Summary: Scientists have bioengineered heart patches out of stem cells and are trying them on patients in a bid to use regenerative medicine to restore full heart function. [This article first appeared on LongevityFacts. Author: Brady Hartman. ]
A team at the University of Colorado (UC) Anschutz Medical Campus are pioneering a new technique in regenerative medicine, by bioengineering new heart tissue to repair defects.
They’ve already shown they can transform stem cells into beating heart tissue, complete with the necessary blood supply.
Right now, they are applying this approach to repairing heart defects in children by bioengineering a beating patch created in the lab from the child’s stem cells. The heart patch would correct the abnormality and then grow along with the child.
Bioengineered heart patches created from stem cells. Courtesy of the NSF.
Spinning a Heart Patch
The UC team is using a process called ‘electrospinning’ to grow the heart patches in the lab. The scientists infuse a scaffold with stem cells harvested from the child. The scaffold gives the patch structure so that it can be sewed into place by the heart surgeon. They’ve already shown that they can grow the blood supply needed for heart tissue, and they also transformed the child’s stem cells into beating heart tissue. The UC team is headed up by bioengineer Jeff Jacot, who says
“The big challenge that we have is making something that can be implanted and stays alive.” adding “We’ve shown that we can grow blood vessels and we can grow the blood supply needed for heart tissue out of those. And we’ve recently shown that we can make cells from amniotic fluid into beating heart cells.”
Once implanted into the patch, the stem cells grow into healthy heart tissue. And the scaffold eventually dissolves away. As Jacot puts it
“It will grow as the infant and child grows and give full heart function back to these infants with heart defects without the need for lifelong operations.”
Trying Out the Heart Patch
Reliable manufacture of bioengineered heart patches is still in the early stages. However, congenital heart surgeon Jim Jaggers, MD says eventually these bioengineered patches will significantly improve the outlook of infants and children with heart defects. Dr. Jaggers is using the patches to rebuild the heart of three-year-old Jaden Senn, who was born with a very complex heart defect. As Dr. Jaggers says
“Any kind of living tissue could improve his heart function, so it’s a big deal. Having something that would grow with the child, something that would have electrical activity, and something that could contract would be a game changer.”
Heart Patches for Adults
Scientists are developing heart patches for adults as well. For example, biomedical engineers at Duke University have created a fully functioning lab-grown human heart muscle large enough to patch over the damage typically suffered in a heart attack.
While Duke’s heart patches are still in their early stages, they appear to be a tremendous improvement over existing cell therapies. Clinical trials are currently testing the tactic of injecting stem cells directly into the affected site in an attempt to restore some of the damaged heart muscle. However, it doesn’t help very much. Fewer than 1% of the injected cells survive in the heart, and even fewer become cardiac muscle cells.
On the other hand, heart patches could potentially be implanted over the dead heart muscle and remain active for a long time, strengthening contractions and providing a conductive circuit for the heart’s electrical signals to travel through. These patches also secrete growth factors and enzymes that could help the recovery of damaged tissue that hasn’t yet died.
Cardiovascular disease is a significant cause of illness and death throughout the world. It’s the leading cause of death in the U.S., killing nearly 801,000 people per year. The heart cannot regenerate itself after a heart attack. Insufficient blood supply to the heart muscle can lead to permanent and progressive damage to the heart, which can further develop into heart failure, which affects over 12 million patients worldwide. The dead heart muscle is often replaced by scar tissue that can no longer contract or transmit electrical signals, both of which are necessary for smooth and forceful heartbeats.
Drugs such as angiotensin receptor blockers, aldosterone antagonists, and beta-blockers have improved the outcomes of patients with heart failure, but they are not able to repair the scar tissue on the heart. A shortage of donor organs and risk of complications makes heart transplantation the option of last resort. Regenerative medicine strategies, most notably stem cell therapies, have gained attention as promising treatment options for heart disease.
The Duke team is headed up by Ilya Shadrin, a biomedical engineering doctoral student, and his advisor Nenad Bursac, a professor of biomedical engineering. The Duke team grows their cells for the heart patch using human pluripotent stem cells. The scientists have successfully made heart patches using various lines of human stem cells, including those derived from embryos and those artificially forced into their pluripotent state, known as induced pluripotent stem cells, or iPSCs for short.
The Duke researchers can grow various types of heart tissue from these stem cells, including the cells that form blood vessels, known as endothelial and smooth muscle cells; the muscle cells that contract the heart called cardiomyocytes; and the cells that provide the support structure of the heart tissue, known as fibroblasts. The scientists place these cells at specific ratios into a jelly-like substance where they self-organize and grow into functioning heart tissue.
Bottom Line on Heart Patches
After 17 years of testing, cardiac cell therapy has met with considerable failure and disappointment. Merely injecting stem cells into a diseased heart is not bearing fruit.
The strategy of replacing parts of diseased organs is more feasible than regrowing entire ones. Scientists have created many types of organ tissues in small sections, including pancreatic, kidney, lung and liver tissue. For example, scientists in China have reported success in restoring small portions of damaged lung tissue using stem cells. Researchers at a biotech firm called ViaCyte have grown a kind of pancreas-in-a-box using stem cells – while not a fully grown pancreas, it contains pancreatic tissues that produce insulin. Moreover, biotech firm Organovo appears close to providing small sections of liver grown from stem cells. Scientists have been able to use stem cells to grow mini-kidneys that produce urine in the research lab, but are a long ways away from growing fully-functioning human kidneys. Bioprinting entire hearts from a patient’s stem cells is still a dream.
As shown by the UC and Duke research teams, bioengineered heart patches, with their support structure and built-in blood supply, are a promising use of stem cell therapy to treat heart disease.
The construction and use of bioengineered heart patches are still in the early stages. However, many feel that eventually, these patches will significantly improve the outlook of patients of all ages with heart disease.
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Cover Photo: Devrimb / Getty Images (adapted).
Miles O’Brien and Kate Tobin. “Bioengineering infant heart patches with the baby’s own heart cells.” National Science Foundation (NSF) – Science Nation. October 2, 2017. Web. Retrieved March 3, 2018. Link to article on NSF.org.
Tang, J.-N., Cores, J., Huang, K., Cui, X.-L., Luo, L., Zhang, J.-Y., Li, T.-S., Qian, L. and Cheng, K. “Concise Review: Is Cardiac Cell Therapy Dead? Embarrassing Trial Outcomes and New Directions for the Future.” STEM CELLS Translational Medicine. February 22, 2018. doi:10.1002/sctm.17-0196. Link to the journal article.
Ilya Y. Shadrin, Brian W. Allen, Ying Qian, Christopher P. Jackman, Aaron L. Carlson, Mark E. Juhas, Nenad Bursac. “Cardiopatch platform enables maturation and scale-up of human pluripotent stem cell-derived engineered heart tissues.” Nature Communications, 2017; 8 (1). Link to article in Nature.
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