Human Brain Organoids in Rats; Perils of Lab-Grown Consciousness

Extraction of embryonic stem cells

Today, those in need of a vital organ transplant might be one on a list of 100,000, but someday that list might be cut down or eliminated completely as scientists experiment with growing brain organoids or “mini-brains” in mice and other animals. Of course, ethical concerns abound on all sides of the argument.

Mini Brains Grown in a Lab 

Scientists break new ground every day in the quest to better understand the way our bodies work, but it isn’t easy to artificially recreate the intricacies of neural networks and the complex functions of our body. So, in an attempt to recreate these functions organically, they’re using the go-to animal test subjects most people are ethically ambivalent about using: rodents.

Essentially, these scientists created what they’re referring to as a mini-brain, which is technically just small pieces of human brain tissue introduced to rodents via stem cells. These pluripotent cells can be used to basically recreate any cell type found in the human body to model disease, development, and reaction to drugs and treatments. So far, these tissue implants have been used to study Alzheimer’s and the Zika virus.

In the future, scientists hope this technology will lead to larger-scale organ recreation or organ hybrids that would grow in a pig or cow, subsequently harvested for transplant to a human body. Thus far, successful attempts with this hybrid technology include creating “chimeras” with pigs in China, though the scientists prevented them from developing past the fetal stage due to ethical concerns.

The Ethical Dilemma of Growing Cerebral Organoids

 In one recent experiment, scientists using organoid brains in mice noticed the human brain tissue they implanted achieved vascularization. Put simply, the brain tissue made circulatory connections with tissue in the mouse’s brain and started sending electrical pulses; it became functionally integrated with the animal’s cortex.


mini brains implanted in mice


If this sounds morally and ethically questionable, that’s because it is. Some researchers claim, at this point, that this type of concern is not yet relevant, and the implants, if anything, are actually diminishing the rodent’s brain function due to its crude implementation. That’s not to say the dystopian fear of an intelligent rodent with human-like consciousness isn’t being taken into consideration, should this technology continue to develop.

Unsurprisingly, there has been controversy surrounding this work from proposed legislation in the U.S. that would ban these types of experiments. Meanwhile, the National Institutes of Health placed a moratorium on funding controversial research of this nature, though there’s been a push to overturn it.

While researchers have made successful connections between human and rodent brain tissue, they’ve found greater success with species that are more closely related. Splicing the genes of rats and mice has produced more prominent and noticeable hybrids, compared to the human-mice combination. While we do share a common ancestor with rodents, our genome is more closely related to swine or bovine DNA. Pigs and humans shared a common ancestor that split off roughly 90 million years ago.

Genetic similarities between us and the animal we would hypothetically use to grow transplantable organs carries less weight than the size of the animal itself. Scientists don’t have to worry about genetic inconsistencies that might reject a human organ when they can use the CRISPR gene editing tool to disable those functions. They proved this by disabling genes in rats to allow the introduction of mouse genes and found significant percentages of mouse cells in the brain, lungs, liver, kidney, eyes, and pancreas.


creating chimeras


The question that begs to be asked is: What happens when the unthinkable occurs and you create a chimera that can think or feel like a human? What if you somehow create a human mind inside of an animal? Will it ever get this far? It also adds to the controversy surrounding the creation of designer babies and biological enhancement for those who can afford it. Will this cerebral organoid technology lead to the creation of more highly developed brains, and is this an inevitable step in our evolution?

Psychedelic Drugs on Mini-Brains

Recent popularity in studying the effects of psychedelic drugs on brain function and for drug-abuse treatment has continued with cerebral organoid technology. A group of Brazilian scientists introduced 5-MeO-DMT, a type of dimethyltryptamine, to mini-brains from stem cells in rats.

The effects of entheogens, commonly known as psychedelics, have been found to be effective treatments for curbing and eliminating depression and drug addiction, in this particular study. It found direct evidence, showing how 5-MeO-DMT upregulates synaptic formation and function, while downregulating pathways that are associated with inflammation and substance abuse. Not only did it influence these functions, but it also influenced proteins responsible for brain plasticity, a term used to describe the brain’s ability to change, often in response to learning.

It is believed that DMT is naturally produced in the pineal gland in our brains. 5-MeO-DMT is structurally similar to serotonin and melatonin, and can stimulate the growth of LTP, a mechanism of learning and memory.

The study also found that 5-MeO-DMT resulted in a down regulation of MGluR5, a receptor that plays a role in the reward system associated with addictive drugs like nicotine, alcohol and cocaine. When this gene is taken away from mice who are exposed to these substances, they showed no desire to self-administer the drugs.

Tests such as these can show the benefits of using small samples of human organoid brain tissue in other animals, and this is only the beginning. With that being said, this nascent phase might be a good place to stop in order to prevent some horrible chimeric hybrid that has only been conceived of in dystopian fiction themes. Or could it be possible to responsibly develop this technology without accidentally reaching that point?

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