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  Glial and vascular contributions to neurodegenerative diseases
October 11, 2022, 15:40 - 16:40
43 and TREM2, in vitro and in vivo, in hTDP-43-expressing transgenic mouse brains. We computationally identified the region within hTDP-43 that interacts with TREM2 and observed the potential interaction in ALS patient tissues. Our data reveal the novel interaction between TREM2 and TDP-43, highlighting that TDP-43 is a potential ligand for microglial TREM2 and the interaction mediates neuroprotection of microglial TREM2 in TDP-43-related neurodegeneration.
Cerebrospinal fluid (CSF) contains a tightly regulated immune system. Yet, little is known about how CSF immunity is altered with aging or neurodegenerative disease. Here, we performed single cell RNA sequencing on CSF collected from 45 cognitively normal subjects ranging from 54-82 years old. We reveal upregulation of lipid transport genes in activated monocytes with age. We then compared this cognitively normal cohort to 14 cognitively impaired subjects. In cognitively impaired subjects, downregulation of lipid transport genes in activated monocytes occurred concomitantly with altered antigen presentation and cytokine signaling to CD8 T cells. Clonally expanded CD8 T cells upregulated C-X-C Motif Chemokine Receptor 6 (CXCR6) in cognitively impaired subjects. The CXCR6 ligand, C-X-C Motif Chemokine Ligand 16 (CXCL16), a chemoattractant and lipoprotein receptor, was elevated in CSF of cognitively impaired subjects. Cumulatively, these results identify CXCL16-CXCR6 signaling as a mechanism for antigen- specific T cell entry into brains with neurodegeneration.
Recent research have suggested that the elimination of senescent brain cells via use of senolytic compounds could constitute an exciting new therapeutic avenue for Alzheimer’s disease (AD) intervention. Much of this data comes from in vivo mouse studies and the particular senescent cell type responsible for cognitive loss is hotly disputed. Whether human neurons in particular undergo a senescent-like phenotype is still under considerable debate. Therapeutic use of senolytics is further complicated by the complex cellular milieu of the human brain and whether senolytic dosages can be identified which are capable of selectively eliminating relevant senescent CNS cell types without eliciting toxic ‘off-target’ effects on healthy non-senescent cells. We recently developed a novel human in vitro model consisting of long- term human primary neuronal:astrocytic cultures. Neurons within these mixed cell populations express the neuronal markers MAP2 and NeuN as well as 3R tau, absent in mice, and 4R tau and astrocytes express GFAP. Both populations develop a senescent-like phenotype following a single treatment with amyloid beta (Aβ) oligomers (AβO) not observed following treatment with Aβ fibrils (AβF). We subsequently utilized these cultures to assess the efficacy of senolytic compounds versus selective senescent cell killing via human natural killer immune cells (NK92). Treatment with NK92, but not the widely-used pharmacological senolytics Navitoclax (NAV) or Dasatinib plus quercetin (DQ), was found to selectively eliminate senescent neurons. In contrast, NAV appeared to indiscriminately eliminate all human neurons while DQ had no effect at the dosages used. Differing effects occurred in astrocytic populations which required much higher dosages of NAV for their elimination resulting in indiscriminate neuronal killing, while neither NK or DQ had
The Parkinson’s disease-associated mutation LRRK2-G2019S alters astrocyte differentiation dynamics and induces senescence in midbrain organoids
Silvia Bolognin1, Lisa Smits, Stefano Magni, Kamil Grzyb, Sarah Nickels, Georgia Woods, Mudiwa Muwanigwa, Paul Antony, Krüger Rejko, Julie Andersen, Enrico Glaab,
Alexander Skupin, Jens Schwamborn
1University Of Luxembourg, Luxembourg
   BACKGROUND: Astrocytes are active players in the etiology of Parkinson’s disease (PD), but the mechanisms through which they might contribute to neurodegeneration are still largely unknown. One of the most common pathogenic mutations causing familial PD is the G2019S mutation in the leucine-rich-repeat-kinase-2 (LRRK2). This mutation is of particular interest because it is a risk factor for sporadic PD besides being associated with the familial form of the pathology.
MATERIAL & METHODS: To investigate the role of astrocytes in PD neurobiology we used autoptic brain samples and human neuroepithelial stem cells (NESCs) derived from patient-specific iPSCs carrying the LRRK2-G2019S mutation and from healthy individuals, both with their isogenic controls. NESCs were either differentiated into astrocytes in 2D or used for the generation of midbrain organoids. RESULTS: We observed that astrocyte differentiation is impaired both in 3D midbrain organoids and 2D cultures from PD patients carrying the LRRK2-G2019S mutations compared to isogenic lines and healthy individual controls. Using single-cell RNA-sequencing, we observed that the LRRK2-G2019S mutation delays the astrocyte differentiation trajectory and reduces the acquisition of functional competence by predisposing to the acquisition of a reactive phenotype. LRRK-G2019S astrocytes are also more inclined to undergo senescence. The treatment with an activator of the transcription factor NR2F1, involved in several phases of brain development, ameliorated the observed astrocyte phenotypes.
CONCLUSIONS: These data show that the LRRK2-G2019S mutation impairs astrocyte specification and predisposes to a senescent phenotype.
Triggering receptor expressed on myeloid cell 2 (TREM2) is a surface receptor that, in the central nervous system, is exclusively expressed on microglia. TREM2 variants have been linked to increased risk for neurodegenerative diseases, but the functional effects of microglial TREM2 remain largely unknown. Here we investigated TAR-DNA binding protein 43 kDa (TDP-43)-related neurodegenerative disease via viral-mediated expression of human TDP-43 protein (hTDP-43) in mice or inducible expression of hTDP43 with defective nuclear localization signals in transgenic mice. We found that TREM2 deficiency impaired microglia phagocytic clearance of pathological TDP-43, and enhanced neuronal damage and motor function impairments. Mass cytometry analysis revealed that hTDP-43 induced a TREM2-dependent subpopulation of microglia with high CD11c expression and higher phagocytic ability. Using mass spectrometry and surface plasmon resonance, we further demonstrated an interaction between TDP-
Cerebrospinal fluid immunity in aging and neurodegenerative disease
David Gate1
1Northwestern University, Chicago, USA
Senescent-like human primary neurons undergo selective human immune NK cell-mediated clearance
Julie Andersen1, Suckwon Lee, Ellen Wang, Chaska Walton
1Buck Institute For Research On Aging, Novato, USA
TREM2 mediates microglial neuroprotection against TDP-43 neurodegeneration
Long-Jun Wu1
1Mayo Clinic, Rochester, USA

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