Faculty of Biological and Environmental Sciences
Recent Submissions
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(2023)The intestinal stem cells (ISCs) adapt in response to environmental factors and continually proliferate to renew the mammalian intestinal epithelium due to its rapid turnover. Overall, intestinal homeostasis is maintained by the differentiation and self-renewal of ISCs, which are regulated by different mechanisms, including epigenetic histone modifications. Earlier studies in the host laboratory have shown that the histone methyltransferase Su(var)3-9 is essential in the nutrient-induced activation of intestinal stem cells. Su(var)3-9 specifically trimethylates histone H3 on lysine 9 (H3K9me3), which is a repressive histone mark, responsible for transcriptional silencing at heterochromatin regions. It influences stem cell maturation, lineage specification, and many other cellular processes. However, the precise mechanisms behind its function in ISCs remain unknown – that knowledge is important for understanding the development of many diseases, including cancer and metabolic disorders. This thesis aimed to investigate the distribution of the heterochromatin mark H3K9me3 in the intestine with an emphasis on ISCs, using the Drosophila midgut and mouse intestinal organoids as models. Confocal microscopy was used together with cell-type-specific fluorescent staining, to obtain the expression of the H3K9me3 specific histone methyltransferase Su(var)3-9, in the midgut. An antibody was used for the detection of H3K9me3 distribution along the anterior/posterior axis in Su(var)3-9 overexpressed flies. Additionally, DNA adenine methyltransferase identification (DamID) was applied in order to find target genes of the H3K9me3 regulation in the genome with the specific chromo domain of M-phase phosphoprotein 8 (MPHOSPH8) that binds to H3K9me3. The number of lineage-labeled differentiated enterocytes was shown to be locally higher in the Su(var)3-9 overexpressed flies compared with the control, although the flies were on starvation without nutrient-induced activation. Moreover, the number of lineage-labeled progenitor cells was not remarkably altered between the samples. However, the intensity of H3K9me3 was significantly higher throughout the whole midguts in the Su(var)3-9 overexpressed flies in comparison to the control. According to one replicate, the DamID in mouse intestinal organoids revealed that the peaks of H3K9me3 were divergent between the samples grown in different conditions. The first sample was assumed to contain more ISCs, whereas the other one was assumed to contain more differentiated intestinal cells. According to my results, the Su(var)3-9 overexpression drives the stem cells against the differentiation of enterocytes. Furthermore, the MPHOSPH8 chromo domain in the organoids was successfully applied in DamID; thus, more replicates should be prepared for additional analysis, because I found several potential target genes of H3K9me3. In the future, it is important to further study the epigenetic regulation of ISCs, for applying the epigenetic marks as targets for the treatment of many human pathophysiological conditions, such as cancer, obesity, and metabolic disorders.
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(2023)Morphological features are considered as markers of microglial functionality, and they show regional heterogeneity in the brain. Recently the sleep-wake cycle was shown to affect microglial morphology in mice and correlate with cortical sleep slow wave activity (SWA). Microglial sizes and ramification increased during the dark period and decreased during the light period in cerebral areas associated with SWA, suggesting that neuronal activation could be affecting microglial morphology through SWA. I studied microglia in the hindbrain areas with and without functional connection to SWA to further investigate the association between SWA and alterations in morphology, and to investigate if there are differences in microglial morphology and their diurnal alterations in brain regions other than those commonly investigated. I examined three hindbrain areas (cerebellar cortex (CC), deep cerebellar nucleus (DCN) and medial vestibular nucleus (MVN)) and somatosensory cortex (SC) of mice (n=15) at two timepoints: 6 hours after the light onset (high SWA) and offset (low SWA). My aims were to answer if there are morphological differences in microglia between 1) the four brain areas at both timepoints and 2) between the two timepoints in each brain area. My hypotheses were that CC and DCN which have functional connections to cortical SWA, would show similar diurnal morphology alterations as demonstrated in the cerebral areas, and MVN that has no known cortical SWA connection, would lack significant alterations. As microglia are heterogenous throughout brain, I expected microglia to differ between different brain areas, especially the hindbrain and the SC. I found that microglial morphologies significantly differed between the hindbrain and the cortex, while the hindbrain areas were more similar in morphology. Moreover, the brain areas demonstrated diurnal morphology alterations of microglia with varying extent: CC and DCN microglial morphology did not correlate with SWA as clearly as SC did, and interestingly, morphological features of MVN microglia showed a pattern opposite to other areas, microglia being larger during the light period than the dark period. These results highlight the importance of the diurnal time to microglial morphology and the heterogeneity of microglia between different brain regions.
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(2023)Microglia, the resident macrophage-like glial cells of the central nervous system (CNS), form the first line of defense against pathogens in the brain, and regulate both innate and adaptive immunity. Any abnormalities in their microenvironment lead to microglial activation, characterized by alterations in their gene expression, morphology, and functional behavior. Once activated, microglia respond to CNS injury and inflammation by, e.g., migrating to the site of damage, releasing pro-inflammatory cytokines, as well as phagocyting cell debris and pathogens. Prolonged activation of microglia expressing pro-inflammatory phenotypes can lead to exacerbated CNS damage. Hence, limiting CNS inflammation by stimulating microglial polarization towards their pro-resolving phenotypes would be of great clinical relevance. The research of our laboratory focuses on CNS injury and repair, as well as finding novel therapies for ischemic stroke. Specialized pro-resolving mediators (SPMs) derived from essential fatty acids have been proposed to offer a potential therapeutic approach for ischemic stroke via promoting resolution of post-stroke inflammation. Previous studies have revealed the ability of SPMs to induce a transformation of macrophages, the immune cells strongly resembling microglia, towards their anti-inflammatory phenotypes. The aim of this study was therefore to assess whether SPMs have similar effects on BV2 microglia, specifically on their lipopolysaccharide (LPS)-induced production of pro-inflammatory cytokines, tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6). In addition to assessing the cytokine levels, our aim was to determine the optimal conditions for studying the effects of SPMs on microglial migration. In the present study, the levels of TNF-α and IL-6 were determined by specific ELISAs, and the transwell assay was used to measure microglial migration. Resolvins E1 (RvE1) and D1 (RvD1), as well as protectin D1 (PD1) and 15-epimer of lipoxin A4 (15-epi-LXA4) were all associated with decreased levels of TNF-α and IL-6, with RvE1 having the most potential as a resolving agent. In addition, we observed that serum starvation notably decreases the release of IL-6 and affects microglial migration. Overall, our results support the idea that SPMs could provide a novel therapeutic strategy for stroke therapy as they contribute to the resolution of CNS inflammation.
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(2023)Research into animal emotions is important for improving animal welfare and understanding behavior. Emotional research also provides a better overview of ecology and helps from the point of view of protection. According to the consensus, animals feel different emotions and express their feelings in many ways. Emotional expression is also an important part of communication between animals. In my research, I wanted to study zoo visitors’ ability to interpret animals’ emotions. The study was conducted in Korkeasaari as a survey, where respondents were asked to rate animals’ valence and arousal based on short video clips. According to several theories, valence and arousal are two important dimensions of emotion. Interpretation is based on movements, expressions, and gestures of one animal or several animals. In my research, I used videos of Barbary macaque, Siberian tiger, and Markhor expressing different emotions. The aim of this study was to explore if there are differences in participants ratings between the species. In addition, I explored whether a specific emotion is interpreted better than others. I expected that, based on an evolutionary distance, the emotions of the Barbary macaque would be interpreted best despite the emotion. Secondly, I expected the best identification of negative Valence and high arousal, which would be important for evolution and survival. I found that the valence of the barbary macaque was interpreted best, but the arousal of the markhor was interpreted as well as the Barbary macaques. Different emotions were interpreted differently in each specie. The interpretation of emotions is also influenced by the participant’s demographic factors such as age and gender. Differences in ratings between the species may also be explained by species-specific factors such as the extent of the emotional scale to be expressed or need to express emotions. Together with other similar studies, the aim of this study is to improve animal welfare and to increase interest and knowledge of animal emotions.
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(2023)Climate change severely threatens ecosystem services and human well-being: vegetation and soils underneath it can be particularly vulnerable to climate warming. Soils hold the largest carbon stock in terrestrial ecosystems, and urban park soils, especially in cool climates, can hold remarkable carbon stocks and may be able to offset some atmospheric CO2 emissions. Land use changes, such as urbanization, influence soil organic carbon formation and soil carbon storages. In this study, I was interested whether three vegetation types (deciduous trees, conifers and lawn) differ in their capacity to store C in their rhizosphere, and whether this is affected by park size. I measured the proportion of tree canopy layer in class A park areas of the city of Helsinki, to estimate soil C storages of these areas and to examine C density (kg C m-2). Proportions of tree canopy layers in different park size groups were measured using QGIS and ortographs. Soil C storages were calculated using existing soil C data and average proportions of conifer and deciduous trees in parks of the city of Helsinki. Park size had a significant effect on proportion of the tree canopy coverage: canopy cover decreases with an increase in park size. Especially large parks are dominated by lawn. The average soil C densities in small, medium and large parks were 23.98 kg C m-2, 23.47 kg C m-2 and 23.15 kg C m-2, respectively. However, the overall proportion of conifer canopy in parks of the city of Helsinki is rather small, resulting in small differences in C densities between different park size categories, despite significant differences in tree canopy coverage between the three size groups. Most of the stored soil C in parks of the city of Helsinki are under lawn, even though it is the least efficient of the three studied vegetation types (deciduous trees, conifers, lawn) in soil C sequestration. Within a park size category and at park level, large parks store the highest amount of carbon per park. Even so, at the city level, the total amount of carbon is highest in the small parks due to their high number. Conifer trees associate with improved C sequestration to soils compared to deciduous trees and lawn. Increasing the amount of conifer trees in urban parks thus likely increase the important C storages of these soils. Results of this study highlight the importance of the contribution of urban parks and especially conifer trees in carbon sequestration. Future research related to urban soil C sequestration and the effects of vegetation type and climatic conditions is needed to better understand soil C accumulation and how the C sequestration of urban park soils could be enhanced.