Thesis
French
ID: <
10670/1.8uas7m>
Abstract
Vibrational microspectroscopy is a rapidly emerging label-free technique that allows the probing of live cell. Thanks to the vibration of the chemical bonds, it makes it possible to locate in the cell biomolecules (proteins, nucleic acids, lipids) associated with organelles. My study consisted in using Coherent Anti-Storage Raman Spectroscopy (CARS) microspectroscopy in the CH zone of the Raman spectrum, a highly resolved (<1 cm-1) and restricted interval (2500-3000 cm-1). Vibrations corresponding to the CH2 and CH3 chemical groups are mainly associated with lipids and proteins, respectively. Using synchronous cultures, I have been able to highlight differences between cells in interphase and cells in mitosis and, more interestingly, the five sub-phases of mitosis, thanks to the evolutions of heterochromatin and endoplasmic reticulum as wel. I also tracked, in cells in interphase, the changes in lipid metabolism following activation of the TrkB receptor, often expressed in tumor cells. Specific lipid droplets showed up in HEK cell expressing TrkB activated. This same type of droplets has been observed in three cell lines derived from three stages of colorectal cancer. I have established a direct link between TrkB activation and the presence of these lipid droplets. Thus, CARS microspectroscopy makes it possible to follow the biogenesis of lipid droplets by analysis in the CH zone. This method could be exploited to find out, without prior labeling, cancer cells in a tissue, making CARS microspectroscopy a useful diagnostic tool.