Visualization of Differential Cardiolipin Profiles in Murine Retinal Cell Layers by High-Resolution MALDI Mass Spectrometry Imaging

The precise fatty acyl chain configuration of cardiolipin (CL), a tetrameric mitochondrial-specific membrane lipid, exhibits dependence on cell and tissue types. A powerful method to map CL profiles in tissue sections in a spatially resolved manner is matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI). To build on and explore this potential, we employed a quadrupole time-of-flight mass spectrometer along with optimized sample preparation protocols. We imaged the CL profiles of individual murine retinal cell layers at a pixel size of 10 μm. In combination with tandem MS, we obtained detailed insights into the CL composition of individual retinal cell layers. In particular, we found differential expression of the polyunsaturated fatty acids (PUFA) linoleic, arachidonic, and docosahexaenoic acids. PUFAs are prone to peroxidation and hence regarded as critical factors in development and progression of retinal pathologies, such as age-related macular degeneration (AMD). The ability of MALDI-MSI to provide cues on the CL composition in neuronal tissue with close to single-cell resolution can provide important insights into retinal physiology in health and disease.