Heart muscle regeneration after myocardial infarction or in heart failure is a hot research topic. When will stem cells fulfill their potential? You are an expert in cardiac transplantation. Dr. Anton Titov, MD. You are also an expert in stem cell technologies. Maybe it's a future and the fantasy question. When stem cells can be used to grow the replacement hearts? Because there is a shortage of donor hearts all around the world. How can stem cells be used today to repair or maybe replace damaged myocardium? Dr. Anton Titov, MD. What are the advantages of the stem cell technologies that we could possibly see in future? Dr. Marc Pelletier, MD. The promise of stem cells to me has been disappointing so far. It is a complex environment. What happens to one type of stem cell? There are many different types of stem cells. There are embryonic stem cells, mesenchymal stem cells, myoblast stem cells. But all of stem cells have a challenge. You can take those stem cells and you try to put them into the heart. Dr. Marc Pelletier, MD. You hope that stem cells will form new heart vessels. Or you hope that stem cells will form new myocardial tissue. It seems that in laboratory we are making really nice advances with stem cells. But it seems that the translation of success in the laboratory to humans is a problem. We have a problem showing a meaningful difference of stem cell treatment in humans. 15 years ago it was very promising and it still is very promising. But we all expected that the stem cell field would grow a little bit faster. Stem cell therapy has grown more slowly than we expected. Dr. Marc Pelletier, MD. Today the ability to use stem cells to regenerate our heart or to create new heart vessels is simply not there right now. Stem cell treatment is in certain clinical trials. In stem cell clinical trials we see some benefits here or there. But we do not always see benefits of stem cells for heart function. Dr. Anton Titov, MD. How does that translate into a viable treatment options for patients? It's just not there right now. What precisely hinders the development of the stem cells? Dr. Anton Titov, MD. What are problems with stem cells in the human clinical trials? The problem is our understanding of exactly what those stem cells can do. Dr. Marc Pelletier, MD. We do not understand fully how stem cells can differentiate. How heart stem cells can grow. A one small cell that starts off as a very basic cell. How does that stem cell grow into a myoblast? How does a stem cell interact with the other cells that are already in the heart? How does stem cell differentiation occur? How many stem cells do you need to put into the heart? Where do you need to put those stem cells in the heart? How do you deliver stem cell to the heart of a patient? How do you get stem cells to the area of the heart? So that stem cells can do what they are supposed to do. Dr. Marc Pelletier, MD. Those are really the target challenges that we're facing right now with stem cell therapy in cardiology. That is what makes stem cell technology quite complicated. The science behind stem cells in heart treatment is absolutely phenomenal. Dr. Anton Titov, MD. Some physicians are doing remarkable work. As time goes on, we will see more advances with stem cell therapy. Dr. Marc Pelletier, MD. Already we are seeing some benefits from stem cell heart therapy in some clinical trials. But it's been a bit hit and miss. Stem cell treatments have not gotten to a point yet where we can adopt it in clinical practice. Where I can have a patient who comes to see me and I say this. "Oh, we are going to use stem cells for your heart!" We're just not there yet.