For the first time, researchers have "printed" a 3-D human heart using a patient’s tissue.

While the first printed heart is small and nonfunctional, the development of a 3-D printable heart could someday save millions of lives. Cardiovascular disease is the number one cause of death globally, according to the World Health Organization, and heart transplant is currently the only treatment for patients with end-stage heart failure.

3-D-printed hearts could help overcome shortages of hearts available for transplantation; because they use the patient’s own tissue, using 3-D-printed hearts could also reduce rejection rates.

Innovative engineers now use three-dimensional printing to create a wide variety of structures, including houses and schools, furniture, automotive parts, prosthetics, pharmaceuticals, and even art and food. Medical researchers are now investigating the use of 3-D printers to replicate human tissues, but success thus far has been limited to printing simple tissues without blood vessels.

Cardiac tissue engineering allows for the integration of cardiac cells and 3-D biomaterials. The biomaterials serve as temporary scaffolds that mechanically support the cardiac cells and promote the reorganization of those cells into a functional tissue.

Following in vitro maturation, surgeons could transplant the engineered cardiac patch onto the defected heart. The biomaterials gradually degrade, leaving behind a functional patch that regenerates the patient’s heart.

Being able to print a new heart using the patient’s own stem cells would certainly revolutionize heart transplants and cardiac care. Unfortunately, generating vascularized and perfusable cardiac patches that completely match the anatomical, cellular, immunological, and biochemical properties of individual patients continues to evade scientists.

Cardiac Engineering and 3-D Printing of a Heart

A group of researchers from Tel Aviv University announced in April that they have created the world’s first complete heart, using a 3-D printer and the patient’s own cells and materials. While the heart is small (about the size of a rabbit’s heart) and non-functional, it is the first engineered and printed anatomically correct heart with cells, blood vessels, ventricles, and chambers.

The research team took biopsies of omental tissue from patients then separated cellular from extracellular material. The scientists reprogrammed the cells to become pluripotent stem cells and differentiated them to cardiomyocytes and endothelial cells.

They converted the noncellular material, which consists of glycoproteins, collagen and other structural components, into a personalized hydrogel. Next, the research team combined the cardiomyocytes and endothelial cells separately with the hydrogel to create "bioinks" to print the blood vessels and parenchymal cardiac tissue. The scientists then created 3-D‐printed thick, vascularized, and perfusable cardiac patches matching the immunological, cellular, biochemical, and anatomical properties of the patient — complete with blood vessels.

In vitro study of the structure and function of the patches and assessment of cardiac cell morphology following transplantation revealed elongated cardiomyocytes with massive actinin striation. Printing cellularized human hears with a natural architecture served as proof of concept. The results of the work support the viability of engineering and 3-D printing of personalized tissues and organs for transplantation or for drug screening and research.

The team’s work demonstrates the ability to print functional vascularized patches specific to a patient’s anatomy. Since the bioinks originate from the patient, the engineered patches will not provoke an immune response, thereby eliminating the need for immunosuppression treatment. There is still more work to do, though.

Lead author Professor Tal Dvir says that the next crucial step is to teach the printed tissues to behave like hearts. "The cells need to form a pumping ability; they can currently contract, but we need them to work together."

"Our hope," Dvir continues, "is that we will succeed and prove our method's efficacy and usefulness."

Professor Dvir and team printed their findings in the journal Advanced Science.