Could a day when a replacement heart is printed on demand be in reach within our lifetimes? Heart disease is the biggest killer of people in the western world. Combined with the fact that there is a global donor shortage, the ability to engineer and print organs would be a hugely beneficial medical advancement.
Every passing year seems to bring us closer to a reality resembling science fiction, so it won’t come as a surprise to many to hear that scientists are already researching ways to 3D print entire human organs. What might surprise you though – is how close we already are.
How does the technology work?
3D printing is when a material is joined or solidified under computer control to make a 3D object, and has been around as a technology since the 1980s. As technology progressed, engineers were able to print more complex and intricate shapes from a variety of materials. The next frontier for this technology is to be able to print complex biological organs through a technique known as bioprinting.
Drop-based bioprinting via a modified inkjet works in a surprisingly similar way to a normal inkjet printer. The key difference being that instead of ink, the printer uses a suspension of living cells and a gel for providing structure. This drop based method is quick, yet not so good for creating a complicated structure like the heart. A more accurate type of printer is the extrusion printer, which uses an extruder to print layer by layer 3D tissue in a similar way to non-biological materials.
In theory, a 3D heart could be created in the following way:
- An MRI scan would be used to create an accurate digital picture of the shape and size of the organ
- Blood is taken from the patient which is then converted into stem cells (special cells that can change into any others). These are in turn converted into heart cells that are mixed into a bio-ink
- The printer lays a ‘scaffold’ of gel to provide structure, then ‘seeds’ the scaffold with living cells
- After several days, the cells will join together and begin to beat like a heart. The scaffolding gel is then removed by a specialised washing process.
So has a human heart actually been bioprinted?
Not quite yet. Although BIOLIFE4D, a biotech start-up company, is hoping to replicate a mouse-sized heart in 2019. It won’t be transplantable, but it could still be used to experiment with under laboratory conditions. Whilst an incredible achievement of modern medicine, the ultimate goal is still to improve the scale and accuracy of 3D bioprinting to the point where a human-sized heart could be printed on demand and used for a transplant.
The heart is a complicated organ though, made up of an intricate assembly of pumps, valves, and tiny capillaries that transport blood and oxygen to all of its cells. There is still some way to go in order to create a fully transplantable human heart, although promising progress has been made.
What about other organs?
Some human organs are easier than others to re-create in a lab. Skin and bladders have already been 3D printed with good success, as flat or hollow organs are more simple to build than a very complex one like a kidney. Hearts are actually somewhere in the middle in terms of difficulty, due to them effectively being a specialised pump and not carrying out any biochemical reactions.
Organovo, a company based in San Diego, have successfully 3D printed a miniature liver that can be used for drug testing. Although they are not yet ready to produce one for transplantation, the early signs show huge promise for one-day replicating a full-scale liver.
Researchers have even managed to create a nephron, a key part of the kidneys, which are one of the most complex organs in the human body. There is also promising research going on into the 3D printing of bone and corneas that could be used for transplants.
What challenges still remain?
One of the most complicated issues with transplants is whether the host body accepts the new organ or not. Patients are given powerful immunosuppressant drugs to stop their own immune systems from attacking the new organ. In theory, a printed heart will be made from a patient’s own cells so should be able to resist rejection. Of course, a human trial is yet to prove this.
Vascularization is another challenge that gets bigger when the size and complexity of an organ increases. Bigger organs have more blood vessels traveling deeper into tissue to transport oxygen and nutrients, making them much harder to recreate than flat or hollow organs.
The idea of organ replacement also raises some ethical issues, such as whether this could be the first step on a path to ‘designer’ humans. Could this lead to a world where the wealthy could replace their organs at will? Without a doubt, it is an interesting topic of debate and one that will only become more relevant as time and technology progress.
Last modified: February 11, 2019