Aged Mouse Brain Research Articles

Transposable element small and long RNAs in aging brains and implications in Huntington's and Parkinson's disease.

Transposable Elements (TEs) are implicated in aging and neurodegenerative disorders, but the impact of brain TE RNA dynamics on these phenomena is not fully understood. Therefore, we quantified TE RNA changes in aging post-mortem human and mouse brains and in the neurodegenerative disorders Huntington's Disease (HD) and Parkinson's Disease (PD). We tracked TE small RNAs (smRNAs) expression landscape to assess the relationship to the active processing from TE long RNAs (lnRNAs). Human brain transcriptomes from the BrainSpan Atlas displayed a significant shift of TE smRNA patterns at age 20 years, whereas aging mouse brains lacked any such marked change, despite clear shift in aging-associated mRNA levels. Human frontal cortex displayed pronounced sense TE smRNAs during aging with a negative relationship between the TE smRNAs and lnRNAs indicative of age associated regulatory effects. Our analysis revealed TE smRNAs dysregulation in HD, while PD showed a stronger impact on TE lnRNAs, potentially correlating with the early average age of death for HD relative to PD. Furthermore, TE-silencing factor TRIM28 was down-regulated only in aging human brains, possibly explaining the lack of substantial TE RNA changes in aging mouse brains. Our study suggests brain TE RNAs may serve as novel biomarkers of human brain aging and neurodegenerative disorders.

Anti-CD49d Ab treatment ameliorates age-associated inflammatory response and mitigates CD8+ T-cell cytotoxicity after traumatic brain injury

Patients aged 65 years and older account for an increasing proportion of patients with traumatic brain injury (TBI). Older TBI patients experience increased morbidity and mortality compared to their younger counterparts. Our prior data demonstrated that by blocking α4 integrin, anti-CD49d antibody (aCD49d Ab) abrogates CD8+ T-cell infiltration into the injured brain, improves survival, and attenuates neurocognitive deficits. Here, we aimed to uncover how aCD49d Ab treatment alters local cellular responses in the aged mouse brain. Consequently, mice incur age-associated toxic cytokine and chemokine responses long-term post-TBI. aCD49d Ab attenuates this response along with a T helper (Th)1/Th17 immunological shift and remediation of overall CD8+ T cell cytotoxicity. Furthermore, aCD49d Ab reduces CD8+ T cells exhibiting higher effector status, leading to reduced clonal expansion in aged, but not young, mouse brains with chronic TBI. Together, aCD49d Ab is a promising therapeutic strategy for treating TBI in the older people.

Increased levels of extracellular matrix proteins associated with extracellular vesicles from brains of aged mice.

Extracellular vesicles (EVs) are secreted by all major cell types of the brain, providing a mode of intercellular communication and a pathway for disposal of cellular debris. EVs help maintain healthy brain function, but may also contribute to diseases affecting the brain. EVs might contribute to aging of the brain, as aging-related processes such as inflammation and cellular senescence may alter EV cargo, promoting further inflammation and senescence. However, the effects of aging on brain EVs and the function of EVs in the aging brain remain poorly understood. To address this question, we measured the levels and protein cargo of EVs isolated from the brains of 4-, 12-, and 22-month-old C57BL/6J mice. We detected no changes in EV levels, but observed age-dependent changes in EV proteins. EV fractions from aged (22 month old) brains contained higher levels of extracellular matrix proteins than EV fractions from young (4 month old) brains, with intermediate levels in 12-month-old brains. Specifically, EV fractions from aged mice contained elevated levels of hyaluronan and proteoglycan link proteins 1 and 2 and several chondroitin sulfate proteoglycans (CSPGs). Analysis of extracellular matrix in several brain regions of aged mice revealed increased immunolabeling for the CSPG aggrecan, but reduced labeling with Wisteria floribunda agglutinin, which binds to chondroitin sulfate side chains of CSPGs. These data are consistent with prior studies showing changes to the composition of extracellular matrix in aged brains, and indicate a novel association of EVs with changes in the extracellular matrix of the aging brain.

Longitudinal autophagy profiling of the mammalian brain reveals sustained mitophagy throughout healthy aging.

Mitophagy neutralizes mitochondrial damage, thereby preventing cellular dysfunction and apoptosis. Defects in mitophagy have been strongly implicated in age-relatedneurodegenerative disorders such as Parkinson's and Alzheimer's disease. While mitophagy decreases throughout the lifespan of short-lived model organisms, it remains unknown whether such a decline occurs in the aging mammalian brain-a question of fundamental importance for understanding cell type- and region-specific susceptibility to neurodegeneration. Here, we define the longitudinal dynamics of basal mitophagy and macroautophagy across neuronal and non-neuronal cell types within the intact aging mouse brain in vivo. Quantitative profiling of reporter mouse cohorts from young to geriatric ages reveals cell- and tissue-specific alterations in mitophagy and macroautophagy between distinct subregions and cell populations, including dopaminergic neurons, cerebellar Purkinje cells, astrocytes, microglia and interneurons. We also find that healthy aging is hallmarked by the dynamic accumulation of differentially acidified lysosomes in several neural cell subsets. Our findings argue against any widespread age-related decline in mitophagic activity, instead demonstrating dynamic fluctuations in mitophagy across the aging trajectory, withstrong implications for ongoing theragnostic development.

Post-injury treatment with 7,8-dihydroxyflavone attenuates white matter pathology in aged mice following focal traumatic brain injury

Traumatic brain injury (TBI) is a major cause of morbidity and mortality, not least in the elderly. The incidence of aged TBI patients has increased dramatically during the last decades. High age is a highly negative prognostic factor in TBI, and pharmacological treatment options are lacking. We used the controlled cortical impact (CCI) TBI model in 23-month-old male and female mice and analyzed the effect of post-injury treatment with 7,8 dihydroxyflavone (7,8-DHF), a brain-derived neurotrophic factor (BDNF)-mimetic compound, on white matter pathology. Following CCI or sham injury, mice received subcutaneous 7,8-DHF injections (5 ​mg/kg) 30 ​min post-injury and were sacrificed on 2, 7 or 14 days post-injury (dpi) for histological and immunofluorescence analyses. Histological assessment with Luxol Fast Blue (LFB)/Cresyl Violet stain showed that administration of 7,8-DHF resulted in preserved white matter tissue at 2 and 7 dpi with no difference in cortical tissue loss at all investigated time points. Treatment with 7,8-DHF led to reduced axonal swellings at 2 and 7 dpi, as visualized by SMI-31 (Neurofilament Heavy Chain) immunofluorescence, and reduced number of TUNEL (Terminal deoxynucleotidyl transferase dUTP nick end labelling)/CC1-positive mature oligodendrocytes at 2 dpi in the perilesional white matter. Post-injury proliferation of Platelet-derived Growth Factor Receptor (PDGFRα)-positive oligodendodrocyte progenitor cells was not altered by 7,8-DHF. Our results suggest that 7,8-DHF can attenuate white matter pathology by mitigating axonal injury and oligodendrocyte death in the aged mouse brain following TBI. These data argue that further exploration of 7,8-DHF towards clinical use is warranted.

Ellagitannin Component Punicalin Ameliorates Cognitive Dysfunction, Oxidative Stress, and Neuroinflammation via the Inhibition of cGAS-STING Signaling in the Brain of an Aging Mouse Model.

Despite remarkable breakthroughs in pharmacotherapy, many potential therapies for aging remain unexplored. Punicalin (PUN), an ellagitannin component, exerts anti-inflammatory, antioxidant, and anti-apoptotic effects. This study investigated the beneficial effects of PUN against age-related brain damage in mice and explored the underlying mechanisms. We validated the protective effects of PUN against D-galactose (D-gal)-induced neuroinflammation and subsequent neuronal damage in BV2 microglia and N2a cells, respectively, in vitro. In vivo experiments were conducted on mice that were administered an 8-week regimen of intraperitoneal injections of D-gal at a dosage of 150 mg/kg/day, concurrently with oral gavage of PUN at the same dose. PUN inhibited the production of D-gal-induced inflammatory cytokines (iNOS, COX2, TNF-α, IL-6, IL-2, and IL-1β) in BV2 cells and conferred protection to N2a cells against synaptic damage mediated by BV2 microglia-induced neuroinflammation. The in vivo findings revealed that PUN considerably improved memory and learning deficits, reduced MDA levels, enhanced GSH-Px, CAT, and SOD activities, and modulated the expression of inflammatory proteins such as iNOS, COX-2, IL-1β, IL-2, IL-6, and TNF-α. Furthermore, PUN inhibited the secretion of SASP factors (ICAM-1, PAI-1, MMP-3, and MMP-9), decreased microglial activation, and reduced astrocytosis. Additionally, PUN suppressed the expression of cGAS, p-STING, p-TBK1, p-p65, and p-IRF3 in aging mouse brains and cultured BV2 microglia. In conclusion, PUN improved cognitive dysfunction in aging mice through antioxidant and anti-inflammatory mechanisms via inhibition of the cGAS-STING pathway, suggesting that it can be a promising therapeutic agent for brain aging and aging-related diseases.

Mitigation of aging-related plasticity decline through taurine supplementation and environmental enrichment

Aging-related biochemical changes in nerve cells lead to dysfunctional synapses and disrupted neuronal circuits, ultimately affecting vital processes such as brain plasticity, learning, and memory. The imbalance between excitation and inhibition in synaptic function during aging contributes to cognitive impairment, emphasizing the importance of compensatory mechanisms. Fear conditioning-related plasticity of the somatosensory barrel cortex, relying on the proper functioning and extensive up regulation of the GABAergic system, in particular interneurons containing somatostatin, is compromised in aging (one-year-old) mice. The present research explores two potential interventions, taurine supplementation, and environmental enrichment, revealing their effectiveness in supporting learning-induced plasticity in the aging mouse brain. They do not act through a mechanism normalizing the Glutamate/GABA balance that is disrupted in aging. Still, they allow for increased somatostatin levels, an effect observed in young animals after learning. These findings highlight the potential of lifestyle interventions and diet supplementation to mitigate age-related cognitive decline by promoting experience-dependent plasticity.

Accumulation of damaged mitochondria in aging astrocytes due to mitophagy dysfunction: Implications for susceptibility to mitochondrial stress

Aging disrupts brain function, leading to cognitive decline and neurodegenerative diseases. Senescent astrocytes, a hallmark of aging, contribute to this process through unknown mechanisms. This study investigates how senescence impacts astrocytic mitochondrial dynamics, which are critical for brain health. Our research, conducted using aged mouse brains, represents the first evidence of morphologically damaged mitochondria in astrocytes, along with functional alterations in mitochondrial respiration. In vitro experiments revealed that senescent astrocytes exhibit an increase in mitochondrial fragmentation and impaired mitophagy. Concurrently, there was an upregulation of mitochondrial biogenesis, indicating a compensatory response to mitochondrial damage. Importantly, these senescent astrocytes were more susceptible to mitochondrial stress, a vulnerability reversed by rapamycin treatment. These findings suggest a potential link between senescence, impaired mitochondrial quality control, and increased susceptibility to mitochondrial stress in astrocytes. Overall, our study highlights the importance of addressing mitochondrial dysfunction and senescence-related changes in astrocytes as a promising approach for developing therapies to counter age-related neurodegeneration and improve brain health.

Visceral adiposity is associated with iron deposition and myelin loss in the brains of aged mice

Iron deposition and myelin loss are observed in the brain with aging, and iron accumulation is suggested to be involved in myelin damage. However, the exact mechanism of iron deposition with aging remains unclear. This study was aimed to determine whether expanded visceral adipose tissue contributes to iron deposition and myelin loss by inducing hepcidin in the brains of aged male mice. Compared with young adult mice, levels of hepcidin in the brain, epididymal adipose tissue, and circulation were increased in aged mice, which had expanded visceral adipose tissue with inflammation. An increase in expressions of ferritin, an indicator of intracellular iron status, was accompanied by decreased levels of proteins related to myelin sheath in the brains of aged mice. These age-related changes in the brain were improved by visceral fat removal. In addition, IL-6 level, activation of microglia/macrophages, and nuclear translocation of phosphorylated Smad1/5 (pSmad1/5) inducing hepcidin expression were reduced in the brains of aged mice after visceral fat removal, accompanied by decreases of pSmad1/5- and ferritin-positive microglia/macrophages and mature oligodendrocytes. These findings indicate that visceral adiposity contributes to hepcidin-mediated iron deposition and myelin loss with inflammation in the aged brain. Our results support the importance of preventing visceral adiposity for maintaining brain health in older individuals.

Morphological correlates of synaptic protein turnover in the mouse brain.

Synaptic proteins need to be replaced regularly, to maintain function and to prevent damage. It is unclear whether this process, known as protein turnover, relates to synaptic morphology. To test this, we relied on nanoscale secondary ion mass spectrometry, to detect newly synthesized synaptic components in the brains of young adult (6 mo old) and aged mice (24 mo old), and on transmission electron microscopy, to reveal synapse morphology. Several parameters correlated to turnover, including pre- and postsynaptic size, the number of synaptic vesicles and the presence of a postsynaptic nascent zone. In aged mice, the turnover of all brain compartments was reduced by ∼20%. The turnover rates of the pre- and postsynapses correlated well in aged mice, suggesting that they are subject to common regulatory mechanisms. This correlation was poorer in young adult mice, in line with their higher synaptic dynamics. We conclude that synapse turnover is reflected by synaptic morphology.

Transcriptomics analysis reveals potential regulatory role of nSMase2 (Smpd3) in nervous system development and function of middle-aged mouse brains.

Neutral sphingomyelinase-2 (nSMase2), gene name sphingomyelin phosphodiesterase-3 (Smpd3), is a key regulatory enzyme responsible for generating the sphingolipid ceramide. The function of nSMase2 in the brain is still controversial. To better understand the functional roles of nSMase2 in the aging mouse brain, we applied RNA-seq analysis, which identified a total of 1462 differentially abundant mRNAs between +/fro and fro/fro, of which 891 were increased and 571 were decreased in nSMase2-deficient mouse brains. The most strongly enriched GO and KEGG annotation terms among transcripts increased in fro/fro mice included synaptogenesis, synapse development, synaptic signaling, axon development, and axonogenesis. Among decreased transcripts, enriched annotations included ribosome assembly and mitochondrial protein complex functions. KEGG analysis of decreased transcripts also revealed overrepresentation of annotations for Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington disease (HD). Ingenuity Pathway Analysis (IPA) tools predicted lower susceptibility to these neurodegenerative disorders, as well as predictions agreeing with stronger synaptic function, learning, and memory in fro/fro mice. The IPA tools identified signaling proteins, epigenetic regulators, and microRNAs as likely upstream regulators of the broader set of genes encoding the affected transcripts. It also revealed 16 gene networks, each linked to biological processes identified as overrepresented annotations among the affected transcripts by multiple analysis methods. Therefore, the analysis of these RNA-seq data indicates that nSMase2 impacts synaptic function and neural development, and may contribute to the onset and development of neurodegenerative diseases in middle-aged mice.

Growth Differentiation Factor 11 Evokes Lung Injury, Inflammation, and Fibrosis in Mice through the Activin A Receptor Type II-Like Kinase, 53kDa–Smad2/3 Signaling Pathway

Growth differentiation factor 11 (GDF11) belongs to the transforming growth factor-β superfamily and participates in various pathophysiological processes. Initially, GDF11 was suggested to act as a rejuvenator by improving age-related phenotypes of the heart, brain, and skeletal muscle in aged mice. However, recent studies demonstrate that GDF11 also serves as an adverse risk factor for human frailty and diseases. However, the role of GDF11 in pulmonary fibrosis (PF) remains unclear. In this study, we explored the role and signaling mechanisms of GDF11 in PF. We discovered that GDF11 expression was markedly up-regulated in fibrotic lung tissues of both humans and mice. Intratracheal administration of commercial recombinant GDF11 caused lung injury, inflammation, and fibrogenesis in mice. Furthermore, adenovirus-mediated secretory expression of mature GDF11 was exacerbated, whereas full-length GDF11 or the GDF11 propeptide (GDF111-298) alleviated bleomycin-induced PF in mice. Invitro experiments demonstrated that GDF11 suppressed the growth of alveolar and bronchial epithelial cells (A549 and BEAS-2B) and human pulmonary microvascular endothelial cells, promoted fibroblast activation, and induced epithelial/endothelial-mesenchymal transition. These effects corresponded to the phosphorylation of Smad2/3, and blocking ALK5-Smad2/3 signaling abolished the invivo and invitro effects of GDF11. In conclusion, our findings provide evidence that GDF11 acts as a potent injurious, proinflammatory, and profibrotic factor in the lungs via the ALK5-Smad2/3 pathway.

Physical Exercise Inhibits Cognitive Impairment and Memory Loss in Aged Mice, and Enhances Pre- and Post-Synaptic Proteins in the Hippocampus of Young and Aged Mice.

The aim of this study was to evaluate the effects of swimming in the brain and behavior of young and aged mice. Forty-eight male C57BL/6J mice were randomly distributed into 4 groups (n = 12 per group, 3 and 18months old). The subdivision of the groups was: 3months-SED, 18months-SED, 3months-EXE, and 18months-EXE. SED mice did not swim, while EXE mice performed the physical exercise protocol. Training was initiated 48h after the adaptation week. Swimming sessions consisted of 30min, with no overload, 5days per week, for 4weeks. After the exercise protocol, it was revealed working and spatial memory were impaired in the 18months-SED group. Pre- and post-synaptic proteins were enhanced in the groups that swam when compared to the 3- and 8months-SED groups. Lipid peroxidation was greater in the aged mice that did not perform the physical exercise protocol and might have contributed to the cognitive impairment in this group. In conclusion, an aerobic physical exercise protocol, performed through regular swimming sessions, inhibited cognitive impairment, memory loss and lipid peroxidation in the aged mice, while pre- and post-synaptic proteins were enhanced in the hippocampus of young and aged mice.

Molecular Signatures of Neurodegenerative Diseases Identified by Proteomic and Phosphoproteomic Analyses in Aging Mouse Brain

A central hallmark of neurodegenerative diseases is theirreversible accumulation of misfolded proteins in the brain by aberrant phosphorylation. Understanding the mechanisms underlying protein phosphorylation and its role in pathological protein aggregation within the context of aging is crucial for developing therapeutic strategies aimed at preventing or reversing such diseases. Here, we applied multi-protease digestion and quantitative mass spectrometry to compare and characterize dysregulated proteins and phosphosites in the mouse brain proteome using three different age groups: young-adult (3-4months), middle-age (10months), and old mice (19-21months). Proteins associated with senescence, neurodegeneration, inflammation, cell cycle regulation, the p53 hallmark pathway, and cytokine signaling showed significant age-dependent changes in abundances and level of phosphorylation. Several proteins implicated in Alzheimer's disease (AD) and Parkinson's disease (PD) including tau (Mapt), Nefh, and Dpysl2 (also known as Crmp2) were hyperphosphorylated in old mice brain suggesting their susceptibility to the diseases. Cdk5 and Gsk3b, which are known to phosphorylate Dpysl2 at multiple specific sites, had also increased phosphorylation levels in old mice suggesting a potential crosstalk between them to contribute to AD. Hapln2, which promotes α-synuclein aggregation in patients with PD, was one of the proteins with highest abundance in old mice. CD9, which regulates senescence through the PI3K-AKT-mTOR-p53 signaling was upregulated in old mice and its regulation was correlated with the activation of phosphorylated AKT1. Overall, the findings identify a significant association between aging and the dysregulation of proteins involved in various pathways linked to neurodegenerative diseases with potential therapeutic implications.

Spinal cord injury disrupts plasma extracellular vesicles cargoes leading to neuroinflammation in the brain and neurological dysfunction in aged male mice

Aged individuals with spinal cord injury (SCI) are prevalent with increased mortality and worse outcomes. SCI can cause secondary brain neuroinflammation and neurodegeneration. However, the mechanisms contributing to SCI-induced brain dysfunction are poorly understood. Cell-to-cell signaling through extracellular vesicles (EVs) has emerged as a critical mediator of neuroinflammation, including at a distance through circulation. We have previously shown that SCI in young adult (YA) male mice leads to robust changes in plasma EV count and microRNAs (miRs) content. Here, our goal was to investigate the impact of old age on EVs and brain after SCI. At 24 h post-injury, there was no difference in particle count or size distribution between YA and aged mice. However, aged animals increased expression of EV marker CD63 with SCI. Using the Fireplex® miRs assay, Proteomics, and mass spectrometry-based Lipidomics, circulating EVs analysis identified distinct profiles of miRs, proteins, and lipid components in old and injury animals. In vitro, plasma EVs from aged SCI mice, at a lower concentration comparable to those of YA SCI mice, induced the secretion of pro-inflammatory cytokines and neuronal apoptosis. Systemic administration of plasma EVs from SCI animals was sufficient to impair general physical function and neurological function in intact animals, which is associated with pro-inflammatory changes in the brain. Furthermore, plasma EVs from young animals had rejuvenating effects on naïve aged mice. Collectively, these studies identify the critical changes in circulating EVs cargoes after SCI and in aged animals and support a potential EV-mediated mechanism for SCI-induced brain changes.

Old age alters inflammation and autophagy signaling in the brain, leading to exacerbated neurological outcomes after spinal cord injury in male mice

Older patients with spinal cord injury (SCI) have different features with regard to neurological characteristics after injury. Recent large-scale longitudinal population-based studies showed that individuals with SCI are at a higher risk of developing dementia than non-SCI patients, indicating that SCI is a potential risk factor for dementia. Aging is known to potentiate inflammation and neurodegeneration at the injured site leading to impaired recovery from SCI. However, no research has been aimed at studying the mechanisms of SCI-mediated cognitive impairment in the elderly. The present study examined neurobehavioral and molecular changes in the brain and the underlying mechanisms associated with brain dysfunction in aged C57BL/6 male mice using a contusion SCI model. At 2 months post-injury, aged mice displayed worse performance in locomotor, cognitive and depressive-like behavioral tests compared to young adult animals. Histopathology in injured spinal cord tissue was exacerbated in aged SCI mice. In the brain, transcriptomic analysis with NanoString neuropathology panel identified activated microglia and dysregulated autophagy as the most significantly altered pathways by both age and injury. These findings were further validated by flow cytometry, which demonstrated increased myeloid and lymphocytes infiltration at both the injured site and brain of aged mice. Moreover, SCI in aged mice altered microglial function and dysregulated autophagy in microglia, resulting in worsened neurodegeneration. Taken together, our data indicate that old age exacerbates neuropathological changes in both the injured spinal cord and remote brain regions leading to poorer functional outcomes, at least in part, through altered inflammation and autophagy function.

Novel intravital approaches to quantify deep vascular structure and perfusion in the aging mouse brain using ultrasound localization microscopy (ULM)

Intra-vital visualization of deep cerebrovascular structures and blood flow in the aging brain has been a difficult challenge in the field of neurovascular research, especially when considering the key role played by the cerebrovasculature in the pathogenesis of both vascular cognitive impairment and dementia (VCID) and Alzheimer’s disease (AD). Traditional imaging methods face difficulties with the thicker skull of older brains, making high-resolution imaging and cerebral blood flow (CBF) assessment challenging. However, functional ultrasound (fUS) imaging, an emerging non-invasive technique, provides real-time CBF insights with notable spatial-temporal resolution. This study introduces an enhanced longitudinal fUS method for aging brains. Using elderly (24-month C57BL/6) mice, we detail replacing the skull with a polymethylpentene window for consistent fUS imaging over extended periods. Ultrasound localization mapping (ULM), involving the injection of a microbubble (<<10 μm) suspension allows for recording of high-resolution microvascular vessels and flows. ULM relies on the localization and tracking of single circulating microbubbles in the blood flow. A FIJI-based analysis interprets these high-quality ULM visuals. Testing on older mouse brains, our method successfully unveils intricate vascular specifics even in-depth, showcasing its utility for longitudinal studies that require ongoing evaluations of CBF and vascular aspects in aging-focused research.

Single cell RNA sequencing reveals immunomodulatory effects of stem cell factor and granulocyte colony-stimulating factor treatment in the brains of aged APP/PS1 mice.

Alzheimers disease leads to progressive neurodegeneration and dementia. Alzheimers disease primarily affects older adults with neuropathological changes including amyloid beta deposition, neuroinflammation, and neurodegeneration. We have previously demonstrated that systemic treatment with combined stem cell factor, SCF, and granulocyte colony stimulating factor, GCSF, reduces amyloid beta load, increases amyloid beta uptake by activated microglia and macrophages, reduces neuroinflammation, and restores dendrites and synapses in the brains of aged APP-PS1 mice. However, the mechanisms underlying SCF-GCSF-enhanced brain repair in aged APP-PS1 mice remain unclear. This study used a transcriptomic approach to identify potential mechanisms by which SCF-GCSF treatment modulates microglia and peripheral myeloid cells to mitigate Alzheimers disease pathology in the aged brain. After injections of SCF-GCSF for 5 consecutive days, single cell RNA sequencing was performed on CD11b positive cells isolated from the brains of 28-month-old APP-PS1 mice. The vast majority of cell clusters aligned with transcriptional profiles of microglia in various activation states. However, SCF-GCSF treatment dramatically increased a cell population showing upregulation of marker genes related to peripheral myeloid cells. Flow cytometry data also revealed an SCF-GCSF-induced increase of cerebral CD45high-CD11b positive active phagocytes. SCF-GCSF treatment robustly increased the transcription of genes implicated in immune cell activation, including gene sets that regulate inflammatory processes and cell migration. Expression of S100a8 and S100a9 were robustly enhanced following SCF-GCSF treatment in all CD11b positive cell clusters. Moreover, the topmost genes differentially expressed with SCF-GCSF treatment were largely upregulated in S100a8-S100a9 positive cells, suggesting a well-conserved transcriptional profile related to SCF-GCSF treatment in resident and peripherally derived CD11b positive immune cells. This S100a8-S100a9-associated transcriptional profile contained notable genes related to proinflammatory and antiinflammatory responses, neuroprotection, and amyloid beta plaque inhibition or clearance. Altogether, this study reveals immunomodulatory effects of SCF-GCSF treatment in the aged brain with Alzheimers disease pathology, which will guide future studies to further uncover the therapeutic mechanisms.

Extracellular vesicles derived from mesenchymal stem cells ameliorate cognitive impairment caused by neuroinflammation in young but not aged mice

Aim: The aim of this work was to study the effects of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) on inflammation-impaired cognitive functions and the brain of mice. Methods: Young mice (~3-month-old) and aged mice (~18-month-old) were injected with bacterial lipopolysaccharide (LPS) and obtained intravenously donor 106 human umbilical cord MSCs, EVs isolated from a similar amount of MSCs or conditioned medium (CM) of MSCs. Subsequently, the mice were examined in behavioral tests and the mouse brains were analyzed for the levels of pro-inflammatory cytokines, α7 nicotinic acetylcholine receptors (α7 nAChRs) and amyloid beta 1-42 (Aβ1-42). Results: EVs prevented LPS-induced memory impairment in mice, whereas CM provided a weaker and temporal effect. Both EVs and MSCs injected once after regular injections of LPS stably improved memory of young mice. In contrast, both cells and EVs provided only transient effect in aged mice injected with LPS. The brains of aged LPS-treated mice contained elevated amounts of IL-1β and IL-6; both MSCs and EVs decreased them significantly. The brains of non-treated aged mice contained decreased levels of α7 nAChRs and increased levels of Aβ1-42 and α7-bound Aβ1-42 compared to the brains of young mice. LPS treatment decreased α7 nAChRs in both young and aged mice, while both MSCs and EVs restored them up to the control level. In young mice, LPS treatment increased the level of Aβ1-42 and α7-bound Aβ1-42, whereas MSCs and EVs decreased it. In contrast, neither LPS nor MSCs/EVs influenced the elevated level of Aβ1-42 but increased α7-bound Aβ1-42 in the brains of aged mice. Conclusions: Regenerative potential of MSCs and MSC-derived EVs is sufficient to support cognitive functions of LPS-treated young mice but is quite poor for aged animals, possibly, due to decreased levels of α7 nAChRs and accumulated Aβ1-42 in their brains.

Menthol-Modified Quercetin Liposomes with Brain-Targeting Function for the Treatment of Senescent Alzheimer's Disease.

Oxidative stress and neuroinflammation in the aging brain are correlated with the development of neurodegenerative diseases, such as Alzheimer's disease (AD). The blood-brain barrier (BBB) poses a significant challenge to the effective delivery of therapeutics for AD. Prior research has demonstrated that menthol (Men) can augment the permeability of the BBB. Consequently, in the current study, we modified Men on the surface of liposomes to construct menthol-modified quercetin liposomes (Men-Qu-Lips), designed to cross the BBB and enhance quercetin (Qu) concentration in the brain for improved therapeutic efficacy. The experimental findings indicate that Men-Qu-Lips exhibited good encapsulation efficiency and stability, successfully crossed the BBB, improved oxidative stress and neuroinflammation in the brains of aged mice, protected neurons, and enhanced their learning and memory abilities.