Extracellular vesicles (EVs) are critical mediators of intercellular communication, carrying molecular cargos such as small noncoding RNAs (ncRNAs) that reflect the physiological and pathological state of their cells of origin. However, studying brain-derived EVs has been challenging due to the blood-brain barrier. Here, we optimized and validated an open-flow microdialysis (OFM) protocol for sampling EVs directly from brain interstitial fluid (ISF) in wild-type and APP/PS1 transgenic mice. Ex-vivo validation using plasma EVs demonstrated that OFM effectively captures the full EV population. In-vivo cerebral OFM (cOFM) enabled successful collection of brain ISF EVs, which were characterized by nanoparticle tracking analysis (NTA), electron microscopy, and western blotting, confirming their similarity to EVs isolated directly from brain tissue and plasma. Identification of small ncRNA cargos revealed that EVs sampled from brain ISF by cOFM were enriched in brain-specific signatures, many of which are associated with neuronal cell populations and biological functions. Furthermore, we observed a unique small ncRNA signature from the brain ISF EVs in the Alzheimer's disease preclinical model compared to wild-type mice. These small ncRNAs were associated with genes considered important in biological functions associated with neurodegeneration. Our findings demonstrate that cOFM is a powerful tool for in-vivo sampling of brain EVs and highlight the unique molecular landscape of ISF EV small ncRNA cargos. This study offers new opportunities for biomarker discovery and mechanistic insights into neurodegenerative diseases, such as Alzheimer's disease.

Tauopathies, including Alzheimer's disease, involve progressive neurodegeneration and sustained neuroinflammation. We present a multi-compartment transcriptomic atlas of 9.6-month-old PS19 tauopathy mice compared with wild-type (WT) controls (n = 8/group), profiling cortical mRNA, cortical non-coding RNA (ncRNA), and plasma small extracellular vesicle (pEV) ncRNA. In the PS19 cortex, mRNA sequencing identified 917 differentially expressed genes (DEGs), with microglial deconvolution revealing an association toward disease-associated microglia (DAM) gene signature and downregulation of genes involved in oxidative phosphorylation and cholesterol biosynthesis relative to WT. Cortical ncRNA profiling identified 466 differentially expressed ncRNAs, primarily circular RNAs (circRNAs; n = 331). In pEVs, 822 ncRNAs were differentially abundant, of which 657 circRNAs were identified in PS19 compared to WT mice. Cross-compartment integration suggest that pEV miRNA gene targets functionally mirrored genes involved in the brain's inflammatory and metabolic failure. We identified a preliminary candidate signature of 33 ncRNAs, including miR-5114 (up in brain, down in pEV), circ_0008242 and circ_0002153 (up in brain and pEV), and circ_0007688 (down in brain and pEV), differentially enriched across both brain and periphery in PS19 compared to WT mice. These results suggest that the pEV non-coding landscape may partially reflect central tau-mediated changes in the brain transcriptional response. This study identifies circRNAs as the most numerically perturbed ncRNA class and provides a foundation for potential peripheral indicators of central brain tau pathology.

Microglia are key players in Alzheimer's disease, but the transcriptional control of their phagocytic function remains unclear. Kim et al. show that mouse microglial Spi1 deletion worsens amyloid pathology by impairing Aβ clearance through Syk, Lyn, and Fcgr1, providing new insight into PU.1-dependent regulatory networks and microglial functions in neurodegeneration.

The decline in mobility with aging is a major health concern, associated with a high risk for disability. Despite the widespread prevalence of gait slowing in elderly adults, this issue has not been adequately addressed. The central nervous system and skeletal muscle system are key regulators of gait speed. However, direct molecular communication along the brain-muscle axis and the role of these interactions in mobility resilience remain poorly studied. Recently, extracellular vesicles (EV), membrane bound vesicles secreted by cells, have emerged as a key player in long distance inter-cellular communication. Nevertheless, the potential of EVs as biological predictor of mobility resilience in older adults has not been yet studied. In the present study, we used serum samples from 23 participants with gait speed >1.0 m/sec (mobility-resilient group) and 22 participants with gait <1.0 m/sec (mobility non-resilient group) from the Health, Aging and Body Composition (Health ABC) study. First, total circulating serum EVs were isolated and characterized for small noncoding RNAs using un-biased small noncoding RNA sequencing. Given the central role of mitochondria in muscle energy metabolism and their emerging link to age-related physical decline, next, muscle-derived EVs (MDE) were isolated and characterized for specific mitochondrial markers (TOM20, mtCox2, PDH, and VDAC) by flow cytometry, the expression of a panel of 13 miRNAs related to mitochondrial function by RT-PCR, and PPAR-γ expression by ELISA. The results showed differential enrichment of various miRNAs, circRNAs, and mitochondrial proteins in total EVs and/or MDE between mobility-resilient and non-resilient groups, highlighting their potential as non-invasive biomarkers for mobility outcomes. Overall, the findings from the present study suggest a role for serum EVs in mediating molecular communication related to functional aging phenotypes and underscores the potential of EV biomarkers in modulating mobility and promoting healthy aging.

Pharmacological activation of brain Retinoid X Receptors (RXRs) enhances cognition and facilitates amyloid-beta (Aβ) clearance in Alzheimer's disease (AD) mouse models, partly by upregulating Apolipoprotein E ( Apoe ), a major AD genetic risk factor. However, the specific cellular contributions to these effects are unclear. Here, we used single-cell transcriptomic profiling to investigate cell subpopulation-specific responses to bexarotene, an RXR agonist, in APP/PS1 mice. Our analysis revealed that bexarotene activated cholesterol biosynthesis and lipid metabolism transcriptional programs in homeostatic astrocytes and oligodendrocytes. Astrocytes also upregulated neurodevelopmental genes, while oligodendrocytes and endothelial cells showed enhanced protein folding and cellular growth pathways. Bexarotene further modulated immune responses, promoting Aβ-responsive signatures in disease-associated microglia and reactive astrocytes, while dampening pro-inflammatory responses in homeostatic microglia and endothelial cells. Furthermore, Apoe expression was significantly elevated across multiple cell types, especially in microglia and oligodendrocytes. Cell-cell communication analysis highlighted increased astrocyte-centered signaling, with APOE-driven pathways emerging as a prominent mediator. These findings clarify the cell-specific complexity of RXR-mediated regulation and underscore APOE as a central mediator of bexarotene's neuroprotective effects. This study provides mechanistic insights into RXR-targeted interventions, and supports APOE-associated pathways as promising therapeutic targets in AD.

Bexarotene, an RXR-specific agonist, has shown neuroprotective effects in Alzheimer's disease (AD) mouse models by improving cognition and increasing amyloid-beta (Aβ) clearance. RXR activation regulates gene networks involved in neural development, neuroinflammation, and metabolism. This study aimed to examine how Bexarotene alters chromatin architecture and gene activity in the brains of APP/PS1 AD mice. APP/PS1de9 mice were treated with Bexarotene (100 mg/kg/d for 10 days) or vehicle (corn oil/DMSO). Mouse brains were dissociated, and cDNA libraries were generated using the 10X platform for single-cell sequencing. Dimensionality reduction and unsupervised clustering were performed with the Seurat pipeline to identify cell populations and analyze gene expression. Changes in chromatin architecture were examined with single-cell ATAC-seq (snATAC-seq). Data from both scRNA-seq and snATAC-seq were integrated using the ArchR pipeline, and differentially accessible peaks were identified using the Signac package. Transcription factor (TF) activity was analyzed with TOBIAS and TF-COMB, with ChIP-seq used for validation. We present a single-cell-resolution map of both transcriptomic and epigenomic changes in Bexarotene-treated AD model mice. We profiled the transcriptional and epigenomic landscapes of 37,640 cells (scRNA-seq) and 61,353 nuclei (snATAC-seq) from 8 samples (4 Bexarotene- and 4 vehicle-treated controls). We identified clusters corresponding to astrocytes, microglia, oligodendrocytes, neurons, blood vessel cells, and macrophages. Gene expression analysis revealed transcriptional responses to Bexarotene, with many genes involved in developmental processes and lipid metabolism pathways. Integration of snATAC-seq and scRNA-seq identified cell-type-specific TFs, and differentially accessible chromatin regions. Microglia and endothelial cells exhibited the most significant changes, with genes primarily associated with developmental functions. TF footprinting and cooccurrence analysis further revealed the binding activity and regulatory network of RXR and its partnered heterodimers, providing insights into the transcriptional regulation underlying the observed gene expression changes in response to Bexarotene treatment. Bexarotene upregulates RXR-controlled gene networks in major brain cell types, including microglia and endothelial cells. The combined analysis of single-cell transcriptomics, ATAC-seq, and ChIP-seq provides new insights into how RXR activation may restore brain homeostasis by regulating neuroinflammation, amyloid deposition, and neuronal damage. This research highlights the complexity of TF signaling pathways and their potential for therapeutic use in AD.

Backgound:Ligand-activated Retinoid X Receptors (RXRs) regulate gene networks essential for neural development, neuroinflammation, and metabolism. Understanding how RXR activation influences chromatin architecture and gene expression may reveal therapeutic strategies for neurodegenerative diseases. Methods:We used Bexarotene-treated APP/PS1ΔE9 mice to study RXR-mediated regulatory mechanisms. To investigate epigenomic and transcriptional effects, we integrated single-nucleus ATAC-seq (snATAC-seq) with single-cell RNA-seq (scRNA-seq) and validated differentially accessible chromatin peaks using RXR ChIP-seq. Transcription factor (TF) footprinting analysis were performed to map regulatory networks activated by ligand-bound RXR. Results:Our integrated analyses revealed a multilayered transcriptional cascade initiated by a single linear RXR signaling event. We identified RXR-centered regulatory circuits involving heterodimer activation, subsequent upregulation of multiple downstream TFs, and induction of metabolic pathways relevant to neural function. The results of a detailed analysis of TF regulatory networks in neuronal systems suggests that Bexarotene doesn't dismantle the fundamental regulatory scaffold in neurons but rather modulates RXR regulatory role through existing TF networks. Conclusions:This study demonstrates that combining scRNA-seq, snATAC-seq, and ChIP-seq enables a comprehensive analysis of RXR-mediated transcriptional regulation. RXR activation orchestrates complex gene networks that may help restore brain homeostasis in the context of amyloid pathology, neuroinflammation, and neuronal injury.

Ligand-activated Retinoid X Receptors (RXRs) regulate gene networks essential for neural development, neuroinflammation, and metabolism. Understanding how RXR activation influences chromatin architecture and gene expression may reveal mechanisms relevant to neurodegenerative diseases. We used Bexarotene-treated APP/PS1ΔE9 mice to study RXR-mediated regulatory mechanisms by integrating single-nucleus ATAC-seq (snATAC-seq) with single-cell RNA-seq (scRNA-seq) and validating differentially accessible chromatin peaks using RXR ChIP-seq. Transcription factor (TF) footprinting analysis mapped regulatory networks activated by ligand-bound RXR. Our integrated analyses revealed a multilayered transcriptional cascade initiated by RXR signaling. We identified RXR-centered regulatory circuits involving heterodimer activation, upregulation of downstream TFs, and induction of metabolic pathways relevant to neural function. Detailed analysis of neuronal TF networks revealed that Bexarotene modulates RXR’s role through existing regulatory scaffolds rather than creating new ones. This study demonstrates that combining scRNA-seq, snATAC-seq, and ChIP-seq enables comprehensive analysis of RXR-mediated transcriptional regulation. RXR activation orchestrates cell-type-specific chromatin remodeling of gene networks controlling neuroinflammation, lipid metabolism, and synaptic signaling, providing mechanistic insights into RXR-dependent transcriptional programs in Alzheimer’s disease pathology.

Treatment with the RXR-specific agonist Bexarotene exerts neuroprotective effects in Alzheimer’s disease (AD) mouse models by improving cognition and increasing Aβ clearance. At the transcriptional level, ligand-activated RXR receptors regulate gene networks linked to neural development, neuroinflammation, and metabolism. This study aimed to reveal the association between changes in chromatin architecture and transcriptional activity in the brain of Bexarotene-treated APP/PS1 mice. APP/PS1D9 mice were treated orally with bexarotene or vehicle (corn oil, DMSO 1%). Mouse brains were dissociated and used for cDNA library generation on a 10x Genomics platform for single-cell resolution. Seurat pipeline was performed to resolve cell populations and for differential expression analysis, followed by GO analysis to reveal cell population-specific transcriptional response to Bexarotene. Changes in chromatin architecture were evaluated by single-cell ATAC-seq. scATAC-seq data were processed and integrated with scRNA-seq using the ArchR pipeline. We present a single-cell-resolution map of transcriptomic and epigenomic changes in Bexarotene-treated mice. We profiled transcriptional and epigenomic landscapes of 37,640 cells (scRNA-seq) and 61,353 individual nuclei (snATAC-seq) from 8 samples (4 Bexa and 4 vehicle controls). To predict candidate upstream regulators that may be shaping the chromatin accessibility landscape of brain cells following ligand activation of RXR and contributing to cell type identity and cell fate specification, we used chromVar. We discovered 67 high-confidence candidate regulators that show strong correlations between TF enrichment and ATAC-inferred expression and between ATAC-inferred expression and RNA-measured expression. Next, we used the integrated single cell RNA-seq and ATAC-seq data to identify cell type- and disease-specific cis -regulatory elements (CREs) and their target genes by correlating gene expression with chromatin accessibility across all nuclei in the dataset. We then asked if the differential gene expression we observed could be mediated by candidate CREs. The majority of the DEGs identified between Bexa and control nuclei had a linked peak in the same cell type where the gene was differentially expressed. An example is Apoe gene located in the Apoe/Apoc locus that was significantly upregulated by Bexa in microglia but not in astrocytes. Results revealed that Bexarotene affected chromatin accessibility in microglia in correlation with Apoe expression.

While small non-coding RNAs (sncRNAs) make up about 1% of the total genome, they maintain a significant role in regulating cellular processes and gene expression. Given the complexity of the brain and the neural cellular responses to Alzheimer's disease (AD) pathologies, sncRNAs likely hold particular importance. This is especially true when considering the coordination of activities between different cell types and disease associated subtypes of glial cells which could potentially be modulated by sncRNAs. We hypothesize that AD model mice will exhibit unique sncRNAs signatures that are neural cell type specific and provide details related to underlying disease mechanisms. Mouse brains from APP/PS1de9 and wildtype mice were dissociated, and microglia, astrocytes and neurons sorted utilizing magnetic activated cell sorting. Subsequently, both sncRNA and mRNA were isolated and individual libraries generated and sequenced. sncRNAs alignment to the mouse microRNAs (miRNAs), small nucleolar RNAs (snoRNAs), transfer RNA (tRNA), small nuclear RNAs (snRNAs), and circular RNAs (circRNAs) were performed utilizing COMPRSA and differential expression with DESeq2. While mRNA alignment and differential expression was performed with edgeR pipeline. We present both the sncRNA and mRNA changes in astrocytes, microglia and neurons of AD model mice. We show high level of alignment to the all the subclasses of sncRNAs for all neural cell types, with a high abundance of circRNAs. This expression patterns show unique signatures in the AD model mice compared to their wildtype controls. Integrative modeling of sncRNA binding, targets and associated genes demonstrated that these expression patterns were associated with gene transcriptional responses in the AD model mice. These associations were related to significant changes in gene primarily associated with inflammatory response, metabolic functions and developmental functions. We observed unique sncRNA signatures in astrocytes, microglia and neurons that were correlated with gene transcriptional changes and association with amyloid pathology. This study is a valuable resource for exploring the role of sncRNA in different neural cell types, unique sncRNA signatures associated with AD like pathologies and their potential use as biomarkers in AD.

Clinical and animal studies have suggested that peripheral inflammation affects the central nervous system (CNS) and may be a major factor in the pathophysiology of neurodegenerative diseases like AD. Furthermore, a variety of signaling factors originating in the periphery, such as inflammatory mediators, have been associated with the regulation of brain barrier functions. Here, we hypothesized that the presence of peripheral inflammation dysregulates brain barriers’ integrity and induces neuroinflammation with consequences on amyloid pathology. In this study, we employed an AD mouse model nasally infected with Staphylococcus aureus to assess the impact of chronic or acute peripheral inflammation on brain transcriptome and amyloid pathology. We utilized both single cell and Spatial Transcriptomics to better determine transcriptional response to peripheral inflammation. The chronic exposure increased the diffuse and compact amyloid plaques and blood cytokine levels. Following a short-term exposure, single-cell and spatial transcriptomics uncovered cell type- and spatial-specific transcriptional changes indicating a dysregulation of the brain barriers, including the blood-brain and the blood-cerebrospinal fluid barriers. Brain macrophages exhibited increased Apoe expression and macrophage-specific genes were upregulated at ventricular areas of infected mice. In addition, we report an increase of disease associated microglia genes around the Ab plaques, together with disbalances in neuronal expression in response to peripheral inflammation. We observed that low-grade peripheral infection triggers transcriptional responses linked to brain barriers and brain infiltrated/resident macrophages indicate a fundamental importance of them in the mechanisms linking peripheral inflammation and AD pathogenesis. Finally, we showed that bacterial infection caused molecular changes restricted to specific cell types and/or brain spatial microenvironments, which highlights the relevance of studying brain molecular responses with high resolution in order to have new insights on AD etiology.

Peripheral inflammation has been linked to various neurodegenerative disorders, including Alzheimer's disease (AD). Here we perform bulk, single-cell, and spatial transcriptomics in APP/PS1 mice intranasally exposed to Staphylococcus aureus to determine how low-grade peripheral infection affects brain transcriptomics and AD-like pathology. Chronic exposure led to increased amyloid plaque burden and plaque-associated microglia, significantly affecting the transcription of brain barrier-associated cells, which resulted in barrier leakage. We reveal cell-type- and spatial-specific transcriptional changes related to brain barrier function and neuroinflammation during the acute infection. Both acute and chronic exposure led to brain macrophage-associated responses and detrimental effects in neuronal transcriptomics. Finally, we identify unique transcriptional responses at the amyloid plaque niches following acute infection characterized by higher disease-associated microglia gene expression and a larger effect on astrocytic or macrophage-associated genes, which could facilitate amyloid and related pathologies. Our findings provide important insights into the mechanisms linking peripheral inflammation to AD pathology.

We have previously demonstrated that circulating extracellular vesicles (EVs) are essential to the beneficial effect of young serum on the skeletal muscle regenerative cascade. Here, we show that infusions of young serum significantly improve age-associated memory deficits, and that these effects are abolished after serum depletion of EVs. RNA-seq analysis of the choroid plexus demonstrates EV-mediated effects on genes involved in barrier function and trans-barrier transport. Comparing the differentially expressed genes to recently published chronological aging clock genes reveals a reversal of transcriptomic aging in the choroid plexus. Following young serum treatment, the hippocampal transcriptome demonstrates significant upregulation of the anti-aging gene Klotho, along with an abrogated effect after EV depletion. Transcriptomic profiling of Klotho knockout and heterozygous mice shows the downregulation of genes associated with transport, exocytosis, and lipid transport, while upregulated genes are associated with activated microglia. The results of our study indicate the significance of EVs as vehicles to deliver signals from the periphery to the brain and the importance of Klotho in maintaining brain homeostasis.

The inheritance of Apolipoprotein E4 (APOEε4) brings the highest genetic risk of Alzheimer’s disease (AD), arguably the highest genetic risk in human pathology. Since the discovery of the association, APOE protein isoforms have been at the center of tens of thousands of studies and reports. While, without a doubt, our knowledge about the normal physiological function of APOE isoforms in the brain has increased tremendously, the questions of how the inheritance of the APOEε4 allele translates into a risk of AD, and the risk is materialized, remain unanswered. Moreover, the knowledge about the risk associated with APOEε4 has not helped design a meaningful preventative or therapeutic strategy. Animal models with targeted replacement of Apoe have been generated and, thanks to the recent NIH/NIA/Alzheimer’s disease Association initiative, are now freely available to AD researchers. While helpful in many aspects, none of the available models recapitulates normal physiological transcriptional regulation of the human APOE gene cluster. Changes in epigenetic regulation of APOE alleles in animal models in response to external insults have rarely been if ever, addressed. However, these animal models provide a useful tool to handle questions and investigate protein–protein interactions with proteins expressed by other recently discovered genes and gene variants considered genetic risk factors of AD, like Triggering Receptor expressed on Myeloid cells 2 (TREM2). In this review, we discuss genetic and epigenetic regulatory mechanisms controlling and influencing APOE expression and focus on interactions of APOE and TREM2 in the context of microglia and astrocytes’ role in AD-like pathology in animal models.

Standardized disease specific PET patterns correctly classify 95% of AD MCI patients. The cost of PET, however, is still prohibitive as a widespread AD diagnostic test. Diagnostic tests using CSF have also been established to measure the levels of Aβ and hyperphosphorylated tau for early diagnosis of AD or to monitor the effects of therapeutics and progression of the disease. CSF biomarkers show a good agreement with amyloid imaging and a combination of CSF Aβ42/Aβ40 increases the agreement between markers of amyloid pathology. Plasma extracellular vesicles (EVs) and their cargo present an opportunity to isolate and profile molecules associated with human pathological conditions. We have recently found small nucleolar non‐coding RNAs (snoRNAs) of box C/D (SNORDs), transcribed from imprinted chromosomal domains SNURF‐SNRPN at human chromosomal region 15q11q13 and DLK1‐DIO3 at region 14q32, highly enriched in plasma EVs of AD patients compared to non‐demented individuals.

Inorganic arsenic is a xenobiotic entering the body primarily through contaminated drinking water and food. There are defined mechanisms that describe arsenic's association with increased cancer incidence, however mechanisms explaining arsenic exposure and neurodevelopmental or aging disorders are poorly defined. In recent years, arsenic effects on epigenome have become a particular focus. We hypothesize that human relevant arsenic exposure during particular developmental windows, or long-term exposure later in life induce pathophysiological neural changes through epigenomic alterations, in particular histone methylation profile, manifesting as cognitive decline. C57BL/6 wild-type mice were continually exposed to sodium arsenite (100 µg/L) in drinking water prior to mating through weaning of the experimental progeny. A second cohort of aged APP/PS mice were chronically exposed to the same level of arsenic. Cognitive testing, histological examination of brains and genome-wide methylation levels of H3K4me3 and H3K27me3 examined after ChIP-seq were used to determine the effects of arsenic exposure. Developmental arsenic exposure caused significantly diminished cognition in wild-type mice. The analysis of ChIP-seq data and experiments with mouse embryonic stem cells demonstrated that epigenetic changes induced by arsenic exposure translated into gene expression alterations associated with neuronal development and neurological disease. Increased hippocampal amyloid plaques levels of APP/PS mice and cognitive decline provided evidence that arsenic exposure aggravated an existing Alzheimer's disease-like phenotype. We show developmental arsenic exposure significantly impacts histone modifications in brain which remain present into adulthood and provide a potential mechanism by which developmental arsenic exposure influences cognitive functions. We also show that human relevant, chronic arsenic exposure has deleterious effects on adult APP/PS mice and exacerbates existing Alzheimer's disease-like symptoms. The results demonstrate how developmental arsenic exposure impacts the brain epigenome, leading to altered gene expression later in life.

A bstract The clinical diagnosis of Alzheimer’s disease, at its early stage, remains a difficult task. Advanced imaging technologies and laboratory assays to detect Aβ peptides Aβ42 and Aβ40, total and phosphorylated tau in CSF provide a set of biomarkers of developing AD brain pathology and facilitate the diagnostic process. The search for biofluid biomarkers, other than in CSF, and the development of biomarker assays have accelerated significantly and now represent the fastest-growing field in AD research. The goal of this study was to determine the differential enrichment of noncoding RNAs (ncRNAs) in plasma-derived extracellular vesicles (EV) of AD patients and Cognitively Normal controls (NC). Using RNA-seq, we profiled four significant classes of ncRNAs: miRNAs, snoRNAs, tRNAs, and piRNAs. We report a significant enrichment of SNORDs – a group of snoRNAs, in AD samples compared to NC. To verify the differential enrichment of two clusters of SNORDs – SNORD115 and SNORD116, localized on human chromosome 15q11-q13, we used plasma samples of an independent group of AD patients and NC. We applied ddPCR technique and identified SNORD115 and SNORD116 with a high discriminatory power to differentiate AD samples from NC. The results of our study present evidence that AD is associated with changes in the enrichment of SNORDs, transcribed from imprinted genomic loci, in plasma EV and provide a rationale to further explore the validity of those SNORDs as plasma biomarkers of AD.

Heterochronic blood exchange (HBE) has demonstrated that circulating factors restore youthful features to aged tissues. However, the systemic mediators of those rejuvenating effects remain poorly defined. We show here that the beneficial effect of young blood on aged muscle regeneration was diminished when serum was depleted of extracellular vesicles (EVs). Whereas EVs from young animals rejuvenate aged cell bioenergetics and skeletal muscle regeneration, aging shifts EV subpopulation heterogeneity and compromises downstream benefits on recipient cells. Machine learning classifiers revealed that aging shifts the nucleic acid, but not protein, fingerprint of circulating EVs. Alterations in subpopulation heterogeneity were accompanied by declines in transcript levels of the prolongevity protein α-Klotho (Klotho), and injection of EVs improved muscle regeneration in a Klotho mRNA-dependent manner. These studies demonstrate that EVs play a key role in the rejuvenating effects of HBE and that Klotho transcripts within EVs phenocopy the effects of young serum on aged skeletal muscle. Circulating factors play an important role in tissue aging. Here, the authors show that serum EV subpopulations and cargoes remodel with age and that EVs from young mouse serum rejuvenate aged skeletal muscle.

APOE and Trem2 are major genetic risk factors for Alzheimer’s disease (AD), but how they affect microglia response to Aβ remains unclear. Here we report an APOE isoform-specific phospholipid signature with correlation between human APOEε3/3 and APOEε4/4 AD brain and lipoproteins from astrocyte conditioned media of APOE3 and APOE4 mice. Using preclinical AD mouse models, we show that APOE3 lipoproteins, unlike APOE4, induce faster microglial migration towards injected Aβ, facilitate Aβ uptake, and ameliorate Aβ effects on cognition. Bulk and single-cell RNA-seq demonstrate that, compared to APOE4, cortical infusion of APOE3 lipoproteins upregulates a higher proportion of genes linked to an activated microglia response, and this trend is augmented by TREM2 deficiency. In vitro, lack of TREM2 decreases Aβ uptake by APOE4-treated microglia only, suggesting TREM2-APOE interaction. Our study elucidates phenotypic and transcriptional differences in microglial response to Aβ mediated by APOE3 or APOE4 lipoproteins in preclinical models of AD.

The clinical diagnosis of Alzheimer's disease, at its early stage, remains a difficult task. Advanced imaging technologies and laboratory assays to detect Aβ peptides Aβ42 and Aβ40, total and phosphorylated tau in CSF provide a set of biomarkers of developing AD brain pathology and facilitate the diagnostic process. The search for biofluid biomarkers, other than in CSF, and the development of biomarker assays have accelerated significantly and now represent the fastest-growing field in AD research. The goal of this study was to determine the differential enrichment of noncoding RNAs (ncRNAs) in plasma-derived extracellular vesicles (EV) of AD patients and Cognitively Normal controls (NC). Using RNA-seq, we profiled four significant classes of ncRNAs: miRNAs, snoRNAs, tRNAs, and piRNAs. We report a significant enrichment of SNORDs – a group of snoRNAs, in AD samples compared to NC. To verify the differential enrichment of two clusters of SNORDs – SNORD115 and SNORD116, localized on human chromosome 15q11-q13, we used plasma samples of an independent group of AD patients and NC. We applied ddPCR technique and identified SNORD115 and SNORD116 with a high discriminatory power to differentiate AD samples from NC. The results of our study present evidence that AD is associated with changes in the enrichment of SNORDs, transcribed from imprinted genomic loci, in plasma EV and provide a rationale to further explore the validity of those SNORDs as plasma biomarkers of AD.