Introduction:

During development, the heart transforms from a linear tube to a multichambered organ. This process requires orchestration of both mechanical and chemical cues between primordial cardiac tissues and the surrounding environment. Errors in these early stages of human cardiogenesis are known to cause congenital heart defects, however, existing in vitro models are insufficient to address the morphometric abnormalities that occur in vivo.

Aims:

Our was to utilise novel bioengineering approaches to reverse engineer an in vitro model of the earliest stage of human heart development, the linear heart tube.

Methods:

Utilising a recently developed bioprinting technology that enables the photo-crosslinking of biopolymers within hydrogels combined with hiPSC, we have created a novel 3D tissue-engineered in vitro model of the embryonic heart tube.

Results:

We are able to finely tune the stiffness of the hydrogel over biologically matched ranges by modulating both the laser power and the number of printing cycles. This enables patterning of mechanical properties with micrometric resolution allowing us to generate regional domains with specific elastic modules. The bioprinted scaffold enables robust cardiomyocyte differentiation from human iPSCs with the formation of a single cell layer around the hydrogel scaffold with correct polarisation and organisation with representative morphology and geometry to what is observed in vivo. The mechanical properties of the tubes can be designed to be compliant with cardiomyocyte contraction with corresponding changes in the luminal cross-section depending on scaffold stiffness. We now envision the creation of controlled small molecule concentration gradients across the different axis of the linear heart tube in an attempt to recreate the patterning process that occurs in vivo.

Conclusion:

We are using this technology to investigate the process of linear heart tube looping, developmental asymmetry and trabeculation. Ultimately, an in vitro model of early-stage human heart development will provide a powerful testbed to explore the mechanism of cardiogenesis and the possibility to develop novel therapies for congenital heart malformations.