DURHAM, North Carolina: Duke University biomedical engineers have created what they say is the world’s first artificial heart muscle that’s large enough to, some day, reduce the need for complicated and expensive heart transplant surgeries.
Because heart muscle cannot regenerate itself after a heart attack, the affected heart muscle dies and turns into scar tissue, leading to congestive heart failure that eventually results in the patient’s death, unless the damaged heart is replaced through transplant surgery.
The Duke scientists say their laboratory-grown tissue, grafted onto a human heart that has been permanently damaged by a heart attack, could allow the heart to transmit electrical signals so that the organ can continue
beating and pumping blood.
The results of the study were published on Wednesday (Thursday in Manila) in Nature Communications. The artificial heart patch, created from human stem cells, functions as a heart muscle that can be seen spasmodically beating on its own in a Petri dish, as captured on film. In the study, conducted by Duke biomedical engineering PhD student Ilya Shadrin, the researchers confirmed their findings in a laboratory and next plan to test the biomedical tissue on pigs.
Nenad Bursac, one of the Duke biomedical engineers on the project, said the use of heart patches on defective human hearts is still at least a decade away. The square patch tested in the study was 4 centimeters by 4 centimeters in size, more than 30 times larger than the previous artificial heart muscle Duke researchers created in 2013.
“It certainly would be addressing a huge problem,” Bursac said. “You would have a cheaper therapy that probably could be applied in a much more universal fashion because we wouldn’t have a shortage of donors like we have with heart transplants.”
A smaller version of the tissue patch has produced muscular contractions and conducted electrical impulses in laboratory rats for one month, the duration of the study. But the larger patch is paper-thin and would need to be at least 2 to 3 millimeters thick to have sufficient muscular strength to pump blood for an adult human.
First for the human heart
Bursac has been working in the area of replacing or rebuilding damaged heart tissue for about 20 years. He said the potential medical breakthroughs in this branch of cardiac research have created a very crowded and competitive field. The patch tested in the Duke study is the first of sufficient size for a human heart.
University of North Carolina researcher Li Qian has been conducting research and developing techniques to genetically reprogram scar tissue into living muscle cells, rather than replace the dead tissue mass. Qian and other researchers were the first to demonstrate the possibility of genetic cell conversions in a 2012 paper in the journal Nature, but their breakthrough was successful on only about 10 percent of the dead cells, and she and others are perfecting the biotechnology.
Qian described the Duke research as a “major breakthrough,” because of the size of the artificial living tissue generated from stem cells.
Grafting lab-spawned tissue onto a human heart would entail some of the same risks and challenges as a heart transplant. The foreign implant could be rejected by the patient, or the artificial muscle could fail over time. The pulsating patch would have to be synchronized to match the beating rate of its host or it would expose the patient’s heart to dangerous arrhythmia.
In the rat study, the patch was not electrically synchronized to match the heart rate. It was grafted onto scar tissue but insulated by the dead muscle from the rest of the rats’ hearts.
A major heart attack can kill up to one-fourth of an adult human heart’s four billion cells in the sections that were cut off from blood flow, Bursac said.
The Duke researchers can grow their artificial tissues in about five weeks. But they require up to four months to develop the stem cells used for the tissue; the stem cells are generated from a skin biopsy or a blood sample by means of genetic reprogramming.
The study, funded by a seven-year, $8.6-million grant from the National Institutes of Health, has six years left to go. As part of the study, researchers at the University of Wisconsin-Madison are providing stem cell types and researchers at the University of Alabama at Birmingham will graft the patches onto pig hearts.
The biotechnology to grow stem cells was developed by a Japanese researcher, Shinya Yamanaka, who won a Nobel Prize in 2012 for discovering that mice cells could be reprogrammed into stem cells that can then develop into any type of cell, such as nerve cells and gut cells.