Citations

Abstract Background The rare APOE3 ‐Christchurch ( APOE3Ch ) variant is associated with remarkable protective effects, delaying the age at onset of PSEN1 ‐E280A driven autosomal dominant Alzheimer's disease (AD). While much of the research on APOE3C h has focused on its role in AD, little is known about how this variant impacts APOE biology under non‐disease conditions. Using cortical organoids as a model system, we aim to investigate the fundamental mechanisms by which APOE3Ch alters APOE biology, including its effects on metabolism and cellular interactions, to better understand its unique properties and potential implications for broader applications. Method Cortical organoids were derived from the isogenic neurodegeneration iPSC line series, with either the APOE3 or APOE3Ch genotype. Single‐cell RNA sequencing (scRNA‐seq) was performed on three independent batches of 6‐month‐old cerebral organoids to identify pathways differentially regulated by APOE3Ch. To further investigate APOE lipidation and its effects on lipid metabolism, lipidomics analysis was conducted on 8‐month‐old cerebral organoids, offering additional insights into APOE3Ch ‐specific biological mechanisms. Validation was also carried out using iPSC‐derived astrocytes and neurons to confirm key findings. Result ScRNA‐seq revealed differences in cell populations and astrocyte subtypes between APOE3 and APOE3Ch organoids, with mitochondrial‐related pathways differentially regulated in APOE3Ch cerebral organoids. These findings were validated in iPSC‐derived astrocytes. APOE3Ch iPSC‐derived astrocytes exhibited increased APOE secretion compared to APOE3 . They also demonstrated enhanced mitochondrial function, as evidenced by increased spare respiratory capacity measured by Seahorse stress assays. Furthermore, APOE3Ch astrocytes showed reduced lipid droplet formation following oleic acid treatment. Lipidomics analysis of APOE3Ch cerebral organoids revealed decreased cholesterol ester levels, suggesting alterations in lipid metabolism. Conclusion Our findings provide novel insights into how the APOE3Ch variant alters APOE biology, revealing differences in mitochondrial function and lipid metabolism. The differential regulation of mitochondrial pathways in APOE3Ch cerebral organoids, along with the enhanced mitochondrial capacity and altered lipid metabolism observed in APOE3Ch astrocytes, highlights the unique properties of this variant. These results offer valuable mechanistic understanding that may inform future therapeutic strategies targeting APOE biology, particularly in the context of AD.

Abstract Background Diffusion MRI (dMRI) measures are increasingly being used as biomarkers for aging and dementia in multi‐center studies. Measurements in longitudinal studies are often acquired on different systems, which can result in systematic differences of machine origin (e.g. vendor, hardware, algorithms). This may warrant harmonization prior to pooling multi‐site data. However, harmonization algorithms may introduce a risk of removing valuable information content and reducing sensitivity to physiological factors (e.g. sex, age, disease). Here, we tested the hypothesis that protocol standardization may minimize machine‐origin differences, obviating a need for post‐acquisition harmonization in a two‐site (Mississippi‐MS and Minnesota‐MN) cohort of the longitudinal Mayo Clinic Study of Aging (MCSA). Methods Two data sets were analyzed: first, a crossover dataset with 80 participants (scanned within 2 days) bridging two different protocols on GE and Siemens scanners; second, participants scanned using standardized protocols from the ongoing MCSA ( N MN‐MCSA =204; N MS‐MCSA =52). Parameters are listed in Figure 1. For crossover data, analyses were repeated with GE data resampled to 2‐mm isotropic resolution, and discarding Siemens‐only b‐shells to artificially reduce protocol disparities. Analysis encompassed visualization of overlain subjectwise histogram‐derived densities obtained from whole‐brain masks for dMRI measures; and median dMRI measures from within the genu of the corpus callosum (GCC) with nonparametric statistical testing. When available, both DTI and NODDI measures were compared. Results Pronounced visual distributional differences seen between MD and FA in crossover data were reduced with resampling of GE data and including only b‐shells shared across acquisitions. For the resampled/reshelled data, significant differences remained for all GCC‐FA comparisons, but not all GCC‐MD (Figure 2). For the ongoing MCSA data from two sites, MD and FA whole‐brain densities were more closely aligned, with GCC‐FA and GCC‐MD showing no significant differences (Figure 3). NODDI measures showed more discordant densities than DTI measures, including shifts in most probable values and differences in distributional arrangement. Conclusions Our work provides further evidence supporting protocol and processing standardization for minimizing machine‐origin differences prior to considering harmonization. Differences in dMRI metrics seen when comparing across unstandardized protocols were reduced when protocols were standardized. NODDI metrics had more apparent sensitivity to site than DTI measures.

Abstract Background The last several decades have seen intense research into Alzheimer’s disease (AD) resulting in several current and emerging disease modifying treatments that target hallmarks of the AD pathology. Previous evidence has indicated that neurologists and primary care physicians (PCPs) frequently lack knowledge of the most recent findings pertaining to the use of biomarkers and antibody‐based therapies in AD. An online CME program was developed to educate neurologists and PCPs on biomarker and therapeutic data in AD from a 2024 dementia conference. Method The online CME activity consisted of a chapterized 30‐minute video presentation featuring dementia specialists who reviewed data from a 2024 dementia conference on biomarkers or therapeutics. Educational effect was assessed by comparing a matched sample of responses to four identical questions presented before and directly after exposure to the intervention. A paired samples t‐test assessed the number of correct responses and for confidence rating; McNemar’s test was used to identify significant differences between pre‐ and post‐assessment question responses. Cohen’s d was used to calculate the effect size of the online education. Data were collected between August 2024 and October 2024. Result A moderate educational effect was observed for both neurologist ( n =88; d =.77, p <0.001) and PCP ( n =141; d =.75, p <.001) learners. Both physician groups demonstrated significant (P <.05) pre‐ vs post‐educational improvements on the following: clinical data on AD diagnostic accuracy comparing blood‐based biomarker testing to a clinical diagnosis made by a physician and risk factors for amyloid‐relating imaging abnormalities associated with an approved anti‐amyloid therapy (AAT). PCPs, but not neurologists, demonstrated a pre‐post educational improvement on a question about outcomes from an open‐label extension study of an approved ATT. Participation in the activity resulted in 44% of neurologists and 48% of PCPs reporting an increase in confidence regarding their ability to apply the latest clinical data on approved AATs in clinical practice. Conclusion The results indicated that a CME‐certified 30‐minute video program was effective at improving knowledge among a diversity of physician learners regarding emerging data from a recent medical conference. Future CME should continue to highlight impactful new data released at medical conferences.

Abstract Background Use of software to “de‐face” research brain images has grown as advances in automated face recognition have made it increasingly possible to re‐identify participants. Imaging studies of Alzheimer's Disease and related diseases have included more participants from historically underrepresented groups, but de‐facing software have primarily been validated using images from mostly non‐Hispanic White participants, and its performance has not been directly compared across ethnoracial groups. Method From The Health and Aging Brain Study: Health Disparities (HABS‐HD) study, we constructed a sample of 305 T1‐weighted MRI from HABS‐HD baseline visits, matched across three ethnoracial groups (non‐Hispanic White (NHW, n = 104), non‐Hispanic African American (AA, n = 104), Mexican American (MA, n = 97)) according to age‐decade, sex, cognitive status (impaired/unimpaired), and MRI scanner model. We ran mri_reface 0.3.5 on each image, and we ran FreeSurfer 7.4.1 on each unmodified image and on each de‐faced output. We then compared regional gray matter (GM) volume and cortical thickness measurements by subtracting each de‐faced image measurement from the corresponding unmodified image measurement. We compared these differences between de‐faced and unmodified images across the three matched groups using GLM analyses adjusted for age, sex, and cognitive status, and Bonferroni corrected. Result When aggregating across all brain regions, differences in cortical thickness measures due to de‐facing were significantly different between the NHW and MA groups, and between AA and MA, but not between NHW and AA (Figure 1). Differences between these group means were <0.005mm. For GM volume, differences were significant between AA and MA (magnitude < 0.2%), but not between NHW and AA or NHW and MA (Figure 2). Examining each region individually (Figure 3), cortical thickness differences were significant for only 4 regions (all with magnitudes <0.03mm), and GM volume differences were significant for only 6 regions (all with magnitudes <2%). Conclusion Effects of mri_reface on FreeSurfer brain measurements were significantly different across ethnoracial groups. Our future work will optimize mri_reface to eliminate these differences. However, the magnitudes of these differences are sufficiently small that they are unlikely to have a practical effect on analyses of data using current versions.

Abstract Background Individuals with spinal cord injury (SCI) are known to have high rates of cardiovascular disease that have traditionally been attributed to inability to engage in adequate intensity exercise. However, individuals with SCI also commonly experience instability in blood pressure. Blood pressure fluctuations are known to contribute to cardiovascular disease in other conditions, though this relationship in SCI is unknown. Objective To evaluate correlations between a clinical history of symptomatic blood pressure instability and objective evidence of vascular endothelial dysfunction in individuals with SCI. Design Case control. Setting Academic medical center. Participants Twenty‐four individuals with SCI, 14 uninjured controls of matched age, gender, and body mass index. Interventions Not applicable. Main Outcome Measures Symptomatic blood pressure instability was measured by the Autonomic Dysfunction Following SCI (ADFSCI) survey. Vascular endothelial dysfunction was quantified by ultrasound recordings of brachial flow mediated dilation following 5 minutes of forearm arterial occlusion. Results Total ADFSCI scores were significantly higher in individuals with SCI compared to controls (41.0 vs. 9.0, p = .002). Both percentage of brachial flow mediated dilation and consensus recommended allometrically scaled percentage of flow mediated dilation were significantly less in individuals with SCI ( p < .001 for both), demonstrating greater vascular dysfunction. More symptoms of blood pressure instability on the ADFSCI survey were correlated with more objective evidence of vascular dysfunction ( R 2 = 0.24, p = .03) for individuals with SCI. This relationship was not seen in uninjured controls. Conclusions In individuals with SCI, more severe symptoms of blood pressure instability are significantly correlated with more severe vascular endothelial dysfunction, making management of orthostatic hypotension and autonomic dysreflexia both high potential, modifiable risk factors for individuals with SCI to mitigate cardiovascular disease.

Abstract Background Apolipoprotein E (apoE) facilitates the fibrillization and deposition of amyloid β (Aβ) in Alzheimer's Disease (AD). Supported by robust literature from various groups, in our current study we have investigated the relative amyloidogenic properties of the three major human APOE alleles. Knowledge from such studies could provide insight into the role of ApoE protein in the deposition, evolution and maturation of parenchymal Aβ. Method We used hAbetaSAA (Jax Labs) mice crossed with human APOE targeted replacement mice to create hAbetaSAA mice homozygous for human APOE E2, E3 and E4 . Furthermore, APPsi mice (hAPPswe/indiana: Borchelt) expressing human APOE E3 or E4 were injected intracerebrally with AD brain lysates to examine the role of APOE genotype on Aβ seeding. Neuropathological examination was conducted via immunohistochemistry, immunofluorescence and immunoblotting. Result hAbetaSAA mice expressing human APOE E4 showed higher Aβ deposition relative to APOE E3 and APOE E2 by 5 months of age and progressing through 8 months and 13 months of age. In comparison, APP mice expressing humanized Aβ (Jax Labs) with human APOE E4 did not develop deposits in their lifetime. hAbetaSAA mice with endogenous mouse Apoe had the highest Aβ plaque deposition, with an approximately 60‐fold increase in Aβ burden compared to SAA APP mice expressing APOE E3 , especially in the earlier deposition phase. Removing mouse Apoe resulted in dose‐dependent reduction in Aβ deposition, consistent with previously published literature. Plaque morphology did not show any notable differences between APOE genotypes, and colocalization of apoE with Aβ were relatively equivalent across different APOE genotypes. Further, in the APPsi model seeded with AD‐derived seeds, we found that mice with APOE E4 or APOE E3 developed equal burdens of diffuse parenchymal Aβ, with no detectable changes in plaque morphology. Conclusion We conclude that apoE variants broadly influence the rate of amyloid deposition, but do not modify the morphology of the resulting deposits or colocalization with Aβ. Notably, when seeding with AD patient brain lysate, there was no significant difference in Aβ burden between APPsi mice expressing APOE E3 and E4 . Our study adds insights into the role of apoE isoforms in determining Aβ‐related phenotype.

Abstract Background Most existing biomarkers for Alzheimer's disease (AD) inform on core AD pathologies in the central nervous system, namely amyloid, tau and neurodegeneration (ATN). However, molecular disease mechanisms underlying AD are complex and heterogeneous, highlighting the need for cost‐effective blood‐based biomarkers that reflect brain molecular changes in AD beyond ATN. Method Using peripheral blood transcriptome data from the Mayo Clinic Study of Aging(MCSA) and the Alzheimer's Disease Neuroimaging Initiative, we identified genes associated with AD or mild cognitive impairment (MCI) diagnosis, cognitive, and harmonized neuroimaging measures in two cohorts, followed by meta‐analysis. We identified consensus gene co‐expression modules in MCSA and ADNI using WGCNA and assessed the association between module eigengenes and aforementioned measures. Using seven bulk brain RNAseq cohorts, we confirmed the preservation of coexpression modules across blood and brain. Enrichment analyses of Gene Ontology (GO) terms and cell‐types were performed using significant and/or hub genes. The MCSA transcriptome was further deconvoluted to obtain cell‐type proportions and cell‐type specific expression. Result Blood transcriptome modules M5 and M8 are upregulated in AD/MCI and associate with worse cognition, whereas M1, M10, M13, M16, and M21 are downregulated in AD/MCI and associate with better cognition. M17 associates with more microhemorrhages. Cell‐type enrichment analysis revealed that M5 is enriched in basophils, monocytes, and neutrophils; M8 in monocytes and neutrophils; M13 in natural kills cells; M17 in megakaryocytes; M21 in B cells. GO analysis shows broad consistency with the cell‐type enrichment analysis. M1, 5, and 8 are preserved in the brain network modules. From these modules, we prioritized transcripts significantly associated with at least one AD‐related phenotype in both blood and brain. Cell‐type deconvolution analysis shows that prioritized transcripts in M1 associate with better cognition and higher metabolic activity in B cells. Conclusion We identified blood transcripts and modules associated with AD/MCI, cognition, or neuroimaging, with three preserved in brain networks. These three modules represent centrally linked peripheral molecular signatures that can reveal perturbed brain pathways and cell level transcriptional changes in AD/MCI. We aim to further investigate the prioritized transcripts in additional datasets to establish them as potential novel biomarkers and therapeutic targets.

Abstract Background Progressive supranuclear palsy (PSP) is a devastating neurodegenerative disorder with rapid progression to death. Multiple efforts to develop a disease‐modifying therapy for PSP have yet to succeed. We previously reported the discovery of three potential therapeutic targets for PSP. These three genes, DDR2, KANK2, and STOM, are consistently upregulated in the brains of PSP patients and mouse models of tauopathy. Reducing their expression in a drosophila model significantly rescued the tau‐induced eye degeneration and tau seeding activity. To translate these targets into the clinic, we are developing antisense oligonucleotides (ASO) as potential therapies. Method We screened candidate ASOs in neuroglioma cell line H4. ASO hits were validated for their potency and safety. We also used iPSC‐derived neurons from PSP patients to test the potency and potential toxicity of our ASOs. To investigate target engagement, therapeutic efficacy and preliminary pharmacodynamic properties, we treated iPSC‐derived midbrain organoids with the ASO leads. Lastly, we will assess the off‐target effects of the ASOs by investigating the levels of mRNA transcripts that share similar sequences as our targets using RNAseq. Result Our in vitro screening identified ASO leads that significantly reduce the target gene expressions at mRNA and protein levels in a dose‐dependent manner. The ASO hits also exhibit low cellular toxicity in the H4 cell line. Upon treating iPSC neurons with ASO hits, we were able to validate the dose‐dependent reduction of target mRNAs. Cell viability analysis indicated low toxicity, suggesting that these ASOs are potent and safe. In midbrain organoid model, DDR2‐targeting ASO showed time‐dependent target engagement and were prioritized for further development. Conclusion We developed candidate therapeutics for PSP using ASOs that silence novel therapeutic targets discovered in our systems based cross‐species screening. We showed that our ASOs have low toxicity and confirmed target engagement at both mRNA and protein levels in vitro. The results suggest a favorable preclinical profile of our ASO leads that warrants additional investigations. Importantly, PSP shares congruent pathophysiological changes with other tauopathies, such as Alzheimer’s disease. These common perturbed pathways indicate that our ASOs can be potentially repurposed for multiple neurodegenerative tauopathies.

BACKGROUND: Cardiac radioablation is emerging as a treatment modality for refractory ventricular tachycardia. This study aimed to evaluate the effects of radiation on the coronary arteries in a swine model of proton beam cardiac radioablation. METHODS: Eighteen swine underwent single-fraction 30 to 40 Gy pencil-beam scanning proton therapy targeting the left ventricle and were euthanized 12 to 40 weeks later. Treatment planning was performed without restricting the dose to the coronary arteries. The maximum point dose (D max ) to the epicardial coronary arteries was calculated. In secondary analyses, the mean (D mean ) and minimum dose received by the highest irradiated 0.01 cm 3 (D 0.01 ) of each coronary artery were also calculated. Coronary artery segments were harvested from the D max sites for histological analysis, and the D max was correlated with stenosis severity. RESULTS: Ninety-six coronary arteries were analyzed. No stenoses were observed by computed tomography imaging preirradiation. By histological analysis posteuthanasia, 25/96 (26%) coronaries sampled at their D max sites had ≥75% stenosis. The median D max was 4.7 Gy for the <75% stenosis group and 29.7 Gy for the ≥75% stenosis group ( P <0.001). The AUC-ROC for the association between D max and stenosis ≥75% was 92.2%. A D max value of 20.1 Gy best predicted stenosis ≥75%, with sensitivity 92.3% and specificity 87.1%. The AUC-ROCs for the associations of D mean and D 0.01 with stenosis ≥75% were 84.8% and 91.6%, respectively. In histopathologic analysis, intimal hyperplasia was the most common coronary artery abnormality at the D max sites, and it was present in 61.5% of all arteries and in 93.9% of arteries with D max ≥20 Gy. CONCLUSIONS: In this preclinical model of proton beam cardiac radioablation, coronary stenoses occurred in a dose-dependent manner, with D max showing the closest correlation with stenosis ≥75%. These data provide for the first time a framework for dose constraint considerations for the coronary arteries during treatment planning for cardiac radioablation and thoracic malignancy radiation.

Abstract Background Our objective is to examine the generalizability of the relationships between four MRI markers of CVD: DTI‐derived free water (FW), fractional anisotropy (FA), perivascular space (PVS) and white matter hyperintensities (WMH) volume, with vascular risk factors (VRF) and cognition in the baseline POINTER Imaging and Framingham Heart Study (FHS) cohorts. Method We studied 907 U.S. POINTER and 797 FHS Offspring participants with available baseline demographic, clinical and imaging data (Table 1). Continuous FW, FA, WMH (log‐transformed) and PVS measurements were regressed against total cranial volume (TCV). Cognitive outcomes included a Global Cognitive Composite and executive function composite score for POINTER and FHS. For each MRI marker, we used linear and logistic regressions to assess the effect of age, sex, hypertension, diabetes and smoking status, adjusting for ethnicity. We then assessed, for each cognitive outcome, the individual effect of MRI markers using separate linear regressions adjusted for demographic and clinical factors, as well as TCV‐adjusted gray matter volume to control for atrophy. Result POINTER and FHS differed across most demographic and biomarker characteristics (Table 1). Despite these differences, there were similar associations between demographic and VRF and the 4 MRI vascular markers in POINTER and FHS (Figure 1): increased age was associated with worse outcomes for the 4 markers, hypertension was associated with increased FW, PVS and lower FA, diabetes was associated with increased FW only, smoking status did not impact any of the four markers. Only exception was that female had lower FW and increased WMH in POINTER and increased PVS in FHS. Associations between CVD measures and cognition were also similar across cohorts: reduced cognitive performance was significantly associated with both decreased FA and increased FW (Figure 2), but not with WMH nor PVS. Conclusion Our study explores four imaging markers representing diverse mechanisms by which CVD could impact brain structure and function in the POINTER and FHS studies. Despite differences in cohort characteristics, we found mostly consistent CVD relationships with demographic, VRF, and cognitive measures between cohorts which supports the generalizability of the relation of these markers with VRF and cognition identified in the POINTER cohort.