Coming dissertations at MedFak
-
Astrocytes in Alzheimer’s disease : Exploring the impact of amyloid-β pathology on neurotoxicity, metabolism and inflammation.
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-525110
Astrocytes play a central role in brain homeostasis, but are also tightly connected to the pathogenesis of Alzheimer’s disease (AD). Yet, their exact role in amyloid-beta (Aβ) pathology and chronic neuroinflammation is unclear. The aim of this thesis was to elucidate the impact of astrocytes in AD progression. For this purpose, astrocytes in different culture set-ups were exposed to soluble Aβ aggregates. The astrocytes engulf and process, but fail to fully degrade the Aβ aggregates, which are instead stored as large intracellular deposits. In Paper I, we show that extracellular vesicles (EVs), secreted from the Aβ-containing cells induce synaptic loss, axonal swelling and vacuolization of primary neurons, which consequently leads to apoptosis.
Astrocytes play a central role in the brain’s energy metabolism and we were therefore interested in how Aβ pathology affects their metabolism. In Paper II, we report that Aβ accumulation in astrocytes disrupts mitochondrial fission/fusion homeostasis, resulting in decreased mitochondrial respiration and altered glycolysis. Interestingly, the astrocytes switch to fatty acid β oxidation with the aid of peroxisomes to maintain stable energy production.
Another important task is to understand how astrocytes modify the ingested Aβ. In Paper III, we characterized the astrocytic Aβ inclusions by isolating them with magnetic beads. Our analysis showed that the astrocytes truncate and pack together the Aβ aggregates. Moreover, we found that astrocytes release specifically truncated forms of Aβ via different routes.
Astrocytes’ involvement in lipid metabolism and inflammation has recently gained much interest, but many questions remain about the connection between these processes. In Paper IV, we show that Aβ pathology causes lipid droplet (LD) accumulation in astrocytes. Moreover, we could show that astrocytes frequently transfer LDs to neighboring cells, both through direct cell-to-cell contacts and via secretion. Astrocytes have previously been reported to express major histocompatibility complex II (MHCII) and have the capacity to perform as professional antigen presenting cells. Interestingly, our results demonstrate that LDs contain MHCII, identifying a link between LDs and inflammation in astrocytes.
Taken together, this thesis contributes with important knowledge of the role of astrocytes in AD pathology.
-
Optimizing the magnetic tracer technique for sentinel lymph node detection and tumour localization in breast cancer surgery
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-525195
Breast cancer is the most common form of cancer in women, and the primary treatment modalities are still breast-conserving surgery (BCS) and sentinel lymph node dissection (SLND) in most cases. Superparamagnetic iron oxide nanoparticles (SPIO) are gaining momentum as a tracer for sentinel lymph node detection. The aim of this thesis is to further refine the magnetic method and investigate its postoperative effects.
Paper I: This feasibility study, involving 79 patients, explored the use of SPIO-guided Magnetic resonance imaging (MRI)-lymphography and magnetic-guided axillary ultrasound (MagUS) with core biopsy for sentinel lymph node (SLN) localization and SLN status. MagUS, outperformed baseline axillary ultrasound and successfully traced SLNs in all cases, detecting macro-metastases accurately and missed only one micro-metastasis. The findings suggest that the MagUS technique enables minimally invasive approach in axillary mapping that can meet tailored patient needs and reduce the need for diagnostic surgery.
Paper II: This study aimed to compare skin staining incidence and size between different doses of SPIO and blue dye (BD), evaluating their persistence over time. Among 270 women receiving SPIO, 204 also received BD. At six months, 21.5% had SPIO stains and 25% had BD stains Incidence and size decreased reciprocally, with no significant difference between the tracers regarding skin staining after 24 months.
Paper III: This study compared the magnetic technique using Magseed® for non-palpable breast tumor localization with guidewire localization and SPIO for sentinel lymph node detection. In a prospective analysis of 426 women, reoperation rates, resection ratios, and SLN detection were assessed. No significant differences were found between the techniques in terms of re-excisions, resection ratios, or SLN detection. However, the magnetic technique showed more successful localizations, shorter operation time, and better overall experience among surgeons, radiologists, and theater coordinators, making it a good alternative for BCS.
Paper IV: In this prospective observational study, the impact of postoperative MRI outcome was explored in patients undergoing BCS with a peritumoral SPIO injection for SLN detection. The study affirms SPIO as a safe tracer for SLN detection without compromising MRI interpretation after BCS, ensuring reliable breast cancer recurrence assessment.
-
Transplantation of stem cell-derived islets as a treatment for type 1 diabetes
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-525235
Type 1 diabetes (T1D) is an autoimmune disease that leads to an immune attack on insulin-producing beta cells, necessitating lifelong insulin therapy. For individuals with brittle diabetes and poor metabolic control, the option of pancreatic human islet transplantation exists. However, the shortage of organ donors and the need for life-long immune suppressive agents pose significant challenges. Stem cell-derived islets (SC-islets) present a promising alternative for diabetes treatment.
This thesis explores the differentiation and transplantation of SC-islets as a treatment for diabetes. In paper I, three months post-transplantation, the ingrowth of recipient blood vessels and the neural density was higher in SC-islet grafts compared to human islet grafts. Furthermore, there was a higher tendency of blood flow, whereas the oxygenation was twice as high in SC-islet grafts. Both transplanted SC-islets and human islets had formation of amyloid depositions, which can affect the long-term survival and function of transplanted cells. In paper II, a humanized mouse model transplanted with SC-islets or human islets was validated. Transplanted SC-islets or human islets were not completely rejected 11 days after injection with human peripheral blood mononuclear cells (PBMCs). In vivo imaging and flow cytometry confirmed the presence of injected human immune cells, demonstrating an effective model for studying the human immune responses of allogeneically transplanted islets or SC-islets. In paper III, positron emission tomography (PET) imaging, using the DGCR2 affibody, for monitoring transplanted beta cells revealed successful binding to SC-islets and human islets in vitro. PET imaging in vivo demonstrated successful detection of the affibody in transplanted SC-islets. Although, the affibody could be optimized since the signal vanished 30 min after administration. However, DGCR2 remains a promising marker for SC-islet imaging. In paper IV, nanofiltration with a virus clearance filter paper during SC-islet differentiation was evaluated. Filter SC-islets expressed essential markers for beta cells during differentiation in comparable amounts as the control. The filtered SC-islets demonstrated physiological insulin-releasing function similar to that of the control. Nanofiltration did not seem to affect the differentiation of SC-islets.
In conclusion, transplantation of SC-islets is a promising future treatment for diabetes, however, long-term effects need to be evaluated.