In this blog post, we’ll explore why the human body cannot regenerate completely and whether animal testing offers a potential way to overcome this limitation.
Humans cannot restore lost body parts, such as a finger or nose severed in an accident, to their original form. Such physical loss is not merely a cosmetic issue; it leads to functional impairment, causing significant inconvenience in daily life. Furthermore, this loss can result in emotional trauma, leading many to experience social isolation or depression. Consequently, those who have lost a body part desperately need a way to restore it. However, the reality is that current medical technology lacks the means to fully resolve this issue.
Many people suffering from incurable diseases are tragically dying because they cannot receive the necessary organ transplants in time. At present, there is no adequate solution to this problem. Organ transplant waiting lists are growing longer every year, forcing families and patients to spend their time in despair and anxiety. The medical community is striving to advance artificial organs and bioprinting technologies, but numerous technical and ethical issues remain before these can be widely applied. However, there are chemical engineers working to bring hope to these individuals.
Charles Vacanti, director of the MIT Medical Center, and many chemical engineers are conducting research to create human ears by implanting bovine cartilage cells into mice. There is currently no way to repair the cartilage that makes up the ear when it is deformed, whether due to congenital or acquired causes. For this reason, led by Charles Vacanti, many researchers are attempting to grow ear-shaped structures from cells on the backs of mice. This research is viewed as a significant breakthrough that could have a major impact on future medical technology, going beyond mere scientific curiosity. This is because, if successful, the research could open the door to restoring other parts of the human body or even organs using a similar method. These mice are called “Vacanti mice.”
Engineers use nude mice in the ear-creation process. If ordinary mice were used, injecting bovine cartilage cells would trigger a rejection response. In contrast, nude mice are not only hairless due to a genetic mutation but also have a very weak immune system. The nude mouse’s weak immune system does not reject externally injected cells, playing a crucial role in the success of this experiment. These nude mice provide a space where bovine cartilage cells can grow well and also serve as an energy source to support their growth.
I will now explain the experimental process in detail. First, a scaffold that helps the bovine cartilage cells grow into the shape of an ear is inserted into the mouse. It is important to note that this scaffold must be inserted between the mouse’s skin and muscle layers. Since the scaffold is made of a material similar to the sutures typically used in surgery, it degrades into water and carbon dioxide within the body after a certain period of time. Additionally, because the scaffold forms a mesh-like structure that is 97% air, it allows the bovine cartilage cells to grow within the empty spaces previously occupied by air. After about three months, the mouse’s blood vessels extend to the bovine cartilage cells, supplying them with nutrients. The cells differentiate through the mesh, and once they have fully formed into the shape of a human ear, the scaffold completely biodegrades.
This experiment has not yet been conducted on humans. Since bovine cells are currently used, researchers have not yet found a method to transplant them into humans without triggering an immune rejection response. Furthermore, researchers emphasize that thorough verification of safety and efficacy is necessary before applying the experiment to humans. This is because it raises a very important ethical issue in the field of biotechnology. However, engineers predict that experiments using human cells will be possible in the not-too-distant future.
In fact, these technological advancements have the potential to bring revolutionary changes to our lives. If it becomes possible to repair damaged organs or body parts, this will contribute significantly not only to extending human lifespan but also to improving quality of life. However, ethical barriers remain. One might worry that when this technology is commercialized, animals will be treated merely as tools for producing organs. In reality, creating internal organs—rather than simple body parts like ears—requires a variety of different animals. Nevertheless, scientists and engineers are conducting their research while giving the utmost consideration to the ethical issues surrounding animal testing. This is to ensure a balance between scientific progress and ethical responsibility. Ethical deliberations regarding animal testing are ongoing, and without such sacrifices, modern biotechnology would not have reached its current level of advancement. Of course, we should always be grateful to these animals, but chemical and biological engineers around the world are continuing their research today for the sake of the countless people who are still suffering right now.
