Dr. Oksana Piven and her colleagues at the Institute of Molecular Biology and Genetics (IMBG) of the National Academy of Sciences of Ukraine are working on developing a unique technique that, if successful, would restore the heart after a heart attack.
According to the World Health Organization, cardiovascular diseases are the number one cause of death globally. An estimated 17.9 million people died from cardiovascular diseases in 2016. Of those deaths, 85% were due to heart attacks and strokes.
In Ukraine alone, there are 40,000 cases of heart attacks each year. The most common cause is the narrowing of vessels that feed the heart. The process is gradual, but at some point the vessels become blocked, leaving part of the heart without a blood supply. When this happens, the cardiac muscle cells – cardiomyocytes – begin to die rapidly.
If blood supply is restored within two hours, there won’t be much damage to the heart muscle. But if people don’t get help in time, which is often the case, there is a 20% chance of death, and half of those who survive will have a disability.
The cardiac muscle cells that die as a result of a heart attack are replaced by connecting cells – cardiac fibroblasts. In simple language, a scar forms on the heart. Fibroblasts are unable to perform the function of the cardiomyocytes, and the heart is never the same.
While modern medicine can’t repair the heart after a heart attack, research is being done in several areas. For example, Japanese scientists are creating patches from a patient’s stem cells that can be surgically placed on the damaged part of the heart.
Changing cell specialization
Oksana and her colleagues have decided to a try a different approach. What if you turn the fibroblasts of the “scar” back into cardiac muscle cells?
Japanese scientist Yamanaka Shinya was awarded the 2012 Noble Prize in Physiology or Medicine for reprogramming cells. Basically, this is what’s going on:
The human body was once a single cell, formed as a result of the union of a human egg and sperm. The average adult body has 37 trillion cells. All of them are descendants of that first cell and they all have the same DNA. In other words, the nerve cells in the brain and the epithelial cells of our skin have identical genes, but they have a different structure and work differently. That’s because in different cells certain genes are working and others are inactive.
If you know which genes to “turn on,” you can turn any “adult” or specialized cell into a stem cell that can become a different kind of “adult” cell. Or you can “turn on” certain genes and change the “specialization” of the cell. For example, you can turn fibroblasts into cardiomyocytes. This is what Oksana's group is doing.
The theory is that if you “press 5 keys”, or “turn on” 5 so-called cardiac master genes: GATA4, MyoD, Tbx5, Mef2c and HAND2, each of them will force a cascade of other genes to work and the cells will become cardiomyocytes.
Waking up genes
The big question is how do you get these 5 genes to start working in the cell? Well, there are different ways. You can, for example, plant them in special viruses that together will penetrate the necessary cell and start working. This method is being successfully used in experiments on cell cultures. But it’s another matter to apply it to a whole organism, moreover a human one. The side effects can be serious, such as cancer.
That’s why researchers at IMBG decided to do something different – not to introduce master genes from outside, but to wake up those genes already in the fibroblasts. To do this, they’re using CRISPR technology. This special protein complex is often called “genetic scissors” for its ability to find and cut a DNA molecule in the right place.
The Ukrainian researchers are using a modified CRISPR system in their experiments on reprogramming fibroblasts. It finds the right sequence of DNA and instead of cutting it, it forces the genes located there to work.
From mice to humans
Today, Oksana's group is working with the embryonic fibroblasts of mice. After many attempts, the researchers were able to use CRISPR to activate all 5 cardiac master genes that should transform these cells into cardiomyocytes. Special tests show that the necessary genes have started to work – the proteins encoded in them are being synthesized in the cells. But the cells don’t contract, like normal cardiac muscle cells should.
“They’re no longer fibroblasts, but they’re not yet cardiomyocytes – they’re something in between,” says Oksana.
There could be several explanations why fibroblasts don’t transform fully. One of them is that the cells need the right environment. In the heart, the cells adjacent to cardiomyocytes send them certain chemical signals.
In the near future, the researchers plan to test how changing the environmental parameters of the cells will change the results of the experiment. After they manage to reprogram embryonic fibroblasts, the experiment will have to be repeated with fibroblasts of adult mice, and then on animals with a modeled heart attack.
If the research is successful, the experiments can be conducted on human cells and ultimately clinical trials can be performed on volunteers. But even in the best case, this is a process that will take more than one year, and of course will require collaboration with other research institutions.
Oksana is reserved in her comments regarding the ability to use the results of this research to treat humans. In the worst case, in her opinion, the treatment simply won’t work, but it won’t harm the patient in any way.
To date, the research has been conducted with a grant from the Science & Technology Center in Ukraine (STCU, grant #6261), but the funding runs out in July and the researchers at IMBG are looking for new sources of funding. They are putting their hope on the National Research Fund, which is supposed to give out funds for research on a competitive basis. However, although the Fund was established, it has yet to begin to work.
You can read more about Oksana's lab at http://www.pivenlab.com.ua/
Photos from Oksana's FB - https://www.facebook.com/opiven
Translated from Ukrainian by USUF
