シアフロー下における上流移動型造血様KG1a細胞の牽引力の測定

Cell migration is critical to leukocyte function, enabling leukocytes to patrol tissues and respond to inflammatory cues. Upstream migration is a distinct form of cell motility which enables leukocytes to move against the direction of fluid flow on Intercellular Adhesion Molecule-1 (ICAM-1) surfaces. Upstream migration is mediated by the leukocyte integrin, Lymphocyte Function-Associated Antigen-1 (LFA-1). While 1upstream migration has been observed across multiple immune cell types, the mechanical forces underlying upstream migration have not been measured. Here, we demonstrate the use of Traction Force Microscopy (TFM) to quantify spatiotemporal patterns of force generation during upstream migration of KG1a cells, a hematopoietic progenitor cell line that exhibits robust upstream migration on ICAM-1 functionalized hydrogels. Under static (no-flow) conditions, KG1a cells displayed random motility 1with dynamic traction forces that fluctuated substantially over time. 1Cells exposed to shear flow 1exhibited sustained upstream migration with significantly amplified traction forces. Population analysis showed that maximum RMS traction forces were significantly elevated during upstream migration compared to static conditions (mean: 1377.9 ± 55.1 nN vs 220.1 ± 20.3 nN, p = 0.0177), as were average RMS forces (mean: 175.0 ± 13.5 nN vs 43.0 ± 4.8 nN, p = 0.0425), while minimum force values remained comparable. 1Quantitative spatial analysis revealed that in the presence or absence of shear flow, cells maintained similar spatial distribution of forces, demonstrating that forces are amplified during upstream migration without spatial reorganization. 1This study 1demonstrates that during upstream migration cells amplify their contractile forces while preserving their spatial organization, revealing how cells adapt their mechanical output under flow. Our methods enable future dissection of molecular regulators coordinating force generation during migration under flow.