Lipid characterization of embryo zones by silica plate laser desorption ionization mass spectrometry imaging (SP-LDI-MSI)

Abstract

Lipid pathways play important biological roles in mammalian embryology, directing early developmental pathways to differentiation. Phospholipids and triglycerides, among others, are the main composing lipids of zona pellucida in several embryo species. Lipid analysis in embryos by mass spectrometry usually requires sample preparation and/or matrix application. This novel approach using silica plate laser desorption/ionization mass spectrometry imaging (SP-LDI-MSI) allows direct single-cell imaging and embryo region discrimination with no matrix coating. Its application is herein described for two- and eight-cell embryos. Lipid biomarkers for blastomere and intact zona pellucida are reported and corroborated by both fragmentation reactions (MS/MS) and images. Results obtained in this work are understood to be of great use for further developments on in vitro bovine fertilization. Since much of the processes can be monitored by characteristic biomarkers, it is now possible to precisely identify cell division errors during early embryo stages, as well as evaluate pre-implantation conditions.

Keywords: 2,5-dihydroxybenzoic acid; Biomarkers; Cer; DHB; Direct analysis; MALDI-MS; Metabolic fingerprinting; PA; PCA; PE; PL; Principal Component Analysis; SP-LDI-MSI; Single-cell; TLC; ZP; ceramide; isoK; isoketals; matrix-assisted laser desorption/ionization mass spectrometry; phosphatidic acid; phosphatidylethanolamine; phospholipid; silica plate laser desorption/ionization mass spectrometry imaging; thin-layer chromatography; zona pellucida.