Twenty years ago, a mouse with a human ear on its body sparked outrage and criticism, but subsequent reality has proven the value of this experiment.
In the 20th century, humanity witnessed significant advancements in the field of science. It is understood that as technology progresses, medicine will develop to the point where every part of the human body can be grown externally and transplanted like replacing parts of a broken machine. Although these scientific theories have been debated for decades, no one was rational enough to wait for it to happen.
The Uniqueness of the Ear
Cosmetic surgery advanced rapidly towards the end of the 20th century, but the ear remained the most challenging body part to recreate, as it is made of cartilage. While cartilage can be cultured, it is difficult to produce from human tissue. As a result, many individuals suffering from ear-related accidents have had to live with abnormally shaped ears or permanently without them.
In the late 1990s, doctors Charles Vacanti, Joseph Vacanti, and Bob Langer aimed to create human body parts in the laboratory. They experimented with creating a “biodegradable scaffold” or structures that could dissolve within a body. One day, Joseph Vacanti overheard a colleague complaining about the difficulty of creating new ears for patients lacking them, due to the ears’ bizarre and complex shapes.
World medicine achieves great success in creating and ‘implanting’ body parts on living organisms. (Source: Theparadise.ng)
This ironic reality spurred the birth of the “ear-mouse project” in the 1990s, led by Charles Vacanti, an expert in tissue engineering and stem cells. In that same year, Charles, with the help of his brother Joseph Vacanti (a tissue regeneration expert), attempted to culture a small piece of human cartilage on a biodegradable scaffold.
The scientists decided to create a scaffold shaped like a human ear and placed bovine cartilage cells on it (cartilage is a semi-rigid tissue found in the human ear, nose, and chest). They then selected a strain of immunocompromised mice, meaning its immune system would not reject the foreign bovine cells. They anesthetized the mouse, made an incision, and placed the ear shape under its skin. As predicted, the mouse’s body nurtured the bovine cartilage cells, and as the scaffold dissolved, only the shape of the artificial ear remained on the mouse, without an eardrum.
The world was astonished when all major news outlets shared the image of the mouse—dubbed the “Vacanti mouse,” “earmouse,” or “ear-mouse”—bearing a human ear. Some expressed great excitement, while most were fearful, and others voiced outrage, questioning the ethics of such experiments.
A backlash against genetic engineering erupted in the Western world due to misunderstandings surrounding this experiment, with claims that the mouse’s DNA had been genetically modified to grow a human ear on its back. Misinformation was further propagated by some news outlets using such keywords to promote the image, unaware that the actual experiment had begun nearly a decade before the photo was taken, and no gene technology was employed in this study.
In fact, the scaffold was made from polyglycolic acid, a synthetic material commonly used in cosmetic surgery. The fibers of this material were molded into a loose mesh shaped like an ear, with 97% air, leaving ample space for cells to fill in. This material would dissolve into carbon dioxide and water as tissue began to develop in the affected area.
If the doctors perfected this technique in mice and subsequently in larger animals, one day they could help humans develop missing body parts. It sounds simple, but the process takes about eight years before it is ready to be implanted into a living organism. Attaching it to human tissue would not be effective as it would not regenerate quickly enough before the original cartilage dissolves. Another issue is that all immune systems in any organism would identify this cartilage as a foreign object and attempt to reject it.
The Special Mouse
The mouse used for this experiment is known as the “nude mouse” because it is hairless. A random mutation that this species underwent resulted in them being hairless and lacking an immune system. The absence of fur does not make much difference, but the lack of an immune system is what makes this mouse special and perfect for the experiment. Without an immune system to fight off foreign objects, the molded cartilage could be filled with cells until it fully developed into the ear.
No special requirements were needed for human cells, as long as they were healthy and grew quickly. The synthetic ear scaffold was created to replicate the ear of a three-year-old child. This ear would continue to grow after being transplanted as the child grows. The synthetic cartilage was surgically placed on the mouse’s back and held there for 12 weeks until the scaffold was filled with living cells.
This artificial ear resembled a natural human ear by 90%, which is quite remarkable given that this experiment did not involve any genetic engineering with human DNA. The ear was later successfully transplanted onto a child.
Despite the misunderstandings, the success demonstrated the possibilities of medicine and science in general. People understand that the future will surpass science fiction films. The Vacanti mouse is not merely an exercise for scientists to learn how to develop body parts in humans using skin and cartilage cells.
In January 2018, doctors in China and Japan published a research study: In 2015, they selected children with congenital deformities on one side of their ears. The scientists scanned images of their normal ears, reversed the shapes using computers, and 3D printed a biodegradable scaffold. They then added cartilage cells from the patients and placed the scaffolds under the skin. As a result, the cases of one-sided ear deformities now had two ears that were nearly normal.
If it weren’t for the aforementioned ear-mouse experiment, such medical advancements may not have occurred. Today, the “implantation” of human ears has been successful; what awaits us in 20 years and beyond?
