Researchers have 3D-printed hearts using silicone and even a patient’s own cells, but they haven’t matched all the real-life features and aren’t very good at repairing hearts. There is progress on this front, however, as a team at Harvard’s Wyss Institute has developed a technique to 3D print long cardiac macrofilaments that morph into contracting muscle-like filaments. The new method mimics the complex alignment of the contracting elements of a heart (a difficult feat so far) while producing tissue thick enough to be used in regenerative cardiac treatments.

The system is a refinement of Wyss’ existing Sacrificial Writing in Functional Tissue (SWIFT) bioprinting technology. Their approach created a platform with 1,050 wells, each with two microscopic pillars. Scientists filled the wells with human-induced pluripotent stem cells (i.e. young cells capable of growing into many forms) along with a protein collagen and cells used to form connective tissue . The whole forms a dense fabric that aligns along the axis connecting the micropillars. The team then lifts the resulting organ building blocks from the pillars, uses them to create bioprinting ink, and uses the movement of the 3D printhead to further aid in alignment.

It’s just a little piece of heart. Although the technology produces a relatively high yield, there is still a lot of work to be done before a fully functional 3D-printed organic heart is available.

The research group believe their work could still be useful long before they reach the whole-heart milestone. The 3D-printed filaments could be used to replace scars after heart attacks or to create improved disease models. They could even plug holes in newborn babies with congenital heart defects and would grow up with these patient children. Simply put, a damaged heart may not be the permanent problem it tends to be today.