Browsing by Subject "mikrovesikkeli"

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  • Aksela, Laura (Helsingfors universitet, 2016)
    Even though cancer treatment modalities have improved during last decades, there is still lack of specific, efficient and curative treatments especially in case of advanced and metastatic cancers. One relatively new approach is to use oncolytic adenoviruses, which selectively infect and kill cancerous cells leaving healthy cells unharmed. These viruses have shown to be effective especially when administered intratumorally and in combination with chemotherapeutics. However this approach has multiple challenges like rapid clearance by antibody neutralization in systemic administration. Another challenge is the cell entry of oncolytic adenovirus, which is mainly mediated by the Coxsackie-Adenovirus receptor and this receptor is downregulated in various cancer cells. Rapid clearance and reduced cell entry thus lead to decreased amount of oncolytic adenovirus in target cells and decreased efficacy. In order to overcome these limitations, this study explored the possibility to use cancer cell derived extracellular vesicles (EVs) as drug delivery system for oncolytic adenovirus. Since oncolytic adenoviruses have shown to be effective especially in combination with chemotherapeutics, the ability of EVs to deliver both oncolytic adenoviruses and chemotherapeutic drug paclitaxel was studied. The aims of this study were to i) study whether oncolytic adenoviruses could be encapsulated inside EVs (EV-virus complex) and load this complex with paclitaxel (EV-virus-PTX complex), ii) discover whether the surface charge or size distribution of EV-virus and EV-virus-PTX complexes differs from the control EVs and iii) study the infectivity/efficacy of EV-virus and EV-virus-PTX complex in comparison to noncapsulated adenovirus in vitro. Since this is a novel approach, the literature review focused on the characteristics, advantages and challenges of oncolytic adenoviruses and EVs. In order to determine whether cancerous cell are able to encapsulate oncolytic adenoviruses inside EVs, A549 lung cancer and PC-3 prostate cancer cells were infected with oncolytic adenovirus and the formed EVs were isolated form conditioned media using differential centrifugation. Paclitaxel was loaded into these EV-virus complexes with incubation. EV-virus complexes were imaged using transmission electron microscopy (TEM) (i). The characteristics of these EV-virus and EV-virus-paclitaxel complexes were studied by determining the surface charge by electrophoretic light scattering and the size distribution by nanoparticle tracking analysis (ii). In order to determine the infectivity/efficacy of these complexes in autologous use, three in vitro level assays were performed (cell viability, immunocytochemistry and transduction assay) (iii). In addition confocal microscopy was used to observe the localization of EV-virus complexes inside the cell. These studies pointed out that both cell lines were able to encapsulate oncolytic adenovirus inside EVs, which was observed by TEM. The size distribution of these EV-virus and EV-virus-PTX complexes may support this observation and the size was in range 50-500 nm. In addition the determined surface charge was shown to be similar in EV-virus and EV-virus-PTX- complexes when compared to control EVs derived from noninfected cells - however more specific assays in order to characterize the surface properties of EV-virus complexes are needed. As a main finding, these EV-virus and EV-virus-PTX complexes were shown to significantly increase the efficacy of oncolytic adenovirus in comparison to free oncolytic adenovirus, paclitaxel and paclitaxel+virus combination in all three in vitro assays. In addition localization of the EV-virus complex was seen with confocal microscopy imaging. These results indicate that EVs may enhance the delivery of oncolytic adenovirus into cancerous cells. Using EVs as a drug delivery system for both oncolytic adenovirus and chemotherapeutic drug paclitaxel was shown to increase the efficacy of oncolytic adenovirus in comparison to free virus. This characteristic could potentially enhance the targeting ability to cancerous cells and thus lead to decreased amount of side-effects of healthy tissues especially in case of chemotherapeutics. These promising results of this novel approach are however preliminary due to relatively low number of repetitions (n~3) and more research is needed especially in order to characterize, purify and concentrate the EV-virus complexes.
  • Valkonen, Sami (Helsingfors universitet, 2014)
    Microvesicles (MVs) are lipid bilayered membranous vesicles containing functional lipids, proteins, RNA and DNA that are produced by most cells. The physiological significance of MVs has become evident, and increased MV counts and the contents of MVs are nowadays also associated with different pathophysiological phenomena. The goal of the field is to use MVs as diagnostic and therapeutic tools. To achieve this, the understanding of the mechanisms of the functions of MVs should be understood better and additionally, reliable methods for the quantification and characterization of MVs should be developed and standardized. The aim of the study was to determine differences in platelet-derived MVs produced by different activation mechanisms. The second aim was to set up and optimize a protocol based on the reaction of sulphur, phosphate and vanillin (SPV) for measuring lipid content of MVs. The third aim was to study the effect of thrombin and proteinase inhibitor PPACK to the vesiculation of platelets. Platelets were isolated from the whole blood of healthy volunteers and vesicles were produced by platelet agonists mediating thrombogenic activation (thrombin and collagen, TC), pathophysiological activation (lipopolysaccharide, LPS) and Ca-ionophore (A23187) as positive control for vesiculation. Quantification and size determination of produced MVs was done using Nanoparticle Tracking Analysis (NTA). MVs were characterized by protein content using bicinchonic acid assay (BCA) and by lipid content using SPV-reaction. MVs had great activation-dependent differences in the lipid and the protein content. Activation with Ca-ionophore produced the most MVs, but the lipid and protein content was only a fraction from (patho)physiologically induced MVs. Only TC increased vesiculation. Vesicle subpopulations had significant difference in lipid content. Thrombin and proteinase inhibitor PPACK mediated inhibition of platelet formation in all of the activations, but the effect was not statistically significant. The mechanism of inhibition was likely to be proteinase inhibitor mediated. The isolation of vesicle populations using differential centrifugation proved to isolate studied populations only partially and the quantification method with NTA was susceptible to concentrated samples. SPV protocol reacted with different intensity to different lipids. In the future, quantification and isolation methods for MVs and the subpopulations of MVs should be improved. Additionally, to understand the physiologically relevant mechanisms of platelet-derived vesicle formation, the inhibitor experiments with PPACK should be continued, because the number of replicates was too low to see significant effects due to a large donor-dependent deviation. Since MVs are heterogenous cellular multitools affecting varying (patho)physiological phenomena, optimization and standardization of methods should be continued in order to study MVs properly.