Skeletal muscle fiber analysis by atmospheric pressure scanning microprobe matrix-assisted laser desorption/ionization mass spectrometric imaging at high mass and high spatial resolution

Abstract

Skeletal muscles are composed of heterogeneous muscle fibers with various fiber types. These fibers can be classified into different classes based on their different characteristics. MALDI mass spectrometric imaging (MSI) has been applied to study and visualize different metabolomics profiles of different fiber types. Here, skeletal muscles were analyzed by atmospheric pressure scanning microprobe MALDI-MSI at high spatial and high mass resolution.

Keywords: Atmospheric pressure MALDI mass spectrometric imaging; Biomedicine; High mass resolution MS; High spatial resolution MS; Metabolomics; Skeletal muscle fiber type.

Figure 1

The optical image of a cross section analyzed by MSI is shown in (A); the MHC IFL image of the section adjacent to the cross section analyzed by MSI is shown in (B); image (C) is the zoom in of the region of the optical image shown in (A) that was submitted for 10 μm spatial resolution MSI analysis., whereas image (D) shows the zoom in of the clustering region of image (B). In the MHC IFL images, the type I fibers were stained with blue fluorescence, type IIA fibers with green fluorescence, and type IIB fibers were stained with red fluorescence; Type IIX fibers were left unstained and give no fluorescence and appeared black.

Figure 2

Display the MHC IFL image of a transverse cross section zoomed in to the region of boundary formed by the two clusters of fibers in (A). The image in (C) is a 10× zoomed-in MS image of m/z 872.557 from F. Figure (D), (E), and (F), are the MS images of m/z 820.525, 832.582, and 872.557, putatively identified as [M+K]⁺ of PC(36:4), [M+Na]⁺ of PC (38:4), and [M+K]⁺ of PC(40:6) based on the accurate mass database search from Metlin database. The image shown in (B) is the overlay of the three MS images in (D), (E), and (F), where panel (D) [M+K]⁺ of PC(36:2) is in red, panel (E) [M+Na]⁺ is in blue, and panel (F) [M+K]⁺ is in green.