The Three-dimensional Environment of Type Ⅰ Collagen Gels With Varying Stiffness Modulates the Immunological Functions of NK Cells

To construct type Ⅰ collagen gels with different stiffness and to investigate the effects of three-dimensional (3D) culture environments of the gels on the morphology, free migration ability, and cell killing function of natural killer (NK) cells. Type Ⅰ collagen was isolated from the tails of Sprague Dawley (SD) rats and collagen gels with different levels of stiffnesses were prepared accordingly. The microstructure of the collagen gels was observed by laser confocal microscopy. The stiffness of the collagen gels was assessed by measuring the plateau modulus with a rheometer. NK-92MI cells were cultured in collagen gels with different levels of stiffness. The morphology of NK-92MI cells was observed by inverted microscope. High content imaging system was used to record the free migration process of NK-92MI cells and analyze the migration speed and distance. NK-92MI cells were cultured with type Ⅰ collagen gels with different levels of stiffness for 24 h and 48 h and, then, co-cultured with human colorectal D