Three-dimensional imaging of lipids and metabolites in tissues by nanospray desorption electrospray ionization mass spectrometry

Abstract

Three-dimensional (3D) imaging of tissue sections is a new frontier in mass spectrometry imaging (MSI). Here, we report on fast 3D imaging of lipids and metabolites associated with mouse uterine decidual cells and embryo at the implantation site on day 6 of pregnancy. 2D imaging of 16–20 serial tissue sections deposited on the same glass slide was performed using nanospray desorption electrospray ionization (nano-DESI)—an ambient ionization technique that enables sensitive localized analysis of analytes on surfaces without special sample pretreatment. In this proof-of-principle study, nano-DESI was coupled to a high-resolution Q-Exactive instrument operated at high repetition rate of >5 Hz with moderate mass resolution of 35,000 (m/Δm at m/z 200), which enabled acquisition of the entire 3D image with a spatial resolution of ~150 μm in less than 4.5 h. The results demonstrate localization of acetylcholine in the primary decidual zone (PDZ) of the implantation site throughout the depth of the tissue examined, indicating an important role of this signaling molecule in decidualization. Choline and phosphocholine—metabolites associated with cell growth— are enhanced in the PDZ and abundant in other cellular regions of the implantation site. Very different 3D distributions were obtained for fatty acids (FA), oleic acid and linoleic acid (FA 18:1 and FA 18:2), differing only by one double bond. Localization of FA 18:2 in the PDZ indicates its important role in decidualization while FA 18:1 is distributed more evenly throughout the tissue. In contrast, several lysophosphatidylcholines (LPC) observed in this study show donut-like distributions with localization around the PDZ. Complementary distributions with minimal overlap were observed for LPC 18:0 and FA 18:2 while the 3D image of the potential precursor phosphatidylcholine 36:2 (PC 36:2) showed a significant overlap with both LPC 18:0 and FA 18:2.

Advanced Multidimensional Separations in Mass Spectrometry: Navigating the Big Data Deluge

“…On the other hand, MSI is conventionally coupled to MS by means of a pulsed ion beam or laser source to provide high speed, discrete ionization of spatial locations on the sample (104,105). Developments in MSI-MS using liquid sampling probes are now beginning to emerge (106,107), which reduces sample pretreatment at a cost of throughput and spatial resolution. Coupling ion mobility to mass spectrometry (IM-MS) requires transferring ions across disparate pressure regions and analyses in an efficient manner, and this challenge has been addressed through electrodynamic ion optics and the nesting of analytical timescales (108,109,84).…”

Review and perspectives on the applications of mass spectrometry imaging under ambient conditions

“…The precise localization of the injection site was visualized by 2D and 3D imaging . 2D and 3D nano‐DESI‐MS images of lipids and metabolites associated with mouse uterine decidual cells and embryo at the implantation site 6 days after fertilization were examined with 2D images of 16–20 serial tissue sections (Figure ) . Localization of acetylcholine in the primary decidual zone (PDZ) of the implantation site throughout the depth of the tissue indicates its fundamental role in decidualization.…”

“…On the other hand, spherical, donut‐shaped distributions of lysophosphatidylcholines were found surrounding the PDZ. A global summary of tissue models using 3D concatenated images adds another dimensional component within MS analysis directed towards a complete representation of the spatial distribution of molecules and their role in biological processes in 3D space providing concomitant depth analysis …”

“…(B) Overlaid 3D images of [FA 18:2 + K] + at m/z 319.204 (green) and [LPC 18:0 + K] + at m/z 562.327 (red); the area in which both signals are present is shown in purple. [(A) and (B) reproduced from Lanekoff et al]…”

Electrospray Modifications for Advancing Mass Spectrometric Analysis

“…Due to the feature of nano-DESI to analyze analytes from surface, it has been applied extensively for imaging from a variety of samples. [128][129][130] Furthermore, it has been applied in pro ling sweat metabolites using hydrogel micropatches as sampling substrates. 131,132) Electrospray for post-ionization e interaction of neutral species using electrospray as the post-ionization source for MS analysis has been investigated for some time.…”