Mouse with a Human Ear

Fixing machines is easy; fixing living creatures is hard. Or is it the other way round?

Mouse with a Human Ear
Illustration credit: Rhea Suresh

Fixing machines is easy; fixing living creatures is hard. Or is it the other way round?

In 2023, a rocket blasted off from the Cape Canaveral Space Force Station. Not an unusual sight in a world where many private companies are moving to space, but this particular rocket was 85% 3D-printed.

3D-printing is a relatively new technology, but it’s already being used in a variety of applications. The basic idea is that you take a digital design, and print it out, layer by layer, into a precisely defined shape.

While a full rocket may be an overkill, 3D-printing is great for space missions. If you thought airport luggage limits were a pain, the problem is even more crucial in spaceflight. That aside, 3D-printed parts can be handy at home and in industrial setups too. And while most 3D printing is made using plastics, people are trying to use other material as well — such as the stuff that makes up your body.

While 3D printing is new, repairing people is an idea that’s been going around for a while.

In 1997, the world was taken aback by a weird scientific image. A white mouse sits wrinkled on a large, white-gloved hand, its red eyes staring nowhere. And, growing out of its back, there is the unmistakable shape of a human ear.

This was no artist’s impression or simulation, but the results of an actual scientific experiment.

In the twentieth century, our world saw rapid technological advancement in animal tissue engineering. During this time, scientists attempted to grow human body parts externally and replace them like broken machine parts. If lizards can grow back their tails and crocodiles can grow back their teeth, then  why couldn’t humans do the same for parts of their bodies?

Despite the fact that these scientific hypotheses had been argued for decades, no one had expected it to happen.

So when the image of the “mouse with a ear on its back” came out, there were mixed reactions. Some were thrilled at the progress of science. Others, though, were terrified about the safety and ethical implications of such an experiment, and the mouse soon triggered a backlash of protests against tissue and genetic engineering in the western world.

And this was before social media.

In 2007, Apple released the first iPhone, a device which was less like a phone and more like a computer in your pocket that also happened to make phone calls.

Today, iPhones and their generic equivalents, smartphones, are practically indispensable. Ever since I got mine before joining college, it’s been my constant companion to keep in touch with people and stay updated on what’s I can’t image life without it!

This is an example of how technology can change the human landscape within the span of a generation. Inevitably, it shakes up the world which we’re used to, which is why any new technology is greeted with apprehension as well as excitement.

But while electronics can change things, biology is a whole different ballgame. To understand where the protests were coming from, let’s take a brief dive into history — because, as Adolf Hitler once said, “the man who has no sense of history is like a man who has no eyes or ears.”

In 1933, the country of Germany saw a new leader come to power. Reeling under a loss in war and economic crises, people saw Adolf Hitler as someone who would make their country great again.

One of Hitler’s philosophies was the use eugenics: the idea that some people (such as Hitler’s community, of course) are genetically superior to others. Using this idea, he began to ruthlessly single out some communities such as the Jews, eventually killing or conducting experiments on them.

This dark  history makes anything to do with genetics a sensitive topic. Combine it with the fact that we’re tampering with complex systems we don’t fully understand: the intricacy of Nature, or God’s creation, depending on your inclination. It’s the equivalent of opening up your computer and plugging in wires when you’re not quite sure what you’re doing.

In all this discussion, though, it’s easy to miss the fact that the mouse in question was itself not genetically modified. It was modified, yes, but not genetically.

In 1972, MIT engineer Bob Langer and Harvard surgeons Joseph and Charles Vacanti began experimenting with strategies to produce human body parts in the lab — starting with an ear.

Why an ear? Even though plastic surgery advanced significantly in the latter half of the twentieth century, the human ear remained the most difficult portion of the body to reconstruct, mainly because of the cartilage that needs to support it from inside. Although cartilage could be manufactured, making it out of human tissue was extremely difficult — which meant that many people who had accidents involving their ears would have to live with a shapeless ear or no ear for the rest of their lives.

To better understand how to do this, the three scientists implanted the shape of a human ear in the back of a mouse. This wasn’t working with genetic code; it was the biological equivalent of attaching on a new part to an existing machine.

The mouse used in this experiment was referred to as a “Nude Mouse”, since it lacked hair due to a random mutation. This same mutation also compromised the mouse’s immune system — which is what made this experiment possible.

It started with a synthetic ear cartilage, made to mimic that of a three-year-old child. This cartilage was surgically implanted on the back of the mouse. Then, it was injected with live stem cells: a special variety of cell that has the potential to grow into any kind of cell depending on the situation. Normally, such a procedure would trigger the mouse’s immune system to combat the foreign tissue — eventually causing it to die. But in this case, due to the mutation, the mouse had none.

Within 12 weeks, the stem cells formed an actual cartilage in the shape of a human ear, and the synthetic part gradually disintegrated over time. In a way, the ear developed from a three-year-old version to a full-fledged adult!

Today, things are moving in a new direction. Just like printers use inks and 3D printers use filaments, bioprinting is a technique for creating cellular structures using ‘bioinks’.

These biomaterials, which can include stem cells are applied layer by layer to ‘print out’ skin, tissue, or even an organ. Human livers, kidneys, and hearts are being bioprinted at laboratories and research institutes. The goal is to make them transplantable as well as to reduce the number of organ donations.

As I excitedly read through all the new developments, my phone battery emits a warning. Newer phones have all their parts fused together, which means I can’t replace my battery without buying a new phone — which, when I think about it, is a common trend in today’s digital technology. Earlier gadgets were repairable anyway, but nowadays we’ve got to use 3D printing to make them so.

Perhaps technology is becoming more complex, in the same way that biology always was?