milliPillar: A Platform for the Generation and Real-Time Assessment of Human Engineered Cardiac Tissues

Engineered
cardiac tissues derived from human induced pluripotent
stem cells (iPSCs) are increasingly used for drug discovery, pharmacology
and in models of development and disease. While there are numerous
platforms to engineer cardiac tissues, they often require expensive
and nonconventional equipment and utilize complex video-processing
algorithms. As a result, only specialized academic laboratories have
been able to harness this technology. In addition, methodologies and
tissue features have been challenging to reproduce between different
groups and models. Here, we describe a facile technology (milliPillar)
that covers the entire pipeline required for studies of engineered
cardiac tissues. We include methodologies for (i) platform fabrication,
(ii) cardiac tissue generation, (iii) electrical stimulation, (iv)
automated real-time data acquisition, and (v) advanced video analyses.
We validate these methodologies and demonstrate the versatility of
the platform by showcasing the fabrication of tissues in different
hydrogel materials and using cardiomyocytes derived from different
iPSC lines in combination with different types of stromal cells. We
also validate the long-term culture of tissues within the platform
and provide protocols for automated analysis of force generation and
calcium flux using both brightfield and fluorescence imaging. Lastly,
we demonstrate the compatibility of the milliPillar platform with
electromechanical stimulation to enhance cardiac tissue function.
We expect that this resource will provide a valuable and user-friendly
tool for the generation and real-time assessment of engineered human
cardiac tissues for basic and translational studies.