A team of researchers from the University of Alabama at Birmingham and the University of Minnesota have been working together to investigate the possibilities of 3D printing a heart muscle patch that can be applied to heart attack victims to prevent them from suffering heart failure.
A heart attack causes damage to the heart muscle and while heart muscle can be repaired naturally, the process takes around eight weeks. Healthy heart tissue cannot be regenerated, instead scar tissue forms on the heart. While the scar tissue is strong enough to allow the heart to continue to beat, the scar tissue is unable to contract as well as healthy heart tissue.
To aid and improve recovery from ischemic myocardial injury, the researchers turned to 3D bioprinting. If a cardiac muscle patch could be 3D printed and applied to the heart, which was capable of beating in rhythm with the heart, the recovery process and patient outcomes could be improved.
However, conventional 3D printing techniques would not work because they are not capable of printing structures of the size at which individual heart cells interact. To create the patch, the researchers would need a different 3D bioprinting technique.
To create the patch, the researchers used multiphoton-excited, 3-dimensional printing (MPE-3DP) to create an extracellular matrix scaffold on which the patch could be grown. The scaffold, which had submicron resolution, was then seeded with a combination of 50,000 cardiomyocytes, smooth muscle cells, and endothelial cells in a 2:1:1 radio. Those cells were differentiated from human induced-pluripotent stem cells (iPSCs).
The iPSC-derived patch began beating within one day of seeding, with the strength of the tissue improving over the space of a week. The patch was then evaluated on mice with surgically induced myocardial infarctions.
The researchers measured cardiac function, apoptosis, infarct size, vascular density, arteriole density and cell proliferation and at week 4, animals with the patch fitted showed significant improvements over mice that were treated with cell-free scaffolds. There was also a marked decrease in dead tissue in mice with the PSC-derived cardiac muscle patch fitted. The team reports that cell engraftment in mice with the iPSC-derived cardiac muscle patch was 24.5% at week 1 and 11.2% at week 4.
While tests on humans have not been performed, the researchers are confident that their 3D printing technique and ECM-based scaffolds can be used to significantly improve recovery from ischemic myocardial injury.
The study shows that 3D printers can be used to create tissue scaffolds on an incredibly small scale and with precision.
The results of the study were published in Circulation Research on January 9, 2017.