DYNAMICS OF CELL MIGRATION IN 3D USING MULTI-PHOTON EXCITATION, SHG AND OCT

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cell migration is an essential process in several physiological events such as wound healing and embryonic development. Additionally, it can contribute to pathological disorders such as inflammation and cancer metastasis.1-3 The process by which cells migrate is a complicated procedure where hundreds of proteins participate in the formation of the cell adhesions to the extra cellular matrix (ECM) and the interactions with the cytoskeleton. The mechanical stimulation that is exerted by the ECM on the cell has been found to be one of the determining factors for cell differentiation.4 Previous studies using correlation analyses in 2D have been performed by our group about the role of Paxilin, an "anchor" protein, that is essential for the formation of cellular adhesions.5,6 The next logical step is to study the cellular interactions in 3D which represents a more realistic biological system. Hence, our model tissue is comprised of cells embedded in a 3D collagen matrix gel where the collagen matrix is used to simulate the ECM. Using the multi-modal system of two-photon excited fluorescence (TPEF), second harmonic generation (SHG) and optical coherence tomography (OCT) built by LAMMP researchers, we are able to image the interactions of the cell with the ECM such as the movement of the cell and the resulting deformation in the ECM. We are able to determine the displacement and the velocities at every point in the image using Spatio-Temporal Image Correlation Spectroscopy STICS)7 from the signals obtained from the OCT and MPM channels. The novelty of this study is that this is the first time that we can detect velocity maps (not related to OCT- Doppler effect) using the signals from OCT channel. The velocity maps obtained from the two images complement each other. We propose to develop cross correlation velocity maps to obtain information about common factors affecting the motion of the cell and of the collagen matrix. We also plan to calculate a true 3D velocity map and we will theoretically model the system to quantify the motion and its relation to the tensile strength of the ECM. In particular, we would like to know the relationship between the collagen matrix degree of polymerization and the movement of the cell. Furthermore we would like to study the relationship between the accumulation of the focal adhesion proteins such as Paxilin and the movement of the cell. Ultimately, as we measure the deformation in the ECM, we would like to extract the force applied at the various cell adhesions.