Growing human hearts

Growing a human heart from a single cell may seem like science fiction, but scientists at the Gladstone Institute at the University of California San Francisco, have taken a huge step forward, by producing the first three-dimensional, beating, human heart chamber. Previously, it had been possible to produce a two dimensional sheet of beating heart cells, but to really gain an understanding of heart formation in a developing foetus and perhaps more importantly, how drugs given to women during pregnancy may affect this development, a three dimensional structure was needed. By treating stem cells with drugs and then confining them to a very small spherical geometry, Bruce Conklin and his team have managed to grow their very own three dimensional model of a human heart, as he explains…

Bruce – the cells around the edge became fibroblasts – a particular type of cell that you use to heal wounds and then only in the very centre were cardiac cells that beat. What this is forming is more of a little organoid is what we call it, where there’s beating cells but there’s also multiple other cell types and that’s what makes it so interesting is that these cell types are somehow talking to each other and somehow collaborating in some way so that they can actually make this structure that we didn’t expect.

Tom – It’s almost like they’re trying to form a heart…

Bruce – That certainly is the impression. They’re heart cells, they’re forming cavities so it could be a model of how parts of human development occurs, but it certainly is not a real human heart in the sense that there’s probably many things that we’re missing. We just have a simplified version with just one chamber, but having it in a controlled way where it happens the same way over and over again we can start asking questions about ‘how do these cells talk to each other?’ So once you have a system which is reproducible you can do experiments to break it in some way or to enhance it in another way.

Tom – What are the applications of this work then?

Bruce – The most obvious application of the work is to study human development. How do cells actually form a heart is something of basic interest. And also, the most common form of birth defects is actually cardiac defects. But the other application is that we can expose these developing human micro-chambers to drugs which are thought to cause developmental defects, specifically of the heart, and in fact one of the key experiments in this study was to use the drug thalidomide which is notorious for causing birth defects. When we expose these cells to the thalidomide they had a dramatic change in the morphology so that you could see that it was altering the developmental process in this micro-chamber. Thalidomide was tested in rodents before it was tried in people and there were no cardiac defects in the rodents. I think that more and more we’re thinking how do we get tests which use real human cells so that we can actually make safer drugs. And in this case say you turn back the hands of time and you had this sort of test perhaps you would have discovered that thalidomide was dangerous before it had gone on to be given to people.

You can listen to the full interview with the Naked Scientists here.

Looking inside your heart

One of the tools available to doctors to see the heart in action is the echocardiogram. This uses ultrasound waves to image the heart as it beats, so the cardiologist can tell whether it’s contracting correctly and that the heart muscle is a healthy shape. I volunteered to be a guinea pig…

Clare – I’m Clare Ward-Jones; I work for Phillips Healthcare and my role is a cardiac ultrasound applications specialist. We’ve got a machine the ETHIC and that is the supreme ultrasound machine for cardiology. We can do a 2D scan on you, we can also do 3D images so we can get a 3D model of the heart.

  • The machine is the same as that used for a scan on a pregnant woman and relies on ultrasound beams which are sent out from the end of the probe and bounce back when they hit structures in the body.
  • Patients must lie on their left-hand side to bring their heart closer to the front of the chest meaning the ultrasound has to travel a shorter distance and therefore produces a clearer image on screen.
  • Electrodes are also applied to the patient to monitor the heart rate during the procedure – mine measured 87 which lies between the normal rate of 60-100 beats per minute.
  • Jelly is applied to the skin to remove any air between the probe and the skin which ultrasound cannot travel through.

Rick – My name is Rick Steeds; I’m a consultant cardiologist. I’m particularly interested in cardiovascular imaging and I’m the current President of the British Society of Echocardiography.

  • Echo sounds are very good at showing the structure of the heart; how strong the muscle is; whether the valves work; whether they leak or whether they’re narrowed, and whether there’s damage to the heart, for example, from a heart attack.
  • The images of my heart show two of the four chambers and the valves between them opening and closing.

You can listen to the full interview for the Naked Scientists here.

The Heart of an Athlete

How does repeated exercise impact your heart? To find out I spoke to St George’s University of London heart specialist Sanjay Sharma. He’s the medical doctor for the London Marathon, the England football team and Andy Murray…

  • Professional athletes push themselves to the limits and regularly do more than 10-15 times the recommended amount of daily exercise.
  • Athlete’s heart is a medical condition that involves up to a 20% increase in the thickness of heart muscles and a 10% increase in the size of the cavities in the heart.
  • At rest the heart pumps 5 litres of blood around the body, whereas during exercise this can increase to 25-30 litres.
  • Your heart behaves like any other muscle in your body and will increase or decrease in size depending on your level of fitness.

You can listen to the full interview for the Naked Scientists here.

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