Autofluorescence lifetime microscopy for label-free detection of cell metabolism for cell biology research

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PROJECT SUMMARY/ABSTRACT This is an application for a Maximizing Investigator’s Research Award (MIRA) submitted by the Early Stage Investigator (ESI), Dr. Alex Walsh. Dr. Walsh’s research program focuses on the characterization and development of autofluorescence lifetime microscopy for the quantification of cell metabolism and mitochondria function of living cells. Abnormal cell metabolism and mitochondria dysfunction is a hallmark of many diseases and pathological states. Furthermore, many drugs and pharmacological agents, including anesthesia, either have direct mechanisms of action through altered metabolism signaling or indirect toxicities due to impaired mitochondria function. Current research assays to evaluate cellular metabolism include cell-based assays such genomic, metabolomic, and oxygen-consumption assays and whole-body imaging assays such as fluorodeoxyglucose-positron emission tomography and carbon-13 magnetic resonance imaging. However, these existing tools have limited spatial and temporal resolutions and the label-dependent nature of the assays prevents assessment of dynamic metabolic states and multiple longitudinal assessments of the same samples. Autofluorescence lifetime imaging of reduced nicotinamide adenine dinucleotide (NADH) within the mitochondria and cytosol and flavin adenine dinucleotide (FAD) within mitochondria presents a unique, label-free, high- resolution technique to evaluate cell metabolism. Autofluorescence lifetime microscopy is not dependent on chemical or antibody labels, is non-contact, broadly applicable to any cell or tissue, well-suited for longitudinal studies, and compatible with secondary assays. However, adoption of autofluorescence lifetime is currently hindered by the advanced expertise needed to design and perform fluorescence lifetime experiments, obscurity in the correlation between fluorescence lifetime metrics and molecular specificity, and a lack of robust models to determine metabolic phenotype and mitochondria function from autofluorescence features. Therefore, Dr. Walsh’s goals for the next five years will address these limitations. Goal 1: Determine the sensitivity and specificity of autofluorescence lifetime imaging to identify cellular metabolic states and pathway utilization. Goal 2: Quantify autofluorescence lifetime imaging features across common lab models to determine the robustness of autofluorescence metrics to report cellular metabolism. Goal 3: Develop, test, and optimize autofluorescence imaging protocols to quantify mitochondria dynamics and function. The outcomes of this proposal will enable metabolic measurements with high temporal resolution and specificity to evaluate cellular metabolism in living cells. Additionally, autofluorescence imaging will provide a platform to evaluate the impacts of drug and pharmacological agents, including anesthetics, on cell metabolism and mitochondria function in living cells, tissues, and in vivo.