Multisensory gamma stimulation promotes glymphatic clearance of amyloid

The glymphatic movement of fluid through the brain removes metabolic waste1-4. Noninvasive 40 Hz stimulation promotes 40 Hz neural activity in multiple brain regions and attenuates pathology in mouse models of Alzheimer's disease5-8. Here we show that multisensory gamma stimulation promotes the influx of cerebrospinal fluid and the efflux of interstitial fluid in the cortex of the 5XFAD mouse model of Alzheimer's disease. Influx of cerebrospinal fluid was associated with increased aquaporin-4 polarization along astrocytic endfeet and dilated meningeal lymphatic vessels. Inhibiting glymphatic clearance abolished the removal of amyloid by multisensory 40 Hz stimulation. Using chemogenetic manipulation and a genetically encoded sensor for neuropeptide signalling, we found that vasoactive intestinal peptide interneurons facilitate glymphatic clearance by regulating arterial pulsatility. Our findings establish novel mechanisms that recruit the glymphatic system to remove brain amyloid.

Human microglial state dynamics in Alzheimer's disease progression

Altered microglial states affect neuroinflammation, neurodegeneration, and disease but remain poorly understood. Here, we report 194,000 single-nucleus microglial transcriptomes and epigenomes across 443 human subjects and diverse Alzheimer's disease (AD) pathological phenotypes. We annotate 12 microglial transcriptional states, including AD-dysregulated homeostatic, inflammatory, and lipid-processing states. We identify 1,542 AD-differentially-expressed genes, including both microglia-state-specific and disease-stage-specific alterations. By integrating epigenomic, transcriptomic, and motif information, we infer upstream regulators of microglial cell states, gene-regulatory networks, enhancer-gene links, and transcription-factor-driven microglial state transitions. We demonstrate that ectopic expression of our predicted homeostatic-state activators induces homeostatic features in human iPSC-derived microglia-like cells, while inhibiting activators of inflammation can block inflammatory progression. Lastly, we pinpoint the expression of AD-risk genes in microglial states and differential expression of AD-risk genes and their regulators during AD progression. Overall, we provide insights underlying microglial states, including state-specific and AD-stage-specific microglial alterations at unprecedented resolution.

Single-cell atlas reveals correlates of high cognitive function, dementia, and resilience to Alzheimer's disease pathology

Alzheimer's disease (AD) is the most common cause of dementia worldwide, but the molecular and cellular mechanisms underlying cognitive impairment remain poorly understood. To address this, we generated a single-cell transcriptomic atlas of the aged human prefrontal cortex covering 2.3 million cells from postmortem human brain samples of 427 individuals with varying degrees of AD pathology and cognitive impairment. Our analyses identified AD-pathology-associated alterations shared between excitatory neuron subtypes, revealed a coordinated increase of the cohesin complex and DNA damage response factors in excitatory neurons and in oligodendrocytes, and uncovered genes and pathways associated with high cognitive function, dementia, and resilience to AD pathology. Furthermore, we identified selectively vulnerable somatostatin inhibitory neuron subtypes depleted in AD, discovered two distinct groups of inhibitory neurons that were more abundant in individuals with preserved high cognitive function late in life, and uncovered a link between inhibitory neurons and resilience to AD pathology.

Melanoma‐derived extracellular vesicles mediate lymphatic remodelling and impair tumour immunity in draining lymph nodes

Tumour‐draining lymph nodes (LNs) undergo massive remodelling including expansion of the lymphatic sinuses, a process that has been linked to lymphatic metastasis by creation of a pre‐metastatic niche. However, the signals leading to these changes have not been completely understood. Here, we found that extracellular vesicles (EVs) derived from melanoma cells are rapidly transported by lymphatic vessels to draining LNs, where they selectively interact with lymphatic endothelial cells (LECs) as well as medullary sinus macrophages. Interestingly, uptake of melanoma EVs by LN‐resident LECs was partly dependent on lymphatic VCAM‐1 expression, and induced transcriptional changes as well as proliferation of those cells. Furthermore, melanoma EVs shuttled tumour antigens to LN LECs for cross‐presentation on MHC‐I, resulting in apoptosis induction in antigen‐specific CD8⁺ T cells. In conclusion, our data identify EV‐mediated melanoma—LN LEC communication as a new pathway involved in tumour progression and tumour immune inhibition, suggesting that EV uptake or effector mechanisms in LECs might represent a new target for melanoma therapy.

Isolation and Fluorescent Labeling of Extracellular Vesicles from Cultured Tumor Cells

Extracellular vesicles (EVs), comprising exosomes, ectosomes, and apoptotic bodies, are an important component of molecular cell-to-cell communication, and are critically involved in the pathophysiology of various diseases, including tumors. In order to study the interaction of tumor cell-derived EVs with their target cells and to investigate their biological functions in comparison to other tumor cell-released factors, efficient isolation of EVs from cultured tumor cells, as well as fluorescent labeling of these EVs, is often necessary. In addition, EVs and EV-like particles are emerging as versatile vehicles for the delivery of therapeutic substances. Here, we describe an easy size exclusion chromatography-based method to isolate EVs from the mouse melanoma cell line B16F10 that yields highly enriched EV samples for subsequent applications such as molecular and functional studies. Our protocol also includes an optional labeling step with the lipophilic dye DiD, which allows tracking of EV uptake by recipient cells in vitro and in vivo.