Did you know that the perfect place to 3D print a human organ is actually in space? In 2019, scientists developed a BioFabrication Facility on the International Space Station dedicated to the gravity-free bioprinting of human tissues. As cool as that sounds, why would they even consider such an endeavor?
Our body has 78 organs that work in harmony to keep us functioning well enough to move throughout our days and years. Unfortunately, there may come a time when one of these components of our biological machine may malfunction or become damaged. Sometimes it can be fixed with medicine or surgery, but other times there is no saving the original organ, and a replacement is the only answer. The damaged or dysfunctional organs are replaced with healthy organs obtained from generous donors.
A sad fact, however, is that there are too many patients in need of organs and not enough viable donors. Organ shortage is a major problem worldwide. In the United States alone, there are over one hundred thousand people waiting for an organ. Even if viable organs are available, the blood type of the donor may not match the recipient, which is absolutely necessary, as a mismatch could be fatal for the recipient. To make matters worse, sometimes organs can be lost in transit or may not reach the intended patient on time.
To combat these very real problems, scientists are attempting to 3D bioprint tissues.
Bioprinting – Printing Living Tissue
Bioprinting is a form of 3D printing technology that prints, or more specifically, bioprints living tissues. Bioink, consisting of stem cells and nutrients for them to grow, is added layer after layer on a scaffold. Why stem cells? Bcause they can turn into any type of cells. After the bioprinting process is completed, the organ is placed inside a bioreactor, where it matures further into a functioning organ.
This same technology is used by the IMF to print face masks in the Mission Impossible movie series. However, in reality, this technology is not that advanced… yet.
The Problem with Earth
If you jump up really high, let’s say, on a trampoline or even from a great height, why do you always land back on the ground? I think we all know the answer to that – gravity! Earth keeps all its inhabitants close to it, regardless of size. Whether you’re as big as a blue whale or as small as a viral particle, gravity’s effects are seen everywhere, even on a cellular level. It’s actually quite important, as it directs the flow and distribution of oxygen and nutrients amongst cells.
However, Earth’s gravity results in two problems for bioprinting:
Gravity causes flattened layers of cells
In tissue culture facilities, cells are typically grown in tissue culture flasks. These flasks, filled with a nutrient-rich liquid media for cells to grow, allow scientists to experiment on life without ethical issues with animals. However, cells in these flasks tend to form flat layers at the bottom of the container. Gravity’s pressure compresses cells and tissues as they grow, forcing them to form flat, 2D layers on top of another. This is not how organs naturally develop.
Inside the body, a tissue forms three-dimensionally. Specific cells of the soon-to-be organ are guided by the unique environment of the human body, which has a structural meshwork of proteins called the extracellular matrix. Along with this matrix, other cells of the organ grow and mature, and as the organ develops, the matrix holds everything together. However, inside the plastic culture vessels, without the manifold interactions in the body, the cells cannot form into fully functional and structurally similar organs.
This brings us to our second problem.
Gravity requires scaffolding
Bioprinting requires scaffolds. Without the extracellular matrix, scaffolds can act as a mold, allowing the initial layers to shape themselves correctly, and providing structural support to the organ. The challenge comes with printing soft and delicate tissues, like capillaries, where using a scaffold isn’t possible. Without the scaffold, the cells used to print these soft tissues tend to collapse under their own weight. So, what can be done to remove scaffolds from the equation?
The Solution? Space
Researchers were scratching their heads to figure out a way to make teeny-tiny tissues without scaffolds. Then, in the 1970s, a few people from NASA’s Johnson Space Center thought of using space as a solution. They hypothesized that if cells could be grown in the absence of Earth’s gravity, they would not settle to the bottom of the culture vessel. Instead, the cells floating in microgravity might assemble into organs in a manner similar to how it happens inside the body.
To test this hypothesis, NASA developed the Rotating Wall Vessel (RWV), a culture vessel used to simulate microgravity—and they were right! Cells cultured in microgravity did not form 2-dimensional layers and were able to stay in the desired shapes without scaffolds. This technology, however, proved quite tedious and expensive on a large scale. An easier option was to simply shift bioprinting to space.
400 km off the surface of the earth, where the ISS is situated, gravity weakens considerably. In fact, it is so weak that objects seem weightless, and float around in space. This weak level of gravity is called microgravity, where “micro” means small. The same cells used to print soft tissues that collapse on earth, are able to maintain their shape in microgravity. Therefore, bioprinting complex and delicate tissues becomes much easier.
Getting started: Space beef
The muscle is a much simpler place to start than other complex human organs, like the kidneys. An even easier place to begin might be with bioprinting steaks in microgravity. One company thought so too. In September of 2019, Aleph Farms, a food-tech venture with Russian and American partners, decided to test the feasibility of printing beef in space. They took cow stem cells to space and successfully bioprinted muscle tissue.
However, nobody knows how this meat tastes. What this experiment did do was conclusively prove the possibility of printing tissues in space. This may, one day, offer not just a convenient food alternative for astronauts, but also a more sustainable way to meet the world’s beef requirement without the high environmental cost of animal husbandry.
Along with meat bioprinting, a trial of organ printing was also conducted. The plan was to bioprint a thyroid gland and cartilage tissue in space.
Getting the organs from space to Earth
These organs may print better in space, but you may be wondering what happens when they’re brought back down to Earth. Indeed, the increased gravity does exert a good amount of physical strain on these bioprinted structures.
Techshot, a company that partnered with NASA to design the BioFabrication Facility, developed a cell culturing system that hardens the tissue, making it somewhat resistant to the effects of gravity. The required tissues are bioprinted in a day and then placed in this vessel for a period of 12-45 days for strengthening. After this maturation process, the newly bioprinted tissue becomes healthier, better functioning, more viable and strong enough to withstand the journey back to Earth.
Regarding the earlier space experiment, the bioprinted thyroid and cartilage tissue will be sent back to Earth. After further testing, we will come to know the internal structure and see the effects that space transit had on them. At this point, we’re still awaiting the results.
As with everything in life, there is some risk to growing organs and tissues off-planet. Cells grown in microgravity, whether on or off the planet, have altered gene expression. Manipulating and modifying stem cells inherently creates a higher possibility of turning cancerous. Playing with nature is clearly never simple!
Mankind is hoping to achieve distant space travel and planetary exploration. It seems to me that the successful completion of this bioprinting project is crucial for such space travel ambitions. The journey to Mars alone takes around 500 days. Should an astronaut undergo a medical emergency in that time, it would be impossible to turn back and abort the mission. Therefore, bioprinting for regenerative medicinal purposes is critical for astronauts traveling through long and perilous space voyages.
Closer to home, if all goes well, bioprinting organs in space could potentially end the long wait for those on the organ transplant list. It could also eliminate the very real and huge risk of organ rejection, as the bioprinted organ could be made out of the patient’s own cells. Of course, the possible carcinogenic side effects would have to be factored in, but all in all, growing organs in space, from your own cells, on-demand, is a much better alternative to our current reality.
I hope none of you, nor myself, ever need an organ transplant, but if we do and this project is successful, we could get a custom-printed organ from space within a month!