Could Mice and Zebrafish Hold Clues to Repairing Damaged Hearts?

Could Mice and Zebrafish Hold Clues to Repairing Damaged Hearts?

Story by Rebecca Evans

When it comes to medical advances, it’s not surprising that cures come from some surprising places, or that drugs develop after learning how to synthesize chemical reactions to mimic natural reactions. What is surprising, though, is where some of those clues that lead to future breakthroughs come from.

For instance, when you think of heart disease, do you think of mice? How about zebrafish?

Perhaps in the future you’ll think of both creatures, as new research suggests that as scientists learn more about unique traits possessed by mice and zebrafish, the science of those traits may well make its way into heart repair.

It isn’t the first time either creature has been used for scientific applications, either.

In particular, there are two traits that scientists are interested in for cardiac applications—the ability to reattach a severed spine  and the ability to patch up an injured heart—shared by the zebrafish and mouse, respectively.

Consider the Zebrafish

Zebrafish are already used in numerous scientific applications. For starters, zebrafish share 70% of the human genome and reproduce incredibly rapidly, making them great for studying genetic components of such disorders as muscular dystrophy. Because zebrafish reproduce so quickly, they’re great for testing how various genes trigger different things, and help scientists understand what different pieces of the human genome do as a result.

But one of the most interesting finds has been how zebrafish are able to regenerate tissue. In fact, you can remove up to 20 percent of a zebrafish’s heart, and within a month, the heart will have completely regenerated. Humans have some of this ability while in embryo, but we lose it shortly after we born.

In the case of zebrafish, this means things as crazy as being able to reattach a severed spine. Just imagine what this could mean for human applications! Not only would it have cardiac applications, but it could change the way we approach a wide range of potential injuries.

Courtesy of the genetic similarity between humans and zebrafish, there’s promising research that suggests we might actually at some point in the future be able to take advantage of exactly that regenerative property that we, as humans, lose and zebrafish maintain through their life. Scientists are learning how to bridge the gap as they study zebrafish’s extracellular matrices, or ECM, which seems to be one of the keys to zebrafish’s regenerative properties. Using ECM to regenerate heart tissue has already been tested and shown to work in mice, and have shown promising gains in helping protect hearts against heart attacks. More study is obviously needed, but it’s a tremendously exciting development.

What about mice?

And mice are also helping attack the problem of what happens to human’s own regenerative capabilities. In particular, human children are born with a large number of heart muscle cells called mononuclear diploid cardiomyocytes, or MNDCMs, but as we age, we rapidly lose those cells.

Researchers have found, however, that some mice keep most of their MNDCMs, and that one particular gene is responsible for keeping those MNDCMs. Researchers are now working on learning how to unlock that gene, so that it might eventually be used in human treatments.

Additionally, while this current line of research is related to stem cell research, which some critics take great issue with, it is not stem cell research—and learning more about MNDCMs in mice may actually allow researchers to continue moving away from stem cells, so this is a win both for research and for critics of stem cell research.

What’s next?

The next step, of course, will be taking these breakthroughs and learning how to turn them into something that can be used in human clinical trials. From here there’s still a long ways to go, and lots of science ahead, but the early returns on what researchers are learning is incredibly promising. The day may yet come when our hearts are able to heal themselves.

Given that cardiovascular disease is responsible for nearly a million American deaths each year? That would be an amazing breakthrough.


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