Development of a Multimodal MRI Study to Characterize Morpho-Functional Features in Rodent Models of Alzheimer's Disease

Alzheimer’s Disease (AD) is the most common form of dementia, recognized by the World Health Organization as a global public health priority. It is a complex pathology characterized by the accumulation of the Amyloid-β (Aβ) peptide as extracellular plaques and of the intracellullar neuro fibrillary tangles (NFT) alongside with different events, such as chronic neuroinflammation and astrogliosis. None of the existing biomarkers is simultaneously specific for the pathology and sensitive to its progression. Metabolic and functional alterations are the earliest events described in the AD pathological cascade but shared with other form of dementia, while specific structural alterations occurs in a later stage of the disease. The use of transgenic models could simplify the development of new imaging biomarkers that would enable early diagnosis and making new treatments more effective. The objective of this work was to develop a multi-modal panel of magnetic resonance imaging (MRI) techniques and automated analysis pipelines, characterized by a high translational impact, in order to investigate the metabolic, functional and structural alterations in the brains of AD transgenic models. Results obtained in the APP23 transgenic mouse show that chemical exchange saturation transfer (CEST) imaging can be used to detect alterations in the brain uptake of the glucose analogue 2-deoxy-d-glucose (2DG) with a better resolution than PET and without the need of radioactive tracers. Moreover, a longitudinal study highlighted that significant structural and metabolic alterations can be found only in a late stage of the pathology. Furthermore, an advanced pipeline for the analysis of the rodent brain functional connectivity has been developed. This thesis demonstrates that the advantage to the experimental design adopted is simplifying longitudinal studies of the same animal cohort. The translation of the analysis pipelines adopted in human studies enables more powerful results and reduces the number of animals involved in research

Investigating changes in blood-cerebrospinal fluid barrier function in a rat model of chronic hypertension using non-invasive magnetic resonance imaging

Chronic hypertension is a major risk factor for the development of neurodegenerative disease, yet the etiology of hypertension-driven neurodegeneration remains poorly understood. Forming a unique interface between the systemic circulation and the brain, the blood-cerebrospinal fluid barrier (BCSFB) at the choroid plexus (CP) has been proposed as a key site of vulnerability to hypertension that may initiate downstream neurodegenerative processes. However, our ability to understand BCSFB’s role in pathological processes has, to date, been restricted by a lack of non-invasive functional measurement techniques. In this work, we apply a novel Blood-Cerebrospinal Fluid Barrier Arterial Spin Labeling (BCSFB-ASL) Magnetic resonance imaging (MRI) approach with the aim of detecting possible derangement of BCSFB function in the Spontaneous Hypertensive Rat (SHR) model using a non-invasive, translational technique. SHRs displayed a 36% reduction in BCSFB-mediated labeled arterial water delivery into ventricular cerebrospinal fluid (CSF), relative to normotensive controls, indicative of down-regulated choroid plexus function. This was concomitant with additional changes in brain fluid biomarkers, namely ventriculomegaly and changes in CSF composition, as measured by T1 lengthening. However, cortical cerebral blood flow (CBF) measurements, an imaging biomarker of cerebrovascular health, revealed no measurable change between the groups. Here, we provide the first demonstration of BCSFB-ASL in the rat brain, enabling non-invasive assessment of BCSFB function in healthy and hypertensive rats. Our data highlights the potential for BCSFB-ASL to serve as a sensitive early biomarker for hypertension-driven neurodegeneration, in addition to investigating the mechanisms relating hypertension to neurodegenerative outcomes

Chemical exchange saturation transfer MRI shows low cerebral 2-deoxy-D-glucose uptake in a model of Alzheimer's Disease

Glucose is the central nervous system's only energy source. Imaging techniques capable to detect pathological alterations of the brain metabolism are useful in different diagnostic processes. Such techniques are also beneficial for assessing the evaluation efficacy of therapies in pre-clinical and clinical stages of diseases. Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) is a possible alternative to positron emission tomography (PET) imaging that has been widely explored in cancer research in humans and animal models. We propose that pathological alterations in brain 2-deoxy-D-glucose (2DG) uptake, typical of neurodegenerative diseases, can be detected with CEST MRI. Transgenic mice overexpressing a mutated form of amyloid precusrsor protein (APP23), a model of Alzheimer's disease, analyzed with CEST MRI showed a clear reduction of 2DG uptake in different brain regions. This was reminiscent of the cerebral condition observed in Alzheimer's patients. The results indicate the feasibility of CEST for analyzing the brain metabolic state, with better image resolution than PET in experimental models

Cognitive deficits and brain myo-Inositol are early biomarkers of epileptogenesis in a rat model of epilepsy

One major unmet clinical need in epilepsy is the identification of therapies to prevent or arrest epilepsy development in patients exposed to a potential epileptogenic insult. The development of such treatments has been hampered by the lack of non-invasive biomarkers that could be used to identify the patients at-risk, thereby allowing to design affordable clinical studies. Our goal was to test the predictive value of cognitive deficits and brain astrocyte activation for the development of epilepsy following a potential epileptogenic injury. We used a model of epilepsy induced by pilocarpine-evoked status epilepticus (SE) in 21-day old rats where 60–70% of animals develop spontaneous seizures after around 70 days, although SE is similar in all rats. Learning was evaluated in the Morris water-maze at days 15 and 65 post-SE, each time followed by proton magnetic resonance spectroscopy for measuring hippocampal myo-Inositol levels, a marker of astrocyte activation. Rats were video-EEG monitored for two weeks at seven months post-SE to detect spontaneous seizures, then brain histology was done. Behavioral and imaging data were retrospectively analysed in epileptic rats and compared with non-epileptic and control animals. Rats displayed spatial learning deficits within three weeks from SE. However, only epilepsy-prone rats showed accelerated forgetting and reduced learning rate compared to both rats not developing epilepsy and controls. These deficits were associated with reduced hippocampal neurogenesis. myo-Inositol levels increased transiently in the hippocampus of SE-rats not developing epilepsy while this increase persisted until spontaneous seizures onset in epilepsy-prone rats, being associated with a local increase in S100β-positive astrocytes. Neuronal cell loss was similar in all SE-rats. Our data show that behavioral deficits, together with a non-invasive marker of astrocyte activation, predict which rats develop epilepsy after an acute injury. These measures have potential clinical relevance for identifying individuals at-risk for developing epilepsy following exposure to epileptogenic insults, and consequently, for designing adequately powered antiepileptogenesis trials

Novel iodoacetamido benzoheterocyclic derivatives with potent antileukemic activity are inhibitors of STAT5 phosphorylation

Signal Transducer and Activator of Transcription 5 (STAT5) protein, a component of the STAT family of signaling proteins, is considered to be an attractive therapeutic target because of its involvement in the progression of acute myeloid leukemia. In an effort to discover potent molecules able to inhibit the phosphorylation-activation of STAT5, twenty-two compounds were synthesized and evaluated on the basis of our knowledge of the activity of 2-(3′,4′,5′-trimethoxybenzoyl)-3-iodoacetamido-6-methoxy benzo[b]furan derivative 1 as a potent STAT5 inhibitor. Most of these molecules, structurally related to compound 1, were characterized by the presence of a common 3′,4′,5′-trimethoxybenzoyl moiety at the 2-position of different benzoheterocycles such as benzo[b]furan, benzo[b]thiophene, indole and N-methylindole. Effects on biological activity of the iodoacetamido group and of different moieties (methyl and methoxy) at the C-3 to C-7 positions were examined. In the series of benzo[b]furan derivatives, moving the iodoacetylamino group from the C-4 to the C-5 or C-6 positions did not significantly affect antiproliferative activity. Compounds 4, 15, 20 and 23 blocked STAT5 signals and induced apoptosis of K562 BCR-ABL positive cells. For compound 23, the trimethoxybenzoyl moiety at the 2-position of the benzo[b]furan core was not essential for potent inhibition of STAT5 activation

Single severe traumatic brain injury produces progressive pathology with ongoing contralateral white matter damage one year after injury

There is increasing recognition that traumatic brain injury (TBI) may initiate long-term neurodegenerative processes, particularly chronic traumatic encephalopathy. However, insight into the mechanisms transforming an initial biomechanical injury into a neurodegenerative process remain elusive, partly as a consequence of the paucity of informative pre-clinical models. This study shows the functional, whole brain imaging and neuropathological consequences at up to one year survival from single severe TBI by controlled cortical impact in mice. TBI mice displayed persistent sensorimotor and cognitive deficits. Longitudinal T2 weighted magnetic resonance imaging (MRI) showed progressive ipsilateral (il) cortical, hippocampal and striatal volume loss, with diffusion tensor imaging demonstrating decreased fractional anisotropy (FA) at up to one year in the il-corpus callosum (CC: − 30%) and external capsule (EC: − 21%). Parallel neuropathological studies indicated reduction in neuronal density, with evidence of microgliosis and astrogliosis in the il-cortex, with further evidence of microgliosis and astrogliosis in the il-thalamus. One year after TBI there was also a decrease in FA in the contralateral (cl) CC (− 17%) and EC (− 13%), corresponding to histopathological evidence of white matter loss (cl-CC: − 68%; cl-EC: − 30%) associated with ongoing microgliosis and astrogliosis. These findings indicate that a single severe TBI induces bilateral, long-term and progressive neuropathology at up to one year after injury. These observations support this model as a suitable platform for exploring the mechanistic link between acute brain injury and late and persistent neurodegeneration