Mechanical tuning of three-dimensional cell culture system

Tissue Engineering has gained increasing attention as a promising means to repair or replace defective tissues. The interrelationship between scaffold and living cells are essential to produce the desired tissue. Mechanical characterizations of scaffold were well acknowledged to regulate cell behaviors including its growth, migration, proliferation, and apoptosis. However, the mechanism of cell mechanosensing to its mechanical environment is still not fully understood. In this project, the nanostructure-function relationship of three dimensional collagen scaffolds as well as its impact on cell adaptation was characterized through computational models calibrated by experimental evidences. Results demonstrated that strain stiffening of collagen scaffold was dominated by fiber alignment, and postponed by thermal undulation of collagen fiber. In addition, mechanical behavior of scaffolds could be fine-tuned by collagen concentration, crosslinking density and matrix configurations affected by glycation. An empirical equation was obtained to guide the design of collagen scaffold with tunable material properties. To produce the specific engineered tissue, it is essential to understand how living cells respond to its mechanical environments. We characterized the mechanical homeostasis that cells try to maintain following the mechanical disturbance. A hypothesis was proposed that cells strived to maintain a pre-set eigenstrain in response to mechanical disturbance. Cell contraction induced traction force was quantified by traction force microscope (TFM). Numerical models were used to integrate the TFM results for both 3T3 fibroblasts and bovine aortic endothelial cells (BAECs). It was observed that BAECs adjusted its stiffness and shape in response to different mechanical environment. The stiffness change of cells could be up to two order of difference, which was accomplished by the cytoskeletal reorganization from actin filaments into stress fibers. The predicted cell mechanics has revealed that cellular strain is indeed the pre-set points for both cell types. In summary, the developed modeling frameworks spanning from fiber-matrix interaction, cell-scaffold interaction to cytoskeletal adaptation offer an effective means to integrate experimental datasets and facilitate investigation of the scaffold/cell mechanics where experimentation is inefficient. These results could help to mechanically fine-tune the three-dimensional cell culture system for better tissue regeneration strategies