Intact Brain Research Articles

Progress in Structural and Functional In Vivo Imaging of Microglia and Their Application in Health and Disease.

The first line of defense for the central nervous system (CNS) against injury or disease is provided by microglia. Microglia were long believed to stay in a dormant/resting state, reacting only to injury or disease. This view changed dramatically with the development of modern imaging techniques that allowed the study of microglial behavior in the intact brain over time, to reveal the dynamic nature of their responses. Over the past two decades, in vivo imaging using multiphoton microscopy has revealed numerous new functions of microglia in the developing, adult, aged, injured, and diseased CNS. As the most dynamic cells in the brain, microglia continuously contact all structures and cell types, such as glial and vascular cells, neuronal cell bodies, axons, dendrites, and dendritic spines, and are believed to play a central role in sculpting neuronal networks throughout life. Following trauma, or in neurodegenerative or neuroinflammatory diseases, microglial responses range from protective to harmful, underscoring the need to better understand their diverse roles and states in different pathological conditions. In this chapter, we introduce multiphoton microscopy and discuss recent advances in structural and functional imaging technologies that have expanded our toolbox to study microglial states and behaviors in new ways and depths. We also discuss relevant mouse models available for in vivo imaging studies of microglia and review how such studies are constantly refining our understanding of the multifaceted role of microglia in the healthy and diseased CNS.

Quantifying Dendritic Arbors In Vitro and In Vivo in Rodent Models.

Dendritic arborization is a critical determinant of neuronal connectivity. The structure of a neuron's dendritic arbor determines the number of synaptic inputs a neuron can receive and how it processes synaptic input from other neurons. Here, we describe methods for visualizing and quantifying the dendritic arbor in primary cell cultures and in the intact rodent brain. These techniques can be used to answer significant scientific questions, such as the effects of disease processes, drugs, growth factors, and diverse environmental stressors on dendritogenesis in both in vitro and in vivo rodent models.

Memory Storage in Distributed Engram Cell Ensembles.

One of the most fascinating aspects of the brain is its ability to acquire new information from experience and retain it over time as memory. The search for physical correlates of memory, the memory engram, has been a longstanding priority in modern neurobiology. Advanced genetic approaches have led to the localization of engram cells in a few brain regions, including the hippocampus and cortex. Additionally, engram cells exhibit learning-induced, persistent modifications and have at least two states, active and silent. However, it has been hypothesized that engrams for a specific memory are distributed among multiple brain regions that are functionally connected, referred to as a unified engram complex. Recent tissue-clearing techniques have permitted high-throughput analyses of intact brain samples, which have been used to obtain a map of the engram complex for a contextual fear memory. Careful examination of these engram complex maps has revealed a potentially underappreciated contribution of subcortical regions, specifically thalamic nuclei, to memory function. These more holistic studies support the unified engram complex hypothesis for memory storage and have important implications for understanding dysfunctional engrams in the context of human disease.

Effects of transcranial magnetic stimulation on cortical structures during motor imagination performance in the brain-computer interface

The aftermath of a stroke can frequently result in impaired motor functions causing problems performing habitual limb movements. These movement disorders stem from damage to the cerebral cortex and disruptions to neuronal connections in the central pyramidal pathways [1]. Restoring motor skills following a stroke is a time-consuming and challenging process, requiring resources from both external medical sources and the patient. Despite these challenges, it is still feasible for patients to regain control over their limb movements. The common approach for stroke neurorehabilitation consists of therapeutic physical activities and kinesiotherapy. These methods rely on afferent information during motor tasks to repair connections between intact brain areas [2]. Through exercising the impacted limbs, synaptic rearrangement happens in the cortex, awakening dormant neurons and increasing cortical areas adjacent to inactive regions. Although these techniques can partially restore movement, a significant number of stroke patients still face impairments. It is crucial to acknowledge the limitations of the current interventions and explore new approaches for better outcomes. Traditional rehabilitation methods often do not fully restore movement control, prompting researchers to explore alternative approaches. Motor-imagery-based brain-computer interfaces (BCIs) have gained attention recently [3, 4]. They allow for integrating various feedback mechanisms, which can be combined with upper and lower limb exoskeletons. The level of control a subject has over a BCI system directly affects the recovery process [5]. Introducing transcranial magnetic stimulation (TMS) into motor-imagery BCIs shows promise for developing a unified and highly efficient approach to post-stroke rehabilitation. Twenty-nine healthy adult participants (21 females) with a mean age of 20.93±2.14 years were recruited for this experiment. All participants were right-handed and had no prior experience with brain-computer interfaces. Ethical approval was obtained from the local ethics committee of Lobachevsky State University of Nizhny Novgorod (ethical approval No. 2, dated 03/19/2021), and written informed consent was obtained from all participants. Subjects were randomly assigned to receive either a sham intervention (n=15) or active TMS (n=14). The experiment displayed tasks on a 24-inch LCD screen placed 2 meters away. Participants sat in a reclining chair with hands on adjustable armrests for EEG signal recording. Motor-imagery-based BCI training took place over two days with four daily tasks: motor performance, quasi-motor, and two motor imaginations of the dominant hand. EEG activity was recorded prior to and after completing the tasks. Each task comprised of 20 trials, each lasting 10 seconds. TMS was administered in between two motor imagination tasks, and a rest period of 2 minutes followed the stimulation. The researcher objectively monitored electromyography (EMG) in real-time during motor tasks. Certified NVX 52 amplifiers with 32 Cl/Ag electrodes positioned according to the international 10-10 system recorded electroencephalography (EEG) signals. The EEG was digitized at a sampling rate of 1000 Hz and filtered with a 50 Hz Notch filter. Disposable electrodes were used to record EMG data from musculus flexor digitorum superficialis on the right hand. EMG signals were digitized at 1000 Hz and filtered using a 50 Hz Notch filter. TMS was applied to the dorsolateral prefrontal cortex (dlPFC) using a figure-8 coil connected to a Neuro MS/D magnetic stimulator. Sham stimulation was performed with the same parameters, except the coil was tilted 90 degrees to simulate the sound of real stimulation. A nonparametric permutation test was conducted to assess the statistically significant dissimilarities between rest periods and periods subsequent to conducting motor imagery after TMS. Significant clusters of the highest event-related desynchronization (ERD) were observed. The analysis demonstrated a significant negative cluster in the theta rhythm (0–6 Hz) that was distinct from the magnetic stimulation site. Similar significant ERD clusters were identified during the first and second series of imaginary movements. The study examined alterations in motor cortex function following targeted rTMS. The results demonstrated that TMS using particular parameters resulted in the pre-activation of brain regions comparable to those stimulated during motor imagery. The implementation of this stimulation protocol increased activity in cortical regions related to motor imagery. The outcomes propose the probable effectiveness of TMS in elevating motor cortex activation during the rehabilitation process.

Magnetic Resonance Imaging in Studies of Perifocal Zone of Brain Gliomas (a Literature Review)

This review provides insight into application of modern MRI modalities including diffusion kurtosis imaging in assessment of perifocal glioma zone. Differentiation of “pure” perifocal vasogenic edema from edema infiltrated by glioma cells, as well as identification of peritumoral intact (on conventional MRI) brain matter infiltration make it possible to determine glial tumor borders more accurately. Analysis of diffusion and perfusion quantitative MR data allow determining glioma borders in areas with unaltered blood-brain barrier. There is a growing possibility to develop a personalized navigation algorithm for surgical removal of the tumor, followed by the determination of an individual plan for radiation and chemotherapy, as well as prediction of disease outcomes.

Integrative multi‐omics for normal brain aging and Alzheimer’s Disease in Drosophila

AbstractBackgroundNormal brain aging and Alzheimer’s Disease (AD) are both characterized by neurodegeneration and share many similarities. However, the mechanisms underlying both their similarities and differences remain largely unknown. Cell‐cell interactions mediate nearly all aspects of an organism’s physiology via cell‐surface proteins; as such, ∼70% of pharmaceutical drugs target cell‐surface proteins. Glial cells play many important roles in cell‐cell communication, plasticity, and immune function; thus, glial cell‐surface proteins present ideal novel biomarkers and drug targets. However, it remains difficult to profile glial cell‐surface proteins from intact brains, or to fully characterize gene expression changes during the progression of age‐related neurodegeneration. MethodTo investigate, we're fully characterizing how glial cells and their cell‐surface proteins differentially contribute to the progression of normal brain aging and AD, integrating state‐of‐the‐art in‐situ cell‐surface proteomics and high‐resolution single‐cell transcriptomics. Our study will be the first to apply in‐situ cell‐surface proteomics to glial cells in Drosophila, and the first to exhaustively profile and integrate the glial cell‐surface proteomes and single‐cell transcriptomes of both aging‐ and AD‐model flies. This will allow us to capture the “full picture” of how dysregulation of glial cell‐surface proteins differentially contributes to normal brain aging and AD, as changes in gene expression at the protein and mRNA levels often show considerable discrepancies.ResultIn total, our glial cell‐surface proteomics identified 872 proteins predicted to be involved in normal brain aging, and strong replicate correlations were observed. A Gene Ontology analysis revealed that most up‐regulated genes were associated with cell localization and transport, while most down‐regulated genes were associated with neural development, circuit organization, and neuroplasticity. We selected 48 candidate genes for further screening, based on which were the most up‐ and down‐regulated. Referencing our transcriptomic data, we found that 9/48 candidate genes identified by our cell‐surface proteomics also showed significant increases/decreases in expression levels, and selected 24 additional candidate genes for further screening.ConclusionCurrently, we are in the process of conducting several GOF/LOF genetic screens to investigate the effects of each candidate gene on lifespan. Based on preliminary data from our lifespan screens, we have identified 5 top candidate genes for further investigation.

Toxoplasma gondii‐induced amyloid reduction and neuroimmune responses in Alzheimer’s disease

AbstractBackgroundToxoplasma gondii is a foodborne parasite that induces monocyte recruitment and microglial activation during infection of the brain. Similarly, in Alzheimer’s disease (AD), activated immune cells are often found in the brain and these localize near amyloid beta plaques. However, after infection with T. gondii in AD mouse models, there are fewer amyloid beta plaques in the brain, increased microglial activation, and decreased severity of AD symptoms. We hypothesize that T. gondii infection activates and enhances the phagocytic ability of microglia to clear amyloid beta.MethodFemale 5xFAD mice were infected with T. gondii or PBS treated, and their brains harvested after 6 weeks of infection. Brain tissue from these animals was analyzed for amyloid (Amyloglo) and immune cell markers for microglia, monocytes, and T cells (IBA1, CD68, CD11c, CD11b, CD45, CD3) by light sheet imaging, confocal microscopy, or flow cytometry. Mice were also fitted with headplates and cranial windows and injected with methoxy‐X04 (10 mg/kg) to enable longitudinal imaging of amyloid over the span of infection.ResultConfocal microscopy of brain sections and light sheet imaging of intact brains from infected and uninfected 5xFAD mice have shown increased microglial activation markers (IBA1 and CD68) and decreased amyloid surface area and volume throughout infected brains in infected animals. Infected mouse brains also have increased co‐localization of amyloid and CD68 compared to uninfected mouse brains. Two‐photon imaging reveals that amyloid plaque area in vivo no longer increases in infected mouse brains as early as three weeks post‐infection and lasts as long as thirteen weeks post‐infection. Additionally, after six weeks of infection, we see an increase in Disease Associate Microglia (DAM) by flow cytometry, as well as an influx of other immune cells in the brain of infected mice as compared to PBS treated control mice.ConclusionOur data show that infection with T. gondii increases microglial markers associated with the DAM profile and these cells likely increase phagocytosis of amyloid beta. Infection with T. gondii appears to modulate the neuroimmune environment, including responding microglial cells, resulting in a neuroprotective phenotype.

RADT-05. SINGLE VERSUS MULTI-FRACTION STEREOTACTIC RADIOSURGERY FOR LARGE BRAIN METASTASES: RATES OF LOCAL PROGRESSION AND NECROSIS

Abstract PURPOSE For large brain metastases, it is unknown whether single fraction stereotactic radiosurgery (sSRS) or multi-fraction stereotactic radiosurgery (fSRS) is optimal. We aimed to compare rates of local progression and necrosis between sSRS and fSRS for large brain metastases. METHODS Patients with intact or resected brain metastases with a target volume ≥ 4.2 cc (corresponding to a diameter ≥ 2 cm) treated with Gamma Knife (GK) or linear accelerator-based SRS from 2014-2022 were included in this retrospective review. RESULTS A total of 343 large brain metastases in 276 patients were included; 171 lesions were treated with sSRS (96% with GK) and 172 lesions with fSRS (100% with linear accelerator). Median lesion volume was 19.8 cc and 8.4 cc for fSRS and sSRS, respectively. Resection was performed prior to SRS in 228 (66%), with the remaining 115 metastases treated intact. There was no difference in rate of local progression between sSRS versus fSRS, or between resected versus intact targets (p >0.8 for both). Cumulative incidence of local progression (with death as a competing risk) at 1 and 3 years for patients receiving sSRS was 24% and 30%, respectively, compared to 22% and 34% for fSRS. FSRS was associated with significantly higher rates of necrosis than sSRS (HR 5.58, 2.38-13.08, p < 0.001). This association remained significant after controlling for target volume. Cumulative incidence of necrosis (with death as a competing risk) at 1 and 3 years for patients receiving sSRS was 1% and 3%, respectively, compared to 10% and 18% for fSRS. Necrosis rates were significantly higher with fSRS for both intact and resected targets (P < 0.02 for both). CONCLUSION While local control for large resected or intact brain metastases appears similar after sSRS or fSRS, this retrospective study shows higher rates of necrosis after fSRS. Prospective validation is needed.

Neuronal plasticity features are independent of neuronal holding membrane potential

Dynamical reversible neuronal features in vitro are typically examined using a fixed holding membrane potential, imitating the physiological conditions of intact brains in an awake state. Here, a set of neuronal plasticity features in synaptic blocked cultures are found to be independent of the holding membrane potential in the range [−95, −50] mV. Specifically, dendritic maximal firing frequency and its absolute refractory period are independent of the holding membrane potential. In addition, the stimulation threshold is also independent of the holding membrane potential in neurons that do not show membrane depolarization in response to sub-threshold stimulations. These robust dendritic plasticity features are a prerequisite for neuronal modeling and for their utilization in interconnected neural networks to realize higher-order functionalities.

A Miniature Ultrasound Source for Neural Modulation.

This work describes a unique ultrasound (US) exposure system designed to create very localized ( [Formula: see text]) sound fields at operating frequencies that are currently being used for preclinical US neuromodulation. This system can expose small clusters of neuronal tissue, such as cell cultures or intact brain structures in target animal models, opening up opportunities to examine possible mechanisms of action. We modified a dental descaler and drove it at a resonance frequency of 96 kHz, well above its nominal operating point of 28 kHz. A ceramic microtip from an ultrasonic wire bonder was attached to the end of the applicator, creating a 100- [Formula: see text] point source. The device was calibrated with a polyvinylidene difluoride (PVDF) membrane hydrophone, in a novel, air-backed, configuration. The experimental results were confirmed by simulation using a monopole model. The results show a consistent decaying sound field from the tip, well-suited to neural stimulation. The system was tested on an existing neurological model, Drosophila melanogaster, which has not previously been used for US neuromodulation experiments. The results show brain-directed US stimulation induces or suppresses motor actions, demonstrated through synchronized tracking of fly limb movements. These results provide the basis for ongoing and future studies of US interaction with neuronal tissue, both at the level of single neurons and intact organisms.

Investigation of NO Role in Neural Tissue in Brain and Spinal Cord Injury

Nitric oxide (NO) production in injured and intact brain regions was compared by EPR spectroscopy in a model of brain and spinal cord injury in Wistar rats. The precentral gyrus of the brain was injured, followed by the spinal cord at the level of the first lumbar vertebra. Seven days after brain injury, a reduction in NO content of 84% in injured brain regions and 66% in intact brain regions was found. The difference in NO production in injured and uninjured brain regions persisted 7 days after injury. The copper content in the brain remained unchanged one week after modeling of brain and spinal cord injury. The data obtained in the experiments help to explain the problems in the therapy of patients with combined brain injury.

Multi-Scale Label-Free Human Brain Imaging with Integrated Serial Sectioning Polarization Sensitive Optical Coherence Tomography and Two-Photon Microscopy.

The study of aging and neurodegenerative processes in the human brain requires a comprehensive understanding of cytoarchitectonic, myeloarchitectonic, and vascular structures. Recent computational advances have enabled volumetric reconstruction of the human brain using thousands of stained slices, however, tissue distortions and loss resulting from standard histological processing have hindered deformation-free reconstruction. Here, the authorsdescribe an integrated serial sectioning polarization-sensitive optical coherence tomography (PSOCT) and two photon microscopy (2PM) system to provide label-free multi-contrast imaging of intact brain structures, including scattering, birefringence, and autofluorescence of human brain tissue. The authors demonstrate high-throughput reconstruction of 4 × 4 × 2cm3 sample blocks and simple registration between PSOCT and 2PM images that enablecomprehensive analysis of myelin content, vascular structure, and cellular information. The high-resolution 2PM images provide microscopic validation and enrichment of the cellular information provided by the PSOCT optical properties on the same sample, revealing the densely packed fibers, capillaries, and lipofuscin-filled cell bodies in the cortex and white matter. It is shown that theimaging system enables quantitative characterization of various pathological features in aging process, including myelin degradation, lipofuscin accumulation, and microvascular changes, which opens up numerous opportunities in the study of neurodegenerative diseases in the future.

Changes in Cortical Microstructure of the Human Brain Resulting from Long-Term Motor Learning.

The mechanisms subserving motor skill acquisition and learning in the intact human brain are not fully understood. Previous studies in animals have demonstrated a causal relationship between motor learning and structural rearrangements of synaptic connections, raising the question of whether neurite-specific changes are also observable in humans. Here, we use advanced diffusion magnetic resonance imaging (MRI), sensitive to dendritic and axonal processes, to investigate neuroplasticity in response to long-term motor learning. We recruited healthy male and female human participants (age range 19-29) who learned a challenging dynamic balancing task (DBT) over four consecutive weeks. Diffusion MRI signals were fitted using Neurite Orientation Dispersion and Density Imaging (NODDI), a theory-driven biophysical model of diffusion, yielding measures of tissue volume, neurite density and the organizational complexity of neurites. While NODDI indices were unchanged and reliable during the control period, neurite orientation dispersion increased significantly during the learning period mainly in primary sensorimotor, prefrontal, premotor, supplementary, and cingulate motor areas. Importantly, reorganization of cortical microstructure during the learning phase predicted concurrent behavioral changes, whereas there was no relationship between microstructural changes during the control phase and learning. Changes in neurite complexity were independent of alterations in tissue density, cortical thickness, and intracortical myelin. Our results are in line with the notion that structural modulation of neurites is a key mechanism supporting complex motor learning in humans.SIGNIFICANCE STATEMENT The structural correlates of motor learning in the human brain are not fully understood. Results from animal studies suggest that synaptic remodeling (e.g., reorganization of dendritic spines) in sensorimotor-related brain areas is a crucial mechanism for the formation of motor memory. Using state-of-the-art diffusion magnetic resonance imaging (MRI), we found a behaviorally relevant increase in the organizational complexity of neocortical microstructure, mainly in primary sensorimotor, prefrontal, premotor, supplementary, and cingulate motor regions, following training of a challenging dynamic balancing task (DBT). Follow-up analyses suggested structural modulation of synapses as a plausible mechanism driving this increase, while colocalized changes in cortical thickness, tissue density, and intracortical myelin could not be detected. These results advance our knowledge about the neurobiological basis of motor learning in humans.

Shadow imaging for panoptical visualization of brain tissue in vivo

Progress in neuroscience research hinges on technical advances in visualizing living brain tissue with high fidelity and facility. Current neuroanatomical imaging approaches either require tissue fixation (electron microscopy), do not have cellular resolution (magnetic resonance imaging) or only give a fragmented view (fluorescence microscopy). Here, we show how regular light microscopy together with fluorescence labeling of the interstitial fluid in the extracellular space provide comprehensive optical access in real-time to the anatomical complexity and dynamics of living brain tissue at submicron scale. Using several common fluorescence microscopy modalities (confocal, light-sheet and 2-photon microscopy) in mouse organotypic and acute brain slices and the intact mouse brain in vivo, we demonstrate the value of this straightforward ‘shadow imaging’ approach by revealing neurons, microglia, tumor cells and blood capillaries together with their complete anatomical tissue contexts. In addition, we provide quantifications of perivascular spaces and the volume fraction of the extracellular space of brain tissue in vivo.

Memantine increases the dendritic complexity of hippocampal young neurons in the juvenile brain after cranial irradiation.

Cranial irradiation (IR) negatively regulates hippocampal neurogenesis and causes cognitive dysfunctions in cancer survivors, especially in pediatric patients. IR decreases proliferation of neural stem/progenitor cells (NSPC) and consequently diminishes production of new hippocampal neurons. Memantine, an NMDA receptor antagonist, used clinically to improve cognition in patients suffering from Alzheimer's disease and dementia. In animal models, memantine acts as a potent enhancer of hippocampal neurogenesis. Memantine was recently proposed as an intervention to improve cognitive impairments occurring after radiotherapy and is currently under investigation in a number of clinical trials, including pediatric patients. To date, preclinical studies investigating the mechanisms underpinning how memantine improves cognition after IR remain limited, especially in the young, developing brain. Here, we investigated whether memantine could restore proliferation in the subgranular zone (SGZ) or rescue the reduction in the number of hippocampal young neurons after IR in the juvenile mouse brain. Mice were whole-brain irradiated with 6 Gy on postnatal day 20 (P20) and subjected to acute or long-term treatment with memantine. Proliferation in the SGZ and the number of young neurons were further evaluated after the treatment. We also measured the levels of neurotrophins associated with memantine improved neural plasticity, brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). We show that acute intraperitoneal treatment with a high, non-clinically used, dose of memantine (50 mg/kg) increased the number of proliferating cells in the intact brain by 72% and prevented 23% of IR-induced decrease in proliferation. Long-term treatment with 10 mg/kg/day of memantine, equivalent to the clinically used dose, did not impact proliferation, neither in the intact brain, nor after IR, but significantly increased the number of young neurons (doublecortin expressing cells) with radial dendrites (29% in sham controls and 156% after IR) and enhanced their dendritic arborization. Finally, we found that long-term treatment with 10 mg/kg/day memantine did not affect the levels of BDNF, but significantly reduced the levels of NGF by 40%. These data suggest that the enhanced dendritic complexity of the hippocampal young neurons after treatment with memantine may contribute to the observed improved cognition in patients treated with cranial radiotherapy.

Reconstructing the origin and early evolution of the snake brain.

Snakes represent one-eighth of terrestrial vertebrate diversity, encompassing various lifestyles, ecologies, and morphologies. However, the ecological origins and early evolution of snakes are controversial topics in biology. To address the paucity of well-preserved fossils and the caveats of osteological traits for reconstructing snake evolution, we applied a different ecomorphological hypothesis based on high-definition brain reconstructions of extant Squamata. Our predictive models revealed a burrowing lifestyle with opportunistic behavior at the origin of crown snakes, reflecting a complex ancestral mosaic brain pattern. These findings emphasize the importance of quantitatively tracking the phenotypic diversification of soft tissues-including the accurate definition of intact brain morphological traits such as the cerebellum-in understanding snake evolution and vertebrate paleobiology. Furthermore, our study highlights the power of combining extant and extinct species, soft tissue reconstructions, and osteological traits in tracing the deep evolution of not only snakes but also other groups where fossil data are scarce.

Safety and Efficacy of Stereotactic Radiosurgery with Concurrent Targeted Systemic Therapy for Brain Metastases

Data describing the safety and efficacy of central nervous system (CNS)-active targeted systemic therapies in combination with stereotactic radiosurgery (SRS, 1 fraction) and/or radiotherapy (SRT, 3-5 fractions) for brain metastases are emerging but limited. We report rates of local and intracranial failure and radiation necrosis in patients receiving CNS-active targeted systemic therapy and SRS/SRT. We retrospectively identified patients with intact brain metastases at two institutions from 2009-2022 who were treated with SRS/SRT and CNS-active targeted systemic therapy in any sequence. Patients were followed for a minimum of 3 months after SRS/SRT with brain MRI. Patients typically stopped the targeted agent 2-4 days prior to radiation and resumed 2-4 days after. Targeted therapies included inhibitors of ALK/ROS1 (Alectinib, Ceritinib, Crizotinib, Lorlatinib), EGFR (Afatinib, Erlotinib, Gefitinib, Osimertinib), BRAF (Dabrafenib, Encorafenib, Vemurafenib), MEK (Binimetinib, Trametinib), CDK 4/6 (Abemaciclib, Palbociclib, Ribociclib), HER2 (Afatinib, Lapatinib, Neratinib, Pertuzumab, Trastuzumab, T-DM1, T-DXd, Tucatinib), KRAS (Adagrasib and Sotorasib), PARP (Niraparib, Olaparib), VEGF(R) (Axitinib, Bevacizumab, Ramucirumab), and less-selective tyrosine (receptor) kinase inhibitors (Bosutinib, Brigatinib, Entrectinib, Lenvatinib, Pazopanib, Sorafenib, Sunitinib). Local failure (LF) and radiation necrosis were determined radiographically with clinical impression (grade 2 (symptomatic) or higher (G2+)) and compared between different systemic agents. The study included 95 patients with 310 metastases (SRS 246, SRT 64 metastases). Most common primary histologies were non-small cell lung cancer (36% 34/95), breast cancer (28% 27/95), and melanoma (16% 15/95). Overall survival at 1 and 2 years was 80% (76/95) and 55% (52/95), respectively. Median follow-up was 16.6 (range 3-91) months. Median tumor size was 7mm (range 1-75mm). Median number of brain metastases per patient was 2.5 (range 1-12). The G2+ radiation necrosis rate was 5.8% (18/310) while the LF rate was 9.7% (30/310) per metastasis. There was no significant difference in G2+ radiation necrosis by class of targeted therapy. Sixty-two percent (59/95) of patients experienced distant intracranial failure. Median intracranial progression free survival (PFS) was 8.0 (range 0.4-61.4) months. Although heterogeneous, patients treated with SRS/SRT and ongoing CNS-active targeted systemic therapies have on average >6 month intracranial PFS and little evidence of significant toxicity. We observed <6% G2+ radiation necrosis for this cohort, and no particular class of agent was associated with a significantly higher rate of G2+ radiation necrosis.

Positive and biphasic extracellular waveforms correspond to return currents and axonal spikes

Multiple biophysical mechanisms may generate non-negative extracellular waveforms during action potentials, but the origin and prevalence of positive spikes and biphasic spikes in the intact brain are unknown. Using extracellular recordings from densely-connected cortical networks in freely-moving mice, we find that a tenth of the waveforms are non-negative. Positive phases of non-negative spikes occur in synchrony or just before wider same-unit negative spikes. Narrow positive spikes occur in isolation in the white matter. Isolated biphasic spikes are narrower than negative spikes, occurring right after spikes of verified inhibitory units. In CA1, units with dominant non-negative spikes exhibit place fields, phase precession, and phase-locking to ripples. Thus, near-somatic narrow positive extracellular potentials correspond to return currents, and isolated non-negative spikes correspond to axonal potentials. Identifying non-negative extracellular waveforms that correspond to non-somatic compartments during spikes can enhance the understanding of physiological and pathological neural mechanisms in intact animals.

Effect of intrathecal injection of γ-Oryzanol on motor function in mice after spinal cord injury

ObjectiveSpinal cord injury (SCI) is usually caused by compression of spinal cord tissue. The main manifestations are the loss of motor or sensory functions. Because injured individuals are usually relatively young and have no effective treatment measures, there is a heavy economic burden on their families and society. Rice was the most abundant source of GORZ. This compound exhibits both antioxidant and anti-inflammatory properties. γ-Oryzanol has been shown to cross the blood–brain barrier intact and benefit brain function. This study is the first time the effect of γ-Oryzanol on the recovery of motor function after SCI in mice. Therefore, we injected γ-Oryzanol into SCI mice in different ways to observe the effect on motor function recovery of mice. Materials and methodsThe mice were randomly divided into 4 groups. In one group, only lamina was opened without damaging the spinal cord tissue (sham group); One group was left untreated after the injured spinal cord tissue (injured group). In the other two groups, mice were given 100 mg/kg of γ-Oryzanol every 2 days through the intraperitoneal or intrathecal for 42 days after injuring the spinal cord. Behavioral tests were performed using the Basso Mouse Scale (BMS) scores and gait analysis. Hematoxylin and Eosin (H&E) and immunofluorescence staining were used to observe changes in the lesion area, demyelination, axonal regeneration, and scar tissue formation. Results1. Behavioral experiments showed that the γ-Oryzanol-treated mice showed better exercise capacity than those in the injured group. 2. The pathology and demyelination at the injury site were improved in γ-Oryzanol-treated mice. 3. γ-Oryzanol-treated mice had more M2-type macrophages at the site of injury. At the same time, γ-Oryzanol-treated mice retained more axons associated with motor function and less scarring. ConclusionsStudies have shown that γ-Oryzanol can promote the recovery of motor function in mice after SCI. And the change was even more pronounced in mice treated with intrathecal injection methods. Although more intensive studies are needed, we suggest that γ-Oryzanol has potential clinical value as a recognized inexpensive dietary phytochemical.

P10.13.A AN ATRAUMATIC ACCESS TO HUMAN GLIOBLASTOMA IN A XENOGRAFT ANIMAL MODEL BY CEREBRAL OPEN FLOW MICROPERFUSION FOR THE ASSESSMENT OF BIOMARKER IN THE TUMOR MICROENVIRONMENT

Abstract BACKGROUND Orthotopic xenograft studies strongly promote the development of targeted/personalized cancer therapies to improve the still poor life expectancy of glioblastoma patients. In recent years, the tumor microenvironment has increasingly become subject of investigations, as it could have an impact on the progression of the cancer. However, examination of the tumor microenvironment with currently available methods inevitably causes trauma that might compromise the reliability of the obtained data. We aimed to implement an atraumatic access to human glioblastoma with cerebral Open Flow Microperfusion (cOFM) by implantation of xenograft cells in rodent’s brain of different species (mouse and rat) with intact blood brain barrier (BBB) and subsequent development of a xenograft glioblastoma at the interface between the cOFM probe and the surrounding brain tissue. Thereafter, we used the cOFM probe to collect interstitial fluid (ISF) from the tumor microenvironment for metabolome and biomarker assessment. MATERIAL AND METHODS Human glioma cells were implanted at a well-defined position into immune-deficient rodent’s brain via cOFM or syringe. Characteristics of the mature tumors from both groups were assessed. ISF from tumor microenvironment was collected without further traumatization by using cOFM, and the collected tumor ISF samples were analyzed using a UHPLC-HRMS metabolomics platform. A targeted (Biocrates MxP®) and an untargeted (Metaboanalyst) approach were used to analyze the metabolomics data. RESULTS For the first time xenograft cells were successfully introduced into rodent brain with intact BBB using cOFM, and the tumor tissue that developed around the cOFM probe was unaffected by the presence of the probe. Thereby, an atraumatic access to the tumor was created. The mature cOFM-induced tumors resembled the syringe-induced ones and showed typical features of human glioblastoma. The cOFM sampling procedure did not alter tumor morphology. CONCLUSION This novel atraumatic access to human glioblastoma in a rodent brain was used to collect ISF from functional tumor microenvironment in vivo without trauma generation. The thereby generated reliable data are likely to promote drug research, biomarker identification, and enable investigation of the BBB of a functional tumor.