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Saturday, November 19, 2022

Human mini-brains were transplanted into rats. Is this ethical?

Julian Savulescu
Originally posted 22 OCT 22

Here is an excerpt:

Are 'Humanized Rats' just rats?

In a world-first, scientists have transplanted human brain cells into the brains of baby rats, offering immense possibilities to study and develop treatment for neurological and psychiatric conditions.

The human brain tissue, known as brain organoids or “mini-organs”, are independent nerve structures grown in a lab from a person’s cells, such as their skin cells, using stem cell technology. Although they can’t yet replicate a full brain, they resemble features or parts of an embryonic human brain.

The study, published in the journal Nature on Oct 12, showed that the human organoids integrated into the rat brain and function, and were even capable of affecting the behaviour of the rats.

A few months later, up to one-sixth of the rat cortex was human. In terms of their biology, they were “humanised rats”.

This is an exciting discovery for science. It will allow brain organoids to grow bigger than they have in a lab, and opens up many possibilities of understanding how early human neurons develop and form the brain, and what goes wrong in disease. It also raises the possibility of organoids being used to treat brain injury.

Indeed, the rat models showed the neuronal defects related to one rare severe disease called Timothy Syndrome, a genetic condition that affects brain development and causes severe autism.

This is one step further along the long road to making progress in brain disease, which has proved so intransigent so far.

The research must go ahead. But at the same time, it calls for new standards to be set for future research. At present, the research raises no significant new ethical issues. However, it opens the door to more elaborate or ambitious research that could raise significant ethical issues.

Moral Status of Animals with Human Tissue

The human tissue transplanted into the rats’ brains were in a region that processes sensory information such as touch and pain.

These organoids did not increase the capacities of the rats. But as larger organoids are introduced, or organoids are introduced affecting more key areas of the brain, the rat brain may acquire more advanced consciousness, including higher rational capacities or self-consciousness.

This would raise issues of how such “enhanced” rats ought to be treated. It would be important to not treat them as rats, just because they look like rats, if their brains are significantly enhanced.

This requires discussion and boundaries set around what kinds of organoids can be implanted and what key sites would be targets for enhancement of capacities that matter to moral status.