MiR-219a-5p Enriched Extracellular Vesicles Induce OPC Differentiation and EAE Improvement More Efficiently Than Liposomes and Polymeric Nanoparticles.

Remyelination is a key aspect in multiple sclerosis pathology and a special effort is being made to promote it. However, there is still no available treatment to regenerate myelin and several strategies are being scrutinized. Myelination is naturally performed by oligodendrocytes and microRNAs have been postulated as a promising tool to induce oligodendrocyte precursor cell differentiation and therefore remyelination. Herein, DSPC liposomes and PLGA nanoparticles were studied for miR-219a-5p encapsulation, release and remyelination promotion. In parallel, they were compared with biologically engineered extracellular vesicles overexpressing miR-219a-5p. Interestingly, extracellular vesicles showed the highest oligodendrocyte precursor cell differentiation levels and were more effective than liposomes and polymeric nanoparticles crossing the blood-brain barrier. Finally, extracellular vesicles were able to improve EAE animal model clinical evolution. Our results indicate that the use of extracellular vesicles as miR-219a-5p delivery system can be a feasible and promising strategy to induce remyelination in multiple sclerosis patients.

Recording and assessment of evoked potentials with electrode arrays.

In order to optimize procedure for the assessment of evoked potentials and to provide visualization of the flow of action potentials along the motor systems, we introduced array electrodes for stimulation and recording and developed software for the analysis of the recordings. The system uses a stimulator connected to an electrode array for the generation of evoked potentials, an electrode array connected to the amplifier, A/D converter and computer for the recording of evoked potentials, and a dedicated software application. The method has been tested for the assessment of the H-reflex on the triceps surae muscle in six healthy humans. The electrode array with 16 pads was positioned over the posterior aspect of the thigh, while the recording electrode array with 16 pads was positioned over the triceps surae muscle. The stimulator activated all the pads of the stimulation electrode array asynchronously, while the signals were recorded continuously at all the recording sites. The results are topography maps (spatial distribution of evoked potentials) and matrices (spatial visualization of nerve excitability). The software allows the automatic selection of the lowest stimulation intensity to achieve maximal H-reflex amplitude and selection of the recording/stimulation pads according to predefined criteria. The analysis of results shows that the method provides rich information compared with the conventional recording of the H-reflex with regard the spatial distribution.

Effects of dietary or injected organic cations on larval Drosophila melanogaster: mortality and elimination of tetraethylammonium from the hemolymph.

This study of larval Drosophila melanogaster examined the effects of injecting the prototypical organic cation tetraethylammonium (TEA) into the hemocoel or adding TEA and/or other organic cations to the diet. Mortality, hemolymph TEA levels, and Malpighian tubule TEA secretion rates were measured. The LD50 for dietary TEA was 158.4 mM and mortality increased if competitive inhibitors of organic cation transporters were also included in the diet. Mortality increased from 24% on TEA (100 mM) alone to 83 and 67% when the diet contained both TEA and quinidine (10 mM) or cimetidine (100 mM), respectively. TEA-selective microelectrode measurements indicated that hemolymph TEA concentration was approximately 3% of that in the diet for larvae maintained on TEA-enriched diet for 24 h. Malpighian tubules isolated from larvae exposed to dietary TEA excreted more TEA than did tubules from controls fed a TEA-free diet. However, the rate of decline of hemolymph TEA concentration following ingestion or injection of TEA into the hemocoel was greater than that explicable by rates of active transport by the gut and Malpighian tubules (MTs). We propose that TEA concentrations in the hemolymph are reduced not only by active transport across the MTs and gut, but also by diffusion into the gut. The latter pathway is particularly important when larvae previously maintained upon TEA-enriched diet are transferred to a TEA-free diet. The ingestion of TEA-free food not only clears the gut lumen, but also creates a TEA-free compartment into which TEA may passively diffuse from the hemolymph.

Diuretic factors and second messengers stimulate secretion of the organic cation TEA by the Malpighian tubules of Drosophila melanogaster.

This study showed that four factors which stimulate transepithelial fluid secretion and inorganic ion transport across the main segment of the Malpighian tubules of Drosophila melanogaster also stimulate transepithelial secretion of the prototypical organic cation tetraethylammonium (TEA). TEA fluxes across the Malpighian tubules and gut were measured using a TEA-selective self-referencing (TEA-SeR) microelectrode. TEA flux across isolated Malpighian tubules was also measured using a TEA-selective microelectrode positioned in droplets of fluid secreted by tubules set up in a modified Ramsay assay. TEA flux was stimulated by the intracellular second messengers cAMP and cGMP, which increase the lumen-positive transepithelial potential (TEP), and also by tyramine and leucokinin-I (LK-I), which decrease TEP. The largest increase was measured in response to 1 micromol l-1 LK-I which increased transepithelial TEA flux by 72%. TEA flux in the lower tubule was stimulated slightly (13%) by 1 micromol l-1 tyramine but not by any of the other factors. TEA flux across the midgut was unaffected by cAMP, cGMP or tyramine. This is the first study to demonstrate the effects of insect diuretic factors and second messengers on excretion of organic cations.