In the past, researchers have tried to 3D-print cardiomyocytes, or heart muscle cells, that were derived from pluripotent human stem cells. These stem cells are cells with the potential to develop into any type of cell in the body. Researchers would reprogram these stem cells to heart muscle cells and then use specialized 3D printers to print them within a three-dimensional structure, called an extracellular matrix. The problem was that scientists could never reach critical cell density for the heart muscle cells to actually function.
Researchers have optimized specialized ink made from extracellular matrix proteins, combined the ink with human stem cells, and used the ink-plus-cells to 3D-print the chambered structure. The stem cells were expanded to high cell densities in the structure first and then they were differentiated to the heart muscle cells. The researchers achieved the goal of high cell density within less than a month to allow the cells to beat together, just like a human heart.
This critical advance in heart research shows how the researchers were able to 3D-print heart muscle cells in a way that the cells could organize and work together. Because the cells were differentiating right next to each other, it is more similar to how the stem cells would grow in the body and then undergo specification to heart muscle cells.
Compared to other research in the past, the new discovery creates a structure that is like a closed sac with a fluid inlet and fluid outlet, where researchers can measure how a heart moves blood within the body. This makes it an invaluable tool for studying heart function. The 3D-printed structure is a model to track and trace what is happening at the cell and molecular level in pump structure that begins to approximate the human heart. Disease and damage can be introduced into the model to study the effects of medicines and other therapeutics.