Speaker: Dr. Chiara Stringari - Laboratory for Optics & Biosciences, Ecole Polytechnique Palaiseau, Paris, FR
Title: Label-free metabolic imaging of living tissues by Fluorescence Lifetime Microscopy of endogenous biomarkers
Cellular metabolism plays a crucial role in several physiological processes such as cancer progression, cell migration, stem cell differentiation, embryo morphogenesis and neurodegenerative diseases. A non-invasive and high resolution mapping of cell metabolism in vivo is fundamental for the understanding of tissue development and for testing effective treatments.
We established a sensitive method for metabolic imaging by combining non-linear optical microscopy and the use of endogenous fluorophores that are naturally present in cells and tissues. Functional images of tissues autofluorescence are provided by two-photon-excitation, fluorescence lifetime microscopy (FLIM) and the metabolic coenzyme nicotinamide adenine dinucleotide (NADH). NADH is the principal electron acceptor in glycolysis and electron donor in oxidative phosphorylation and it is a very informative intrinsic biomarker for metabolism. Fluorescence lifetime measurements of free and protein-bound NADH sense small changes in cellular redox state and quantify different rates of oxidative phosphorylation and glycolysis in single cells within the tissue microenvironment. FLIM of NADH has the capability to discriminate different metabolic states of undifferentiated progenitor stem cells and differentiated cells, to predict stem cell fate to different lineages, to identify proliferating cancer cells and delineate tumor borders.
In conclusion, optical metabolic imaging by FLIM of endogenous biomarkers represents a promising experimental technique for measuring single-cell metabolic phenotype in intact tissues with minimal phototoxicity and can be widely applied non-invasively for longitudinal studies in vivo.