A heart attack is a life-threatening event in which blood flow through a coronary artery—and blood flow to the heart muscle itself—stops. If that blood flow is not quickly restored, heart muscle dies. A heart attack can be deadly if the heart is too badly damaged.
If someone experiences a heart attack, the heart muscle may be permanently weakened. Instead of having heart muscle that contracts to pump blood, the damaged heart tissue becomes full of fibers (fibrotic tissue) and is basically useless.
Regenerative Medicine has allowed scientists to reconsider whether this fibrotic tissue is permanently lost. Can stem cells prevent this fibrotic tissue from developing? Can new, healthy heart muscle be formed in its place? Recent research offers some tantalizing clues.
Researchers set out to determine whether mesenchymal stem cells taken from human umbilical cord could protect heart muscle cells (cardiomyocytes) after a heart attack. Specifically, the researchers were interested in learning whether exosomes collected from those stem cells (rather than the stem cells themselves) could protect cardiomyocytes.
To test this hypothesis, they created a heart attack in laboratory rats and administered exosomes they had gathered from mesenchymal stem cells. These particular mesenchymal stem cells were collected from human umbilical cord samples—the tissue that is normally thrown away after a baby is born.
The results of these experiments were interesting for several reasons. First, stem cell exosomes tipped the balance between fibrotic tissue (fibroblasts) and heart tissue (myofibroblasts). In other words, after an experimental heart attack, exosomes caused the heart to regrow more normal tissue than diseased tissue. Second, exosomes decreased the inflammation that occurs after a heart attack. It is believed that inflammation makes a heart attack worse. Lastly and perhaps most importantly, exosomes protected cardiomyocytes (heart muscle cells) from dying (through apoptosis).
Taken together, these results suggest that exosomes collected from umbilical cord mesenchymal stem cells protect heart muscle cells from the damaging effects of a heart attack in at least three important ways.
As these are early in Regenerative Medicine research, it is important to note that these experiments were performed in rats, and not humans. Interestingly, though, the stem cells were taken from human umbilical cords, and they were able to achieve these impressive effects in a different species (rodents). Obviously clinical trials are needed to determine whether this effect is applicable in humans; however, studies that use whole stem cells from human umbilical cord strongly suggest scientists are on the right track.
Reference: Shi, Y. et al. (2017). Exosomes Derived from Human Umbilical Cord Mesenchymal Stem Cells Promote Fibroblast-to-Myofibroblast Differentiation in Inflammatory Environments and Benefit Cardioprotective Effects. Stem Cells and Development. 2019 Jun 15;28(12):799-811.