Poster Presentation HUPO 2019 - 18th Human Proteome Organization World Congress

Integrating MALDI Imaging Mass Spectrometry with shotgun proteomics for the studies of neuropathology of Alzheimer's disease (#886)

Yumiko Toyama 1 , Nobuto Kakuda 1 , Ryo Kajita 2 , Takashi Nirasawa 2 , Tomohiro Miyasaka 1 , Shigeo Murayama 3 , Yasuo Ihara 4 , Masaya Ikegawa 1
  1. Department of Life and Medical Systems, Doshisha University, Kyotanabe, Kyoto, Japan
  2. Bruker Japan K.K., Yokohama, Kanagawa, Japan
  3. The Brain Bank for Aging Research, Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology , Tokyo, Japan
  4. Graduate School of Brain Science, Doshisha University, Kyotanabe, Kyoto, Japan

Neuropathology of Alzheimer’s disease (AD) is characterized by the accumulation and aggregation of Amyloid β (Aβ) peptides into extracellular plaques of the brain. The Aβ peptides are generated from amyloid precursor proteins by β- and γ-secretases. Aβ deposited not only in cerebral parenchyma but also in leptomeningeal and cerebral vessel walls. This has been known as cerebral amyloid angiopathy. 

Here, we adopt MALDI-imaging mass spectrometry (MALDI-IMS) on autopsied brain tissues to obtain a comprehensive protein mapping. Human cortical specimens for IMS were obtained from brains that were removed, processed, and stored at -80 ˚C within 8 h postmortem at the Brain bank at Tokyo Metropolitan Institute of Gerontology. Each brain specimen was taken from the occipital cortex of five AD patients and five non-pathological controls. This study was approved by the ethics committee at each hospital or institute. Cryosections were cut and transferred to Indium-Tin-Oxide coated glass slides. Spectra were acquired using the rapifleX in positive linear mode, whereas ions were detected in a mass range of m/z 2,000-20,000 with spatial resolution of 20-100 µm. Matrix was uniformly deposited on the slide using the HTX-sprayer. Visualization and statistical analysis were used flexImaging and SCiLS Lab. 

The current analysis clarifies that Aβ1-42 and Aβ1-43 were selectively deposited to senile plaque and shorter Aβ peptides were deposited to leptomeningeal blood vessels. In order to deepen proteomic information with the current specimen, we have dissected a small piece of tissues from leptomeningeal vessels as well as parenchymal area with laser micro dissection and were applied to LC-TIMS-TOF-MS/MS analysis. Data analysis was done with Proteinscape. From single vascular structure and adjacent cortical parenchyma dissected with 0.25-0.5 mm2 yields a thousand of protein annotation. Further analysis including detected peptide fragments as well as immunohistochemistry with a specific epitope recognition will validate the current strategy.