Research ArticleNeurology

Imaging synaptic density in the living human brain

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Science Translational Medicine  20 Jul 2016:
Vol. 8, Issue 348, pp. 348ra96
DOI: 10.1126/scitranslmed.aaf6667
  • Fig. 1. 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.

  • Fig. 2. PET imaging evaluation of SV2A-specific tracer [11C]UCB-J in healthy human subjects.

    (A) PET summation images 40 to 60 min after [11C]UCB-J injection in subject 1. Regional radioactivity was normalized to injected radioactivity and body weight and expressed as the SUV. Images for subjects 2 to 5 are shown in fig. S3. (B) TACs for regional brain radioactivity in putamen, frontal cortex, cerebellum, and centrum semiovale of subject 1. The solid lines show curve fitting with the 1T compartment model. Curves for subjects 2 to 5 are depicted in fig. S4. (C) Regional volumes of distribution (VT) obtained by the 1T model applied to TACs. (D) Regional influx rate (K1) values obtained by the 1T model applied to TACs. (E) BPND values. Data in (C) to (E) are means ± SD (n = 5). Individual subject values for VT, K1, and BPND are shown in tables S3 to S5.

  • Fig. 3. [11C]UCB-J binds to SV2A in the healthy human brain.

    (A and B) Regional TACs of VT values in four brain regions after [11C]UCB-J administration by a bolus plus constant infusion protocol in three control subjects under baseline (A) or displacement conditions in which levetiracetam (1500 mg) was intravenously infused 60 to 65 min after the start of [11C]UCB-J infusion (B). Data are means (n = 3); the SD was not displayed for the sake of clarity. Individual subject data are shown in fig. S5. (C) PET summation images 40 to 60 min or 90 to 120 min after [11C]UCB-J injection in subject 8. In the displacement study, levetiracetam (1500 mg) was intravenously infused 60 to 65 min after the start of [11C]UCB-J infusion. Individual subject images are shown in fig. S6.

  • Fig. 4. PET evaluation with [11C]UCB-J reveals unilateral mesial temporal sclerosis in epilepsy patients.

    (A) MR images, corresponding BPND maps of [11C]UCB-J, and overlay in three TLE patients with unilateral mesial temporal sclerosis. The white arrows indicate loss of [11C]UCB-J binding in the mesial temporal lobe. (B to D) Regional TACs for radioactivity in hippocampus and centrum semiovale after intravenous injection of [11C]UCB-J in three epilepsy subjects. (E) Asymmetry indices between left and right hemispheres for healthy control subjects and between ipsilateral and contralateral hemispheres for epilepsy patients. Data are individual subjects, including original control subjects 1 to 5.

Supplementary Materials

  • www.sciencetranslationalmedicine.org/cgi/content/full/8/348/348ra96/DC1

    Methods

    Fig. S1. Saturation studies of [11C]UCB-J in regions of the baboon brain.

    Fig. S2. Scatchard plots of [11C]UCB-J in regions of the baboon brain.

    Fig. S3. PET summation images after bolus injection of [11C]UCB-J in healthy human subjects.

    Fig. S4. Regional TACs after bolus injection of [11C]UCB-J in healthy human subjects.

    Fig. S5. Regional TACs of VT values after bolus plus constant infusion of [11C]UCB-J in additional healthy human subjects.

    Fig. S6. PET summation images after bolus plus constant infusion of [11C]UCB-J in human subjects.

    Table S1. Unchanged [11C]UCB-J fraction in plasma in five control subjects evaluated with bolus injection of [11C]UCB-J.

    Table S2. Plasma free fraction of [11C]UCB-J in five control subjects evaluated with bolus injection of [11C]UCB-J.

    Table S3. Regional VT values after bolus injection of [11C]UCB-J in five control subjects.

    Table S4. Regional K1 values after bolus injection of [11C]UCB-J in five control subjects.

    Table S5. BPND values after bolus injection of [11C]UCB-J in five control subjects.

    References (5457)

  • Supplementary Material for:

    Imaging synaptic density in the living human brain

    Sjoerd J. Finnema,* Nabeel B. Nabulsi, Tore Eid, Kamil Detyniecki, Shu-fei Lin, Ming-Kai Chen, Roni Dhaher, David Matuskey, Evan Baum, Daniel Holden, Dennis D. Spencer, Joël Mercier, Jonas Hannestad, Yiyun Huang, Richard E. Carson

    *Corresponding author. Email: sjoerd.finnema{at}yale.edu

    Published 20 July 2016, Sci. Transl. Med. 8, 348ra96 (2016)
    DOI: 10.1126/scitranslmed.aaf6667

    This PDF file includes:

    • Methods
    • Fig. S1. Saturation studies of [11C]UCB-J in regions of the baboon brain.
    • Fig. S2. Scatchard plots of [11C]UCB-J in regions of the baboon brain.
    • Fig. S3. PET summation images after bolus injection of [11C]UCB-J in healthy human subjects.
    • Fig. S4. Regional TACs after bolus injection of [11C]UCB-J in healthy human subjects.
    • Fig. S5. Regional TACs of VT values after bolus plus constant infusion of [11C]UCB-J in additional healthy human subjects.
    • Fig. S6. PET summation images after bolus plus constant infusion of [11C]UCB-J in human subjects.
    • Table S1. Unchanged [11C]UCB-J fraction in plasma in five control subjects evaluated with bolus injection of [11C]UCB-J.
    • Table S2. Plasma free fraction of [11C]UCB-J in five control subjects evaluated with bolus injection of [11C]UCB-J.
    • Table S3. Regional VT values after bolus injection of [11C]UCB-J in five control subjects.
    • Table S4. Regional K1 values after bolus injection of [11C]UCB-J in five control subjects.
    • Table S5. BPND values after bolus injection of [11C]UCB-J in five control subjects.
    • References (5457)

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