Orientation selective stimulation with tetrahedral electrodes of the rat infralimbic cortex to indirectly target the amygdala.

Introduction: Deep brain stimulation (DBS) is a rapidly developing therapeutic intervention with constantly expanding neurological and psychiatric indications. A major challenge for the approach is the precise targeting and limitation of the effect on the desired neural pathways. We have introduced a new approach, orientation selective stimulation (OSS) that allows free rotation of the induced electric field on a plane when using a probe with three parallel electrodes forming an equilateral triangle at the tip. Here, we expand the technique by introducing a tetrahedral stimulation probe that enables adjustment of the primary electric field direction freely at any angle in a 3D space around the stimulating probe. OSS in 3D will enable better targeting of the electric field according to the local brain anatomy. We tested its utility in a rat model of DBS for treatment-resistant depression. The stimulation directed to the subgenual anterior cingulate cortex (sgACC) has yielded dramatic improvement in individual patients suffering from therapy resistant depression, but no consistent benefit in larger series. This failure has been ascribed to the challenging anatomy of sgACC with several crossing neural tracts and individual differences in the local anatomy. Methods: We stimulated infralimbic cortex (IL), the rat analog of sgACC, and recorded local electrical responses in amygdala (AMG) that is monosynaptically connected to IL and plays a central role in emotional states. We further traced AMG-IL connections using a viral vector and tractography using diffusion magnetic resonance imaging (MRI). Finally, we mimicked the clinical situation by delivering sustained 130 Hz stimulation at IL at the most effective field orientation and followed changes in resting-state functional connectivity with IL using functional MRI. To help interpretation of responses in functional connectivity, we stimulated only the left IL, which we did not expect to evoke measurable changes in the rat behavior. Results: The AMG evoked responses depended systematically on the IL stimulation field orientation and yielded the maximum response in near vertical field orientation in accordance with tractography. Sustained 130 Hz stimulation at a field orientation yielding the strongest AMG evoked responses increased functional connectivity between IL and AMG on the stimulation side. Conclusion: These findings suggest that OSS in 3D provides a new approach to optimize the DBS for every individual patient with a single stimulation probe implantation.

AAV8-mediated sVEGFR2 and sVEGFR3 gene therapy combined with chemotherapy reduces the growth and microvasculature of human ovarian cancer and prolongs the survival in mice.

Background: Vascular endothelial growth factors (VEGFs) are major regulators of intratumoral angiogenesis in ovarian cancer (OVCA). Overexpression of VEGFs is associated with increased tumor growth and metastatic tendency and VEGF-targeting therapies are thus considered as potential treatments for OVCA. Here, we examined the antiangiogenic and antitumoral effects on OVCA of adeno-associated virus 8 (AAV8)-mediated expression of soluble VEGF receptors (sVEGFRs) sVEGFR2 and sVEGFR3 together with paclitaxel and carboplatin chemotherapy. Materials and methods: Immunodeficient mice were inoculated with human OVCA cell line SKOV-3m. Development of tumors was confirmed with magnetic resonance imaging (MRI) and mice were treated with gene therapy and paclitaxel and carboplatin chemotherapy. The study groups included (I) non-treated control group, (II) blank control vector AAV8-CMV, (III) AAV8-CMV with chemotherapy, (IV) AAV8-sVEGFR2, (V) AAV8-sVEGFR3, (VI) AAV8-sVEGFR2 and AAV8-sVEGFR3, and (VII) AAV8-sVEGFR2 and AAV8-sVEGFR3 with chemotherapy. Antiangiogenic and antitumoral effects were evaluated with immunohistochemical stainings and serial MRI. Results: Reduced intratumoral angiogenesis was observed in all antiangiogenic gene therapy groups. The combined use of AAV8-sVEGFR2 and AAV8-sVEGFR3 with chemotherapy suppressed ascites fluid formation and tumor growth, thus improving the overall survival of mice. Antitumoral effect was mainly caused by AAV8-sVEGFR2 while the benefits of AAV8-sVEGFR3 and chemotherapy were less prominent. Conclusion: Combined use of the AAV8-sVEGFR2 and AAV8-sVEGFR3 with chemotherapy reduces intratumoral angiogenesis and tumor growth in OVCA mouse model. Results provide preclinical proof-of-concept for the use of soluble decoy VEGFRs and especially the AAV8-sVEGFR2 in the treatment of OVCA.

Whole-brain studies of spontaneous behavior in head-fixed rats enabled by zero echo time MB-SWIFT fMRI.

Understanding the link between the brain activity and behavior is a key challenge in modern neuroscience. Behavioral neuroscience, however, lacks tools to record whole-brain activity in complex behavioral settings. Here we demonstrate that a novel Multi-Band SWeep Imaging with Fourier Transformation (MB-SWIFT) functional magnetic resonance imaging (fMRI) approach enables whole-brain studies in spontaneously behaving head-fixed rats. First, we show anatomically relevant functional parcellation. Second, we show sensory, motor, exploration, and stress-related brain activity in relevant networks during corresponding spontaneous behavior. Third, we show odor-induced activation of olfactory system with high correlation between the fMRI and behavioral responses. We conclude that the applied methodology enables novel behavioral study designs in rodents focusing on tasks, cognition, emotions, physical exercise, and social interaction. Importantly, novel zero echo time and large bandwidth approaches, such as MB-SWIFT, can be applied for human behavioral studies, allowing more freedom as body movement is dramatically less restricting factor.

Event-recurring multiband SWIFT functional MRI with 200-ms temporal resolution during deep brain stimulation and isoflurane-induced burst suppression in rat.

PURPOSE: To develop a high temporal resolution functional MRI method for tracking repeating events in the brain. METHODS: We developed a novel functional MRI method using multiband sweep imaging with Fourier transformation (SWIFT), termed event-recurring SWIFT (EVER-SWIFT). The method is able to image similar repeating events with subsecond temporal resolution. Here, we demonstrate the use of EVER-SWIFT for detecting functional MRI responses during deep brain stimulation of the medial septal nucleus and during spontaneous isoflurane-induced burst suppression in the rat brain at 9.4 T with 200-ms temporal resolution. RESULTS: The EVER-SWIFT approach showed that the shapes and time-to-peak values of the response curves to deep brain stimulation significantly differed between downstream brain regions connected to the medial septal nucleus, resembling findings obtained with traditional 2-second temporal resolution. In contrast, EVER-SWIFT allowed for detailed temporal measurement of a spontaneous isoflurane-induced bursting activity pattern, which was not achieved with traditional temporal resolution. CONCLUSION: The EVER-SWIFT technique enables subsecond 3D imaging of both stimulated and spontaneously recurring brain activities, and thus holds great potential for studying the mechanisms of neuromodulation and spontaneous brain activity.

Infantile status epilepticus disrupts myelin development.

Temporal lobe epilepsy (TLE) is the most prevalent type of epilepsy in adults; it often starts in infancy or early childhood. Although TLE is primarily considered to be a grey matter pathology, a growing body of evidence links this disease with white matter abnormalities. In this study, we explore the impact of TLE onset and progression in the immature brain on white matter integrity and development utilising the rat model of Li-pilocarpine-induced TLE at the 12th postnatal day (P). Diffusion tensor imaging (DTI) and Black-Gold II histology uncovered disruptions in major white matter tracks (corpus callosum, internal and external capsules, and deep cerebral white matter) spreading through the whole brain at P28. These abnormalities were mostly not present any longer at three months after TLE induction, with only limited abnormalities detectable in the external capsule and deep cerebral white matter. Relaxation Along a Fictitious Field in the rotating frame of rank 4 indicated that white matter changes observed at both timepoints, P28 and P72, are consistent with decreased myelin content. The animals affected by TLE-induced white matter abnormalities exhibited increased functional connectivity between the thalamus and medial prefrontal and somatosensory cortex in adulthood. Furthermore, histological analyses of additional animal groups at P15 and P18 showed only mild changes in white matter integrity, suggesting a gradual age-dependent impact of TLE progression. Taken together, TLE progression in the immature brain distorts white matter development with a peak around postnatal day 28, followed by substantial recovery in adulthood. This developmental delay might give rise to cognitive and behavioural comorbidities typical for early-onset TLE.

Corrigendum: RAFF-4, Magnetization Transfer and Diffusion Tensor MRI of Lysophosphatidylcholine Induced Demyelination and Remyelination in Rats.

[This corrects the article DOI: 10.3389/fnins.2021.625167.].

Statistical Evaluation of Different Mathematical Models for Diffusion Weighted Imaging of Prostate Cancer Xenografts in Mice.

PURPOSE: To evaluate fitting quality and repeatability of four mathematical models for diffusion weighted imaging (DWI) during tumor progression in mouse xenograft model of prostate cancer. METHODS: Human prostate cancer cells (PC-3) were implanted subcutaneously in right hind limbs of 11 immunodeficient mice. Tumor growth was followed by weekly DWI examinations using a 7T MR scanner. Additional DWI examination was performed after repositioning following the fourth DWI examination to evaluate short term repeatability. DWI was performed using 15 and 12 b-values in the ranges of 0-500 and 0-2000 s/mm2, respectively. Corrected Akaike information criteria and F-ratio were used to evaluate fitting quality of each model (mono-exponential, stretched exponential, kurtosis, and bi-exponential). RESULTS: Significant changes were observed in DWI data during the tumor growth, indicated by ADCm, ADCs, and ADCk. Similar results were obtained using low as well as high b-values. No marked changes in model preference were present between the weeks 1-4. The parameters of the mono-exponential, stretched exponential, and kurtosis models had smaller confidence interval and coefficient of repeatability values than the parameters of the bi-exponential model. CONCLUSION: Stretched exponential and kurtosis models showed better fit to DWI data than the mono-exponential model and presented with good repeatability.

Spinal cord fMRI with MB-SWIFT for assessing epidural spinal cord stimulation in rats.

PURPOSE: Electrical epidural spinal cord stimulation (SCS) is used as a treatment for chronic pain as well as to partially restore motor function after a spinal cord injury. Monitoring the spinal cord activity during SCS with fMRI could provide important and objective measures of integrative responses to treatment. Unfortunately, spinal cord fMRI is severely challenged by motion and susceptibility artifacts induced by the implanted electrode and bones. This pilot study introduces multi-band sweep imaging with Fourier transformation (MB-SWIFT) technique for spinal cord fMRI during SCS in rats. Given the close to zero acquisition delay and high bandwidth in 3 dimensions, MB-SWIFT is demonstrated to be highly tolerant to motion and susceptibility-induced artifacts and thus holds promise for fMRI during SCS. METHODS: MB-SWIFT with 0.78 × 0.78 × 1.50 mm3 spatial resolution and 3-s temporal resolution was used at 9.4 Tesla in rats undergoing epidural SCS at different frequencies. Its performance was compared with spin echo EPI. The origin of the functional contrast was also explored using suppression bands. RESULTS: MB-SWIFT was tolerant to electrode-induced artifacts and respiratory motion, leading to substantially higher fMRI sensitivity than spin echo fMRI. Clear stimulation frequency-dependent responses to SCS were detected in the rat spinal cord close to the stimulation site. The origin of MB-SWIFT fMRI signals was consistent with dominant inflow effects. CONCLUSION: fMRI of the rat spinal cord during SCS can be consistently achieved with MB-SWIFT, thus providing a valuable experimental framework for assessing the effects of SCS on the central nervous system.

Brain fMRI during orientation selective epidural spinal cord stimulation.

Epidural spinal cord stimulation (ESCS) is widely used for chronic pain treatment, and is also a promising tool for restoring motor function after spinal cord injury. Despite significant positive impact of ESCS, currently available protocols provide limited specificity and efficiency partially due to the limited number of contacts of the leads and to the limited flexibility to vary the spatial distribution of the stimulation field in respect to the spinal cord. Recently, we introduced Orientation Selective (OS) stimulation strategies for deep brain stimulation, and demonstrated their selectivity in rats using functional MRI (fMRI). The method achieves orientation selectivity by controlling the main direction of the electric field gradients using individually driven channels. Here, we introduced a similar OS approach for ESCS, and demonstrated orientation dependent brain activations as detected by brain fMRI. The fMRI activation patterns during spinal cord stimulation demonstrated the complexity of brain networks stimulated by OS-ESCS paradigms, involving brain areas responsible for the transmission of the motor and sensory information. The OS approach may allow targeting ESCS to spinal fibers of different orientations, ultimately making stimulation less dependent on the precision of the electrode implantation.

RAFF-4, Magnetization Transfer and Diffusion Tensor MRI of Lysophosphatidylcholine Induced Demyelination and Remyelination in Rats.

Remyelination is a naturally occurring response to demyelination and has a central role in the pathophysiology of multiple sclerosis and traumatic brain injury. Recently we demonstrated that a novel MRI technique entitled Relaxation Along a Fictitious Field (RAFF) in the rotating frame of rank n (RAFFn) achieved exceptional sensitivity in detecting the demyelination processes induced by lysophosphatidylcholine (LPC) in rat brain. In the present work, our aim was to test whether RAFF4, along with magnetization transfer (MT) and diffusion tensor imaging (DTI), would be capable of detecting the changes in the myelin content and microstructure caused by modifications of myelin sheets around axons or by gliosis during the remyelination phase after LPC-induced demyelination in the corpus callosum of rats. We collected MRI data with RAFF4, MT and DTI at 3 days after injection (demyelination stage) and at 38 days after injection (remyelination stage) of LPC (n = 12) or vehicle (n = 9). Cell density and myelin content were assessed by histology. All MRI metrics detected differences between LPC-injected and control groups of animals in the demyelination stage, on day 3. In the remyelination phase (day 38), RAFF4, MT parameters, fractional anisotropy, and axial diffusivity detected signs of a partial recovery consistent with the remyelination evident in histology. Radial diffusivity had undergone a further increase from day 3 to 38 and mean diffusivity revealed a complete recovery correlating with the histological assessment of cell density attributed to gliosis. The combination of RAFF4, MT and DTI has the potential to differentiate between normal, demyelinated and remyelinated axons and gliosis and thus it may be able to provide a more detailed assessment of white matter pathologies in several neurological diseases.

Docetaxel chemotherapy response in PC3 prostate cancer mouse model detected by rotating frame relaxations and water diffusion.

MRI is a common method of prostate cancer diagnosis. Several MRI-derived markers, including the apparent diffusion coefficient (ADC) based on diffusion-weighted imaging, have been shown to provide values for prostate cancer detection and characterization. The hypothesis of the study was that docetaxel chemotherapy response could be picked up earlier with rotating frame relaxation times TRAFF2 and TRAFF4 than with the continuous wave T1ρ , adiabatic T1ρ , adiabatic T2ρ , T1 , T2 or water ADC. Human PC3 prostate cancer cells expressing a red fluorescent protein were implanted in 21 male mice. Docetaxel chemotherapy was given once a week starting 1 week after cell implantation for 10 randomly selected mice, while the rest served as a control group (n = 11). The MRI consisted of relaxation along a fictitious field (RAFF) in the second (RAFF2) and fourth (RAFF4) rotating frames, T1 and T2 , continuous wave T1ρ , adiabatic T1ρ and adiabatic T2ρ relaxation time measurements and water ADC. MRI was conducted at 7 T, once a week up to 4 weeks from cell implantation. The tumor volume was monitored using T2 -weighted MRI and optical imaging. The histology was evaluated after the last imaging time point. Significantly reduced RAFFn, T1ρ, T2ρ and conventional relaxation times 4 weeks after tumor implantation were observed in the treated tumors compared with the controls. The clearest short- and long-term responses were obtained with T1 , while no clear improvement in response to treatment was detected with novel methods compared with conventional methods or with RAFFn compared with all others. The tumor volume decreased after a two-week time point for the treated group and increased significantly in the control group, which was supported by increasing red fluorescent light emission in the control tumors. Decreased relaxation times were associated with successful chemotherapy outcomes. The results indicate altered relaxation mechanisms compared with higher dose chemotherapies previously published.

Multi-band SWIFT enables quiet and artefact-free EEG-fMRI and awake fMRI studies in rat.

Functional magnetic resonance imaging (fMRI) studies in animal models provide invaluable information regarding normal and abnormal brain function, especially when combined with complementary stimulation and recording techniques. The echo planar imaging (EPI) pulse sequence is the most common choice for fMRI investigations, but it has several shortcomings. EPI is one of the loudest sequences and very prone to movement and susceptibility-induced artefacts, making it suboptimal for awake imaging. Additionally, the fast gradient-switching of EPI induces disrupting currents in simultaneous electrophysiological recordings. Therefore, we investigated whether the unique features of Multi-Band SWeep Imaging with Fourier Transformation (MB-SWIFT) overcome these issues at a high 9.4 T magnetic field, making it a potential alternative to EPI. MB-SWIFT had 32-dB and 20-dB lower peak and average sound pressure levels, respectively, than EPI with typical fMRI parameters. Body movements had little to no effect on MB-SWIFT images or functional connectivity analyses, whereas they severely affected EPI data. The minimal gradient steps of MB-SWIFT induced significantly lower currents in simultaneous electrophysiological recordings than EPI, and there were no electrode-induced distortions in MB-SWIFT images. An independent component analysis of the awake rat functional connectivity data obtained with MB-SWIFT resulted in near whole-brain level functional parcellation, and simultaneous electrophysiological and fMRI measurements in isoflurane-anesthetized rats indicated that MB-SWIFT signal is tightly linked to neuronal resting-state activity. Therefore, we conclude that the MB-SWIFT sequence is a robust preclinical brain mapping tool that can overcome many of the drawbacks of conventional EPI fMRI at high magnetic fields.

Characterizing valve dynamics in mice by high-resolution cine-MRI.

AIMS: In calcific aortic valve disease (CAVD), progressive valvular sclerosis and calcification cause narrowing of the orifice and an impairment of the valve's function. We applied high-resolution cine-MRI to perform quantitative analysis of the dynamics of the aortic valve in a mice model of CAVD. METHODS AND RESULTS: LDLr-/- ApoB100/100 mice were fed a Western diet (WD) or a standard diet (control) for 22 weeks. The mice were imaged in a 7 T horizontal MRI scanner, and aortic valve dynamics was examined by imaging the cross-section of the aorta at valve level using cine sequences. From these images, the area of the aortic valve orifice was determined during the heart cycle. MRI results were compared with echocardiographic and histopathologic results. The data revealed evidence of clear aortic valve dysfunction in WD mice as compared with control mice (interaction P < 0.001). MRI showed narrowing (14%, P < 0.05) of the orifice area, and this was also seen in histology (34%, P < 0.05), indicating more severe aortic stenosis after WD than in controls. Additionally, MRI revealed a reduction in the ejection fraction (EF) (-11%, P < 0.01), a result confirmed with echocardiography (-27%, P < 0.001) in mice fed with WD. EF detected by MRI and echocardiography also correlated strongly with the degree of stenosis assessed by histology. CONCLUSIONS: Cine-MRI can be used for quantitative analysis of the aortic valve orifice over the cardiac cycle in mice. MRI showed the cusps clearly, and we were able to detect aortic valve dysfunction over time through the cardiac cycle.

Deletion of Lymphangiogenic and Angiogenic Growth Factor VEGF-D Leads to Severe Hyperlipidemia and Delayed Clearance of Chylomicron Remnants.

Objective- Dyslipidemia is one of the key factors behind coronary heart disease. Blood and lymphatic vessels play pivotal roles in both lipoprotein metabolism and development of atherosclerotic plaques. Recent studies have linked members of VEGF (vascular endothelial growth factor) family to lipid metabolism, but the function of VEGF-D has remained unexplored. Here, we investigated how the deletion of VEGF-D affects lipid and lipoprotein metabolism in atherogenic LDLR-/- ApoB100/100 mice. Approach and Results- Deletion of VEGF-D (VEGF-D-/-LDLR-/-ApoB100/100) led to markedly elevated plasma cholesterol and triglyceride levels without an increase in atherogenesis. Size distribution and hepatic lipid uptake studies confirmed a delayed clearance of large chylomicron remnant particles that cannot easily penetrate through the vascular endothelium. Mechanistically, the inhibition of VEGF-D signaling significantly decreased the hepatic expression of SDC1 (syndecan 1), which is one of the main receptors for chylomicron remnant uptake when LDLR is absent. Immunohistochemical staining confirmed reduced expression of SDC1 in the sinusoidal surface of hepatocytes in VEGF-D deficient mice. Furthermore, hepatic RNA-sequencing revealed that VEGF-D is also an important regulator of genes related to lipid metabolism and inflammation. The lack of VEGF-D signaling via VEGFR3 (VEGF receptor 3) led to lowered expression of genes regulating triglyceride and cholesterol production, as well as downregulation of peroxisomal ß-oxidation pathway. Conclusions- These results demonstrate that VEGF-D, a powerful lymphangiogenic and angiogenic growth factor, is also a major regulator of chylomicron metabolism in mice.

Capturing exchange using periodic radiofrequency irradiation.

The dynamics of spin system coupled by chemical exchange between two sites with different chemical shifts during periodic radiofrequency (RF) irradiation was here investigated. When the instantaneous π-flip of effective frequency during the course of frequency sweep was applied, a significant increase of exchange-induced relaxation rate constants was observed for small tip angle of magnetization in the laboratory frame of reference. This increase of the rate constants corresponds to the side bands generated by the periodic irradiation during the RF pulses. The exchange - induced relaxation rate constants depend on the exchange conditions, the RF power and the irradiation period. The described phenomenon promises applications for studying protein dynamics and for generating exchange specific relaxation contrasts in MRI.

Quantification of myocardial infarct area based on TRAFFn relaxation time maps - comparison with cardiovascular magnetic resonance late gadolinium enhancement, T1ρ and T2 in vivo.

BACKGROUND: Two days after myocardial infarction (MI), the infarct consists mostly on necrotic tissue, and the myocardium is transformed through granulation tissue to scar in two weeks after the onset of ischemia in mice. In the current work, we determined and optimized cardiovascular magnetic resonance (CMR) methods for the detection of MI size during the scar formation without contrast agents in mice. METHODS: We characterized MI and remote areas with rotating frame relaxation time mapping including relaxation along fictitious field in nth rotating frame (RAFFn), T1ρ and T2 relaxation time mappings at 1, 3, 7, and 21 days after MI. These results were compared to late gadolinium enhancement (LGE) and Sirius Red-stained histology sections, which were obtained at day 21 after MI. RESULTS: All relaxation time maps showed significant differences in relaxation time between the MI and remote area. Areas of increased signal intensities after gadolinium injection and areas with increased TRAFF2 relaxation time were highly correlated with the MI area determined from Sirius Red-stained histology sections (LGE: R2 = 0.92, P < 0.01, TRAFF2: R2 = 0.95, P < 0.001). Infarct area determined based on T1ρ relaxation time correlated highly with Sirius Red histology sections (R2 = 0.97, P < 0.01). The smallest overestimation of the LGE-defined MI area was obtained for TRAFF2 (5.6 ± 4.2%) while for T1ρ overestimation percentage was > 9% depending on T1ρ pulse power. CONCLUSION: T1ρ and TRAFF2 relaxation time maps can be used to determine accurately MI area at various time points in the mouse heart. Determination of MI size based on TRAFF2 relaxation time maps could be performed without contrast agents, unlike LGE, and with lower specific absorption rate compared to on-resonance T1ρ relaxation time mapping.

T2 , T1ρ and TRAFF4 detect early regenerative changes in mouse ischemic skeletal muscle.

The identification of areas with regenerative potential in ischemic tissues would allow the targeting of treatments supporting tissue recovery. The regeneration process involves the activation of several cellular and molecular responses which could be detected using magnetic resonance imaging (MRI). However, to date, magnetic resonance (MR) relaxation parameters have received little attention in the diagnosis and follow-up of limb ischemia. The purpose of this study was to evaluate the feasibility of different MRI relaxation and diffusion tensor imaging parameters in the detection of areas showing early signs of regeneration in ischemic mouse skeletal muscles. T2 and T1ρ relaxation time constants, together with TRAFFn , T1 and diffusion tensor imaging, were evaluated to differentiate areas of regeneration in a mouse hind limb ischemia model before and 0, 1, 4, 7, 14 and 30 days after ischemia. All the measured relaxation times were longer in the areas of early regeneration compared with normal muscle tissue. The relaxation times increased after ischemia in the ischemic muscles, reaching a maximum at 4-7 days after occlusion, coinciding with the appearance of early signs of regeneration. Fractional anisotropy decreased significantly (p < 0.05) on days 1-4, whereas mean diffusivity, λ1 and λ2 decreased later, starting at day 7 after ischemia compared with the pre-operational time point. The percentages of areas with different tissue morphologies were determined based on histological analysis of the ischemic muscle cross-sections, and correlations between the percentages obtained and different relaxation times were calculated. The highest correlation between relaxation times and histology was achieved with T2 , T1ρ and TRAFF4 (R2 = 0.96, R2 = 0.92 and R2 = 0.84, respectively, p < 0.01). Early regenerative changes were visible using T2 , T1ρ and TRAFF4 MR relaxation time constants in skeletal muscle after ischemia. These markers could potentially be used for the identification of targets for therapies supporting muscle regeneration after ischemic injury.

Tuning Neuromodulation Effects by Orientation Selective Deep Brain Stimulation in the Rat Medial Frontal Cortex.

Previous studies that focused on treating major depressive disorder with conventional deep brain stimulation (DBS) paradigms produced inconsistent results. In this proof-of-concept preclinical study in rats (n = 8), we used novel paradigms of orientation selective DBS for stimulating the complex circuitry crossing the infralimbic cortex, an area considered analogous to human subgenual cingulate cortex. Using functional MRI at 9.4 T, we monitored whole brain responses to varying the electrical field orientation of DBS within the infralimbic cortex. Substantial alterations of functional MRI responses in the amygdala, a major node connected to the infralimbic cortex implicated in the pathophysiology of depression, were observed. As expected, the activation cluster near the electrode was insensitive to the changes of the stimulation orientation. Hence, our findings substantiate the ability of orientation selective stimulation (OSS) to recruit neuronal pathways of distinct orientations relative to the position of the electrode, even in complex circuits such as those involved in major depressive disorder. We conclude that OSS is a promising approach for stimulating brain areas that inherently require individualisation of the treatment approach.

The follow-up of progressive hypertrophic cardiomyopathy using magnetic resonance rotating frame relaxation times.

Magnetic resonance rotating frame relaxation times are an alternative non-contrast agent choice for the diagnosis of chronic myocardial infarct. Fibrosis typically occurs in progressive hypertrophic cardiomyopathy. Fibrosis has been imaged in myocardial infarcted tissue using rotating frame relaxation times, which provides the possibility to follow up progressive cardiomyopathy without contrast agents. Mild and severe left ventricular hypertrophy were induced in mice by transverse aortic constriction, and the longitudinal rotating frame relaxation times (T1ρ ) and relaxation along the fictitious field (TRAFF2 , TRAFF3 ) were measured at 5, 10, 24, 62 and 89 days after transverse aortic constriction in vivo. Myocardial fibrosis was verified using Masson's trichrome staining. Increases in the relative relaxation time differences of T1ρ , together with TRAFF2 and TRAFF3 , between fibrotic and remote tissues over time were observed. Furthermore, TRAFF2 and TRAFF3 showed higher relaxation times overall in fibrotic tissue than T1ρ . Relaxation time differences were highly correlated with an excess of histologically verified fibrosis. We found that TRAFF2 and TRAFF3 are more sensitive than T1ρ to hypertrophic cardiomyopathy-related tissue changes and can serve as non-invasive diagnostic magnetic resonance imaging markers to follow up the mouse model of progressive hypertrophic cardiomyopathy.

Aggravated Postinfarct Heart Failure in Type 2 Diabetes Is Associated with Impaired Mitophagy and Exaggerated Inflammasome Activation.

Type 2 diabetes mellitus (T2DM) is a major risk factor for heart disease. Mortality rates after myocardial infarction (MI) are significantly increased in T2DM patients because of dysfunctional left ventricle (LV). However, molecular pathways underlying accelerated heart failure (HF) after MI in T2DM remain unclear. We investigated the underlying mechanisms by inducing MI in a well-established model of T2DM and control mice. Cardiac imaging revealed a significantly decreased global left ventricular ejection fraction in parallel with increased mortality after MI in T2DM mice compared with control mice. Genome-wide mRNA sequencing, immunoblot, electron microscopy, together with immunofluorescence staining for LC3 and p62 indicated an impaired mitophagy in peri-infarct regions of LV in T2DM mice compared with control mice. Furthermore, defective mitophagy was associated with an increased release of mitochondrial DNA, resulting in Aim2 and NLRC4 inflammasome and caspase-I hyperactivation in cardiomyocytes and cardiac macrophages in peri-infarct regions of LV in T2DM mice. Consistent with inflammasome and caspase-I hyperactivation, cardiomyocyte death and IL-18 secretion were increased in T2DM mice. Our results indicate that T2DM aggravates HF after MI through defective mitophagy, associated exaggerated inflammasome activation, cell death, and IL-18 secretion, suggesting that restoring mitophagy and inhibiting inflammasome activation may serve as novel targets for the prevention and treatment of HF in T2DM.