Low impedance and highly transparent microelectrode arrays (MEA) for in vitro neuron electrical activity probing

International audienceIn this study, we present the microfabrication and characterization of a transparent microelectrode array (MEA) system based on PEDOT:PSS for electrophysiology. The influence of the PEDOT:PSS electrode dimensions on the impedance was investigated and the stability over time under physiological environment was demonstrated. A very good transparency value was obtained by our system displaying one of the best impedance and transmittance values when compared to other transparent MEA. After biocompatibility validation, we successfully recorded spontaneous neuronal activity of primary cortical neurons cultured over 4 weeks on the transparent PEDOT:PSS electrodes. This work shows that microelectrodes composed of PEDOT:PSS are very promising as a new tool for both electrophysiology and fluorescence microscopy studies on neuronal cell cultures

Isolation of microglia-derived extracellular vesicles: towards miRNA signatures and neuroprotection

International audienceThe functional preservation of the central nervous system (CNS) is based on the neuronal plasticity and survival. In this context, the neuroinflammatory state plays a key role and involves the microglial cells, the CNS-resident macrophages. In order to better understand the microglial contribution to the neuroprotection, microglia-derived extracellular vesicles (EVs) were isolated and molecularly characterized to be then studied in neurite outgrowth assays. The EVs, mainly composed of exosomes and microparticles, are an important cell-to-cell communication process as they exhibit different types of mediators (proteins, lipids, nucleic acids) to recipient cells. The medicinal leech CNS was initially used as an interesting model of microglia/neuron crosstalk due to their easy collection for primary cultures. After the microglia-derived EV isolation following successive methods, we developed their large-scale and non-targeted proteomic analysis to (i) detect as many EV protein markers as possible, (ii) better understand the biologically active proteins in EVs and (iii) evaluate the resulting protein signatures in EV-activated neurons. The EV functional properties were also evaluated in neurite outgrowth assays on rat primary neurons and the RNAseq analysis of the microglia-derived EVs was performed to propose the most representative miRNAs in microglia-derived EVs. This strategy allowed validating the EV isolation, identify major biological pathways in EVs and corroborate the regenerative process in EV-activated neurons. In parallel, six different miRNAs were originally identified in microglia-derived EVs including 3 which were only known in plants until now. The analysis of the neuronal proteins under the microglial EV activation suggested possible miRNA-dependent regulation mechanisms. Taken together, this combination of methodologies showed the leech microglial EVs as neuroprotective cargos across species and contributed to propose original EV-associated miRNAs whose functions will have to be evaluated in the EV-dependent dialog between microglia and neurons

Reversal of RNA toxicity in myotonic dystrophy via a decoy RNA-binding protein with high affinity for expanded CUG repeats

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