline for 4 months (induced, right panels). Original magnification, 20×. The images are representative of more than 5 mice from each group.