lunes, 23 de abril de 2018

BioEdge: Human brain organoids flourish in the heads of mice

BioEdge: Human brain organoids flourish in the heads of mice

Bioedge

Human brain organoids flourish in the heads of mice
     
Human brain tissue integrates and thrives in the brains of mice, according to a report in Nature Biotechnology. Using brain organoids created from human pluripotent stem cells, scientists transplanted them into mice. The organoids developed blood vessels within 5 days; by 90 days after implantation, axons had extended deep into the brains of the mice. The neurons were firing in synchronised patterns, suggesting that an active neural network had been established.

The integration of human brain cells into the brains of mice obviously raises delicate ethical questions about the creation of interspecies chimeras. However, the scientists tested the mice and found no difference in their intelligence.

“It brings up some pretty interesting questions about what allows us, ethically, to do research on mice in the first place — namely, that they’re not human,” Josephine Johnston, a bioethicist at The Hastings Center, commented last year. “If we give them human cerebral organoids, what does that do to their intelligence, their level of consciousness, even their species identity?”

If this line of research succeeds, the organoids could be very useful in studying brain diseases and could even be used to repair damage cause by traumatic brain injuries, strokes, and other neurological conditions.
Bioedge

“Personhood” is a concept that is of great relevance to a range of bioethics debates. These include embryo research, abortion, the withdrawal and withholding of treatment, and euthanasia. Ironically, conservative bioethicists argue for a liberal definition of personhood, while liberal bioethicists tend to defend a more restrictive account of who classifies as a person. The former suggest that personhood pertains to a radical capacity for conscious activity, and all human beings, regardless of whether they have actualised this capacity or not, are persons.

The latter argue that the unborn and the radically incapacitated do not have a capacity for conscious self-awareness, and do not count as persons.

Yet the way in which we define personhood has a relevance that goes beyond debates about human beings. It also has significant bearing on debates about animal rights.

Some bioethicists argue that certain non-human animals, such as chimpanzees, should be recognised as “persons”. NYU animal studies professor Jeff Sebo, for example, says that chimps have many of the traits – self-recognition, use of language, friendships and the pursuit of goals – that we take to be constitutive of personhood. As such, we should include them in our definition of personhood. Sebo has championed a protracted legal campaign in New York State to have two chimpanzees, Kiko and Tommy, recognised as persons.

Here’s what Sebo had to say in a recent New York Times op-ed:

Sometimes when we are overwhelmed by the complexity of an issue, it can help to start by stating a simple truth and going from there. In this case, the simple truth is that Kiko and Tommy are not mere things. Whatever else we say about the nature and limits of moral and legal personhood, we should be willing to say at least that. The only alternative is to continue to accept an arbitrary and exclusionary view about what it takes to merit moral and legal recognition. Kiko and Tommy deserve better than that, and so do the rest of us.
I wonder if these two different debates – the limits of human personhood and the scope of animal personhood – have implications for each other. Perhaps those who defend the rights of the unborn and severely incapacitated humans must also acknowledge the need to afford greater legal recognition to intelligent non-human animals. And perhaps those who advocate for a definition of personhood that includes intelligent animals should also include those at the margins of human life.

XAVIER SYMONS 
Deputy Editor


 
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