Browsing by study line "Regenerative medicine"

Intestinal epithelium is capable of rapid regeneration, which is associated with transient changes in cellular identity. Some of these changes involve an enrichment of fetal-like gene expression and simultaneous suppression of adult stem cell signature. Interestingly, the upregulation of fetal-like marker Stem cell antigen 1 (Sca1) is modulated by extracellular matrix (ECM) which is known to guide epithelial cells during regeneration. Our recently published decellularized small intestinal ECM (iECM) system retains the composition and topology of natural ECM. This makes it an attractive system for ex vivo studies addressing regeneration. This thesis aimed to gain insight into the fetal-like identity and its dynamics using an ex vivo iECM system. Intriguingly, Sca1 expressing cells on iECM displayed migratory features, such as a leading edge and changes in nuclear morphology. Curiously, these features are typical for epithelial cells during development. Furthermore, based on marker gene expression during iECM re-epithelization, fetal-like state was upregulated while adult stem cell state was downregulated, revealing a gradually emerging inverse correlation. Additionally, data suggests that circadian rhythms may have a role in modulating the fetal-like state. iECM from an active-state mice indicated a reduced capability to induce fetal-like identity and overall re-epithelization compared to the rest-state iECM. The results of this thesis suggest further potential of iECM system in studying emergence of fetal-like state during re-epithelization and circadian rhythm impact on it.

MELAS syndrome is a multi-organ disorder with a wide range of clinical manifestations, including hearing loss, cardiomyopathy, retinopathy, and stroke-like events. It can also be associated with type 2 diabetes. Eighty per cent of MELAS Syndrome cases have a 3243A>G mutation in the MTTL1 gene, which codes for tRNA (Leu-UUR). Although the exact cause of MELAS syndrome remains unknown, microvascular angiopathy and endothelial dysfunction, which result in reduced microvascular perfusion, are assumed to have a role in the reported phenotype. Yet, it is unclear how important this depicted angiopathy is in general and how it relates to the disease-specific stroke-like episodes in particular. In this thesis, I employed MELAS-patient-derived human induced pluripotent stem cell (hiPSC)-derived endothelial cells (EC) under flow as a disease model to investigate the possibility of an altered endothelial cell phenotype or function that could account for the disease phenotype. I used hiPSCs from healthy controls and patient-derived iPS-cell lines from MELAS patients with the 3243A>G mutation with different levels of heteroplasmy in all the experiments. Transcriptional patterns reflecting the flow response were observed, demonstrating that the MELAS hiPSC-EC cells respond to a flow stimulus. In the high-heteroplasmy cell lines, there was a significant downregulation of genes related to one carbon folate metabolism and serine biosynthesis, especially in response to flow, and these changes were also indicated in basal conditions. This is interesting as the same metabolic pathways have been shown dysregulated in other mitochondrial diseases. This study showed no appreciable difference in the mitochondrial oxygen respiration rate between MELAS-patient and control hiPSC-EC. These findings could link the disease phenotype to this web of pathways and explain the mechanism underlying the pathophysiology of MELAS syndrome.