In vivo and ex vivo imaging of luciferase activity was performed as described previously [24], [26]. For in vivo imaging, mice were anesthetized with isoflurane and injected intraperitoneally 150 mg/kg d-luciferin. Five minutes later, mice were placed in the chamber and imaged for 1 min with the camera set at the highest sensitivity by IVIS Imaging System® 200 Series (Xenogen, Hopkinton, MA, USA). Photons emitted from tissues were quantified using Living Image® software (Xenogen). Signal intensity was quantified as the sum of all detected photon counts from mice and presented as photon/sec. For ex vivo imaging, mice were anesthetized and injected with luciferase intraperitoneally. Five minutes later, mice were sacrificed and tissues were rapidly removed. Tissues were placed in the IVIS system and imaged with the same setting used for in vivo studies. Signal intensity was quantified as the sum of all detected photon counts per second within the region of interest after subtracting the background luminescence and presented as photon/sec/cm2/steradian (photon/sec/cm2/sr).
