Reviving cells in a pig’s brain could change medicine
It’s 2019, and scientists can now revive brain cells in a decapitated pig hours after death. While the pig brains did not come close to regaining consciousness, scientists noted metabolic activity in some cells, raising a host of ethical, religious and philosophical questions about life and death.
It’s easy to overlook our underlying ignorance about how the brain produces consciousness with the blockbuster research published this week in the journal Nature. Still, this study could lead us to that seminal moment of the human brain understanding itself. Most importantly, this work could supercharge research into better repairing our most complex organ.
While the Yale researchers who authored the publication made a huge leap forward in medical neuroscience, the work doesn’t move us much closer towards the first brain transplant. Suspending a conscious brain in a vat of solution also remains the stuff of science fiction for now.
Regardless, the experiment marks an important scientific achievement. The researchers retrieved pig heads severed at the neck from a food processing facility, surgically removed the brains and connected some of the arteries to a device they dubbed BrainEx, a contraption cobbled together from commercially available parts made by 15 different companies. One researcher told me the lab, filled with the wily array of tubing, pumps, analyzers, reservoirs and dialysis membranes “looks like the junk closet in an oft-repaired spaceship.”
BrainEx then pumped the brain with the artificial blood product Hemopure, a processed hemoglobin manufactured from cow’s blood, which is key to the project’s success. Given that Hemopure is used during transplants to keep organs alive longer, it makes sense that it was used to revive the cells in brains that had been without blood and at room temperature for four hours.
The fact that some people managed to survive hypothermia so severe that their hearts stopped beating probably gave researchers hope that their feat with BrainEx could work. But BrainEx’s big advance actually isn’t in reviving dead tissue — it’s long been known that we can see cellular function in tissues well after the host organism has died, and scientists have even done this with human brain tissue.
What BrainEx offers is the possibility of keeping much of the brain alive separate from the body. This represents a new research model for experimental work on a whole array of brain injuries, not just the kind where the heart stops. By isolating the brain and hooking it up to BrainEx, scientists could potentially add various medications to the artificial blood stream to see how they work, and experiment with different repairing procedures on a living brain without dealing with the rest of the body.
While the BrainEx technique raises questions about the blurred line between life and death, we’re still a long ways off from seeing the practical applications of the study play out in hospitals around the country. In conducting the BrainEx study, scientists inflicted serious damage to the brain it was keeping alive — they tied off all of the major arteries feeding the brain and brainstem save two major ones. In practice, this would cause numerous strokes, especially to the brainstem, which is in charge of directing all of the brain’s output and input.
And while the scientists showed that they were able to pump the artificial blood through the brain’s arteries, many tiny blood vessels called capillaries remained closed off. The study presented the data in a bar graph without specifying the exact numbers, but it appears about 10% of capillaries didn’t open up. A brain with 10% of its capillaries suddenly closed would be terribly dysfunctional, with widely distributed brain cell death.
Proving individual cells can perform basic metabolic functions, or send a neural impulse when stimulated, is quite far from activating the complex networks that somehow generate conscious awareness, a process we still do not fully understand. A considerably more advanced technique producing far less brain damage would likely be necessary to see the alpha and beta electroencephalography waves we associate with consciousness.
Looking at the possibility of a brain transplant, we currently have no means of connecting a brain to the spinal cord, or the brainstem to the head and neck nerves. A stroke at the brainstem can leave a patient temporarily or permanently with no control of the body and only limited eye movement. Brain transplant results would be far worse: no feeling, hearing, or sight, and with no tenable means for communicating with the outside world. The results of such a procedure, which no scientific review board would approve, would be even more horrific than what the Italian “head transplant” surgeon claims he wants to do one day.
The body isn’t a machine, and death isn’t flipping a switch. Biomedical scientists know this intellectually, but law and society do not understand this medical fact very well. Despite our current scientific limitations, it’s not too early to consider the ethics of reviving consciousness in a disembodied brain, and question whether brain transplants should ever be allowed. In an accompanying Nature article, two bioethicists worry about what a brain life support system might mean for people awaiting organ transplants. Could death become such a blurry issue that families aren’t willing to part with their loved one’s remaining organs while they wait to see whether the brain might be revived? I suspect that by the time we are dealing with this dilemma, we’ll have lab grown artificial livers, hearts and kidneys to fill such a void.
The future is coming, with technologies that can be used for good or ill, but this study deserves more celebration than consternation. Better treatments for strokes, anoxic or traumatic brain injuries, and more, are closer at hand with this new research tool.