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.
-
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.
-
The role of imaging in follow-up and prognosis of patients radically operated for melanoma
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-525153
Cutaneous malignant melanoma (CMM) is the cancer type in Sweden with the most rapidly increasing incidence. This thesis investigated if whole-body imaging improves the follow-up scheme post-surgery in high-risk CMM patients and explored the long-term outcomes for early-stage melanoma patients compared to the general population.
We launched the nationwide randomized phase III study: “Trial to assess the Role of Imaging after radical surgery of CMM stage IIB-C and III (TRIM study, NCT 03116412)” with allocation to physical examinations for three years according to Swedish national guidelines +/- five scheduled whole-body imaging procedures. Primary endpoint is overall survival (OS) at five years. Secondary endpoints include Health-Related Quality of Life (HRQoL) outcomes.
In paper I, the TRIM study protocol and the recruitment status were described and evaluated. Based on enrollment of more than 550 patients at 19 centra, we found the study protocol feasible and identified some obstacles for optimal inclusion rate.
In paper II, we evaluated HRQoL and anxiety/depression in > 200 patients in the TRIM study who responded to the Hospital Anxiety and Depression (HAD) scale and the EORTC Quality of Life Questionnaire (QLQ)-C30 at baseline and after one year. No statistically significant differences were found between the study arms. Levels of anxiety and depression symptoms were generally low.
The Malignant Melanoma Database Sweden (MMBaSe) was created by record linkages between the Swedish Melanoma Register and several population-based registers. The MMBaSe includes 67 000 individuals diagnosed with CMM or melanoma in situ (MIS) between 1996 and 2018 and matched, randomly selected, melanoma-free comparators representing the general population.
Overall survival and mortality risks were assessed in two cohort studies in patients with MIS (paper III) and thin CMM (≤ 1 mm) (paper IV) in comparison to their matched comparators. Mortality risks were adjusted for socioeconomic status (SES) and comorbidities. We found several statistically significant differences. Individuals diagnosed with melanoma had higher SES and a lower comorbidity burden. While melanoma patients were at higher risk of dying from CMM, they had lower risks of dying from several other diseases.
In paper III we found a better OS and a lower risk of death in MIS patients, findings that remained after adjustments.
In paper IV, patients with thin CMM had a similar OS as the general population. In individuals with stage T1a disease (< 0.8 mm), the OS at 5 years was slightly better than in comparators.