Nanoscopic spatial reorganization of selectin ligands, CD44 and PSGL-1, during the initial step of hematopoietic stem/progenitor cell (HSPC) homing, tethering and rolling of migrating cells over E-selectins, has been recently reported. However, the exact spatial distribution of these ligands and their spatial reorganization during the cell rolling on E-selectins are still an open question. The spatiotemporal characterization at the nanoscale level requires high resolution imaging methods. In this study, I quantitatively characterize nanoscopic spatiotemporal behavior of the selectin ligands on the migrating cells to understanding the molecular mechanism of the cell rolling at the nanoscale level by means of a microfluidics-based 3D super-resolution fluorescence microscopy technique. The obtained results suggest that PSGL-1 on the cell shows significant change in the axial distribution on the cell during the cell rolling on E-selectin whereas the spatial distribution of CD44 along the axial direction is not affected significantly by the cell rolling. These findings indicate that each selectin ligand has a distinct contribution to the initial step of the HSPC homing because of their distinct spatial localizations on the cells that regulate at least partly the accessibility of these ligands to the surface E-selectin.
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