Building a heart from scratch: A how to guide.

A few weeks ago I wrote a post called ‘How can you mend a broken heart?’ which you can find here, and now i find myself being able to talk about the extraordinary feat of actually building one from scratch.

There has always been a shortage in the amount of heart transplants available for those patients who need them, mainly due to damage through illness or resuscitation attempts. Whilst some efforts to resolve this problem have involved trying to get more people to donate their hearts after they die, one lab in America is attempting to circumvent this problem completely, by growing them from scratch instead.

It’s an easy enough thing to say, but in practice the growth of whole human organs has proven incredible difficult. Some success has been achieved with the growth of the most simple, hollow organs like the trachea and the bladder, but the amount of coordination required between dozens of different cell types within a complex organ makes it near impossible.

Because of this, researchers quickly realised that they would need an already functioning biological scaffold to build their heart around. That scaffold came in the form of a different recently deceased heart which had been stripped of its cells (decellularization). This left behind only the supporting extracellular matrix and collagen which could then be repopulated by new cells (recellularization). Now, that might not seem to make much sense. Why would you take an already functioning heart and strip it of all its cells, only to then later replace those cells? To answer that we need to think about the main problem facing tissue transplants, which is tissue rejection.

If any of you have ever watched ER or House, and a patient in need of an organ transplant is being treated, you’ll probably have heard the phrase ‘is there a tissue match?’ That means that for an organ to be transplanted into a patient, that organ needs to be similar enough to the patient so that their immune system doesn’t reject it. This results in a lot of people who need an organ being left without, due to the fact that any available organs aren’t a ‘tissue match’.

With this new method of organ growth, tissue rejection isn’t a possibility. This is because of the source of cells that are used to regrow the heart tissue – the patient needing the transplant.  By using adult cells from the patient, and reprogramming them into thinking that they’re stem cells (turning them into induced pluripotent stem cells or iPS cells), the cells of the new heart will be an identical genetic match to the patient, ensuring that the new organ won’t be rejected.

If that were the end of the story then we would have solved the problem of organ shortage and a lot of people would be much better off. However, in science things don’t always go to plan. It might be easy to say ‘let’s use stem cells to regrow the heart’, but in reality the number of factors that contribute to the growth of an organ are exponential, all of which need to be recreated to grow an organ in the lab. Cells are able to sense the environment around them, including the pressure being forced upon them from other cells, the beating action of a functioning heart, as well as the nutrients and oxygen around them. To try and recreate these conditions, researchers placed the heart in a bioreactor that attempts to mimic the hearts natural environment. This provided some positive results, with organs being transplanted into rats and fully functioning, even if only for a short period of time.

This marks a monumental step forward in our ability to grow organs that are specifically tailored to the needs of a patient. However, there are some sceptics.  Many believe that there are too many complications in the field of tissue regeneration for this to ever be a viable source of organs, and that the most we can ever hope to achieve is the generation of parts of an organ, such as lobes of a kidney or valves of a heart. Well, let’s just hope that they’re wrong. 

What do you think about this research? Write below with your comments or questions, and join the mailing list at the top right of this page to get emails every time I leave a post.