Plaque Density Research Articles

Sex-Specific Association Patterns of Bone Microstructure and Lower Leg Arterial Calcification.

In conversations about bone loss and the importance of calcium homeostasis, patients frequently inquire about the association with arterial calcifications. Although a relationship between bone loss and the occurrence of vascular calcifications is suspected, it is not yet fully investigated and understood. This study aims to analyze associations between bone mineralization, structure, and vascular calcification at the lower leg in patients with low bone mineral density in HR-pQCT. We retrospectively analyzed 774 high-resolution quantitative computed tomography (HR-pQCT) scans of the distal tibia for the presence of vascular calcifications. After sex-specific propensity score matching for age and BMI to account for confounders, 132 patients remained for quantification of bone microstructure, bone density, lower leg arterial calcification (LLAC), and laboratory parameters of bone turnover. The interactions between bone parameters and vascular calcification were quantified by regression analyses. The calcium metabolism was not different between individuals with and without LLAC, nor oral calcium supplementation. Female patients with LLAC had a higher cortical perimeter (p = 0.016) compared to female patients without LLAC, whereas male patients with LLAC had lower cortical pore diameter than male patients without LLAC (p = 0.027). The appearance of LLAC was sex specifically associated with bone parameters.In female patients, only plaque density was associated with HR-pQCT bone parameters and age, whereas in male patients, plaque volume was associated with HR-pQCT parameters of the distal tibia. Female patients exhibit an increasing plaque density depended on age and trabecular thinning. Decreasing cortical pore diameter and trabecular number along with increasing bone mineralization are linked to increasing plaque volume in male patients.

Human Alzheimer's Disease ATN/ABC Staging Applied to Aging Rhesus Macaque Brains: Association With Cognition and MRI-Based Regional Gray Matter Volume.

The brain changes of Alzheimer's disease (AD) include Abeta (Aβ)amyloid plaques ("A"), abnormally phosphorylated tau tangles ("T"), and neurodegeneration ("N"). These have been used to construct in vivo and postmortem diagnostic and staging classifications for evaluating the spectrum of AD in the "ATN" and "ABC" ("B" for Braak tau stage, "C" for Consortium to Establish a Registry for Alzheimer's Disease [CERAD] neuritic plaque density) systems. Another common AD feature involves cerebral amyloid angiopathy (CAA). We report the first experiment to examine relationships among cognition, brain distribution of amyloid plaques, CAA, tau/tangles, and magnetic resonance imaging (MRI)-determined volume changes (as a measure of "N") in the same group of behaviorally characterized nonhuman primates. Both ATN and ABC systems were applied to a group of 32 rhesus macaques aged between 7 and 33 years. When an immunohistochemical method for "T" and "B" was used, some monkeys were "triple positive" on ATN, with a maximum ABC status of A1B2C3. With silver or thioflavin S methods, however, all monkeys were classified as T-negative and B0, indicating the absence of mature neurofibrillary tangles (NFTs) and hence neuropathologically defined AD. Although monkeys at extremes of the ATN and ABC classifications, or with frequent CAA, had significantly lower scores on some cognitive tests, the lack of fully mature NFTs or dementia-consistent cognitive impairment indicates that fully developed AD may not occur in rhesus macaques. There were sex differences noted in the types of histopathology present, and only CAA was significantly related to gray matter volume.

FAM19A5 Deficiency Mitigates the Aβ Plaque Burden and Improves Cognition in Mouse Models of Alzheimer's Disease.

FAM19A5, a novel secretory protein highly expressed in the brain, is potentially associated with the progression of Alzheimer's disease (AD). However, its role in the AD pathogenesis remains unclear. Here, we investigated the potential function of FAM19A5 in the context of AD. We generated APP/PS1 mice with partial FAM19A5 deficiency, termed APP/PS1/FAM19A5+/LacZ mice. Compared with control APP/PS1 mice, APP/PS1/FAM19A5+/LacZ mice exhibited significantly lower Aβ plaque density and prolonged the lifespan of the APP/PS1 mice. To further explore the therapeutic potential of targeting FAM19A5, we developed a FAM19A5 antibody. Administration of this antibody to APP/PS1 mice significantly improved their performance in the Y-maze and passive avoidance tests, indicating enhanced cognitive function. This effect was replicated in 5XFAD mice, a model of early-onset AD characterized by rapid Aβ accumulation. Additionally, FAM19A5 antibody treatment in 5XFAD mice led to enhanced exploration of novel objects and increased spontaneous alternation behavior in the novel object recognition and Y-maze tests, respectively, indicating improved cognitive function. These findings suggest that FAM19A5 plays a significant role in AD pathology and that targeting with FAM19A5 antibodies may be a promising therapeutic strategy for AD.

The GLP-1 medicines semaglutide and tirzepatide do not alter disease-related pathology, behaviour or cognitive function in 5XFAD and APP/PS1 mice

ObjectiveThe development of glucagon-like peptide-1 receptor (GLP-1R) agonists for the treatment of type 2 diabetes and obesity has been accompanied by evidence for anti-inflammatory and cytoprotective actions in the heart, blood vessels, kidney, and brain. Whether GLP-1R agonists might be useful clinically for attenuating deterioration of cognitive dysfunction and reducing the progression of Alzheimer's disease remains uncertain. MethodsHere we evaluated the actions of semaglutide and tirzepatide, clinically distinct GLP-1 medicines, in two mouse models of neurodegeneration. ResultsSemaglutide reduced body weight and improved glucose tolerance in 12-month-old male and female 5XFAD and APP/PS1 mice, consistent with pharmacological engagement of the GLP-1R. Nevertheless, amyloid plaque density was not different in the cerebral cortex, hippocampus, or subiculum of semaglutide-treated 12-month-old 5XFAD and APP/PS1 mice. IBA1 and GFAP expression were increased in the hippocampus of 5XFAD and APP/PS1 mice but were not reduced by semaglutide. Moreover, parameters of neurobehavioral and cognitive function evaluated using Open Field testing or the Morris water maze were not improved following treatment with semaglutide. To explore whether incretin therapies might be more effective in younger mice, we studied semaglutide and tirzepatide action in 6-month-old male and female 5XFAD mice. Neither semaglutide nor tirzepatide modified the extent of plaque accumulation, hippocampal IBA1+ or GFAP+ cells, or parameters of neurobehavioral testing, despite improving glucose tolerance and reducing body weight. mRNA biomarkers of inflammation and neurodegeneration were increased in the hippocampus of male and female 5XFAD mice but were not reduced after treatment with semaglutide or tirzepatide. ConclusionsCollectively, these findings reveal preservation of the metabolic actions of two GLP-1 medicines, semaglutide and tirzepatide, yet inability to detect improvement in structural and functional parameters of neurodegeneration in two mouse models of Alzheimer's disease.

A novel imaging biomarker for prediction of cerebrovascular ischemic events: Pericarotid fat density

BackgroundTo investigate the relationship between pericarotid fat density measured in carotid CTA and vulnerable carotid plaque. MethodsThis retrospective study included 374 participants who underwent carotid CTA between June 1, 2021, and December 1, 2021 (234 males, median age 68 years [interquartile range: 61–75]). Two groups, symptomatic and asymptomatic, were defined based on either diffusion-weighted MRI or a clinical history of acute ischemia or TIA within 6 months before or after CTA. The relationship between pericarotid fat density and cerebrovascular ischemic events was assessed using receiver operating characteristic analysis and binary logistic regression analysis. ResultsIn the symptomatic group (n = 135), mean pericarotid fat density (−63.3 ± 21.7 vs. -81.7 ± 16.9 HU, respectively; p < 0.001) and median maximum plaque thickness (4 [interquartile range: 3–6] vs. 3.7 [interquartile range: 2.6–4.7] mm, respectively; p = 0.002) were higher, while plaque density (42.1 ± 19.6 vs. 50.6 ± 20.4 HU, respectively; p = 0.001) was lower compared to the asymptomatic group. Pericarotid fat density (OR: 1.038, 95% CI: 1.023–1.053, p < 0.001) was identified as an independent predictor for symptomatic patients. The optimal cut-off value for pericarotid fat density predicting symptomatic patients was estimated as −74 HU (area under the curve: 0.753, 95% CI:0.699–0.808, p < 0.001). Inter-reader agreement for pericarotid fat density was found to be almost perfect (intraclass correlation coefficient: 0.818, 95% CI: 0.770–0.856, p < 0.001). ConclusionPericarotid fat density may serve as an imaging biomarker in predicting acute cerebrovascular ischemic events.

Improved Detection of Small and Low-Density Plaques in Virtual Noncontrast Imaging-based Calcium Scoring at Photon-Counting Detector CT.

Purpose To investigate the impact of plaque size and density on virtual noncontrast (VNC)-based coronary artery calcium scoring (CACS) using photon-counting detector CT and to provide safety net reconstructions for improved detection of subtle plaques in patients whose VNC-based CACS would otherwise be erroneously zero when compared with true noncontrast (TNC)-based CACS. Materials and Methods In this prospective study, CACS was evaluated in a phantom containing calcifications with different diameters (5, 3, and 1 mm) and densities (800, 400, and 200 mg/cm3) and in participants who underwent TNC and contrast-enhanced cardiac photon-counting detector CT (July 2021-March 2022). VNC images were reconstructed at different virtual monoenergetic imaging (55-80 keV) and quantum iterative reconstruction (QIR) levels (QIR,1-4). TNC scans at 70 keV with QIR off served as the reference standard. In vitro CACS was analyzed using standard settings (3.0-mm sections, kernel Qr36, 130-HU threshold). Calcification detectability and CACS of small and low-density plaques were also evaluated using 1.0-mm sections, kernel Qr44, and 120- or 110-HU thresholds. Safety net reconstructions were defined based on background Agatston scores and evaluated in vivo in TNC plaques initially nondetectable using standard VNC reconstructions. Results The in vivo cohort included 63 participants (57.8 years ± 15.5 [SD]; 37 [59%] male, 26 [41%] female). Correlation and agreement between standard CACSVNC and CACSTNC were higher in large- and medium-sized and high- and medium-density than in low-density plaques (in vitro: intraclass correlation coefficient [ICC] ≥ 0.90; r > 0.9 vs ICC = 0.20-0.48; r = 0.5-0.6). Small plaques were not detectable using standard VNC reconstructions. Calcification detectability was highest using 1.0-mm sections, kernel Qr44, 120- and 110-HU thresholds, and QIR level of 2 or less VNC reconstructions. Compared with standard VNC, using safety net reconstructions (55 keV, QIR 2, 110-HU threshold) for in vivo subtle plaque detection led to higher detection (increased by 89% [50 of 56]) and improved correlation and agreement of CACSVNC with CACSTNC (in vivo: ICC = 0.51-0.61; r = 0.6). Conclusion Compared with TNC-based calcium scoring, VNC-based calcium scoring was limited for small and low-density plaques but improved using safety net reconstructions, which may be particularly useful in patients with low calcium scores who would otherwise be treated based on potentially false-negative results. Keywords: Coronary Artery Calcium CT, Photon-Counting Detector CT, Virtual Noncontrast, Plaque Size, Plaque Density Supplemental material is available for this article. © RSNA, 2024.

AI-enabled Cardiac Chambers Volumetry and Calcified Plaque Characterization in Coronary Artery Calcium (CAC) Scans (AI-CAC) Significantly Improves on Agatston CAC Score for Predicting All Cardiovascular Events: The Multi-Ethnic Study of Atherosclerosis.

Coronary artery calcium (CAC) scans contain valuable information beyond the Agatston Score which is currently reported for predicting coronary heart disease (CHD) only. We examined whether new artificial intelligence (AI) algorithms applied to CAC scans may provide significant improvement in prediction of all cardiovascular disease (CVD) events in addition to CHD, including heart failure, atrial fibrillation, stroke, resuscitated cardiac arrest, and all CVD-related deaths. We applied AI-enabled automated cardiac chambers volumetry and automated calcified plaque characterization to CAC scans (AI-CAC) of 5830 individuals (52.2% women, age 61.7±10.2 years) without known CVD that were previously obtained for CAC scoring at the baseline examination of the Multi-Ethnic Study of Atherosclerosis (MESA). We used 15-year outcomes data and assessed discrimination using the time-dependent area under the curve (AUC) for AI-CAC versus the Agatston Score. During 15 years of follow-up, 1773 CVD events accrued. The AUC at 1-, 5-, 10-, and 15-year follow up for AI-CAC vs Agatston Score was (0.784 vs 0.701), (0.771 vs. 0.709), (0.789 vs.0.712) and (0.816 vs. 0.729) (p<0.0001 for all), respectively. The category-free Net Reclassification Index of AI-CAC vs. Agatston Score at 1-, 5-, 10-, and 15-year follow up was 0.31, 0.24, 0.29 and 0.29 (p<.0001 for all), respectively. AI-CAC plaque characteristics including number, location, and density of plaque plus number of vessels significantly improved NRI for CAC 1-100 cohort vs. Agatston Score (0.342). In this multi-ethnic longitudinal population study, AI-CAC significantly and consistently improved the prediction of all CVD events over 15 years compared with the Agatston score.

Anthrometric dimensions and their impact on cardiovascular risk factors.

Central obesity is an important risk factor for cardiovascular disease. The abdominal subcutaneous adipose tissue thickness (ASATT) can be used to evaluate central obesity. The objective of this study was to compare ASATT with cardiovascular risk factors and other anthropometric parameters to show that ASATT can be a useful tool for the early assessment of heart disease risk. In this observational cross-sectional study, anthropometric measurements of 100 autopsied decedents, including waist circumference, hip circumference, waist/height and waist/hip ratio, aortic outlet and coronary artery atheroma plaque densities, heart weight, ventricular wall thickness, and ASATT, were assessed. The research data were evaluated using the Statistical Package for the Social Sciences for Windows 25.0. The average ASATT of the male group was 40.36 mm (SD: 11.00), and the average of female cases was 46.34 mm (SD: 18.12). There was no statistically significant difference between the sexes and both age groups in terms of the ASATT score (P > .05). There was a positive correlation between ASATT and waist circumference, hip circumference, and waist/height ratio in both sexes (P < .05). While ASATT was not related to atheroma density in the coronary arteries of men (P > .05), it was correlated with atheroma density in all 3 coronary arteries of women (P < .05). In the male group, the aortic inner surface atheroma density was positively correlated with ASATT (P < .05). In both sexes, there was a positive correlation (P < .05) between ASATT and heart weight; however, no such correlation was observed with right and left ventricular wall thickness (P > .05). ASATT is related to other anthropometric measurements, atherosclerosis of critical vessels, and heart weight, and can be used to scan the patient population for heart disease risk assessment with noninvasive methods.

Microdose lithium improves behavioral deficits and modulates molecular mechanisms of memory formation in female SAMP-8, a mouse model of accelerated aging.

Alzheimer's disease (AD) is the most common neuronal disorder that leads to the development of dementia. Until nowadays, some therapies may alleviate the symptoms, but there is no pharmacological treatment. Microdosing lithium has been used to modify the pathological characteristics of the disease, with effects in both experimental and clinical conditions. The present work aimed to analyze the effects of this treatment on spatial memory, anxiety, and molecular mechanisms related to long-term memory formation during the aging process of a mouse model of accelerated aging (SAMP-8). Female SAMP-8 showed learning and memory impairments together with disruption of memory mechanisms, neuronal loss, and increased density of senile plaques compared to their natural control strain, the senescence-accelerated mouse resistant (SAMR-1). Chronic treatment with lithium promoted memory maintenance, reduction in anxiety, and maintenance of proteins related to memory formation and neuronal density. The density of senile plaques was also reduced. An increase in the density of gamma-aminobutyric acid A (GABAA) and α7 nicotinic cholinergic receptors was also observed and related to neuroprotection and anxiety reduction. In addition, this microdose of lithium inhibited the activation of glycogen synthase kinase-3beta (GSK-3β), the classical mechanism of lithium cell effects, which could contribute to the preservation of the memory mechanism and reduction in senile plaque formation. This work shows that lithium effects in neuroprotection along the aging process are not related to a unique cellular mechanism but produce multiple effects that slowly protect the brain along the aging process.

Bearded capuchin monkeys as a model for Alzheimer's disease.

The absence of a natural animal model is one of the main challenges in Alzheimer's disease research. Despite the challenges of using nonhuman primates in studies, these animals can bridge mouse models and humans, as nonhuman primates are phylogenetically closer to humans and can spontaneously develop AD-type pathology. The capuchin monkey, a New World primate, has recently attracted attention due to its skill in creating and using instruments. We analyzed one capuchin brain using structural 7T MRI and performed a neuropathological evaluation of three animals. Alzheimer-type pathology was found in the two of the capuchins. Widespread β-amyloid pathology was observed, mainly in focal deposits with variable morphology and a high density of mature plaques. Notably, plaque-associated dystrophic neurites associated with disruption of axonal transport and early cytoskeletal alteration were frequently found. Unlike in other species of New World monkeys, cerebral arterial angiopathy was not the predominant form of β-amyloid pathology. Additionally, abnormal aggregates of hyperphosphorylated tau, resembling neurofibrillary pathology, were observed in the temporal and frontal cortex. Astrocyte hypertrophy surrounding plaques was found, suggesting a neuroinflammatory response. These findings indicate that aged capuchin monkeys can spontaneously develop Alzheimer-type pathology, indicating that they may be an advantageous animal model for research in Alzheimer's disease.

Correlation of Presynaptic and Postsynaptic Proteins with Pathology in Alzheimer's Disease.

Synaptic transmission is essential for nervous system function and the loss of synapses is a known major contributor to dementia. Alzheimer's disease dementia (ADD) is characterized by synaptic loss in the mesial temporal lobe and cerebral neocortex, both of which are brain areas associated with memory and cognition. The association of synaptic loss and ADD was established in the late 1980s, and it has been estimated that 30-50% of neocortical synaptic protein is lost in ADD, but there has not yet been a quantitative profiling of different synaptic proteins in different brain regions in ADD from the same individuals. Very recently, positron emission tomography (PET) imaging of synapses is being developed, accelerating the focus on the role of synaptic loss in ADD and other conditions. In this study, we quantified the densities of two synaptic proteins, the presynaptic protein Synaptosome Associated Protein 25 (SNAP25) and the postsynaptic protein postsynaptic density protein 95 (PSD95) in the human brain, using enzyme-linked immunosorbent assays (ELISA). Protein was extracted from the cingulate gyrus, hippocampus, frontal, primary visual, and entorhinal cortex from cognitively unimpaired controls, subjects with mild cognitive impairment (MCI), and subjects with dementia that have different levels of Alzheimer's pathology. SNAP25 is significantly reduced in ADD when compared to controls in the frontal cortex, visual cortex, and cingulate, while the hippocampus showed a smaller, non-significant reduction, and entorhinal cortex concentrations were not different. In contrast, all brain areas showed lower PSD95 concentrations in ADD when compared to controls without dementia, although in the hippocampus, this failed to reach significance. Interestingly, cognitively unimpaired cases with high levels of AD pathology had higher levels of both synaptic proteins in all brain regions. SNAP25 and PSD95 concentrations significantly correlated with densities of neurofibrillary tangles, amyloid plaques, and Mini Mental State Examination (MMSE) scores. Our results suggest that synaptic transmission is affected by ADD in multiple brain regions. The differences were less marked in the entorhinal cortex and the hippocampus, most likely due to a ceiling effect imposed by the very early development of neurofibrillary tangles in older people in these brain regions.

Abstract TP176: Radiological Reporting Frequencies of High-Risk Non-Stenosing Carotid Plaque Features: A Follow-Up Observational Study

Background: High-risk non-stenosing carotid plaque features are emerging as a possible source of embolism in the setting of ESUS. Unless there is a hemodynamically significant stenosis, neuroradiology reports tend to be rarely descriptive of these features. Methods: In our previous study published in September 2022, we analyzed a patient sample drawn from the stroke registry of the HFHS between June 2016 and June 2021. Our results showed a higher incidence of high-risk plaque features including plaque ulceration (19.08% vs 5.26%, p&lt;0.0001), plaque thickness &gt;3mm: (19.08% vs 7.24%, p=0.001), and length &gt;1cm (13.16% vs 5.92%, p=0.0218) ipsilateral to ESUS. In this subsequent study, we utilized the same patient dataset and used CTA reports on EPIC to explore how frequently neuroradiologists had mentioned those features. We utilized Fisher’s exact test to compare the frequencies of reporting each plaque characteristic. Results: We analyzed 152 CTA reports in depth. Our findings indicate that the frequency of reporting plaque ulceration compared to the frequency of reporting plaque calcification was significantly different (8.1% vs 100%, p&lt; 0.00001), this is also noticed with plaque length (4.6%, p&lt; 0.00001) and soft plaques (72.1%, p&lt; 0.00001). Notably, none of the CTA reports had commented on any plaque thickness or the presence of any “high-risk” features when encountering stroke ipsilaterally. Conclusion: When carotid plaques are not causing hemodynamically significant stenosis, neuroradiology reports frequently mention the density of plaques, but unfortunately overlook other characteristics. It is essential to conduct algorithms, scoring systems and prediction models to determine which plaque features are highly associated with embolism. These models should help prioritize the description of these features, alongside commonly reported metrics such as plaque density and the degree of stenosis.

Naringin Reduced the Density and Total Number of Aβ Plaques and Restored Memory Function and Volume of Hippocampal CA1 Area in Alzheimer's Disease Model Rats: A Stereological Study

Background: Alzheimer's disease (AD), the most prevalent form of dementia worldwide, is characterized by memory impairment and the accumulation of tau and beta-amyloid (Aβ) plaques. Naringin, a flavonoid, has exhibited strong anti-inflammatory, anti-oxidant, and anti-apoptotic properties. Objectives: In this study, we aimed to demonstrate the neuroprotective effects of naringin on memory function, the total number and density of Aβ plaques, and the volume of the hippocampal CA1 region in a scopolamine (SCO)-induced AD model in rats. Methods: Forty male Wistar rats were randomly divided into the following groups: A control group, a saline + SCO (3 mg/kg) group (pretreated with 200 µL saline), and 3 treatment groups receiving naringin at doses of 50 mg/kg/day + SCO, 100 mg/kg/day + SCO, and 200 mg/kg/day + SCO (pretreated with 50, 100, or 200 mg/kg of naringin) for 14 consecutive days via intraperitoneal (IP) injection. After the 14-day pretreatment period, the saline + SCO and 3 naringin treatment groups received SCO (3 mg/kg) to induce an AD-like condition. Memory function was assessed using the inhibitory passive avoidance test. Following brain harvesting, paraffin-embedded coronal brain slices were stained with Congo red, and the density and the total number of Aβ plaques and the volume of the hippocampal CA1 area were estimated using unbiased stereological techniques. Results: The results indicated that naringin significantly improved memory function, with the most pronounced effect observed in the naringin 200 mg/kg + SCO group. Stereological analysis revealed that SCO reduced the volume of the hippocampal CA1 area and increased the total number and density of Aβ plaques. Pretreatment with naringin significantly restored the hippocampal CA1 volume in the 200 mg/kg + SCO group compared to the saline + SCO group. Additionally, naringin reduced the total number and density of Aβ plaques, with the most significant decrease observed in the 200 mg/kg + SCO group. Conclusions: Naringin restored memory function and the volume of the hippocampal CA1 region while reducing the total number and density of Aβ plaques in a SCO-induced AD model in rats. This stereological study complements previous molecular research on naringin's neuroprotective effects in AD-like pathogenesis.

Effect of hormone replacement therapy on amyloid beta (Aβ) plaque density in the rhesus macaque amygdala.

Amyloid beta (Aβ) plaque density was examined in the amygdala of rhesus macaques, to elucidate the influence of age, diet and hormonal environment. Luminex technology was used to measure cerebrospinal fluid (CSF) concentrations of Aβ40 and Aβ42 across three decades, while immunohistochemistry was used to examine Aβ plaque density in the amygdala. Aβ40 was found to be the predominant isoform of Aβ in the CSF, but neither Aβ40 or Aβ42 concentrations showed an age-related change, and the ratio of Aβ42 to Aβ40 showed only a marginal increase. Significantly fewer Aβ plaques were detected in the amygdala of old ovariectomized animals if they received estradiol HRT (p < 0.001); similar results were obtained regardless of whether they had been maintained on a regular monkey chow for ∼48 months or on a high-fat, high-sugar, Western-style diet for ∼30 months. The results demonstrate that HRT involving estrogen can reduce Aβ plaque load in a cognitive brain region of aged non-human primates. The results from this translational animal model may therefore have clinical relevance to the treatment of AD in post-menopausal women, whether used alone, or as a supplement to current pharmacological and monoclonal antibody-based interventions.

To what extent does PLCG2 expression have a positive impact on AD

Late-onset Alzheimer’s disease (LOAD) is a prevalent form of AD that lacks a cure. Previous research has shown that PLCG2, associated with inflammatory response, influences AD by affecting amyloid plaque density. Inflammation plays a crucial role in AD progression, as Aβ activates microglia, triggering an inflammatory response with varied consequences for neuronal survival. This study aims to explore the impact of different PLCG2 expression levels on AD using 5xFAD mouse models. Four experiments were conducted to investigate the effect of PLCG2 expression on inflammation, amyloid plaque density, and cognitive function. The GAL4-UAS system and CRISPR-Cas9 system were employed for genetic modification, while immunofluorescence staining and the Morris water navigation task were used for analysis. Results indicate a positive correlation between PLCG2 expression and immune response, with the PLCG25x mice exhibiting the highest immune response. Additionally, higher PLCG2 expression levels were associated with slower growth in amyloid plaque density. The optimal PLCG2 expression level was found to be PLCG22x, which had a positive impact on AD conditions. This research provides valuable insights into the role of PLCG2 in AD pathogenesis and highlights the potential for PLCG2-directed therapeutics as a promising avenue for developing novel treatments for LOAD.

Longitudinal Quantification of Sub‐Regional Hippocampal Amyloid‐Beta Burden in Ex‐Vivo slices from the AppNL‐G‐F Mouse Model of Alzheimer’s Disease

AbstractBackgroundAmyloid‐beta (Aβ) pathology is suggested to precede the onset of clinical Alzheimer’s disease symptoms by up to two decades. The humanised AppNL‐G‐F knock‐in model of amyloidopathy has accelerated pathogenesis and can be used to study AD progression. Here we used it to quantify the temporal and spatial characteristics of Aβ plaque accumulation as they first appear in the hippocampus, and as pathology continues to develop.MethodAppNL‐G‐F knock‐in mice and wild‐type mice at 1, 3, 6, and 9 months of age were transcardially perfused with PBS followed by 4% paraformaldehyde (PFA), followed by preparation of coronal slices for immunohistochemistry analysis. Samples were stained with anti‐Aβ antibody (6E10) together with a neuronal marker, NeuN, and DAPI. Images were taken of sub‐hippocampal regions (CA1, CA3, DG), in left/right hemispheres, and ventral/dorsal segments using a confocal microscope (Leica SP8). Summation of intensity across Z‐stacks in Fiji was used to quantify Aβ plaques in regions of interest.ResultWe found age to be a statistically significant factor on determining area density, with hippocampal deposition observed by 3 months. Bin analysis showed a near‐exponential reduction in plaque number with increasing plaque size, increasing with age. Regionally, there was an increase in plaque density in CA3, with non‐linear regression analysis indicating area density for CA3 is most strongly correlated with age. Within the CA1 region, the densest plaque formation was in the pyramidal cell layer. Further analysis at the aged 9‐month time point suggested a differential pathology across the axial plane and greater left‐hemispheric lateralisation.ConclusionThis data provides further evidence for the protracted timeline to which AppNL‐G‐F knock‐in mice recapitulate key AD neuropathologies including insoluble amyloidosis beginning before 3 months in the hippocampus. It also indicates potentially novel differential sub‐regional Aβ accumulation patterns, axial variations, and hemispheric asymmetries, offering mechanistic insights for plaque localisation and differential susceptibility to Aβ. This could aid advancement of Αβ‐targeting therapies.

Correlations between [18F]flutemetamol PET and region‐matched postmortem integrated density measures of cyano‐flutemetamol signal in Aβ plaques

AbstractBackgroundThe binding substrates of [18F]flutemetamol and [11C]PiB PET consist of fibrillar amyloid‐β (Aβ) aggregates in morphologically and structurally distinct diffuse plaques (DP) and cored plaques (CP) which are present at different proportions across brain regions in Alzheimer’s disease (AD). To account for this heterogeneity, an unbiased quantitative measure integrating plaque size and density of amyloid‐β (Aβ) fibrils in plaques could help avoid false positive results, improve imaging‐to‐autopsy correlations, and further advance our understanding of pathological substrates for binding of amyloid PET tracers.MethodSixteen subjects underwent [18F]flutemetamol PET imaging in the pivotal Phase III end‐of‐life study (Study GE067‐007 and GE067‐026) and later came to autopsy (mean imaging‐to‐autopsy interval was 111 ± 87.6 days). [18F]flutemetamol SUVRpons values in four neocortical regions were correlated with region‐matched postmortem measures of cyano‐flutemetamol labeling of all plaques, as well as CP and DP separately, using percent area coverage, mean grayscale intensity of fluorescence, or a combination of the two measures referred to as integrated density.ResultIn the analysis of all cyano‐flutemetamol‐labeled plaques, [18F]flutemetamol SUVRpons values were more closely associated with integrated density measures than percent area coverage and mean grayscale values. Similarly, when CP and DP were analyzed separately, the integrated density values showed the closest association with neocortical region‐matched [18F]flutemetamol SUVRpons values. When area coverage of CP and DP were each expressed as a fraction of total plaque area coverage with or without integrating fluorescence intensity values, [18F]flutemetamol SUVRpons values within each region of interest were associated with the DP, but not the CP, area coverage measure.ConclusionThe association of antemortem [18F]flutemetamol PET and region‐matched postmortem integrated density measurements of cyano‐flutemetamol labeled plaques further supports the hypothesis that amyloid PET signal is influenced both by plaque size and Aβ fibril density within DP and CP. Further elucidating the relative contributions of each plaque type to the retention of amyloid PET radioligands could influence how a positive amyloid PET signal is interpreted in relation to postmortem pathology data.

Correlations between [18F]flutemetamol PET and region‐matched postmortem integrated density measures of cyano‐flutemetamol signal in Aβ plaques

AbstractBackgroundThe binding substrates of [18F]flutemetamol and [11C]PiB PET consist of fibrillar amyloid‐ß (Aß) aggregates in morphologically and structurally distinct diffuse plaques (DP) and cored plaques (CP) which are present at different proportions across brain regions in Alzheimer’s disease (AD). To account for this heterogeneity, an unbiased quantitative measure integrating plaque size and density of amyloid‐ß (Aß) fibrils in plaques could help avoid false positive results, improve imaging‐to‐autopsy correlations, and further advance our understanding of pathological substrates for binding of amyloid PET tracers.MethodSixteen subjects underwent [18F]flutemetamol PET imaging in the pivotal Phase III end‐of‐life study (Study GE067‐007 and GE067‐026) and later came to autopsy (mean imaging‐to‐autopsy interval was 111 ± 87.6 days). [18F]flutemetamol SUVRpons values in four neocortical regions were correlated with region‐matched postmortem measures of cyano‐flutemetamol labeling of all plaques, as well as CP and DP separately, using percent area coverage, mean grayscale intensity of fluorescence, or a combination of the two measures referred to as integrated density.ResultIn the analysis of all cyano‐flutemetamol‐labeled plaques, [18F]flutemetamol SUVRpons values were more closely associated with integrated density measures than percent area coverage and mean grayscale values. Similarly, when CP and DP were analyzed separately, the integrated density values showed the closest association with neocortical region‐matched [18F]flutemetamol SUVRpons values. When area coverage of CP and DP were each expressed as a fraction of total plaque area coverage with or without integrating fluorescence intensity values, [18F]flutemetamol SUVRpons values within each region of interest were associated with the DP, but not the CP, area coverage measure.ConclusionThe association of antemortem [18F]flutemetamol PET and region‐matched postmortem integrated density measurements of cyano‐flutemetamol labeled plaques further supports the hypothesis that amyloid PET signal is influenced both by plaque size and Aß fibril density within DP and CP. Further elucidating the relative contributions of each plaque type to the retention of amyloid PET radioligands could influence how a positive amyloid PET signal is interpreted in relation to postmortem pathology data.

A novel 3D imaging method to establish baseline amyloid‐beta plaque load and analyze compound efficacy in pre‐clinical Alzheimer’s disease animal models

AbstractBackgroundAmyloid‐beta (Aß) plaque deposition in the brain represents a significant hallmark of Alzheimer’s Disease (AD). Standard laboratory approaches assessing Aß lack the ability to pair high‐throughput whole‐organ imaging with region‐specific quantitation, and often require tissue homogenization. To analyze changes in Aß spatiotemporally, we developed a novel Serial Two‐Photon Plus (STP2) pipeline to quantify plaque progression and depression as a function of brain region, resulting in indexed brain sections for secondary analysis using MALDI HiPLEX‐IHC with imaging mass spectrometry (IMS).MethodPlaques in the well characterized 5XFAD mouse model of AD were labeled with Methoxy‐X04, an Aß plaque‐specific compound, prior to transcardial perfusion and whole‐brain excision. The STP2 platform uses a TissueCyte system to produce high‐resolution multi‐channel datasets, yielding 3D models of each brain. The Allen Mouse Brain Common Coordinate Framework (CCFv3) was registered to each brain, and our automated pipeline quantified plaque load and density per brain region. Select resulting sections were analyzed using AmberGen MALDI HiPLEX‐IHC and Bruker Daltonics IMS for Aß42, pTau, GFAP, GLUT1, MBP, NeuN, NF‐L, PVALB, SNCA and SYN‐I.ResultQuantifying baseload plaque distribution in the 5XFAD model at 2, 3, 4, and 6‐months revealed significant changes in density of Aß plaques both spatially and temporally. STP2 imaging, combined with CCFv3 mapping and secondary proteomic analysis allows for targeted evaluation of compound treatment on the Aß plaques.ConclusionThe STP2 pipeline produces translational high‐throughput pre‐clinical AD data with enhanced sensitivity and precision, with resulting sections remaining in‐tact for further secondary analysis of spatial proteomics and pharmacodynamics in the brain.

Change on the Repeatable Battery for the Assessment of Neuropsychological Status and its relationship to brain amyloid

AbstractBackgroundThe Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) has been associated with commonly used biomarkers of Alzheimer’s disease (AD), including brain amyloid plaque density. However, less is known about if changes in the RBANS across time are also related to brain amyloid deposition. The current study sought to expand on prior work by examining the relationship between changes over time on the RBANS and amyloid deposition via positron emission tomography (PET).MethodOne‐hundred twenty‐six older adults with intact or impaired cognition and daily functioning underwent repeat assessment with the RBANS across nearly 16 months, as well as had a baseline amyloid PET scan.ResultIn the entire sample, amyloid deposition was significantly related to change on all five Indexes and the Total Scale score of the RBANS (rs = ‐0.28 – ‐0.61), with greater amyloid deposition being associated with worsening cognition. This pattern was also observed in 11 of 12 subtests. In the intact individuals, this pattern was only observed on change in the Immediate Memory Index (r = ‐0.32). In the subjects with MCI, this pattern was only observed on change in the Delayed Memory Index (r = ‐0.35). There was no association between change on the RBANS and brain amyloid deposition in those with AD.ConclusionWhereas prior studies have identified a relationship between baseline RBANS and amyloid status, the current findings support that changes in the RBANS are also indicative of AD brain pathology. Although replication in a more diverse sample is needed, these results continue to support the use of the RBANS in AD clinical trials.