Postmortem brain tissue was fixed in periodate-lysine-paraformaldehyde (PLP) for at least 3 months at 4 °C. The neuropathological assessment was performed using procedures previously established [58 (link), 76 (link)]. Neuropathological evaluations were made by board-certified neuropathologists (ACM, TDS, BRH) according to published diagnostic criteria and were kept blinded to antemortem clinical information [58 (link)]. Cerebral arteriolosclerosis, atherosclerosis, and CAA were evaluated on a semiquantitative scale [12 (link), 73 (link)].
For immunohistochemical assessment, 20 µm slides from paraffin-embedded tissue blocks from the DLF were prepared and stained for AT8 as previously described [16 (link)]. Slides were scanned, digitized at 20× magnification, and analyzed for AT8 density (total area in the sulcus positive for AT8 staining divided by the total area of tissue analyzed) using Aperio Scanscope (Leica) as previously described [17 ]. The depth of the cortical sulcus was defined as the bottom third of two connecting gyri. Ki67 staining was completed using Leica’s Ready-to-Use Ki67 antibody reagent on the BOND staining system (Leica, Deer Park, IL) and imaged on the Vectra Polaris slide scanner (Akoya, Marlborough, MA).
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