How To Mend A Broken Heart

This artificial heart story is part of an expanded series on regenerative medicine. For more stories on this topic see williamhaseltine.com and look for Regenerative Medicine. My definition of Regenerative Medicine is any medical method that returns us to normal health when we are damaged by disease, injured by trauma, disadvantaged by birth, or exhausted by time. Modalities include: chemicals, genes, proteins and cells used as medicines, gene editing, prosthetics and mind-machine interfaces.

Heart disease affects approximately 82.6 million people in the United States and is a leading killer of both men and women. One solution for patients with advanced heart failure is heart transplantation. Unfortunately, there is currently a nationwide shortage of human donor hearts. Scientists have tried making artificial hearts or using pig organs instead of human hearts in transplant operations. However, current methods of making artificial hearts are generally unsuccessful, and the use of pig organs for transplants can lead to serious infections.

Now a group at Harvard University is tackling this problem with a new, innovative method for growing artificial hearts. By building an artificial structure and implanting heart cells, the researchers were able to grow the heart cells in a pattern that mimicked the natural organization of muscles in the heart. This study serves as an important stepping stone to the development of fully functional artificial hearts.

The heart is mostly made up of muscles arranged in a spiral. When the heart contracts, its spiral-patterned muscles rotate to push blood out of the heart. In fact, this helical patterning is predicted to be a critical feature of healthy, functioning hearts. Many people who suffer from cardiac dysfunction also have abnormal muscle patterns.

In the past, several studies have attempted to grow artificial hearts with spiral patterns using 3D printers. These studies have been largely unsuccessful due to the inability of 3D printers to achieve the minute details of heart structure in a reasonable amount of time. For example, it could take a 3D printer hundreds of years to print even a small portion of the heart’s structures with enough detail for the cells to grow in the right patterns.

How did Harvard University scientists accomplish this feat?

Knowing that a simple 3D printer has significant limitations, Chang et al. turned to another technique: fiber spinning. Fiber spinning is a method that uses similar materials to 3D printers, but can create much finer, high-resolution structures.

Traditionally, materials are heated and extruded from a tiny hole to create individual fibers on a microscopic scale. The fibers can then be collected or processed into 3D structures.

Fiber spinning can produce structures with very high resolutions. However, traditional methods of fiber spinning are often imprecise and would not be able to form the heart’s consistent spiral patterns. This prompted Chang et al. to develop a new method of fiber spinning that would not only allow them to create the 3D structure of the heart on a microscopic scale, but would also be precise enough to form the heart’s spiral pattern.

Chang et al. has developed a new fiber spinning device with two essential design features. First, rather than simply extruding the material in one direction at random, the fiber spinning apparatus contains a “spinneret” that rotates at high speed. As the heated material is pushed into the device, the fibers are then extruded through a small hole in the side of the spinneret. This causes the fibers to gather in a cloud around the device.

The second innovation by Chang et al. was to incorporate a powerful airflow at the tip of the spinneret that could align the fibers to resemble strips of muscle. From this, Chang et al. could collect the fibers at an angle and eventually create the spiral patterns of the heart muscle.

Using this method, Chang et al. was able to create 3D frames that resembled human heart chambers. When the frames were seeded with human heart cells, the resulting tissues retained the spiral pattern of the frame.

Surprisingly, Chang et al. observed spontaneous contractions that resembled the natural activity of the human heart. This indicated that the Chang et al. could be used to study how muscle patterns affect heart function.

To address this question, Chang et al. created model ventricles with spirally aligned cells and ventricles with abnormal circumferentially aligned cells.

The researchers then suspended both model ventricles in a liquid containing fluorescent beads. By following the displacement of the beads, Chang et al. was able to determine how many were being pumped through the ventricles at the same time. This strategy allowed the researchers to calculate the total volume of fluid that the model ventricles could pump.

After testing both the spirally patterned ventricle and the abnormally patterned ventricle, Chang et al. found that the spiral-patterned ventricle was able to pump significantly higher volumes of fluid. This showed that abnormal alignment of heart cells actually reduces the heart’s ability to function.

After all, not only Chang et al. able to create model heart chambers that could contract, but by using their innovative fiber spinning method, the researchers were able to recreate all four chambers of the heart. These individual chambers were then assembled to eventually create a life-size model of the human heart.

Overall, this study represents a significant advance in our ability to create a fully functional artificial heart. While more work needs to be done to scale up functional model ventricles to full-size heart models, this study shows real potential for using innovative fiber spinning techniques for the intricate formation of whole organs.