Study Of Mice With Human Brain Cells Raises Ethical Concerns


A study conducted by Dr. Steven A. Goldman, Professor of Neuroscience and Neurology at the University of Rochester Medical Center, recently concluded that mice injected with human brain cells were four times as smart as other mice. The mice were injected with human glial cells extracted from donated human fetuses, which multiplied and ultimately displaced the native cells over the course of a year.

As Goldman explains to New Scientist, the human cells did not affect the fundamental nature of the mice brains; they simply strengthened the connections between the existing cells. “It’s still a mouse brain, not a human brain. But all the non-neuronal cells are human,” Goldman said. “It’s like ramping up the power of your computer.”

The brains of the mice used in the study were definitely enhanced, as they performed four times as well as other mice in memory tests. “These were whopping effects,” Goldman said. “We can say they were statistically and significantly smarter than control mice.” 

The study was conducted in order to better understand human brain diseases by studying them in live animals with whole brains. Goldman and his team are already expanding their research efforts to use rats as test subjects. Rats, which are more intelligent than mice, could potentially provide more insight. 

For now, however, the studies will stop with rodents. “We briefly considered [putting human cells into monkeys] but decided not to because of all the potential ethical issues,” Goldman said. Within the scientific community, this is a reasonable statement. Mice and rats are commonly used in medical research, with only animal rights organizations such as PETA finding fault with the methods. A mouse with a half-human brain is an interesting concept with potentially beneficial results, but one that’s unlikely to upset the larger community. 

As scientific study progresses, however, our treatment of all animals should be more carefully considered. Nearly 99% percent of the mouse genome is similar to humans. Like monkeys, they are some of our closest relatives. Their level of intelligence is obviously much lower than those of primates, but that doesn't change the fundamental ethical concerns involving animal testing. 

Until 2002, rats and mice weren’t even covered by the Animal Welfare Act, the 1966 federal law regulating the treatment of animals in research, exhibition and transport. As this FAQ sheet released by the Animal Plant and Health Inspection Service explains, a standard of care for those animals was established just 12 years ago, with one notable exception. The sheet reads as follows: “In 2002, the passage of the Farm security and Rural Investment Act, also known as the 2002 Farm Bill, amended the AWA’s definition of animal to include rats of the genus Rattus, mice of the genus Mus, and birds – with the exception of those bred for use in research.” So rats and mice are covered by the AWA, unless they’re being used in laboratories. There, essentially anything goes. 

According to PETA, more than 100 million rats and mice are killed in U.S. laboratories each year. Mice feel pain and contract the same diseases as humans, including mental disorders such as depression. It’s these similarities to humans that make them useful as test subjects, as well as their accelerated life span, low cost of care and their small size. Yet the negative aspects of human research on rodents is almost completely disregarded by scientists, and comes with little federal regulation. 

If a scientist is unwilling to conduct a test on a monkey because of ethical concerns, should that same test be conducted on a mouse? Society as it is now would say yes. Mice are bred to be test subjects, and our understanding of their neurological systems will only help us further our understanding of our own. It’s worth killing a mouse if it helps save a human being. Mice have, in many cases, been the key to developing drug therapies and making medical discoveries. As both science and technology progress, however, humans need to be more cognizant of the undeniable pain and suffering being repeatedly inflicted upon an entire species. It’s impossible to fully empathize with an animal like a mouse, but it’s important not to forget that the reason they’re being used in these studies is because they’re not as different from humans as they appear.


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