From single cells to complex tissues: advances in ambient ionization mass spectrometry for observing small molecules in biological samples

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Metabolites are small biomolecules such as lipids, sugars, and amino acids that are involved in all biological processes. The field of metabolomics is the targeted and non-targeted profiling of metabolites in biological samples. Profiling an organism's dynamic metabolome can help understand fundamental biological processes, and provide objective diagnosis of diseases. However, the structural diversity of metabolites in biology is vast, and includes non-polar species such as cholesterols and signalling lipids, and highly polar molecules like amino acids. To complicate matters further, the natural abundance of metabolites found in organisms can range by several orders of magnitude. Traditional analytical approaches for measuring metabolites in tissues typically requires homogenization of samples and extraction metabolites before analysis by mass spectrometry. As a result, the spatial information detailing metabolite localization to specific cellular regions in heterogeneous tissues is lost. In order to make further advances in the field, there is an urgent need for new analytical techniques to map complex mixtures of biomolecules in a wide array of samples. Through the course of this research, my group will create and engineer new ambient ionization mass spectrometry tools to profile dynamic organismal metabolomes. These tools will be developed and validated using model biological systems spanning from single mammalian cells to complex heterogeneous tissues. In the short term, we will build a new platform to comprehensively map the distribution of metabolites in tissue using mass spectrometry imaging, combine an integrate technologies for mapping metabolites and proteins in a single sample, and measure the metabolite profiles in living single cells. Used synergistically, these new techniques form an innovative analytical pipeline to profile metabolites from a diverse set of biological samples. Future applications of this novel pipeline will aid in elucidating the role of metabolites in fundamental biological pathways, or impacted metabolic pathways from exposure to chemical toxicants. Further, this Discovery Grant will develop new technology to study the relationship between individual single-cell metabolism to the metabolism of cells in tissue. This important information will provide a new perspective to help understand how cells behave in isolated conditions versus their native tissue environments. Ultimately, the technology developed in my research program will leverage transformative approaches to reveal the spatial distribution of metabolites in complex biological samples, and link observed metabolites to spatially defined protein abundances and known functions.