Lachner, Christian

Abstract Neurofibrillary tangles are dynamic neuropathologic hallmarks of Alzheimer’s disease with a hypothesized lifespan morphologically-defined by three maturity levels: pretangles, mature tangles, and ghost tangles. To better understand the progression of tangle pathophysiology, we characterized tangle maturity level predilection of 15 tau antibodies recognizing a broad range of linear, phosphorylation, conformational, and truncation epitopes in the hippocampus of 24 postmortem brains. We developed the tangle maturity scoring system to semi-quantitatively evaluate each tangle maturity level. Based on proportions of tangle maturity levels, we classified antibodies as “early” (mostly pretangles and mature tangles), “middling” (mature tangles with pretangles and ghost tangles), and “advanced” (mostly ghost tangles and mature tangles) tangle maturity markers. To summarize tangle maturity predilection, we developed the tangle maturity scale to integrate individual tangle maturity scores. Correlations showed stronger relationships between tangle maturity scale and subsector thickness for more advanced tangle maturity markers in CA1 and subiculum, whereas Braak tangle stage remained consistently correlated throughout markers of the tangle lifespan. To aid in scoring hippocampi, we used machine learning to recognize tangle maturity levels, which performed comparably to a domain expert and showed similar relationships by Spearman correlation. Pattern recognition software was used to assess tangle and neuritic tau burden separately, which generally correlated with Braak stage and neuronal counts. However, tangle-derived tau burden more consistently correlated with hippocampal subsector thickness. In conclusion, we developed manual and automated scoring systems to evaluate tangle maturity levels, demonstrating early 4R, phosphorylated, and oligomeric tau accumulation preceding more advanced 3R and truncated tau. Our study provides supportive evidence of disease-relevant ordering of tau posttranslational modifications in the brain, which may have implications for theragnostic development. These findings underscore the promise of computerized quantitative analyses (i.e., pathomics) for high-throughput feature extraction from whole-slide images to enhance our understanding of microscopically observed morphologic changes.

Abstract INTRODUCTION Plasma biomarkers of Alzheimer's disease (AD) represent accessible alternatives to positron emission tomography (PET) and cerebrospinal fluid (CSF)‐based biomarkers in well‐characterized cohorts. It remains to be determined whether performance is maintained in outpatient clinics comprised of patients with multiple causes of cognitive impairment. METHODS Plasma phosphorylated tau217 (p‐tau217) and amyloid beta (Aβ) 42/40 were measured in 509 patients evaluated in a tertiary‐care memory clinic. Biomarker performance was compared across diagnoses, referencing established cutpoints for positive and negative biomarkers. RESULTS Plasma p‐tau217 distinguished patients with diagnoses of symptomatic AD with 95% sensitivity and 82% specificity. Integration of Aβ42 measurements (p‐tau217/Aβ42) incrementally improved specificity (86%). Plasma p‐tau217 and p‐tau217/Aβ42 concentrations closely associated with established CSF biomarkers of AD (area under the curve [AUC]: 0.94 and 0.96, respectively). Reduced kidney function associated with elevated plasma p‐tau217 and p‐tau217/Aβ42 concentrations in patients without AD (referencing CSF biomarkers). DISCUSSION Plasma p‐tau217 and p‐tau217/Aβ42 concentrations demonstrated robust diagnostic performance in a heterogeneous clinical cohort; interpretation requires consideration of kidney function. Highlights Plasma phosphorylated tau217 (p‐tau217) reliably identified clinic patients with Alzheimer's disease. A two‐cutpoint strategy yielded definitive results in 86% of patients. Integration of plasma amyloid beta (Aβ; p‐tau217/Aβ42) minimally improved diagnostic performance. Plasma p‐tau217 levels were increased in patients with kidney dysfunction.

AbstractBackgroundSAAs represent a promising biomarker of Lewy Body disease (LBD), with high sensitivity (87.3%, 95%CI: 0.755‐0.947) and specificity (97.2%, 95%CI: 0.922‐0.994) for detection of patients in the Parkinson’s Progression Markers Initiative repository with positive DaT SPECT; and reasonable sensitivity (78.7%, 95%CI: 0.66‐0.88) and specificity (89.5%, 95%CI: 0.78‐0.96 referencing clinical diagnoses in participants included within national research repositories. However, test performance in heterogeneous clinical cohorts is unknown.MethodPatients with typical (n=122) and rapid progressive dementia (n=76) consented to banking of CSF at the time of clinically‐indicated diagnostic lumbar puncture. Clinical data were deidentified and uploaded to a secure research database and clinical (etiologic) diagnoses established by two neurologists following independent review of available records. SAA (SYNTap™) were run on stored CSF by Amprion Diagnostics (San Diego, CA).ResultMedian participant age was 69.1 years (18.4‐86.1); 56.3% were female. CSF was sampled median 1.4 years (0‐10.3) after symptom onset. Pathological alpha‐synuclein was detected in 28/122 patients with typically progressive dementia (including 6/18 patients with presumed LBD; sensitivity 33%, specificity 79%) and 11/76 patients with rapid progressive dementia (including 3/9 patients with presumed LBD; sensitivity 33%, specificity 88%). “Positive” SAA was associated with tremor (OR=3.2, 95%CI: 1.3‐7.8), visual hallucinations (OR=6.14, 95%CI 1.6‐23.6), and REM behavior disorder (OR=3.7, 95%CI: 1.4‐9.5) in patients with typical but not rapid progressive dementia. Brain autopsies were completed in 17 patients: Lewy bodies were detected in 2/3 patients with positive SAA and no patients with negative SAA.Conclusion“Positive” SAA demonstrated reasonable specificity but low sensitivity for the diagnosis of LBD. Additional studies in heterogeneous cohorts with neuropathologic data are needed to optimize clinical applications of SAA.

AbstractBackgroundThe prevalence of dementia in populations that are underrepresented in research is projected to increase with population aging. Latino and Black individuals, the largest underrepresented populations in the US, experience a higher dementia burden than non‐Hispanic White individuals, which is not explained by ethnoracial biological factors. Disparities in structural and social determinants of health may contribute to the preponderance of medical conditions known to increase dementia risk, including potentially modifiable factors in Latino and Black communities. To assess the scope of this problem, we measured the frequency of common modifiable dementia risk factors in community‐dwelling, cognitively normal, Latino and Black adults.MethodCognitively normal community‐dwelling Latino and Black adults, ≥45‐years‐old, were enrolled within our longitudinal study of memory and aging at Mayo Clinic in Florida (Jacksonville, FL) and completed a baseline assessment between 3/2022 and 10/2023. Demographics, and self‐reported race/ethnicity and history of dementia risk factors were recorded. Dementia risk factors were objectively sampled through clinical interview (depression: Geriatric Depression Scale ≥5), examination (hypertension: BP >130/80 mmHg; obesity: BMI≥30), and serum analyses (hyperlipidemia: total cholesterol<200mg/dL, HDL>50mg/dL, LDL<100mg/dL, Triglycerides<150mg/dL; diabetes: HbA1C >5.6%, vitamin B12 deficiency: <350 ng/dL).Result86 participants (43 Latino, 43 Black), 65.8 (8.8) years‐old, female (62.8%), with 16 (2.4) years of education were assessed. Dementia risk factors were frequent in Latino and Black participants, including hypertension (63%, 90%; p = 0.005), hyperlipidemia (93%, 89%; p = 0.702), obesity (33%, 44%; p = 0.370), diabetes (60%, 47%; p = 0.370), vitamin B12 deficiency (21%, 21%; p = 0.989), and depression (5%, 24%; p = 0.781). These risk factors were unrecognized or suboptimally managed in a substantial proportion of Latino and Black participants: hypertension (56%, 73%; p = 0.170), hyperlipidemia (80%, 73%; p = 0.591), diabetes (57%, 47%; p = 0.502), vitamin B12 deficiency (21%, 21%; p = 0.789), and depression (5%, 3%; p>0.99).ConclusionPotentially modifiable dementia risk factors were detected in the majority of community‐dwelling Latino and Black cognitively normal older‐adults and were frequently unrecognized or suboptimally managed. Proactive screening for known dementia risk factors may provide opportunities for targeted interventions to improve brain health and decrease dementia disparities in underrepresented populations.

Importance Factors associated with clinical heterogeneity in Alzheimer disease (AD) lay along a continuum hypothesized to associate with tangle distribution and are relevant for understanding glial activation considerations in therapeutic advancement. Objectives To examine clinicopathologic and neuroimaging characteristics of disease heterogeneity in AD along a quantitative continuum using the corticolimbic index (CLix) to account for individuality of spatially distributed tangles found at autopsy. Design, Setting, and Participants This cross-sectional study was a retrospective medical record review performed on the Florida Autopsied Multiethnic (FLAME) cohort accessioned from 1991 to 2020. Data were analyzed from December 2022 to December 2023. Structural magnetic resonance imaging (MRI) and tau positron emission tomography (PET) were evaluated in an independent neuroimaging group. The FLAME cohort includes 2809 autopsied individuals; included in this study were neuropathologically diagnosed AD cases (FLAME-AD). A digital pathology subgroup of FLAME-AD cases was derived for glial activation analyses. Main Outcomes and Measures Clinicopathologic factors of heterogeneity that inform patient history and neuropathologic evaluation of AD; CLix score (lower, relative cortical predominance/hippocampal sparing vs higher, relative cortical sparing/limbic predominant cases); neuroimaging measures (ie, structural MRI and tau-PET). Results Of the 2809 autopsied individuals in the FLAME cohort, 1361 neuropathologically diagnosed AD cases were evaluated. A digital pathology subgroup included 60 FLAME-AD cases. The independent neuroimaging group included 93 cases. Among the 1361 FLAME-AD cases, 633 were male (47%; median [range] age at death, 81 [54-96] years) and 728 were female (53%; median [range] age at death, 81 [53-102] years). A younger symptomatic onset (Spearman ρ = 0.39, P &amp;lt; .001) and faster decline on the Mini-Mental State Examination (Spearman ρ = 0.27; P &amp;lt; .001) correlated with a lower CLix score in FLAME-AD series. Cases with a nonamnestic syndrome had lower CLix scores (median [IQR], 13 [9-18]) vs not (median [IQR], 21 [15-27]; P &amp;lt; .001). Hippocampal MRI volume (Spearman ρ = −0.45; P &amp;lt; .001) and flortaucipir tau-PET uptake in posterior cingulate and precuneus cortex (Spearman ρ = −0.74; P &amp;lt; .001) inversely correlated with CLix score. Although AD cases with a CLix score less than 10 had higher cortical tangle count, we found lower percentage of CD68-activated microglia/macrophage burden (median [IQR], 0.46% [0.32%-0.75%]) compared with cases with a CLix score of 10 to 30 (median [IQR], 0.75% [0.51%-0.98%]) and on par with a CLix score of 30 or greater (median [IQR], 0.40% [0.32%-0.57%]; P = .02). Conclusions and Relevance Findings show that AD heterogeneity exists along a continuum of corticolimbic tangle distribution. Reduced CD68 burden may signify an underappreciated association between tau accumulation and microglia/macrophages activation that should be considered in personalized therapy for immune dysregulation.