title: Identification of oligosaccharides from histopathological sections by MALDI imaging mass spectrometry.
abstract: Direct tissue analysis using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) provides the means for in situ molecular analysis of a wide variety of biomolecules. This technology--known as imaging mass spectrometry (IMS)--allows the measurement of biomolecules in their native biological environments without the need for target-specific reagents such as antibodies. In this study, we applied the IMS technique to formalin-fixed paraffin-embedded samples to identify a substance(s) responsible for the intestinal obstruction caused by an unidentified foreign body. In advance of IMS analysis, some pretreatments were applied. After the deparaffinization of sections, samples were subjected to enzyme digestion. The sections co-crystallized with matrix were desorbed and ionized by a laser pulse with scanning. A combination of α-amylase digestion and the 2,5-dihydroxybenzoic acid matrix gave the best mass spectrum. With the IMS Convolution software which we developed, we could automatically extract meaningful signals from the IMS datasets. The representative peak values were m/z 1,013, 1,175, 1,337, 1,499, 1,661, 1,823, and 1,985. Thus, it was revealed that the material was polymer with a 162-Da unit size, calculated from the even intervals. In comparison with the mass spectra of the histopathological specimen and authentic materials, the main component coincided with amylopectin rather than amylose. Tandem MS analysis proved that the main components were oligosaccharides. Finally, we confirmed the identification of amylopectin by staining with periodic acid-Schiff and iodine. These results for the first time show the advantages of MALDI-IMS in combination with enzyme digestion for the direct analysis of oligosaccharides as a major component of histopathological samples.
authors.affiliation: Department of Surgery, Kansai Medical University, 2-3-1 Shin-machi, Hirakata, Osaka 573-1191, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Yamada
authors.forename: Ikuko
authors.initials: I
authors.lastname: Yao
authors.forename: Takahiro
authors.initials: T
authors.lastname: Hayasaka
authors.forename: Masaru
authors.initials: M
authors.lastname: Ushijima
authors.forename: Masaaki
authors.initials: M
authors.lastname: Matsuura
authors.forename: Hideho
authors.initials: H
authors.lastname: Takada
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Shikata
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Setou
authors.forename: A-Hon
authors.initials: AH
authors.lastname: Kwon
authors.forename: Seiji
authors.initials: S
authors.lastname: Ito
mesh_terms: D000687:Amylopectin / Q000737:chemistry; D002240:Carbohydrate Sequence; D005557:Formaldehyde; D005841:Gentisates / Q000737:chemistry; D005936:Glucans / Q000737:chemistry; D006801:Humans; D007415:Intestinal Obstruction / Q000473:pathology* / Q000601:surgery; D007421:Intestine, Small / Q000473:pathology / Q000601:surgery; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000032:analysis*; D016612:Paraffin Embedding; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013213:Starch / Q000737:chemistry; D053719:Tandem Mass Spectrometry / Q000379:methods; D016707:Tissue Fixation / Q000379:methods; D000516:alpha-Amylases / Q000737:chemistry
chemical_list: D005841:Gentisates; D005936:Glucans; D009844:Oligosaccharides; D005557:Formaldehyde; D013213:Starch; D000687:Amylopectin; D000516:alpha-Amylases