Citations

Abstract Background Hispanic individuals are at a 1.5‐times higher risk for Alzheimer's disease and related dementias yet remain underrepresented in research. Longitudinal Hispanic cohorts provide antemortem biospecimen, cognitive, and epidemiological data, and GWAS/admixture mapping analyses identify Hispanic ancestry as a modifier of Alzheimer's disease‐associated gene expression. Additionally, antemortem‐based studies suggest an altered pathological burden in Hispanic individuals, with neuropathological reports revealing a disproportional anatomy‐dependent burden of Alzheimer's pathologies in Hispanic decedents. Despite these advances, few analyses investigate differential gene expression in dementia from postmortem brain of Hispanic decedents. To address the current knowledge gap, we investigated neuroinflammatory gene expression in Hispanic decedents with single or mixed etiology dementia. Method To quantify gene expression, RNA was extracted from postmortem frontal cortex brain tissue of Hispanic and non‐Hispanic decedents with Alzheimer's disease (AD, n = 6), cerebrovascular disease (CVD, n = 6), or a mixture of the two etiologies (ADCVD, n = 6). Following quality control, extracted RNA was hybridized to the NanoString Human Neuroinflammation panel, and gene expression quantified via SPRINT nCounter. Analysis was completed with NanoString Advanced Analysis criteria via ROSALIND®. Low counts and low background genes were omitted from analysis. Result Comparison of Hispanic decedents with either AD or ADCVD to non‐Hispanic decedents reveals shared pathway enrichment of the Astrocyte Function gene set. Respective to non‐Hispanic decedents, we find two genes in Hispanic AD and seven genes in Hispanic ADCVD that are differentially expressed. Across all samples, gene expression analysis indicates P2RY12, NRP2, PRKACB , and seven other genes are increased at the transcript level in the frontal cortex of Hispanic decedents with CVD when compared to either Hispanic or non‐Hispanic decedents with other etiologies. Conclusion These preliminary findings suggest an ancestry‐ and etiology‐specific transcriptional profile in CVD, and point to few genes modified by ancestry in AD and ADCVD. Ongoing experiments aim to determine differential gene expression relative to pathology, and to develop functional genetic models for screening. Overall, we seek to identify Hispanic ancestry‐ and disease‐specific genes among dementia etiologies as an avenue for precision medicine dementia care among an at‐risk, underrepresented population.

Background and Aims: Hypothermic oxygenated machine perfusion (HOPE) improves outcomes in orthotopic liver transplantation (OLT), but reliance on University of Wisconsin machine perfusion solution (UW-MPS) increases costs and logistical burden. Histidine-tryptophan-ketoglutarate (HTK) has potential as a single-solution alternative for HOPE. This study evaluated the safety and efficacy of HTK versus UW-MPS during HOPE. Methods: A retrospective, propensity score-matched cohort study including 46 patients who received donation after brain death (DBD) grafts that were preserved with HOPE at the Medical University of Vienna between May 2018 and October 2024 was conducted. A total of 23 patients received grafts perfused with HTK; another 23 patients transplanted with organs perfused with UW-MPS were matched based on recipient age and sodium model of end-stage liver disease score, donor age and sex, cold ischemia time, and perfusion time. Postoperative outcomes, perfusion parameters, and cost differences were assessed. Results: The HTK and UW-MPS cohorts demonstrated comparable perfusion dynamics and vascular resistance. While arterial pressure and flow were higher in the UW-MPS group, clinical outcomes—including early allograft dysfunction (47.8% each), ICU stay, and comprehensive complication index—were statistically similar. A trend toward fewer biliary complications (13.0% vs. 30.4%) and reduced hemodialysis requirement (17.4% vs. 30.4%) was observed in the HTK group. Use of HTK reduced perfusion-related costs by approximately EUR 560 per procedure. Conclusion: HTK is a viable alternative to UW-MPS during HOPE in OLT of DBD grafts, offering comparable short-term outcomes and relevant cost savings. Prospective studies are warranted to validate these findings and explore broader applications of single-solution perfusion strategies.

Abstract Background Neuropathologic evaluation is essential for diagnosing and treating dementia, but definitive diagnoses is only available after post‐mortem brain autopsy. Positron emission tomography (PET) offers a potential in vivo proxy for predicting neuropathology. This study proposes a semi‐supervised learning (SSL) model using a single FDG‐PET image to predict underlying neuropathology. Method The SSL model leverages a self‐organized graph structure based on a patient similarity network (PSN) created from 1,495 FDG‐PET images across the aging and neurodegenerative spectrum. Each patient is represented by a node, with edges indicating image similarity derived from principal component analysis features and cosine similarity weights. The PSN structure connects 20 nearest neighbors. Neuropathologic labels were available for 204 autopsied patients. The Poisson Learning Method was employed to propagate labels from these annotated nodes to unlabeled nodes, guided by the PSN structure. FDG‐PET images were collected from clinical and research participants at the Mayo Clinic and processed using an MRI‐free pipeline. Neuropathologic labels were assigned based on widely accepted diagnostic criteria. Leave‐one‐out cross‐validation (LOOCV) was used to assess model performance. Results The confusion matrix demonstrated high accuracy in predicting Alzheimer's disease, frontotemporal lobar degeneration with tau inclusions, and Lewy body disease pathology. A Sankey diagram and label distribution analysis revealed strong correlations between clinical and predicted neuropathologic labels. Conclusion This study highlights the potential of a graph‐based SSL pipeline to predict neuropathological changes using FDG‐PET imaging data, despite limited pathology labels. The findings underscore the value of SSL in bridging the gap between abundant neuroimaging data and scarce neuropathologic labels, contributing to improved dementia diagnosis and understanding.

Abstract Background The locus coeruleus (LC) degenerates early in Alzheimer's disease (AD), with profound volume and neuronal loss. The loss of noradrenergic LC projection neurons results in alterations in attention, memory, and arousal, and constitutes the first site of neurofibrillary tangle accumulation preceding the onset of cognitive symptoms. We sought to investigate the relationship between LC neuronal density and clinical heterogeneity in a neuropathologically‐diagnosed series of AD cases. Methods The FLorida Autopsied Multi‐Ethnic (FLAME) cohort database was queried for neuropathologically‐diagnosed AD cases with a clinical diagnosis of AD dementia or an atypical, non‐amnestic clinical syndrome (e.g., corticobasal syndrome, posterior cortical atrophy). AD cases were selected based on high AD neuropathologic change (ADNC) and lack of frontotemporal lobar degeneration or hippocampal sclerosis, resulting in 591 AD cases and an additional 74 none‐low ADNC controls. Databased clinical diagnosis for AD cases was classified as amnestic or non‐amnestic. Hematoxylin & eosin‐stained slides were digitized and neuronal density was quantified using an in‐house developed macro on 900µmx900µm region of interest using Aperio technology (Leica Biosystems). LC level was classified using neuroanatomic landmarks as rostral, middle, or caudal. Results Control cases had greater neuronal density in the LC compared to AD cases at all three levels, p <0.05. In AD cases, we observed an association between age and neuronal density. Examining these differences along the rostrocaudal‐axis, we found that a younger age at symptomatic onset was associated with lower LC neuronal density in the rostral (correlation coefficient: 0.48; p <0.001) and middle LC (correlation coefficient: 0.28; p <0.001), no association between age at onset and neuronal density was observed at the caudal level. Stratifying our analysis by clinical syndrome, we found fewer neurons in the rostral and middle LC in non‐amnestic AD compared to amnestic AD ( p = 0.006 and 0.029 respectively, Table 1). No significant differences between amnestic and non‐amnestic cases were observed in the caudal LC. Conclusions The locus coeruleus, especially the rostral and middle levels, are especially vulnerable in young‐onset and atypical forms of AD. The loss of noradrenergic neuromodulation may contribute to the atypical symptomatology.

ABSTRACT Objective Aging alters mesenchymal stromal cell (MSC) function, leading to dysregulated adipogenesis across tissues through biased lineage commitment. Fat redistribution from adipose depots to skeletal muscle and bone marrow is common in aging, but the underlying mechanisms remain unclear. This study investigates how MSC senescence modulates adipogenesis. Methods Primary MSCs were isolated from mouse skeletal muscle (FAPs), adipose tissue (APCs), and bone marrow (BMSCs). Single‐cell RNA sequencing was performed to compare transcriptional profiles among these populations. In vitro adipogenic differentiation and DNA damage–induced senescence assays were conducted, and the effects of autologous conditioned media from senescent MSCs on adipogenesis were assessed. Results Transcriptional analyses revealed that FAPs and APCs share greater similarity with each other than with BMSCs. All MSC types exhibited adipogenic potential and developed a robust senescence‐associated secretory phenotype (SASP) upon senescence induction. Conditioned media from senescent MSCs enhanced adipogenesis in BMSCs but inhibited adipogenesis in FAPs and APCs, revealing tissue‐specific paracrine effects. Conclusions MSC senescence reprograms adipogenic bias in a tissue‐dependent, non–cell autonomous manner, contributing to age‐related fat redistribution among adipose tissue, skeletal muscle, and bone marrow. Understanding these mechanisms may provide new therapeutic approaches for improving tissue composition and function in the context of aging.

Abstract Background Neurodegenerative tauopathies, characterized by the aggregation of misfolded tau protein, poses a significant clinical and scientific challenge. Tau interaction with other proteins affects the formation of ‘tau‐seed’ but less is known about its effects on tau‐seed properties. Our previous study revealed that Bassoon (BSN), a presynaptic protein, interacts with tau‐seed, exacerbating its toxicity. A parallel study also associated missense mutations in BSN with tau aggregation in patients, prompting an investigation into the influence of BSN and its mutations in neurodegeneration for potential therapeutic insights. Method We generated a knock‐in mouse model (BSNKI) harboring the disease‐associated p.Pro3866Ala mutation in endogenous Bsn. Cognitive and motor abilities were evaluated throughout the lifespan of heterozygous and homozygous BSNKI mice, along with analyses of BSN and tau patterns, gliosis, and gene expression changes in their brains. Additionally, we conducted single‐nucleic RNA sequencing to identify changes at the cellular level. Result BSNKI mice displayed progressive motor and memory impairments on the rotarod and fear conditioning assays, respectively. At 10 months, their brains displayed somatic BSN and pathological tau accumulation, with the gene expression changes indicating alterations of microglia, classical complement cascade, and synapse pruning pathways, as well as dysregulation of protein quality control pathways. Neuropathological data suggests that the BSN P3866A mutation instigates robust microglia activation, increased microglia‐mediated synapse engulfment, and a co‐deposition of proteasomal subunits with BSN. Furthermore, snRNA‐seq data suggest changes in neuronal populations and cell signaling. Conclusion Our BSNKI mouse model revealed the contributions of BSN P3866A mutation to tau pathogenesis and neurodegeneration. BSNKI animals displayed progressive motor and memory impairments, deposits of endogenous tau and BSN, as well as changes in gene expression and neuronal populations. Notably, BSN likely plays a dual role, promoting tau aggregation and sequestering protein degradation molecules, leading to tau and protein accumulation at the soma and synapse, which in turn could trigger neuroinflammation and other cellular changes. These findings propose BSN as a promising therapeutic target for tauopathies, underscoring the need for further exploration to elucidate underlying mechanisms and therapeutic implications.

Abstract Background We previously identified a novel mechanism describing how pathological tau transfers via extracellular vesicles (EVs) in Alzheimer's disease (AD). Targeting EV secretion to mitigate tau transfer is, therefore, a promising therapeutic approach for AD. P2X purinoreceptor 7 (P2RX7), an ATP‐gated cationic channel predominantly expressed in microglia, regulates the secretion and biogenesis of EVs. Here we investigated the effect of P2rx7 deficiency in PS19 tauopathy mouse model and by proteomic profiling of brain EVs. Method PS19: P2rx7 –/– mice at 9‐10 months of age were tested for fear conditioning and their brain sections were assessed for brain atrophy. Tau pathology was evaluated using ELISA and immunofluorescence against phosphorylated (AT8) and misfolded (Alz50) tau. Brain tissues were further assessed by bulk and single cell RNA‐seq (scRNA‐seq) and brain‐EVs were subjected to proteomic profiling by mass‐spectrometry. P2rx7 –/– mice were intracranially injected with viral vectors expressing P301L tau in neurons and mEmerald‐CD9 in microglia to visualize the secretion of microglial EVs in vivo . Mice conditional knockout (cKO) for P2rx7 in microglia, neurons and astrocytes were injected with a viral vector expressing P301L tau in entorhinal cortex for tau propagation assessment. Result PS19: P2rx7 –/– mice showed significant improvement in contextual and cued memory compared to age‐matched PS19 mice, which was accompanied by preserved cortical and hippocampal volume, and significant reduction of hippocampal synapse loss and tau pathology. By weighted gene co‐expression network analysis (WGCNA) we identified a microglial and EV‐related module strongly correlated with tau pathology which was remarkably downregulated in PS19: P2rx7 –/– mice hippocampus. PS19 mice showed increased secretion of EVs containing tau and mitochondrial proteins in the mouse brain parenchyma, which was significantly downregulated in PS19: P2rx7 –/– mice. scRNA‐seq analysis showed that P2rx7 is required for microglia conversion to inflammatory phenotype with increased expression of EV genes in PS19 mice. P2rx7 deficiency reduced microglial mEmerald‐CD9 + ‐EV secretion in mice expressing P301L tau. Moreover, microglia and neuron‐specific deletion of P2rx7 inhibit tau propagation from the entorhinal cortex to the mouse hippocampus. Conclusion Our study demonstrated a microglial P2RX7‐EV axis with potential implications on neuroinflammation and neurodegeneration associated with tau pathology, further indicating the therapeutic potential of targeting P2rx7 to ameliorate AD progression.

Abstract Background pTau217 is a well validated plasma biomarker for Alzheimer's disease (AD), sensitive to the accumulation of amyloid pathology in the preclinical stages of disease. We leveraged whole blood RNA sequencing and plasma pTau217 measures of amyloid burden to identify blood transcriptomic gene‐network changes that relate to plasma pTau217 levels in cognitively normal older adults. We then quantified the abundance of cell populations from the transcriptomic data to identify blood cell abundance alterations that correlate with plasma ptau217 levels. Method Whole blood RNA sequencing and plasma pTau217 data were obtained from 1739 participants in the Anti‐Amyloid Treatment in Asymptomatic Alzheimer's Disease (A4) Study. RNAseq data were aligned, sorted, counted, batch normalized, and iteratively adjusted for covariates. 20,718 genes were available for analysis following quality control. Plasma samples ( n = 1597) were analyzed for pTau217 using the Eli Lilly and Company Diagnostics Laboratory immunoassay. Samples from 724 participants (63% females, mean age 71, 61% amyloid+) with RNA sequencing and biomarker data were used for analysis. Cell fractions were quantified using CIBERSORTx (LM22 used as reference) and WGCNA was used to calculate gene co‐expression modules. Linear regression related gene module expression or cell fraction to mean pTau217 levels covarying for age, sex, education, APOE ε2 and ε4 status. Correction for multiple comparisons used the false discovery rate. Gene enrichment was performed using Gene Ontology. Result Five gene modules were associated with plasma pTau217. For the turquoise module (β=‐0.81, p.fdr=0.005), higher expression was associated with higher p ‐tau217 while higher expression in the blue (β=‐0.70, p.fdr=0.01), lightcyan (β=‐0.68, p.fdr=0.01), grey60 (β=‐0.64, p.fdr=0.02), and brown (β=‐0.55, p.fdr=0.04) modules were associated with lower p ‐tau217. These modules were enriched for phagocytosis, ribonucleoprotein complex biogenesis, immunoglobulin mediated immune response, nucleosome assembly, and cytoplasmic translation pathway genes. In cell fraction analysis, higher predicted abundance of neutrophils related to ptau217 levels (β=0.33, p.fdr=0.03). Conclusion Our results demonstrate an association between immune response and epigenetic pathway genes with plasma pTau217 levels in preclinical AD. Future work will seek to clarify whether these signatures also relate to brain amyloid PET to evaluate blood transcription networks as complementary biomarkers to improve preclinical prediction.

Abstract Background Early mechanisms of neuronal damage in Alzheimer's Disease (AD) include mitochondrial dysfunction and abnormal energy homeostasis. AD‐associated mitochondrial signaling was shown to occur upstream of amyloid precursor protein processing, Ab production, apolipoprotein E (APOE) expression, and tau pathology. However, whether alterations in mitochondrial function are sufficient to instigate AD remains unclear. Mitochondrial complex I (mtCI) is a rate‐limiting enzyme in the oxidative phosphorylation (OXPHOS) machinery. Changes in mtCI activity influence ATP and ROS production, cellular energy and redox homeostasis. We examined how reduced activity of mtCI due to a knockout of one of its accessory subunits Ndufs4 in mice affects transcriptional networks in the brain. We also determined whether reduced activity of mtCI abrogates neuroprotective properties of a small molecule CP2. Method RNA‐sequencing of the brain tissue was performed using Ndufs4 ‐/‐ and control mice ( n = 3–5 per group). The co‐expression modules of differentially expressed genes were compared to the AMP‐AD patient cohort data. Key mechanisms, including mitophagy signaling, were confirmed using ELISA and western blot analyses; the effect on mtCI activity was confirmed using functional assays. Results In Ndufs4 ‐/‐ mice, a residual activity of mtCI was ∼50% of the control. This loss of function led to a global disruption of mitochondrial homeostasis, energy metabolism, synaptic function, significant increase in mitophagy and a reduction in biogenesis. Transcriptomic signatures in brain tissue of male and female Ndufs4 ‐/‐ mice overlapped with changer reported for AD patients and AD mouse models with Ab and p ‐tau pathologies. These changes were partially rescued by a neuroprotective mitochondria‐targeting small molecule CP2. Consistent with studies in AD mice, CP2 treatment in Ndufs4 ‐/‐ mice augmented the expression of genes associated with mitochondrial biogenesis and turnover, synaptic activity, autophagy, redox balance, and reduced expression of genes related to inflammation. Sex‐specific differences included better adaptation to a reduced activity of mtCI and to CP2 treatment in female mice. Conclusion Reduced mtCI activity was sufficient to induce the AD‐like transcriptomic changes in brain. Residual mtCI function was sufficient to mediate neuroprotective effect of CP2, emphasizing a key role of mitochondria in AD development and treatment.