Dynamic bioreactors with integrated microfabricated devices for mechanobiological screening.

Biomechanical stimulation is a common strategy to improve the growth, maturation, and function of a variety of types of engineered tissues. However, identifying optimized biomechanical conditioning protocols is challenging, as cell response to mechanical stimuli are modulated by other multifactorial microenvironmental cues, including soluble factors and biomaterial properties. Traditional bioreactors lack the throughput necessary for combinatorial testing of cell activity in mechanically-stimulated engineered tissues. Microfabricated systems can improve experimental throughput, but often do not provide uniform mechanical loading, are challenging to use, lack robustness, and offer limited amounts of cells and tissue for analysis. To address the need for higher-throughput, combinatorial testing of cell activity in a tissue engineering context, we developed a hybrid approach, in which flexible polydimethylsiloxane microfabricated inserts were designed to simultaneously generate multiple tensile strains when stretched cyclically in a standard dynamic bioreactor. In the embodiment presented here, each insert contained an array of 35 dog bone-shaped wells in which cell-seeded microscale hydrogels can be polymerized, with up to eight inserts stretched simultaneously in the bioreactor. Uniformity of the applied strains, both along the length of a microtissue and across multiple microtissues at the same strain level, was confirmed experimentally. In proof-of-principle experiments, the combinatorial effects of dynamic strain, biomaterial stiffness, and TGF-β1 stimulation on myofibroblast differentiation were tested, revealing both known and novel interaction effects and suggesting tissue engineering strategies to regulate myofibroblast activation. This platform is expected to have wide applicability in systematically probing combinations of mechanobiological tissue engineering parameters for desired effects on cell fate and tissue function.