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Instytut Biologii Doświadczalnej im. Marcelego Nenckiego PAN
Contributor:Wilczyński, Grzegorz M. (1975-2020) : Supervisor ; Włodarczyk, Jakub : Supervisor ; Wojtkowski, Maciej (1975- ): Second supervisor ; Malinowska, Monika : Assistant supervisor
Publisher:Instytut Biologii Doświadczalnej im. M. Nenckiego PAN
Place of publishing: Date issued/created: Description:139 pages : illustrations ; 30 cm ; Summary of professional accomplishments: access to original works available only in the thesis' manuscript stored at the library collection ; Bibliography ; General part of the text parallely in Polish and English ; Summary in Polish and English
Degree grantor:Instytut Biologii Doświadczalnej im. Marcelego Nenckiego PAN
Type of object: Subject and Keywords:Angiography ; Brain imaging ; Glioblastoma ; Optical Coherence Tomography (OCT) ; Stroke
Abstract:Both stroke and glioblastoma are brain diseases that affect enormous numbers of people around the world. The development of innovative techniques for in-vivo imaging of brain pathological changes may significantly accelerate the process of searching for new therapeutic agents. Such a technique is Optical Coherence Tomography (OCT).OCT is a non-invasive, non-contact, interferometric imaging method based on detection of backscattered light from external and internal structural elements of the examined object. OCT without the need of contrast agents allows for fast, three-dimensional imaging with high resolution of a few microns. The aim of the study was to evaluate the applicability of OCT for imaging of structural and angiographic changes in the brain of mice in models of phototoxic stroke and glioblastoma and an attempt to correlate of OCT signals with changes in the nervous tissue and vessels. Developed prototype OCT system was optimized during subsequent stages of the project and validated for quantifying disease biomarkers. First, I used an OCT system to provide in-vivo imaging of the cerebral cortex through the cranial window 24 hours after a stroke. The cerebral vascular network was visualized with high temporal and spatial resolution before, during and after the phototoxic stroke, in which a single branch of the Middle Cerebral Artery was illuminated with green light. I found that despite reperfusion of the brain's surface arteries 24 hours after the stroke, there was no blood flow in the vessels in the deeper regions of the cortex. Moreover, after 24 hours, the angiographic images in the area of the stroke showed an enhancement of the scattering signal in the area of large vessels.Subsequently, the OCT system was optimized by changing the interferometer and the scanning beam type. This modification increased the stability of the OCT system, which had a positive effect on reproducibility and quality of acquired images. The system was used for long-term (14 days) in-vivo imaging of glioblastoma tumor development in the mouse brain. The method was developed to inject Gl261 glioblastoma cells into the cerebral cortex, which finally was covered with a cranial window. Structural OCT images revealed hyporeflective (dark) tumor region, surrounded by a hyper-reflective (bright) region of normal tissue. Strong angiogenesis has been demonstrated in the area of glioblastoma growth at successive time points, with characteristic irregularly shaped newly formed vessels. Finally, an assessment of angiogenesis in the ischemic area after focal stroke was performed and an attempt was made to correlate the hypo- and hyper-reflective areas with changes in the nervous tissue and vessels visualized histologically. The region of the cortex with limited blood flow was clearly visible on angiographic images as a dark area devoid of blood vessels. During the next 14 days, blood vessels appeared in this area due to angiogenesis and reperfusion. During the first 7 days after the stroke, angiographic images revealed vessels mainly in the surface layer, and on day 14 also in the deeper layers of the cortex. On the third day after the stroke, structural OCT images showed a hyporeflective area in the ischemic core, the area of which was reduced by 70% on day 14. This area correlated with the area with microglia/macrophages presence. In some mice, the hyporeflective area was surrounded by a hyperreflective halo that correlated with the presence of activated astrocytes.This study demonstrated that the prototype multifunctional OCT system is a good tool for stroke induction and imaging of changes in the brain after stroke. The analysis of scattering signals identified in the ischemia area by OCT and their histological verification allowed for their correlation with changes at the cellular level. It has been shown that the OCT technique can be used to assess the growth of a mouse brain tumor in-vivo and to observe angiogenesis in its environment
Resource type: Detailed Resource Type: Source: Language: Language of abstract: Digitizing institution:Nencki Institute of Experimental Biology of the Polish Academy of Sciences
Original in:Library of the Nencki Institute of Experimental Biology PAS
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