title: Biophysical modeling of high field diffusion MRI demonstrates micro-structural aberration in chronic mild stress rat brain.
abstract: Depression is one of the leading causes of disability worldwide. Immense heterogeneity in symptoms of depression causes difficulty in diagnosis, and to date, there are no established biomarkers or imaging methods to examine depression. Unpredictable chronic mild stress (CMS) induced anhedonia is considered to be a realistic model of depression in studies of animal subjects. Stereological and neuronal tracing techniques have demonstrated persistent remodeling of microstructure in hippocampus, prefrontal cortex and amygdala of CMS brains. Recent developments in diffusion MRI (d-MRI) analyses, such as neurite density and diffusion kurtosis imaging (DKI), are able to capture microstructural changes and are considered to be robust tools in preclinical and clinical imaging. The present study utilized d-MRI analyzed with a neurite density model and the DKI framework to investigate microstructure in the hippocampus, prefrontal cortex, caudate putamen and amygdala regions of CMS rat brains by comparison to brains from normal controls. To validate findings of CMS induced microstructural alteration, histology was performed to determine neurite, nuclear and astrocyte density. d-MRI based neurite density and tensor-based mean kurtosis (MKT) were significantly higher, while mean diffusivity (MD), extracellular diffusivity (Deff) and intra-neurite diffusivity(DL) were significantly lower in the amygdala of CMS rat brains. Deff was also significantly lower in the hippocampus and caudate putamen in stressed groups. Histological neurite density corroborated the d-MRI findings in the amygdala and reductions in nuclear and astrocyte density further buttressed the d-MRI results. The present study demonstrated that the d-MRI based neurite density and MKT can reveal specific microstructural changes in CMS rat brains and these parameters might have value in clinical diagnosis of depression and for evaluation of treatment efficacy.
authors.affiliation: Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Ahmad Raza
authors.initials: AR
authors.lastname: Khan
authors.affiliation: Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Andrey
authors.initials: A
authors.lastname: Chuhutin
authors.affiliation: Translational Neuropsychiatry Unit, Aarhus University, Risskov, Denmark.
authors.forename: Ove
authors.initials: O
authors.lastname: Wiborg
authors.affiliation: Advanced Imaging Research Center, Oregon Health & Science University, Portland, Oregon, United States.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Kroenke
authors.affiliation: Stereology and Electron Microscopy Laboratory, Centre for Stochastic Geometry and Advanced Bioimaging, Aarhus University, Aarhus, Denmark.
authors.forename: Jens R
authors.initials: JR
authors.lastname: Nyengaard
authors.affiliation: Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Brian
authors.initials: B
authors.lastname: Hansen
authors.affiliation: Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark.|Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark.
authors.forename: Sune Nørhøj
authors.initials: SN
authors.lastname: Jespersen
mesh_terms: D000679:Amygdala / Q000166:cytology / Q000000981:diagnostic imaging*; D000818:Animals; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006624:Hippocampus / Q000166:cytology / Q000000981:diagnostic imaging*; D008297:Male; D008954:Models, Biological; D016501:Neurites; D017397:Prefrontal Cortex / Q000166:cytology / Q000000981:diagnostic imaging*; D051381:Rats; D017208:Rats, Wistar; D013315:Stress, Psychological / Q000000981:diagnostic imaging*
keywords: Amygdala; Chronic mild stress; Diffusion; Histology; Kurtosis; Neurite density