Black, Keith L

Abstract Background Sensitive, accessible biomarkers of the pathologies underlying Alzheimer's disease and related dementias (ADRD) are critical for accurate diagnosis, deeper understanding of disease mechanisms, and development of new therapies with validated target engagement. The retina is connected to the brain via the optic nerve, which may facilitate the transmission and spread of amyloid beta (Aβ) and tau species. In postmortem studies, retinal Aβ deposits have been associated with neuritic Aβ‐plaque and neurofibrillary tangle burden, particularly in the entorhinal and temporal cortices. The goal of the current study was to evaluate associations between retinal perivascular amyloid and cognition, as well as to explore effect modification by hippocampal volumetry. Method Participants, aged ≥40 years, underwent retinal imaging, brain MRI, FDG‐PET, and a comprehensive neuropsychological assessment. Retinal amyloid imaging was conducted following curcumin ingestion and pupil dilation using a confocal scanning laser ophthalmoscope. Perivascular Aβ plaque counts were quantified in the superotemporal peripheral region following manual identification and tracking of retinal arteries and veins. Associations between retinal perivascular Aβ plaque counts with cognitive domains were evaluated using linear regression models adjusted for age, sex, and estimated premorbid functioning. Where significant associations were detected ( p ‐value<0.05), effect modification by hippocampal volumetry was examined with additional adjustment for intracranial volume. Result The sample included 26 participants (mean age 65±7 years, 50% female). Higher amyloid plaque counts in the perivascular secondary small and tertiary branches and in the periarteriolar tertiary branch were associated with poorer verbal and visual memory (Table 1). Significant interactions were observed between amyloid plaque count in the perivascular secondary small branch (β(95% Confidence Interval) = 0.397(0.037‐0.756), p = 0.033) and periarteriolar tertiary branch (β(95% Confidence Interval) = 0.756(0.165–1.346), p = 0.017) with hippocampal volumetry for visual memory. Conclusion Our pilot study provides preliminary evidence that perivascular Aβ accumulation in smaller vessels of the superotemporal retina may be a marker of memory impairment that may interact synergistically with hippocampal atrophy. Longitudinal studies consisting of multimodal ophthalmic assessments, brain imaging, ADRD biofluid markers, and cognitive testing will be necessary to capture the temporal sequence of retinal pathological changes and their associations with those in the brain.

Abstract Background The interplay between vascular dysfunction and brain amyloidosis in driving Alzheimer's disease (AD) pathogenesis and cognitive decline is increasingly recognized. The retina, sharing an embryonic origin with the brain, offers an accessible CNS organ for high‐resolution, noninvasive imaging of AD‐related vascular pathology. However, the exact nature of retinal vascular damage in AD—especially in early disease stages—and its relationship with cerebral amyloid angiopathy (CAA) and cognitive impairment remain understudied. Method We examined vascular abnormalities in retinas of MCI and AD via histopathology and in‐vivo imaging studies. Postmortem retinas from 53–62 individuals (CN: 22; MCI/AD: 31–40) underwent immunohistochemistry for pericyte integrity, vascular Aβ42/40, and endothelial TJ proteins, with dysregulated proteins quantified by mass spectrometry in 12 additional AD/CN cases. Retinal curcumin‐amyloid imaging by scanning‐laser ophthalmoscope in 28–34 live participants (CN[MOCA>26]: 8–15; MCI/AD[MOCA≤26]: 13–19) assessed peri‐arteriolar/venular amyloid plaques (APs). Perivascular AP burden was correlated with MRI measures (hippocampal volume, WMH lesions) and cognitive/neuropsychiatric parameters. Result Retinal pericyte loss, reflected by PDGFRβ deficiency and apoptosis, was evident in MCI and AD patients and correlated with vascular Aβ42/40 accumulation and CAA severity (r=0.68–0.84; p <0.01–0.0001). Retinal endothelial ZO‐1 and claudin‐5 levels were significantly reduced, correlating with arteriolar Aβ40 deposition, suggesting impaired retinal Aβ clearance. Retinal capillary claudin‐5 and arteriolar Aβ40 strongly associated with CAA (r=0.75–0.77, p <0.0001), while ZO‐1 moderately correlated with brain amyloidosis/tauopathy, CAA, and cognitive decline (r=0.43–0.57, p <0.01–0.001). Both histological and in‐vivo imaging studies revealed greater Aβ deposition in retinal arterioles, particularly in secondary and tertiary branches, compared to venules or capillaries ( p <0.01–0.0001). Retinal perivascular APs in secondary/tertiary branches imaged in living patients correlated with cognitive impairment (global CDR, MOCA), hippocampal atrophy, and WMH lesions (r=0.51–0.66, p <0.05–0.001). Perivascular APs in the secondary (β=0.397, p = 0.033) and tertiary (β=0.756, p = 0.017) arteriolar branches showed significant interactions with hippocampal volumetry for visual memory. Conclusion Retinal arteriolar Aβ accumulation, pericyte loss, and TJ dysfunction contribute to early AD vascular pathology. If validated in larger cohorts, these findings support retinal vascular biomarkers as tools for predicting cognitive decline, monitoring AD progression, and assessing CAA severity.