Browsing by Subject "Brain Ischemia"
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Item Alterations in Neural Stem Cell Fate Following Focal Ischemia(2014-02-04) Nguyen, Derek; Vemireddy, Vamsidhara; Mashimo, Tomoyuki; Battiste, James; Maher, Elizabeth; Bachoo, RobertINTRODUCTION: The purpose of this experiment is to determine the differentiation identity of the neural stem cells (NSC) in the subventricular zone (SVZ) of adult mouse brain after a middle cerebral artery occlusion (MCAO). Injury to the brain causes a large number of changes including inflammation and apoptosis, but the reaction of NSC's has been more difficult to characterize because of the transient nature of their response. Previously, adult neural stem cells (NSC) in the SVZ have been observed to differentiate predominantly into cells with neuronal characteristics. This theory is questioned via a tamoxifen-inducible cre-recombinase (Cre-ERT2) expression mouse model system. METHOD: The Cre-ERT2 expression mouse model system is driven by the Cystatin-C promoter to label NSC's in a time specific manner and track their cell fate after MCAO. After the ischemia, these brain sections were stained with different immunohistochemicals at three separate time points. One set was co-labeled with GFAP, an astrocyte marker, and BrdU, a proliferation marker. Another set was co-labeled with DCX, a neuronal marker, and BrdU. This was used to differentiate between latent NSCs and proliferating NSCs by comparing the ipsilateral side (ischemic) with the contralateral side (control) of the brain. RESULTS: Compared to the contralateral, the ipsilateral side had a significant increase in GFAP/BrdU positive cells between day 3 and day 7 time points. The cell quantity dropped between day 7 to day 14 time points. Compared to the contralateral, the ipsilateral side had a decrease in DCX/BrdU positive cells between day 3 and day 7 time points. The cell quantity significantly increased between day 7 to day 14 time points, and the quantity at day 14 was about twice to that of the day 3 time point. DISCUSSION: This data demonstrated that after the MCAO, the stem cells are not just undergoing neurogenesis, but are for certain period of time, also differentiating into astrocytes that are migrating towards the site of injury. This phenomenon is only witnessed in the NSCs towards the day 7 time point. Afterwards and leading up to day 14, the NSCs seem to be changing their cell fate programming from the astrocyte pathway back to the intended neuronal pathway. Thus, the staining results verify that after an ischemia, NSCs within the SVZ regions of the brain undergo a constant change of programmed cell fate, alternating between immature neurons and astrocytes implicating future aims for "programmed" neurogenesis in the development of therapeutic strategies for the treatment of brain damage and disease.Item BDNF-Producing B Cells Mediate Plasticity in the Recovering Brain After Stroke(2021-11-29) Torres, Vanessa; Monson, Nancy L.; Stowe, Ann; Goldberg, Mark P.; Vitetta, Ellen S.; Volk, Lenora J.; Satterthwaite, Anne B.Neuronal networks require significant neurotrophic support for functional plasticity after stroke, but the delivery of neurotrophins has failed thus far in clinical trials. Therefore, identifying endogenous mechanisms that could enhance neurotrophic support in the recovering brain after stroke is essential. B cells, a lymphocyte known to infiltrate the post-stroke brain, possess the ability to produce neurotrophins, including brain-derived neurotrophic factor (BDNF). Depleting B cells after stroke results in motor and cognitive deficits that are mediated by specific brain regions (e.g., hippocampus) outside the initial infarct. We propose that B cells migrate to specific brain regions after stroke and respond to local signals that enhance their neurotrophic capacities to promote neuroplasticity. To investigate whether B cells are a potential source of endogenous BDNF support after stroke, we must identify 1.) the spatial distribution of B cells within the post-stroke brain, 2.) the type of neurotrophic support B cells provide to ischemic-injured neurons and 3.) the impact that the post-stroke microenvironment exerts on the neurotrophic capacity of B cells. Using whole brain microscopy, we discovered that B cells migrate to specific remote brain regions areas outside of the initial infarct that regulate motor and cognitive function after stroke. To understand how B cells support ischemic-injured neurons, we used ex vivo electrophysiology and in vitro models of ischemic injury to assess functional and structural neuroplasticity in the presence or absence of B cells. We discovered that B cells support synaptic transmission in the dentate gyrus region of the hippocampus after stroke and through the production of BDNF, B cells protect against the ischemic-induced loss of neurons and neuronal dendrites. After stroke, neuronal BDNF production is dependent on glutamate-induced activity of the N-methyl-D-aspartate receptor (NMDAR) downstream of the GluN2A subunit. Given that B cells also express NMDARs, we investigated whether glutamate can similarly upregulate BDNF in B cells downstream of their NMDARs. Using microscopy, flow cytometry and qPCR, we discovered that stroke and glutamate differentially regulate B cell gene and surface expression of GluN2A. Additionally, both mouse and human B cells elicit a functional response to glutamate and can induce autocrine BDNF signaling. Collectively, the data presented in this thesis are the first to demonstrate a glutamate-induced neurotrophic role for B cells in the ischemic brain. Understanding the mechanisms by which neuroinflammation supports neuroplasticity after stroke enables the development of immune-based therapeutics that harness endogenous neurotrophic support from B cells to ameliorate pathology.Item Long-Term T Cell Responses in the Ischemic Brain(2019-11-14) Selvaraj, Uma Maheswari; Niederkorn, Jerry Y.; Stüve, Olaf; Farrar, J. David; Stowe, Ann; Goldberg, Mark P.Stroke is a debilitating and devastating disorder with significant annual mortality and morbidity rates worldwide. Following ischemic injury, blood-brain barrier integrity is disrupted and multiple inflammatory cascades are initiated both in the central nervous system and in the peripheral immune system. These early inflammatory responses result in the recruitment of systemic immune cells into the brain parenchyma. T lymphocytes, part of the adaptive arm of the immune response, are present bordering the infarct region within days after stroke. Accumulation of these cells in the early inflammatory phase peaks 3 to 4 days after stroke injury. However, T cells persists as late as 7 weeks post-stroke and it is unclear if they are beneficial or detrimental to functional recovery in this chronic phase post-stroke. We found significant numbers of CD4 T cells and CD8 T cells in the brain parenchyma long-term post-stroke. These long-term CD8 T cells were mainly present in the injured tissue area and potentially function through IFN-g secretion. We further determined that the long-term post-stroke CD8 T cells affected inflammation and functional recovery post-stroke. CD8 T cell-depleted mice demonstrated better recovery in the rotarod behavior test and had fewer immune cells recruited to the brain parenchyma post-stroke. We also observed the presence of CNS-specific T cells in the post-stroke spleens and cervical lymph nodes. Taken together, these data reveal a role for CD8 T cells in the chronic phase post-stroke that can be therapeutically targeted. Furthermore, long-term post-stroke immune cells in the brain parenchyma regulate chronic inflammatory responses and functional recovery after stroke.Item Modulation as an Acidosis-Evoked Current by A1 Adenosine Receptors in the CA1 Region of the Mouse Hippocampus(2006-05-15) Galanis, Victor Chris; Greene, Robert W.Acidosis, along with hypoxia and hypoglycemia are immediate metabolic consequences of reduced blood flow to the brain. Acidosis exacerbates ischemic brain injury by activating non-selective cation currents that induce neuronal damage in a calcium-dependent manner, independent of glutamate receptor activation. Adenosine is released during periods of metabolic stress and exerts a neuroprotective role mediated by adenosine A1 receptor stimulation. The purpose of this project was to study the effect of adenosine A1 receptor stimulation in an in vitro model of acidosis. The findings suggest that acidosis activates a non-selective sustained cation current which is directly inhibited by adenosine, consistent with the neuroprotective role of adenosine.Item Targeting Cholinergic Neuromodulation in Stroke Recovery(2017-07-10) Becker, April Melissa; Meeks, Julian P.; Huber, Kimberly M.; Kilgard, Michael; Rennaker, Robert; Goldberg, Mark P.After ischemic stroke, patients can have significant deficits that limit their daily function. Most patients experience some degree of spontaneous recovery in the weeks after stroke. However, this recovery is often incomplete, and there are no treatment approaches which have been established to substantially restore lost function. Better functional assessment in the mouse model and investigation into controlling functional plasticity in the injured brain could each be key to producing better recovery in stroke patients. To work toward better functional assessment of stroke deficit and recovery in the mouse model, I developed an automated reach task in the mouse model that produces a longer lasting behavioral deficit after cortical infarct than most tests. A modified version of this test demonstrates that cortical ischemic stroke in the mouse recapitulates human-typical patterns of precise distal forelimb muscle control deficits. After developing, validating, and characterizing this task I used it to investigate the role of neuromodulation on stroke recovery. The results of these studies show that NB cholinergic cells in the mouse are necessary for typical recovery from stroke, and increasing their activation during successful rehabilitation movements may improve recovery.