Although 3D printing has advanced in leaps and bounds over the past few years, using it to print functioning human organs is still a far-flung dream. Recently, however, scientists have brought this dream one step closer.
Cardiovascular disease is the leading cause of death in the United States.
Once it has progressed to its final stages, the only treatment option is a heart transplant.
Because there are too few heart donors, the wait for a life-saving transplant is long.
Scientists are keen to find ways of patching up existing heart tissue to remove or postpone the need for a transplant.
For instance, if surgeons could impant a material into the heart, it could form a temporary scaffold to support cells and boost cellular reorganization.
This so-called cardiac tissue engineering has a number of problems; primarily, scientists need to find a type of material that the body would not reject. Researchers have already tried a range of materials and methods, but the perfect candidates are cells from the body of the patient.
Bioink and stem cells
During recent years, researchers have made some progress toward artificially replicating human tissue.
A group of scientists from Tel Aviv University in Israel has taken this work one step further and moved cardiac tissue engineering to the next stage.
"This is the first time anyone anywhere has successfully engineered and printed an entire heart replete with cells, blood vessels, ventricles, and chambers."
Lead researcher Prof. Tal Dvir
The scientists have designed a groundbreaking approach that allows them to create the closest thing to an artificial heart to date.
Their first step was to take a biopsy of fatty tissue from the patient; then, they separated cellular material from noncellular material.
The researchers reprogrammed the cells of the fatty tissue to become pluripotent stem cells, which can develop into the range of cell types necessary to grow a heart.
The noncellular material consists of structural components, such as glycoproteins and collagen; the scientists modified these to turn them into a "bioink."
Then, they mixed this bioink with the stem cells. The cells differentiated into cardiac or endothelial cells (which line blood vessels), which the scientists could use to create cardiac patches, including blood vessels.
They describe their methods in detail in a recent paper published in the journal Advanced Science.
'The size of a rabbit's heart'
"This heart is made from human cells and patient-specific biological materials. In our process these materials serve as the bioinks, substances made of sugars and proteins that can be used for 3D printing of complex tissue models," says Prof. Dvir.
He goes on to say: "People have managed to 3D-print the structure of a heart in the past, but not with cells or with blood vessels. Our results demonstrate the potential of our approach for engineering personalized tissue and organ replacement in the future."
To demonstrate the potential of their technique, the scientists created a small but anatomically precise heart, complete with blood vessels and cells.
"At this stage, our 3D heart is small, the size of a rabbit's heart," says Prof. Dvir. "But larger human hearts require the same technology."
It is worth noting that this technology is still very far from being able to replace heart transplants. This is just another step along the path — albeit a rather large step.
The crucial next task, as Prof. Dvir says, is to teach them to behave like hearts; he explains that they "need to develop the printed heart further. The cells need to form a pumping ability; they can currently contract, but we need them to work together."
"Our hope," he goes on, "is that we will succeed and prove our method's efficacy and usefulness."
There is still a long road ahead, but the researchers are excited about how far they have come.
"Maybe, in 10 years, there will be organ printers in the finest hospitals around the world, and these procedures will be conducted routinely."
Prof. Tal Dvir