A group of researchers succeeded in reestablishing certain neuronal functions in the brains of pigs who had died a few hours ago, a landmark worthy of science fiction, but does not prove that resurrection is possible. The study published Wednesday in the journal Nature indicates that in the brains studied there was no "no electrical activity that would imply a phenomenon of consciousness or perception."
"They are not living brains, but brains whose cells are active," says one of the study's authors, Nenad Sestan. According to this researcher at Yale University, these studies demonstrate that "we underestimate the brain's ability to restore cellularity." In addition, they suggest that deterioration of neurons as a consequence of "disruption of blood flow could be a long-lasting process," according to a statement from Nature. The brains of mammals are very sensitive to the decrease of oxygen provided by the blood. Therefore, when the flow stops, the brain stops being oxygenated and the damage is irreparable.
The researchers used 32 brains of dead pigs four hours ago. Thanks to a pumping system named BrainEx, they were irrigated for six hours with a solution at a temperature equivalent to that of the body (37 degrees). This solution, a blood substitute, is designed to oxygenate tissues and protect them from the degradation derived from disruption of blood flow. The results were surprising: decreased destruction of brain cells, preservation of circulatory functions, and even restoration of synaptic activity (electrical or chemical signals in the contact zone between neurons).
According to the researchers, the study could allow a better understanding of the brain, studying how it degrades "post mortem". It would also pave the way for future techniques to preserve the brain after a heart attack, for example. Theoretically, in the long run, it could serve to resuscitate a dead brain, something impossible for now.
Dead or alive?
"The immediate challenges that these results imply are mainly ethical," says Professor David Menon, of the University of Cambrigde, who did not participate in the study. The study reopens the question of "what causes an animal or a man to be alive," say other scientists in a parallel study published in Nature.
According to Nita Farahany, Henry Greely and Charles Giattino, respectively Professor of Philosophy and Neuroscience experts, "This study used brains from pigs that had not received oxygen, glucose or other nutrients for four hours.
The study could call into question two scientific principles, according to these experts. "First, the fact that neuronal activity and consciousness stops definitely after seconds or minutes of disruption of blood flow in the mammalian brain." "Second, the fact that unless the blood circulation is rapidly restored, an irreversible process that leads to the death of the cells and then to that of the organ is activated," they say.
These three experts urge to establish "directives on the scientific and ethical issues that this study raises."
In another review published by Nature, bioethics experts point out that the development of the BrainEx technique could in the long run hinder organ donation. For transplants, most organs are extracted from donors in a state of brain death. If it is considered that this state is reversible, what will happen to the donation?
The trio Farahany, Greely and Giattino cite a phrase from the 1987 American film "The Princess Bride": "There is a small difference between being almost dead and completely dead … Almost dead, you are still a little alive" , says a healer in the film.