Volumetric MRI and MRS provide sensitive measures of Alzheimer's disease neuropathology in inducible Tau transgenic mice (rTg4510).

The purpose of this study was to determine if in vivo high resolution 3D MRI and localized 1H MR spectroscopy (MRS) can detect brain findings resembling Alzheimer's disease in a transgenic mouse model of Tau pathology. Seven double transgenic rTg4510 female mice and 7 age-matched wild-type (wt) female mice were evaluated at 5months of age. To confirm the usefulness and consistency of in vivo MRI/S, we also scanned the brains of 14 male mice (7 rTg4510 and 7 age-matched wt) at 8months of age. Mean hippocampal and cerebral cortex volumes in the female rTg4510 mice were 26.7% and 20.6% smaller than that in the wt controls (p<0.0001), respectively. Mean hippocampal and cerebral cortex volumes in the male rTg4510 mice were 18.4% and 16.9% smaller than that in the wt controls (p<0.00005), respectively. The mean volumes of the cerebellum were not statistically different between the rTg4510 and the wt groups. MRS assessment revealed that the myo-inositol to total creatine ratios (mIns/tCr), a measure of gliosis, were significantly higher in the hippocampus of rTg4510 mice relative to wt mice (p=0.03 for the females; p=0.005 for the males). Immunohistochemistry and histology in the same animals verified previously published data showing elevation of hyperphosphorylated Tau, glial activation and cortical and hippocampal neuronal loss. This study demonstrates that in vivo MRI/S can be a non-invasive biomarker to assess brain atrophy and related biochemical changes in the rTg4510 mouse model.