Mechanical Properties Affect Primary T Cell Activation in 3D Bioprinted Hydrogels

T cellsplay a critical role in the adaptive immune response ofthe body, especially against intracellular pathogens and cancer. In vitro, T cell activation studies typically employ planar(two-dimensional, 2D) culture systems that do not mimic native cell-to-extracellularmatrix (ECM) interactions, which influence activation. The goal ofthis work was to study T cell responses in a cell line (EL4) and primarymouse T cells in three-dimensional (3D) bioprinted matrices of variedstiffness. Cell-laden hydrogels were 3D bioprinted from gelatin methacryloyl(GelMA) using a digital light processing (DLP)-based 3D bioprinteroperated with visible light (405 nm). Mechanical characterizationrevealed that the hydrogels had pathophysiologically relevant stiffnessesfor a lymph node-mimetic tissue construct. EL4, a mouse T cell lymphomaline, or primary mouse T cells were 3D bioprinted and activated usinga combination of 10 ng/mL of phorbol myristate acetate (PMA) and 0.1 & mu;M of ionomycin. Cellular responses revealed differences between2D and 3D cultures and that the biomechanical properties of the 3Dbioprinted hydrogel influence T cell activation. Cellular responsesof the 2D and 3D cultures in a soft matrix (19.83 & PLUSMN; 2.36 kPa)were comparable; however, they differed in a stiff matrix (52.95 & PLUSMN;1.36 kPa). The fraction of viable EL4 cells was 1.3-fold higher inthe soft matrix than in the stiff matrix. Furthermore, primary mouseT cells activated with PMA and ionomycin showed 1.35-fold higher viablecells in the soft matrix than in the stiff matrix. T cells bioprintedin a soft matrix and a stiff matrix released 7.4-fold and 5.9-foldhigher amounts of interleukin-2 (IL-2) than 2D cultured cells, respectively.Overall, the study demonstrates the changes in the response of T cellsin 3D bioprinted scaffolds toward engineering an ex vivo lymphoid tissue-mimetic system that can faithfully recapitulateT cell activation and unravel pathophysiological characteristics ofT cells in infectious biology, autoimmunity, and cancers.

Automated summary

T cells play a critical role in the immune response and their activation and response can be influenced by the 3D bioprinted matrix and its stiffness. The study reveals differences between 2D and 3D cultures and the impact of matrix stiffness on T cell activation and cytokine release.