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Temporal Analysis of the Thalamic Neuronal Degeneration, Demyelination and Inflammation after Cortical Ischemic Stroke

Kher, Keshav (2024) MOBN03 20232
Degree Projects in Molecular Biology
Abstract
Stroke is a highly debilitating disease of the central nervous system occurring as a result of cerebral ischemia – deprivation of a cerebral tissue from blood that supplies it with oxygen and glucose, causing the cells in affected tissue to die, bringing about a large number of downstream effects and responses. Localized infarction in the brain also triggers tissue death and related responses in remote, directly unaffected, yet connected parts of brain. In case of a cortical stroke, a secondary degeneration in some areas of thalamus has been described, also known as “secondary thalamic degeneration”. This phenomenon also encompasses an elaborate immune response activated against this degeneration. The whole process of cell death and... (More)
Stroke is a highly debilitating disease of the central nervous system occurring as a result of cerebral ischemia – deprivation of a cerebral tissue from blood that supplies it with oxygen and glucose, causing the cells in affected tissue to die, bringing about a large number of downstream effects and responses. Localized infarction in the brain also triggers tissue death and related responses in remote, directly unaffected, yet connected parts of brain. In case of a cortical stroke, a secondary degeneration in some areas of thalamus has been described, also known as “secondary thalamic degeneration”. This phenomenon also encompasses an elaborate immune response activated against this degeneration. The whole process of cell death and entailing immune response is highly dynamic and progresses in stages that are marked by specific cellular and molecular characteristics. We aimed to unravel this progress from stroke onset to acute stage followed by a chronic stage. To this end, we mimicked a clinical stroke in a rodent model. The primary focus of this study is to characterize the dynamic changes in the secondary degenerative lesions in thalamus at the cellular level, focusing specifically on the chronic phase of stroke. Immunohistochemistry followed by tissue imaging was employed as the main technique to immunostain and visualize the cells present in the region of interest. An artificial intelligence-based software was then applied to quantify these changes at cellular level with reference to different parameters like loss in cell number, area, density etc. High magnification images were then taken in selected sections to observe the morphological changes at cellular level in greater detail. The obtained results show significant changes in terms of neuronal loss as well as demyelination of neuronal axons in the ventro-posterior nucleus of the thalamus as a consequence of cortical stroke. A cascade of inflammatory response was also observed, mediated by astrocytes and microglia. This study uncovers some of these basic changes and an extensive delineation of the processes at molecular and possibly genetic level is warranted. (Less)
Popular Abstract
Dynamics of Secondary Degeneration and Inflammation post a Cortical Ischemic Stroke

The rapid progress and innovations in medical field have markedly enhanced the average survivable age of human population. This has caused an increase in incidence of age-related diseases, the risks of which grow with advancing age. One such condition is stroke which is known to be the second-most common cause of death worldwide and a major cause of disability. Ischemic stroke, which involves about 85% of stroke cases is a result of occlusion by a clot or a lipid plaque, of a blood vessel that supplies blood to the brain.
Brain comprises different types of cells apart from its fundamental units called neurons. These other types of cells include... (More)
Dynamics of Secondary Degeneration and Inflammation post a Cortical Ischemic Stroke

The rapid progress and innovations in medical field have markedly enhanced the average survivable age of human population. This has caused an increase in incidence of age-related diseases, the risks of which grow with advancing age. One such condition is stroke which is known to be the second-most common cause of death worldwide and a major cause of disability. Ischemic stroke, which involves about 85% of stroke cases is a result of occlusion by a clot or a lipid plaque, of a blood vessel that supplies blood to the brain.
Brain comprises different types of cells apart from its fundamental units called neurons. These other types of cells include oligodendrocytes, astrocytes and microglia (as well as infiltrating macrophages). A blockage in the brain, thus deprives it of oxygen and nutrients leading to damage and ultimately death of some cell types. The brain as a tissue is an elaborately connected one, where an injury at a primary site brings about neuropathologic changes in nearby and distant unaffected parts of brain. Such neuropathologic changes also include some other cell types responding to it by mounting an inflammatory response. This is called secondary damage which also includes degradation of myelin and one site of this damage is the thalamus. Thus, a stroke in the superficial layers of brain for example, also damages the inner, deeper parts like thalamus leading to development of sensory disorders, cognitive impairment and poor neurofunctional outcomes. The timeline or the course of these events however, is not well understood resulting in lack of therapies. Thus, the goal of this project is to develop a temporal analysis of the events occurring in thalamus after an ischemic stroke, allowing us to obtain valuable information to identify the ideal therapeutic time-window in the treatment of stroke focused on avoiding symptoms associated with secondary degeneration.

Approach and findings…
Clinical stroke was mimicked in a rodent model by artificially obstructing a specific blood vessel in the brain. Immunohistochemistry was then used as the main technique to stain the brain tissue in order to note the changes quantitatively as well as qualitatively that happen in an acute stage at 3 months compared to the changes that can be observed chronically at 6 months. Quantitative analysis was done using an AI-driven software called Visiopharm®.
Our main findings include a significant loss of neurons in a particular part of thalamus also leading to its shrinkage, possibly beginning at a time point before 3 months, but progressing to completion by 6 months. The loss of neurons is an effect of neuronal death which eventually also causes degradation of myelin that surrounds the neuronal axons. The debris produced by this damage triggers an activation and transforms astrocytes and microglia into a reactive cell type that results in an intricate inflammatory response. Both the cell types change expression of their proteins allowing them to change morphology and bringing about processes like gliosis, phagocytosis and formation of glial scar that consequentially clears the debris caused by dead cells, while also limiting the damage in brain and preventing it from spreading to healthy tissue. This inflammatory response however, as expected, is observed to be subside by 6 month-time-point compared to 3 months. These results give a valuable insight into stroke progression which can be used to design ideal therapies to target specific cell types and/or processes based on the time-point a patient is brought in for treatment.

Master’s Degree Project in Molecular Biology, 60 credits 2023-2024, Department of Biology, Lund University

Advisors: Zaal Kokaia, Sara Palma-Tortosa, Laboratory of Stem Cells & Restorative Neurology, Lund Stem Cell Centre, Department of Clinical Sciences, Faculty of Medicine, Lund University Biomedical Centre (Less)
Please use this url to cite or link to this publication:
author
Kher, Keshav
supervisor
organization
course
MOBN03 20232
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9176134
date added to LUP
2024-10-04 16:02:31
date last changed
2024-10-04 16:02:31
@misc{9176134,
  abstract     = {{Stroke is a highly debilitating disease of the central nervous system occurring as a result of cerebral ischemia – deprivation of a cerebral tissue from blood that supplies it with oxygen and glucose, causing the cells in affected tissue to die, bringing about a large number of downstream effects and responses. Localized infarction in the brain also triggers tissue death and related responses in remote, directly unaffected, yet connected parts of brain. In case of a cortical stroke, a secondary degeneration in some areas of thalamus has been described, also known as “secondary thalamic degeneration”. This phenomenon also encompasses an elaborate immune response activated against this degeneration. The whole process of cell death and entailing immune response is highly dynamic and progresses in stages that are marked by specific cellular and molecular characteristics. We aimed to unravel this progress from stroke onset to acute stage followed by a chronic stage. To this end, we mimicked a clinical stroke in a rodent model. The primary focus of this study is to characterize the dynamic changes in the secondary degenerative lesions in thalamus at the cellular level, focusing specifically on the chronic phase of stroke. Immunohistochemistry followed by tissue imaging was employed as the main technique to immunostain and visualize the cells present in the region of interest. An artificial intelligence-based software was then applied to quantify these changes at cellular level with reference to different parameters like loss in cell number, area, density etc. High magnification images were then taken in selected sections to observe the morphological changes at cellular level in greater detail. The obtained results show significant changes in terms of neuronal loss as well as demyelination of neuronal axons in the ventro-posterior nucleus of the thalamus as a consequence of cortical stroke. A cascade of inflammatory response was also observed, mediated by astrocytes and microglia. This study uncovers some of these basic changes and an extensive delineation of the processes at molecular and possibly genetic level is warranted.}},
  author       = {{Kher, Keshav}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Temporal Analysis of the Thalamic Neuronal Degeneration, Demyelination and Inflammation after Cortical Ischemic Stroke}},
  year         = {{2024}},
}