Loss of the heterogeneous expression of flippase ATP11B leads to cerebral small vessel disease in a normotensive rat model.

Cerebral small vessel disease (SVD) is the leading cause of vascular dementia, causes a quarter of strokes, and worsens stroke outcomes. The disease is characterised by patchy cerebral small vessel and white matter pathology, but the underlying mechanisms are poorly understood. This microvascular and tissue damage has been classically considered secondary to extrinsic factors, such as hypertension, but this fails to explain the patchy nature of the disease, the link to endothelial cell (EC) dysfunction even when hypertension is absent, and the increasing evidence of high heritability to SVD-related brain damage. We have previously shown the link between deletion of the phospholipase flippase Atp11b and EC dysfunction in an inbred hypertensive rat model with SVD-like pathology and a single nucleotide polymorphism (SNP) in ATP11B associated with human sporadic SVD. Here, we generated a novel normotensive transgenic rat model, where Atp11b is deleted, and show pathological, imaging and behavioural changes typical of those in human SVD, but that occur without hypertension. Atp11bKO rat brain and retinal small vessels show ECs with molecular and morphological changes of dysfunction, with myelin disruption in a patchy pattern around some but not all brain small vessels, similar to the human brain. We show that ATP11B/ATP11B is heterogeneously expressed in ECs in normal rat and human brain even in the same transverse section of the same blood vessel, suggesting variable effects of the loss of ATP11B on each vessel and an explanation for the patchy nature of the disease. This work highlights a link between inherent EC dysfunction and vulnerability to SVD white matter damage with a marked heterogeneity of ECs in vivo which modulates this response, occurring even in the absence of hypertension. These findings refocus our strategies for therapeutics away from antihypertensive (and vascular risk factor) control alone and towards ECs in the effort to provide alternative targets to prevent a major cause of stroke and dementia.

Progression and regression of left ventricular hypertrophy and myocardial fibrosis in a mouse model of hypertension and concomitant cardiomyopathy.

BACKGROUND: Myocardial fibrosis is observed in multiple cardiac conditions including hypertension and aortic stenosis. Excessive fibrosis is associated with adverse clinical outcomes, but longitudinal human data regarding changes in left ventricular remodelling and fibrosis over time are sparse because of the slow progression, thereby making longitudinal studies challenging. The purpose of this study was to establish and characterize a mouse model to study the development and regression of left ventricular hypertrophy and myocardial fibrosis in response to increased blood pressure and to understand how these processes reverse remodel following normalisation of blood pressure. METHODS: We performed a longitudinal study with serial cardiovascular magnetic resonance (CMR) imaging every 2 weeks in mice (n = 31) subjected to angiotensin II-induced hypertension for 6 weeks and investigated reverse remodelling following normalisation of afterload beyond 6 weeks (n = 9). Left ventricular (LV) volumes, mass, and function as well as myocardial fibrosis were measured using cine CMR and the extracellular volume fraction (ECV) s. RESULTS: Increased blood pressure (65 ± 12 vs 85 ± 9 mmHg; p < 0.001) resulted in higher indices of LV hypertrophy (0.09 [0.08, 0.10] vs 0.12 [0.11, 0.14] g; p < 0.001) and myocardial fibrosis (ECV: 0.24 ± 0.03 vs 0.30 ± 0.02; p < 0.001) whilst LV ejection fraction fell (LVEF, 59.3 [57.6, 59.9] vs 46.9 [38.5, 49.6] %; p < 0.001). We found a strong correlation between ECV and histological myocardial fibrosis (r = 0.89, p < 0.001). Following cessation of angiotensin II and normalisation of blood pressure (69 ± 5 vs baseline 65 ± 12 mmHg; p = 0.42), LV mass (0.11 [0.10, 0.12] vs 0.09 [0.08, 0.11] g), ECV (0.30 ± 0.02 vs 0.27 ± 0.02) and LVEF (51.1 [42.9, 52.8] vs 59.3 [57.6, 59.9] %) improved but remained impaired compared to baseline (p < 0.05 for all). There was a strong inverse correlation between LVEF and %ECV during both systemic hypertension (r = - 0.88, p < 0.001) and the increases in ECV observed in the first two weeks of increased blood pressure predicted the reduction in LVEF after 6 weeks (r = - 0.77, p < 0.001). CONCLUSIONS: We have established and characterized angiotensin II infusion and repeated CMR imaging as a model of LV hypertrophy and reverse remodelling in response to systemic hypertension. Changes in myocardial fibrosis and alterations in cardiac function are only partially reversible following relief of hypertension.

Robust Revascularization in Models of Limb Ischemia Using a Clinically Translatable Human Stem Cell-Derived Endothelial Cell Product.

Pluripotent stem cell-derived differentiated endothelial cells offer high potential in regenerative medicine in the cardiovascular system. With the aim of translating the use of a human stem cell-derived endothelial cell product (hESC-ECP) for treatment of critical limb ischemia (CLI) in man, we report a good manufacturing practice (GMP)-compatible protocol and detailed cell tracking and efficacy data in multiple preclinical models. The clinical-grade cell line RC11 was used to generate hESC-ECP, which was identified as mostly endothelial (60% CD31+/CD144+), with the remainder of the subset expressing various pericyte/mesenchymal stem cell markers. Cell tracking using MRI, PET, and qPCR in a murine model of limb ischemia demonstrated that hESC-ECP was detectable up to day 7 following injection. Efficacy in several murine models of limb ischemia (immunocompromised/immunocompetent mice and mice with either type I/II diabetes mellitus) demonstrated significantly increased blood perfusion and capillary density. Overall, we demonstrate a GMP-compatible hESC-ECP that improved ischemic limb perfusion and increased local angiogenesis without engraftment, paving the way for translation of this therapy.

The inhalation effects of by-products from chlorination of heated indoor swimming pools on spinal development in pup mice.

INTRODUCTION: It has been postulated that swimming in heated indoor swimming pools in the first year of life is associated with the development of spinal deformity in children. We explored in pup mice whether exposure to certain disinfection by-products resulting from chlorination of heated pools would affect the future development of the spinal column. METHODS: Mice, from birth and for 28 consecutive days, were exposed to chemicals known to be created by disinfection by-products of indoor heated swimming pools. The study made use of a body fluid analogue and a chlorine source to recreate the conditions found in municipal pools. A cohort of 51 wild-type C57B6 mice, male and female, were divided into two groups: experimental (n = 29) and controls (n = 22). 24 mice were observed for 8 months (32 weeks), with 27 culled at 4 months (16 weeks). Serial CT scanning was used to assess the spines. RESULTS: Exposure to disinfection by-products resulted in an increase in the normal thoracic kyphotic spinal angle of the mice when compared with their controls at 10 weeks; experimental mice kyphosis range 35-82° versus 29-38° in controls. At 14 weeks the kyphosis of the experimental mice had reduced in size but never to that of the control group. CONCLUSION: We have demonstrated the ability to influence spinal development in pup mice through environmental factors and shown that the developmental deformity became evident only after a significant latent period.

Serelaxin as a potential treatment for renal dysfunction in cirrhosis: Preclinical evaluation and results of a randomized phase 2 trial.

BACKGROUND: Chronic liver scarring from any cause leads to cirrhosis, portal hypertension, and a progressive decline in renal blood flow and renal function. Extreme renal vasoconstriction characterizes hepatorenal syndrome, a functional and potentially reversible form of acute kidney injury in patients with advanced cirrhosis, but current therapy with systemic vasoconstrictors is ineffective in a substantial proportion of patients and is limited by ischemic adverse events. Serelaxin (recombinant human relaxin-2) is a peptide molecule with anti-fibrotic and vasoprotective properties that binds to relaxin family peptide receptor-1 (RXFP1) and has been shown to increase renal perfusion in healthy human volunteers. We hypothesized that serelaxin could ameliorate renal vasoconstriction and renal dysfunction in patients with cirrhosis and portal hypertension. METHODS AND FINDINGS: To establish preclinical proof of concept, we developed two independent rat models of cirrhosis that were characterized by progressive reduction in renal blood flow and glomerular filtration rate and showed evidence of renal endothelial dysfunction. We then set out to further explore and validate our hypothesis in a phase 2 randomized open-label parallel-group study in male and female patients with alcohol-related cirrhosis and portal hypertension. Forty patients were randomized 1:1 to treatment with serelaxin intravenous (i.v.) infusion (for 60 min at 80 µg/kg/d and then 60 min at 30 µg/kg/d) or terlipressin (single 2-mg i.v. bolus), and the regional hemodynamic effects were quantified by phase contrast magnetic resonance angiography at baseline and after 120 min. The primary endpoint was the change from baseline in total renal artery blood flow. Therapeutic targeting of renal vasoconstriction with serelaxin in the rat models increased kidney perfusion, oxygenation, and function through reduction in renal vascular resistance, reversal of endothelial dysfunction, and increased activation of the AKT/eNOS/NO signaling pathway in the kidney. In the randomized clinical study, infusion of serelaxin for 120 min increased total renal arterial blood flow by 65% (95% CI 40%, 95%; p < 0.001) from baseline. Administration of serelaxin was safe and well tolerated, with no detrimental effect on systemic blood pressure or hepatic perfusion. The clinical study's main limitations were the relatively small sample size and stable, well-compensated population. CONCLUSIONS: Our mechanistic findings in rat models and exploratory study in human cirrhosis suggest the therapeutic potential of selective renal vasodilation using serelaxin as a new treatment for renal dysfunction in cirrhosis, although further validation in patients with more advanced cirrhosis and renal dysfunction is required. TRIAL REGISTRATION: ClinicalTrials.gov NCT01640964.

Functionalized superparamagnetic iron oxide nanoparticles provide highly efficient iron-labeling in macrophages for magnetic resonance-based detection in vivo.

BACKGROUND AIMS: Tracking cells during regenerative cytotherapy is crucial for monitoring their safety and efficacy. Macrophages are an emerging cell-based regenerative therapy for liver disease and can be readily labeled for medical imaging. A reliable, clinically applicable cell-tracking agent would be a powerful tool to study cell biodistribution. METHODS: Using a recently described chemical design, we set out to functionalize, optimize and characterize a new set of superparamagnetic iron oxide nanoparticles (SPIONs) to efficiently label macrophages for magnetic resonance imaging-based cell tracking in vivo. RESULTS: A series of cell health and iron uptake assays determined that positively charged SPIONs (+16.8 mV) could safely label macrophages more efficiently than the formerly approved ferumoxide (-6.7 mV; Endorem) and at least 10 times more efficiently than the clinically approved SPION ferumoxytol (-24.2 mV; Rienso). An optimal labeling time of 4 h at 25 µg/mL was demonstrated to label macrophages of mouse and human origin without any adverse effects on cell viability whilst providing substantial iron uptake (>5 pg Fe/cell) that was retained for 7 days in vitro. SPION labeling caused no significant reduction in phagocytic activity and a shift toward a reversible M1-like phenotype in bone marrow-derived macrophages (BMDMs). Finally, we show that SPION-labeled BMDMs delivered via the hepatic portal vein to mice are localized in the hepatic parenchyma resulting in a 50% drop in T2* in the liver. Engraftment of exogenous cells was confirmed via immunohistochemistry up to 3 weeks posttransplantation. DISCUSSION: A positively charged dextran-coated SPION is a promising tool to noninvasively track hepatic macrophage localization for therapeutic monitoring.

AMP-activated Protein Kinase Deficiency Blocks the Hypoxic Ventilatory Response and Thus Precipitates Hypoventilation and Apnea.

RATIONALE: Modulation of breathing by hypoxia accommodates variations in oxygen demand and supply during, for example, sleep and ascent to altitude, but the precise molecular mechanisms of this phenomenon remain controversial. Among the genes influenced by natural selection in high-altitude populations is one for the adenosine monophosphate-activated protein kinase (AMPK) α1-catalytic subunit, which governs cell-autonomous adaptations during metabolic stress. OBJECTIVES: We investigated whether AMPK-α1 and/or AMPK-α2 are required for the hypoxic ventilatory response and the mechanism of ventilatory dysfunctions arising from AMPK deficiency. METHODS: We used plethysmography, electrophysiology, functional magnetic resonance imaging, and immediate early gene (c-fos) expression to assess the hypoxic ventilatory response of mice with conditional deletion of the AMPK-α1 and/or AMPK-α2 genes in catecholaminergic cells, which compose the hypoxia-responsive respiratory network from carotid body to brainstem. MEASUREMENTS AND MAIN RESULTS: AMPK-α1 and AMPK-α2 deletion virtually abolished the hypoxic ventilatory response, and ventilatory depression during hypoxia was exacerbated under anesthesia. Rather than hyperventilating, mice lacking AMPK-α1 and AMPK-α2 exhibited hypoventilation and apnea during hypoxia, with the primary precipitant being loss of AMPK-α1 expression. However, the carotid bodies of AMPK-knockout mice remained exquisitely sensitive to hypoxia, contrary to the view that the hypoxic ventilatory response is determined solely by increased carotid body afferent input to the brainstem. Regardless, functional magnetic resonance imaging and c-fos expression revealed reduced activation by hypoxia of well-defined dorsal and ventral brainstem nuclei. CONCLUSIONS: AMPK is required to coordinate the activation by hypoxia of brainstem respiratory networks, and deficiencies in AMPK expression precipitate hypoventilation and apnea, even when carotid body afferent input is normal.

Complement inhibition and statins prevent fetal brain cortical abnormalities in a mouse model of preterm birth.

Premature babies are particularly vulnerable to brain injury. In this study we focus on cortical brain damage associated with long-term cognitive, behavioral, attentional or socialization deficits in children born preterm. Using a mouse model of preterm birth (PTB), we demonstrated that complement component C5a contributes to fetal cortical brain injury. Disruption of cortical dendritic and axonal cytoarchitecture was observed in PTB-mice. Fetuses deficient in C5aR (-/-) did not show cortical brain damage. Treatment with antibody anti-C5, that prevents generation of C5a, also prevented cortical fetal brain injury in PTB-mice. C5a also showed a detrimental effect on fetal cortical neuron development and survival in vitro. Increased glutamate release was observed in cortical neurons in culture exposed to C5a. Blockade of C5aR prevented glutamate increase and restored neurons dendritic and axonal growth and survival. Similarly, increased glutamate levels - measured by (1)HMRS - were observed in vivo in PTB-fetuses compared to age-matched controls. The blockade of glutamate receptors prevented C5a-induced abnormal growth and increased cell death in isolated fetal cortical neurons. Simvastatin and pravastatin prevented cortical fetal brain developmental and metabolic abnormalities -in vivo and in vitro. Neuroprotective effects of statins were mediated by Akt/PKB signaling pathways. This study shows that complement activation plays a crucial role in cortical fetal brain injury in PTL and suggests that complement inhibitors and statins might be good therapeutic options to improve neonatal outcomes in preterm birth.

Imaging learned fear circuitry in awake mice using fMRI.

Functional magnetic resonance imaging (fMRI) of learned behaviour in 'awake rodents' provides the opportunity for translational preclinical studies into the influence of pharmacological and genetic manipulations on brain function. fMRI has recently been employed to investigate learned behaviour in awake rats. Here, this methodology is translated to mice, so that future fMRI studies may exploit the vast number of genetically modified mouse lines that are available. One group of mice was conditioned to associate a flashing light (conditioned stimulus, CS) with foot shock (PG; paired group), and another group of mice received foot shock and flashing light explicitly unpaired (UG; unpaired group). The blood oxygen level-dependent signal (proxy for neuronal activation) in response to the CS was measured 24 h later in awake mice from the PG and UG using fMRI. The amygdala, implicated in fear processing, was activated to a greater degree in the PG than in the UG in response to the CS. Additionally, the nucleus accumbens was activated in the UG in response to the CS. Because the CS signalled an absence of foot shock in the UG, it is possible that this region is involved in processing the safety aspect of the CS. To conclude, the first use of fMRI to visualise brain activation in awake mice that are completing a learned emotional task is reported. This work paves the way for future preclinical fMRI studies to investigate genetic and environmental influences on brain function in transgenic mouse models of disease and aging.

Application of kt-BLAST acceleration to reduce cardiac MR imaging time in healthy and infarcted mice.

OBJECT: We evaluated the use of kt-broad-use linear acquisition speed-up technique (kt-BLAST) acceleration of mouse cardiac imaging in order to reduce scan times, thereby minimising physiological variation and improving animal welfare. MATERIALS AND METHODS: Conventional cine cardiac MRI data acquired from healthy mice (n = 9) were subsampled to simulate kt-BLAST acceleration. Cardiological indices (left ventricular volume, ejection fraction and mass) were determined as a function of acceleration factor. kt-BLAST threefold undersampling was implemented on the scanner and applied to a second group of mice (n = 6 healthy plus 6 with myocardial infarct), being compared with standard cine imaging (3 signal averages) and cine imaging with one signal average. RESULTS: In the simulations, sufficient accuracy was achieved for undersampling factors up to three. Cardiological indices determined from the implemented kt-BLAST scanning showed no significant differences compared with the values determined from the standard sequence, and neither did indices derived from the cine scan with only one signal average despite its lower signal-to-noise ratio. Both techniques were applied successfully in the infarcted hearts. CONCLUSION: For cardiac imaging of mice, threefold undersampling of kt-space, or a similar reduction in the number of signal averages, are both feasible with subsequent reduction in imaging time.

Microglia protect against age-associated brain pathologies.

Microglia are brain-resident macrophages that contribute to central nervous system (CNS) development, maturation, and preservation. Here, we examine the consequences of permanent microglial deficiencies on brain aging using the Csf1rΔFIRE/ΔFIRE mouse model. In juvenile Csf1rΔFIRE/ΔFIRE mice, we show that microglia are dispensable for the transcriptomic maturation of other brain cell types. By contrast, with advancing age, pathologies accumulate in Csf1rΔFIRE/ΔFIRE brains, macroglia become increasingly dysregulated, and white matter integrity declines, mimicking many pathological features of human CSF1R-related leukoencephalopathy. The thalamus is particularly vulnerable to neuropathological changes in the absence of microglia, with atrophy, neuron loss, vascular alterations, macroglial dysregulation, and severe tissue calcification. We show that populating Csf1rΔFIRE/ΔFIRE brains with wild-type microglia protects against many of these pathological changes. Together with the accompanying study by Chadarevian and colleagues1, our results indicate that the lifelong absence of microglia results in an age-related neurodegenerative condition that can be counteracted via transplantation of healthy microglia.

An anatomically unbiased approach for analysis of renal BOLD magnetic resonance images.

Oxygenation defects may contribute to renal disease progression, but the chronology of events is difficult to define in vivo without recourse to invasive methodologies. Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI) provides an attractive alternative, but the R2* signal is physiologically complex. Postacquisition data analysis often relies on manual selection of region(s) of interest. This approach excludes from analysis significant quantities of biological information and is subject to selection bias. We present a semiautomated, anatomically unbiased approach to compartmentalize voxels into two quantitatively related clusters. In control F344 rats, low R2* clustering was located predominantly within the cortex and higher R2* clustering within the medulla (70.96 ± 1.48 vs. 79.00 ± 1.50; 3 scans per rat; n = 6; P < 0.01) consistent anatomically with a cortico-medullary oxygen gradient. An intravenous bolus of acetylcholine caused a transient reduction of the R2* signal in both clustered segments (P < 0.01). This was nitric oxide dependent and temporally distinct from the hemodynamic effects of acetylcholine. Rats were then chronically infused with angiotensin II (60 ng/min) and rescanned 3 days later. Clustering demonstrated a disruption of the cortico-medullary gradient, producing less distinctly segmented mean R2* clusters (71.30 ± 2.00 vs. 72.48 ± 1.27; n = 6; NS). The acetylcholine-induced attenuation of the R2* signal was abolished by chronic angiotensin II infusion, consistent with reduced nitric oxide bioavailability. This global map of oxygenation, defined by clustering individual voxels on the basis of quantitative nearness, might be more robust in defining deficits in renal oxygenation than the absolute magnitude of R2* in small, manually selected regions of interest defined exclusively by anatomical nearness.

Imaging the healing murine myocardial infarct in vivo: ultrasound, magnetic resonance imaging and fluorescence molecular tomography.

Improved understanding of the processes involved in infarct healing is required for identification of novel therapeutic targets to limit infarct expansion and consequent long-term ventricular remodelling after myocardial infarction. Infarct healing can be modelled effectively in murine models of coronary artery ligation. While imaging the murine heart is challenging due to its size and high rate of contraction, advances in preclinical imaging now permit accurate assessment of myocardial structure and function in vivo after myocardial infarction. Furthermore, rapid development of a range of molecular probes for use in a number of imaging modalities allows more detailed in vivo analysis of processes, including inflammation, fibrosis and angiogenesis. Here we consider the practical application of in vivo imaging by magnetic resonance imaging, ultrasound and fluorescence molecular tomography for assessment of infarct healing in the mouse.

A urine-concentrating defect in 11ß-hydroxysteroid dehydrogenase type 2 null mice.

In aldosterone target tissues, 11ß-hydroxysteroid dehydrogenase type 2 (11ßHSD2) is coexpressed with mineralocorticoid receptors (MR) and protects the receptor from activation by glucocorticoids. Null mutations in the encoding gene, HSD11B2, cause apparent mineralocorticoid excess, in which hypertension is thought to reflect volume expansion secondary to sodium retention. Hsd11b2(-/-) mice are indeed hypertensive, but impaired natriuretic capacity is associated with significant volume contraction, suggestive of a urine concentrating defect. Water turnover and the urine concentrating response to a 24-h water deprivation challenge were therefore assessed in Hsd11b2(-/-) mice and controls. Hsd11b2(-/-) mice have a severe and progressive polyuric/polydipsic phenotype. In younger mice (∼2 mo of age), polyuria was associated with decreased abundance of aqp2 and aqp3 mRNA. The expression of other genes involved in water transport (aqp4, slc14a2, and slc12a2) was not changed. The kidney was structurally normal, and the concentrating response to water deprivation was intact. In older Hsd11b2(-/-) mice (>6 mo), polyuria was associated with a severe atrophy of the renal medulla and downregulation of aqp2, aqp3, aqp4, slc14a2, and slc12a2. The concentrating response to water deprivation was impaired, and the natriuretic effect of the loop diuretic bumetanide was lost. In older Hsd11b2(-/-) mice, the V2 receptor agonist desmopressin did not restore full urine concentrating capacity. We find that Hsd11b2(-/-) mice develop nephrogenic diabetes insipidus. Gross changes to renal structure are observed, but these were probably secondary to sustained polyuria, rather than of developmental origin.

Non-invasive in vivo assessment of 11ß-hydroxysteroid dehydrogenase type 1 activity by 19F-Magnetic Resonance Spectroscopy.

11ß-Hydroxysteroid dehydrogenase type 1 (11ß-HSD1) amplifies tissue glucocorticoid levels and is a pharmaceutical target in diabetes and cognitive decline. Clinical translation of inhibitors is hampered by lack of in vivo pharmacodynamic biomarkers. Our goal was to monitor substrates and products of 11ß-HSD1 non-invasively in liver via 19Fluorine magnetic resonance spectroscopy (19F-MRS). Interconversion of mono/poly-fluorinated substrate/product pairs was studied in Wistar rats (male, n = 6) and healthy men (n = 3) using 7T and 3T MRI scanners, respectively. Here we show that the in vitro limit of detection, as absolute fluorine content, was 0.625 µmole in blood. Mono-fluorinated steroids, dexamethasone and 11-dehydrodexamethasone, were detected in phantoms but not in vivo in human liver following oral dosing. A non-steroidal polyfluorinated tracer, 2-(phenylsulfonyl)-1-(4-(trifluoromethyl)phenyl)ethanone and its metabolic product were detected in vivo in rat liver after oral administration of the keto-substrate, reading out reductase activity. Administration of a selective 11ß-HSD1 inhibitor in vivo in rats altered total liver 19F-MRS signal. We conclude that there is insufficient sensitivity to measure mono-fluorinated tracers in vivo in man with current dosage regimens and clinical scanners. However, since reductase activity was observed in rats using poly-fluorinated tracers, this concept could be pursued for translation to man with further development.

Human biliary epithelial cells from discarded donor livers rescue bile duct structure and function in a mouse model of biliary disease.

Biliary diseases can cause inflammation, fibrosis, bile duct destruction, and eventually liver failure. There are no curative treatments for biliary disease except for liver transplantation. New therapies are urgently required. We have therefore purified human biliary epithelial cells (hBECs) from human livers that were not used for liver transplantation. hBECs were tested as a cell therapy in a mouse model of biliary disease in which the conditional deletion of Mdm2 in cholangiocytes causes senescence, biliary strictures, and fibrosis. hBECs are expandable and phenotypically stable and help restore biliary structure and function, highlighting their regenerative capacity and a potential alternative to liver transplantation for biliary disease.

Ex vivo water diffusion tensor properties of the fibroid uterus at 7 T and their relation to tissue morphology.

PURPOSE: To investigate the water diffusion tensor properties of ex vivo tissue in the fibroid uterus, including the influence of degeneration, and the relevance of the principal eigenvector orientation to the underlying tissue structure. MATERIALS AND METHODS: Following hysterectomy, high-resolution structural T(2) -weighted and diffusion tensor magnetic resonance imaging (DT-MRI) were performed on nine uteri at 7 T. Mean diffusivity (MD), fractional anisotropy (FA), and principal eigenvector orientation were measured in myometrium and in myxoid and dense tissue in fibroids. Imaging data and measurements of water diffusion parameters were compared with histopathology findings. RESULTS: The nine uteri yielded 23 fibroids. MD was 50% higher in regions of myxoid degeneration compared to dense fibroid tissue (P = 0.001), while myometrium was intermediate in value (dense fibroid tissue, P = 0.15; myxoid degeneration, P = 0.23). FA was lower in dense fibroid tissue than in myometrium (P = 3 × 10(-5) ), but higher than in myxoid tissue (P = 0.003). Principal eigenvector orientation corresponded qualitatively with that of uterine smooth muscle fibers. CONCLUSION: The water diffusion tensor measured ex vivo in the fibroid uterus is a sensitive probe of tissue type, myxoid degeneration, and morphology.

Impaired Glymphatic Function and Pulsation Alterations in a Mouse Model of Vascular Cognitive Impairment.

Large vessel disease and carotid stenosis are key mechanisms contributing to vascular cognitive impairment (VCI) and dementia. Our previous work, and that of others, using rodent models, demonstrated that bilateral common carotid stenosis (BCAS) leads to cognitive impairment via gradual deterioration of the neuro-glial-vascular unit and accumulation of amyloid-ß (Aß) protein. Since brain-wide drainage pathways (glymphatic) for waste clearance, including Aß removal, have been implicated in the pathophysiology of VCI via glial mechanisms, we hypothesized that glymphatic function would be impaired in a BCAS model and exacerbated in the presence of Aß. Male wild-type and Tg-SwDI (model of microvascular amyloid) mice were subjected to BCAS or sham surgery which led to a reduction in cerebral perfusion and impaired spatial learning acquisition and cognitive flexibility. After 3 months survival, glymphatic function was evaluated by cerebrospinal fluid (CSF) fluorescent tracer influx. We demonstrated that BCAS caused a marked regional reduction of CSF tracer influx in the dorsolateral cortex and CA1-DG molecular layer. In parallel to these changes increased reactive astrogliosis was observed post-BCAS. To further investigate the mechanisms that may lead to these changes, we measured the pulsation of cortical vessels. BCAS impaired vascular pulsation in pial arteries in WT and Tg-SwDI mice. Our findings show that BCAS influences VCI and that this is paralleled by impaired glymphatic drainage and reduced vascular pulsation. We propose that these additional targets need to be considered when treating VCI.

A Review of Translational Magnetic Resonance Imaging in Human and Rodent Experimental Models of Small Vessel Disease.

Cerebral small vessel disease (SVD) is a major health burden, yet the pathophysiology remains poorly understood with no effective treatment. Since much of SVD develops silently and insidiously, non-invasive neuroimaging such as MRI is fundamental to detecting and understanding SVD in humans. Several relevant SVD rodent models are established for which MRI can monitor in vivo changes over time prior to histological examination. Here, we critically review the MRI methods pertaining to salient rodent models and evaluate synergies with human SVD MRI methods. We found few relevant publications, but argue there is considerable scope for greater use of MRI in rodent models, and opportunities for harmonisation of the rodent-human methods to increase the translational potential of models to understand SVD in humans. We summarise current MR techniques used in SVD research, provide recommendations and examples and highlight practicalities for use of MRI SVD imaging protocols in pre-selected, relevant rodent models.

Functional brain defects in a mouse model of a chromosomal t(1;11) translocation that disrupts DISC1 and confers increased risk of psychiatric illness.

A balanced t(1;11) translocation that directly disrupts DISC1 is linked to schizophrenia and affective disorders. We previously showed that a mutant mouse, named Der1, recapitulates the effect of the translocation upon DISC1 expression. Here, RNAseq analysis of Der1 mouse brain tissue found enrichment for dysregulation of the same genes and molecular pathways as in neuron cultures generated previously from human t(1;11) translocation carriers via the induced pluripotent stem cell route. DISC1 disruption therefore apparently accounts for a substantial proportion of the effects of the t(1;11) translocation. RNAseq and pathway analysis of the mutant mouse predicts multiple Der1-induced alterations converging upon synapse function and plasticity. Synaptosome proteomics confirmed that the Der1 mutation impacts synapse composition, and electrophysiology found reduced AMPA:NMDA ratio in hippocampal neurons, indicating changed excitatory signalling. Moreover, hippocampal parvalbumin-positive interneuron density is increased, suggesting that the Der1 mutation affects inhibitory control of neuronal circuits. These phenotypes predict that neurotransmission is impacted at many levels by DISC1 disruption in human t(1;11) translocation carriers. Notably, genes implicated in schizophrenia, depression and bipolar disorder by large-scale genetic studies are enriched among the Der1-dysregulated genes, just as we previously observed for the t(1;11) translocation carrier-derived neurons. Furthermore, RNAseq analysis predicts that the Der1 mutation primarily targets a subset of cell types, pyramidal neurons and interneurons, previously shown to be vulnerable to the effects of common schizophrenia-associated genetic variants. In conclusion, DISC1 disruption by the t(1;11) translocation may contribute to the psychiatric disorders of translocation carriers through commonly affected pathways and processes in neurotransmission.