The meningothelial AG capsule is irregularly perforated by fissures, sinuses, and crypts. (A) Low-power montage image of human leptomeninges highlights vimentin⁺ meningothelium covering collagen of arachnoid mater (AM, white arrowhead) and AG cores (AG, yellow arrowhead). In the lower panels, AG capsules are shown in young, middle-aged, and old individuals. (B) The percentages of vimentin label (i.e., % AM and AG coverage) are shown for each person according to age. (C) The capsule thicknesses (i.e., maximum thickness of vimentin⁺ layer) for AM and AG are summarized for each person. (D) The percent coverage of AG is additionally summarized according to lobe type. (E) AG arachnoid thickness is summarized according to lobe type. (F) Multichannel image of an AG lobule is shown and depicts multifocal capsular interruption. (G) As shown on an H&E-stained cross-section of a unilobed AG, the capsular interruptions correspond to surface sinus and crypt openings. (H–J) Capsules, fissures, and/or crypts are further demonstrated on 3D CLARITY (H), TEM (I), and schematic (J) images. (K and L) Maximum crypt diameters are shown according to age (K) and lobe type (L). (A, F, and H) Red/CY3, pan-collagen; green/FITC, vimentin; blue, vimentin or DAPI; DIC, differential interference contrast. Scale bars: (A [upper and lower panels]) 500 µm; (A [second panel] and F) 10 µm; (A [third panel] and G) 20 µm; (H) 200 µm; (I) 2 µm. Bi, bilobed; C, crypt; F, fissure; Max, maximum; Multi, multilobed pedunculated; S, sinus; Tri, trilobed; Uni, unilobed. Multichannel images represent confocal Z-stack images. The asterisks (*) in A denote the subcapsular space. Vimentin⁺ areas also expressed e-cadherin and epithelial membrane antigen (EMA) in similar pattern and displayed nuclear pseudoinclusions, indicative of arachnoid cells. Additional images from the lower panel of A are shown in Fig. S2. Data represent mean or median values from 400 frontal pole granulations from 20 decedents and are from more than two independent experiments.