In Vitro Bioreactor for Mechanical Control and Characterization of Tissue Constructs

Heart failure (HF) currently affects over 6 million Americans, 50% of whom die within 5 years of their initial diagnosis. A major contributor to the onset of HF is cardiac fibrosis in the myocardium, which arises when fibroblasts (FBs) are activated in response to heightened mechanical stress from overload conditions like hypertension. Activated FBs remodel the extracellular matrix (ECM) and secrete ECM proteins including collagen. FB remodeling has been studied in the past by applying forces and/or deformations to three-dimensional, cell-seeded gels and tissue constructs in vitro. Unfortunately, previous stretching platforms have traditionally not enabled mechanical property assessment to be performed with an efficient throughput, thereby limiting the full potential of in vitro mechanobiology studies. We developed a novel in vitro platform to study cell-populated tissue constructs under dynamic mechanical stimulation while also performing repeatable, non-destructive stress-strain tests in living constructs. The multi-well platform is 3D printed out of a Dental LT resin with each well housing a magnetic piston grip. Cell populated tissue constructs were grown within the wells to attach to magnetic grips opposite from stationary grips. Uniaxial mechanical tension was applied to the tissues by a computer-controlled electromagnet placed beside the well plate, which enabled both dynamic stimulation during long-term culture as well as repeatable, non-destructive stress-strain tests for simultaneously comparing tissue stiffnesses across all wells. We have successfully utilized our platform to stretch cell-populated tissue constructs composed of both primary murine and primary human cardiac fibroblasts within 3D fibrin gels. Cyclically stretching cardiac fibroblasts within a 3D fibrin matrix led to collagen accumulation and increased tissue stiffness. Results from these studies validated our novel platform’s ability to enable dynamic mechanical characterization of cell-mediated tissue remodeling in vitro - a capability not possible in standard 3D tissue culture. This multiwell platform offers potential as a high-throughput screening tool for assessing the effect of different treatments on clinically relevant metrics of tissue stiffness using automated measurements