Broken hearts are notoriously difficult to repair. After a heart attack this vital organ remains damaged, which can eventually lead to heart failure and death. Now, researchers have managed to use placental stem cells to regenerate heart cells in mice, which could lead to groundbreaking new treatments for heart attack victims.
According to the World Health Organization, cardiovascular diseases are the biggest killers of people in modern times, and it's largely due to the heart's inability to repair itself properly. Even if a person survives the initial cardiac arrest event, scar tissue renders the heart less effective at pumping blood and more likely to suffer future heart attacks.
Stem cells have long been investigated as a solution, but despite their regenerative prowess in other parts of the body, they've not been as successful in matters of the heart. Injecting stem cells into the heart can cause complications, and it turns out that cardiac stem cells might not even exist. Other studies have tried using stem cell "messengers" instead, or converting other heart cells into beating heart cells.
For the new study, researchers from the Icahn School of Medicine at Mount Sinai examined Cdx2 cells, a kind of stem cell derived from the placenta that has previously shown particular promise in repairing heart tissue.
The team tested them out on three groups of male mice that had suffered heart attacks. One group received a treatment of Cdx2 stem cells, a second group received other placenta cells while the third just had saline as a control. MRIs were taken of all the mice immediately after the heart attacks and again three months after their treatment.
By the three-month mark, every mouse in the Cdx2 group showed regeneration of healthy heart tissue, forming new cardiomyocytes – the heart muscle cells that beat – as well as new blood vessels. Meanwhile the other two groups showed no sign of regeneration, and many went into heart failure.
The results are exciting for a number of reasons. Alongside all the regenerative abilities of embryonic stem cells, the team found that placental stem cells also have a few extra abilities of their own that makes them more suited to treatments.
"Cdx2 cells have historically been thought to only generate the placenta in early embryonic development, but never before were shown to have the ability to regenerate other organs, which is why this is so exciting," says Hina Chaudhry, principal investigator of the study. "These findings may also pave the way to regenerative therapy of other organs besides the heart. They almost seem like a super-charged population of stem cells, in that they can target the site of an injury and travel directly to the injury through the circulatory system and are able to avoid rejection by the host immune system."
On top of that, since they're derived from the placenta they can skirt the potential ethical issues of using embryonic stem cells, and should be far easier to obtain in useable amounts.
"We have been able to isolate Cdx2 cells from term human placentas also; therefore, we are now hopeful that we can design a better human stem cell treatment for the heart than we have seen in the past," says Chaudhry. "Past strategies tested in humans were not based on stem cell types that were actually shown to form heart cells, and use of embryonic stem cells for this goal is associated with ethics and feasibility concerns. Placentas are routinely discarded around the world and thus almost a limitless source."