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Présentation du projet

Bourses d’excellence Marie Skłodowska-Curie

L’unité travaille notamment sur les protéinopathies, les myélinopathies, la remyélinisation, les neurostéroïdes et la neuroinflammation au sein du réseau hospitalier Bicêtre. Nous accompagnons les jeunes scientifiques vers une position permanente via les bourses d’excellence Marie Skłodowska-Curie.

Sujet de recherche

Therapeutic modulation of microglia by CSF1R inhibition in Alzheimer's disease

Alzheimer's disease is neuropathologically characterized by the abnormal accumulation of aggregated proteins that form β-amyloid plaques, leading to the formation and spread of tau protein aggregates within neurons. These lesions contribute to neurodegeneration, which causes cognitive impairment. Microglia, the brain's resident innate immune cells, are key regulators of Alzheimer's disease. These cells maintain brain integrity by phagocytosing protein debris and repairing damaged synapses. In the context of Alzheimer's disease, microglia proliferate and become activated in response to the presence of amyloid and tau lesions. However, this microglial reactivity triggers a pro-inflammatory response suspected of exacerbating the progression of Alzheimer's disease. Today, the nature of the interactions between microglial functions and the pathophysiology of Alzheimer's disease remains to be elucidated in order to develop therapies that direct microglia towards a protective role against Alzheimer's disease. Pharmacological modulation of microglia using CSF1R inhibitors has shown beneficial effects in amyloid mouse models, including improved memory, reduced Aβ plaques, prevention of synaptic degeneration [1, 2]. However, transgenic AD mouse models poorly recapitulate human microglial signatures [3], highlighting the need to assess microglial regulation in primates before human studies. The AD-induced mouse lemur, developed in our laboratory by intracerebral inoculation of human AD brain extracts, recapitulates key features of human AD [4]. This project aims to investigate the impact of microglial regulation via a CSF1R inhibitor on AD pathology in this primate model.

Our laboratory has already developed cohorts of AD-induced mouse lemurs (iAD, n=5) and control animals (iCTL, n=5). A second iAD cohort (n=5) received CSF1R inhibitor treatment for six months starting at 12 months post-injection (mpi). Already available results indicate a beneficial cognitive effect, and the current work aims to elucidate the underlying protective mechanisms. The main work involved in this project concerns the evaluation of neuropathological changes underlying cognitive improvements in 18 mpi animals. Neuropathological investigation will involve Aβ and tau pathologies, microglia and astrocytes evolution as well as neuronal and synaptic impairments. In parallel, thanks to an already initiated work, transcriptomic changes underlying AD pathology and cognitive improvements will be implemented.

Overall, this project will define the neuropathological and molecular changes underlying cognitive improvement in AD. It will provide key insight into microglial roles in AD and supports development of neuroimmune therapeutic strategies.

Techniques utilisées

• Neuropathological evaluation (Immunohistochemistry & Histology).
• Microscopy, image analysis and particle quantification (ImageJ).
• Evaluation of Aβ and tau pathologies, neuroinflammation (Microglia/Astrocytes), and synaptic integrity.
• Transcriptomic data implementation and molecular analysis.

Références clés

1. Olmos-Alonso A et al. (2016) Regulation of Colony-Stimulating Factor 1 Receptor Fastens Microglial Proliferation and Ameliorates Progression of Alzheimer's Disease. Brain.
2. Hu Y et al. (2021) CSF1R inhibitor attenuates neuroinflammation and microglial reactivity in Alzheimer's models.
3. Boche D et al. (2021) Transgenic AD mouse models and human microglial signatures discrepancy.
4. Lam S et al. (2021) Intracerebral inoculation of human AD brain extracts in mouse lemurs recapitulates human AD features.

Sujet de recherche

Characterization and targeting of proteopathic seed-containing extracellular vesicles in neurodegenerative diseases

Neurodegenerative diseases are highly diverse in terms of pathophysiology and associated clinical profiles but share overlapping underlying mechanisms. The aggregation of relatively few different proteins such as α-synuclein (αSyn), Tau, and amyloid-β (Aβ) are responsible for a large number of proteinopathies. These include α-synucleinopathies such as Parkinson disease (PD), tauopathies such as Alzheimer disease (AD), or mixed pathologies such as AD and dementia with Lewy bodies (DLB). The spreading of protein deposits within the brain is key to the evolution of the clinical symptoms. This prion-like process involves the transmission of proteopathic Tau, αSyn and Aβ ‘seeds’ to unaffected cells where they act as templates for further aggregation of soluble homotypic proteins. Accordingly, intensive efforts have been made to block proteopathic seeding with specific antibodies against oligomeric and/or fibrillar pathological proteins, with only a few promising results in clinical studies. The efficacy of immunotherapy depends critically on the route by which proteopathic seeds are transmitted from one neuron to the next. Whereas free proteins in the extrasynaptic space can in principle be easily targeted by antibodies, membrane-encapsulated forms as in extracellular vesicles (EVs) may escape sequestration and inactivation because their protein cargo could be hidden from antibodies.

Brain-derived EVs are lipid bilayer-enclosed nanosized particles released by both neurons and glial cells. EVs are heterogeneous, displaying a broad range of sizes, macromolecular cargo (proteins, nucleic acids, metabolites) and (sub)cellular origins. EVs have the potential to cross biological barriers, including the blood-brain barrier, and can be isolated from cerebrospinal fluid and postmortem brain tissue. Furthermore, their content reflect the physiological state of the brain in both healthy and disease conditions, which makes them a promising source of biomarkers. Of particular interest is the significant role played by EVs in the propagation of proteopathic Tau, Aβ and αSyn seeds. Which EV subpopulations carry seeds and whether they differ among different neurodegenerative pathologies remains poorly documented.

Our working hypothesis is that the EVs containing seeds bear distinct molecular features and that deciphering these specific signatures will not only improve our knowledge of the mechanisms underlying these diseases, but could also help identify effective therapeutic targets and novel diagnostic and prognostic biomarkers. The objectives of this project are 1) to isolate and characterize EV sub-populations containing pathological αSyn and Tau seeds from AD and DLB brains; 2) to measure the efficacy of antibodies and nanobodies to specifically target seed-containing EVs using seed amplification assays as a readout.

Techniques utilisées

• Biochemistry: EV isolation, Western blots, immunoprecipitation, protein purification, TRPS, seed amplification assays.
• Flow cytometry.
• Electron microscopy.
• Super-resolution microscopy (SMLM).

Sujet de recherche

Interluminescent modulation of neural circuits to promote rehabilitation after spinal cord injury [optoSCI]

Spinal cord injury (SCI) is a major public health concern for which there is still no cure. While epidural electrical stimulation is a promising strategy to promote rehabilitation, it requires sophisticated spatiotemporal modulation to operate in humans. Interluminescence—light across a synapse—allows for non-invasive, activity-dependent, and self-regulating modulation of neural circuits. Our hypothesis is that interluminescent neuromodulation of genetically targeted proprioceptive interneurons can improve functional outcomes after SCI.

The project is structured around three main aims. First, we will identify cross-species genetic markers of V1 and V2a interneurons, which are crucial in reorganizing spinal circuits. This involves single nuclei transcriptomic analysis of human spinal cord samples to determine clusters homologous to mouse subpopulations. Second, we will achieve targeted delivery of interluminescent tools using a single ConVERGD vector injected into the lumbar spinal cord of triple-transgenic mice. This allows the expression of presynaptic luciferase and postsynaptic ChRmine opsin to confirm interluminescence-mediated neural activity. Finally, we will test the potential of this strategy to promote locomotor recovery in a mouse model with a T10 crush injury, assessing kinematics and utilizing snRNA-seq prioritization.

Impact and Significance: This project will provide a new translational framework for genetically targeted, synapse-specific, and noninvasive modulation of spinal circuits. By adopting a more “ecological” and self-regulating approach, our interluminescent strategy has the potential to overcome the main hurdles toward successful targeted neuromodulation after SCI.

Techniques utilisées

• Transcriptomics & Bioinformatics: Single nuclei RNA sequencing (snRNA-seq) on human and mouse tissues, Machine Learning classifiers.
• Optogenetics & Bioluminescence: Interluminescent tools (luciferase/opsin), ConVERGD vector design and viral tracing.
• In vivo models: Stereotaxic intraspinal injections, T10 crush spinal cord injury model in triple-transgenic mice.
• Behavioral & Histological Analysis: Quantitative kinematics for locomotor recovery, cFos markers for neural activity validation.