1. Fig. 1. In vivo–in vitro validation of [11C]UCB-J as a synaptic density biomarker in the baboon brain.
In vivo–in vitro validation of [11C]UCB-J as a synaptic density biomarker in the baboon brain. (A) Template MRI and PET summation images of baboon brain 30 to 120 min after intravenous injection of [11C]UCB-J. (B) TACs of regional brain radioactivity in the insular cortex, frontal cortex, thalamus, and centrum semiovale and [11C]UCB-J plasma concentration. The solid lines show curve fitting with the 1T compartment model. (C) Western blot analyses of 12 baboon brain regions. Western blot was performed with a polyclonal anti-SV2A antibody (83 kD; top and bottom), a monoclonal anti-SYN antibody (38 kD; top), and a monoclonal anti–β-actin antibody (42 kD; bottom). For each brain region, individual wells were loaded with 2 μg of protein. (D) Correlation between regional in vitro SV2A [optical density (OD) by Western blot] and in vivo SV2A (VT by PET measures). Data are 12 brain regions. (E) Correlation between in vitro SV2A and in vitro SYN density in gray matter regions determined using Western blot analyses. Data are nine brain regions. (F) Saturation studies of [11C]UCB-J were performed for 12 brain regions. Data are for the temporal cortex (each measurement was performed in duplicate), with 11 other regions in fig. S1. Membranes were incubated with increasing concentrations of UCB-J for 30 min at 37°C. Nonspecific binding was determined as the residual binding measured in the presence of 1 mM levetiracetam. Specific binding was determined by subtraction of the nonspecific from the total binding. (G) Scatchard plot from the transformed data of the temporal cortex in (F). Eleven other regions are shown in fig. S2. (H) Correlation between regional SV2A density (Bmax) measured in vitro using tissue homogenate binding and regional [11C]UCB-J binding measured in vivo in a baboon using PET. Data are 12 brain regions. (I) Correlation between regional SV2A density (Bmax) measured in vitro using tissue homogenate binding and SV2A density using in vitro Western blot analyses (OD). Data are 12 brain regions. (J) Low-power confocal microscopy imaging of 4′,6-diamidino-2-phenylindole (DAPI), SYN, and SV2A in white matter and cortical gray matter in baboon brain. The dotted white line indicates the border between the white matter (WM; left) and the gray matter (GM; right). (K) High-power confocal microscopy of DAPI, SYN, and SV2A in the gray matter of the baboon brain from (J). Labeling for SYN and SV2A is evident as punctate staining in the neuropil, particularly surrounding neuronal cell bodies and proximal dendrites (yellow arrow), but absent in neuronal cell bodies (white arrows). Nuclei are indicated by the DAPI stain in blue.
Sjoerd J. Finnema et al., Sci Transl Med 2016;8:348ra96
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