Lipid MALDI Imaging of Prenatal Human Archival Brain Tissue with Prolonged Fixation Period

Objective: Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) was employed to investigate lipid composition and spatial distribution in the human fetal temporal lobe during prenatal development (21 gestational weeks, GW). Methods: An optimized protocol was established for archival formalin-fixed tissue. Results: Comparative analysis of matrices revealed that 1,5-diaminonaphthalene (DAN) enabled detection of significantly more lipid species than 2,5-dihydroxybenzoic acid (DHB). Tandem mass spectrometry facilitated in situ lipid identification directly on tissue sections. Differential lipid detection was observed between ionization modes: in positive mode mostly phosphatidylcholines (PCs) were detected whereas in negative mode phosphatidylinositols (PIs) and phosphatidic acids (PAs) detection was strongly enchanced. Conclusions: Spatially resolved analysis uncovered heterogeneous lipid distribution across developing cortical structures at GW 21: ventricular/subventricular zones, cortical plate and basal nuclei—PC (total fatty acid carbon : double bond count is 30 : 0), PC (34 : 1), PC (36 : 7), PC (38 : 8), PA (16 : 0/18 : 1), intermediate zone and subplate—PC (32 : 0), PC (34 : 2), PC (36 : 4). This study establishes the possibility of MALDI-IMS of archival human fetal brain after prolonged fixation.