Major Step Toward Artificial Biological Hearts

Harvard bioengineers have advanced toward the fabrication of artificial hearts.

"This work is a major step forward for organ biofabrication and brings us closer to our ultimate goal of building a human heart for transplant," says research leader Kit Parker in a press release issued by Harvard University.

Unlike other organs, the heart cannot repair itself after injury. But tissue bioengineering could eventually enable the fabrication of an entire human heart for transplant.

To build a human heart from the ground up, researchers need to replicate the unique structures that make up the heart. This includes recreating helical geometries, which create a twisting motion as the heart beats.

A research paper is published in Science. It describes the first biohybrid model of human ventricles with helically aligned beating cardiac cells. And it shows that helical alignment dramatically increases how much blood the ventricle can pump with each contraction.

The bioengineers used a new method of additive textile manufacturing called Focused Rotary Jet Spinning (FRJS). It's an additive manufacturing approach that enables rapid fabrication of micro/nanofiber scaffolds with programmable alignments in three-dimensional geometries, to control the alignment of spun fibers on which they could grow cardiac cells. Using FRJS, the bioengineers built helically aligned fibers with diameters ranging from several micrometers to hundreds of nanometers.

"The human heart actually has multiple layers of helically aligned muscles with different angles of alignment," explains researcher Huibin Chang. "With FRJS, we can recreate those complex structures in a really precise way, forming single and even four chambered ventricle structures."

Unlike 3D printing, which gets slower as features get smaller, FRJS can quickly spin fibers at the single micron scale. That's about fifty times smaller than a single human hair. This is important when it comes to building a heart from scratch.

"Since 2003, our group has worked to understand the structure-function relationships of the heart and how disease pathologically compromises these relationships," says Parker. "In this case, we went back to address a never tested observation about the helical structure of the laminar architecture of the heart.”

The observation, advanced by Edward Sallin in 1969, is that the heart's helical alignment is critical to pump large amounts of blood with each contraction.

“Fortunately, Professor Sallin published a theoretical prediction more than a half century ago and we were able to build a new manufacturing platform that enabled us to test his hypothesis and address this centuries-old question," continues Parker. "Our goal was to build a model where we could test Sallin's hypothesis and study the relative importance of the heart's helical structure," adds researcher John Zimmerman.

The bioengineers demonstrated that the process can be scaled up to the size of an actual human heart and even a whale heart. Harvard University has protected the intellectual property relating to this project and is exploring commercialization opportunities. Other applications for the FRJS platform are being explored.