The brain cells of dead pigs have been “reactivated”. But what does it mean?

The brain cells of dead pigs have been
We are in the week of Easter, it is true, but the scientific news that has been around the world in the last few hours has nothing to do with the resurrection of living beings. No scientist, let alone Nature in his scientific publication, spoke of bringing a dead animal back to life. Instead, it was the restoration of the cerebral circulation and some functions at the molecular and cellular level in the explanted brains of some pigs destined for slaughter.
What exactly was done?
Scientists from Yale University (Connecticut, United States) led by neuroscientist Nedan Sestan conducted an experiment on 32 pig brains. Four hours after the killing, the brains were treated with an instrument called BrainEx, which pumped an artificial blood substitute called B-Ex perfusate into the cerebral blood vessels.
This solution, which includes protective substances, stabilizing substances and contrast agents, led to the restoration of few (but significant) functions at the cellular and circulatory level after six hours, keeping them active for about a day and a half.
The effect of the treatment, therefore, was the marked slowing down of the processes of cell death and tissue degradation, to which was added the appearance of some synapses, reflecting how the individual neurons had been successfully reactivated. To reinforce the result is the evidence that oxygen and glucose have been consumed, demonstrating that metabolic activity has also been restored. The two main novelties, as the researchers themselves explained, are the execution of the whole experiment at room temperature (instead of in cryogenic conditions) and the use of a very large animal brain, however with several analogies with the human one.
The recovery of activity even after hours from the circulatory block, as well as the continuing activity for over a day, surprised the scientists. Until now it was believed, in fact, that this reactivation – although very partial – was impossible to obtain.

What this result is for, in practice
The applications of the discovery are many, but they do not include bringing a dead animal back to life. A first example of development is the possibility to deepen the knowledge of the brain taking advantage of a longer time for the post mortem study. Added to this is the possibility of experimenting with new explants and drugs on an explanted brain ( ex vivo), guaranteeing a much more realistic test case than has been possible so far. Finally, systems could be developed to contain or mitigate brain damage due to trauma, disease or surgery.

It goes without saying that, as is repeated over and over again in many fields of research, these are not applications that we will see from tomorrow morning, but that will progressively enter into the standard of research centers from now on. Among the most interesting fields of study are in particular Alzheimer’s disease, Parkinson’s, strokes and brain tumors.

The idea is precisely to transform these brains at the disposal of researchers in (semi) living laboratories composed of living cells and blood flows similar to those of a perfectly functioning brain.

Among the next objectives of the study, there is above all the prolongation of brain maintenance time, which is associated with the need to replace the artificial blood used so far with fluid more similar to the true animal blood. Finally, the hope of those who conducted the study is that with the optimization of the process it is possible to obtain an even wider reactivation, which includes other brain functions.

Why can’t we say that pigs have been revived?

Any reference to the idea that pigs have been brought back to life, revived or resurrected would mean misrepresenting the meaning of research. The recorded electrical activity, in fact, concerns the single neurons, which have been able to create synapses and therefore send and receive electrical signals. What has not been observed, however, is the reactivation of global electrical activity. With a somewhat risky comparison, one could say that the single musical instruments of the orchestra have resumed producing notes, but have not coordinated their sounds in something harmonious and catchy.

In other words, the brain electroencephalogram has always been flat. It is not possible, therefore, that in the experiments conducted so far something has been activated that has to do with sensory perception, with consciousness, with memory, with pain or with any other higher-order function. Also because, as the researchers’ goal was certainly not to resurrect a corpse, the cerebral cortex(site of complex mental and cognitive functions) was removed before starting brain reactivation. What has been achieved is, therefore, to keep single cells and tissues alive, but not the organ as a whole or even something that can be considered a living being.

Small journalistic exaggerations
As it was easy to foresee, in some cases the enthusiasm for the result of the research led to a magnification of the conclusions, arriving at some modest jarring. The interest in the subject by many newspapers is due to the presence in the team of Yale University of an Italian researcher, Francesca Talpo of the University of Pavia.

The first to generate a certain ambiguity was the title of the popular explanation article published by the same Nature together with the paper. The choice to speak from the title of “living brains”, in fact, although understandable has given rise to some misunderstanding.

History and ethics
Of course the news, which in the latest issue of Nature deserved the cover, brings with it a large number of legal and moral implications. From the border between life and death, to the ethical perimeter within which to contain animal experimentation, up to the limit in which it will be possible to arrive at experiments on human brains, the questions are numerous and complex. However, this is not a novelty for the scientific community, which has long wondered about these issues. The news that these studies, in particular, were in progress was also circulated already in April of last year when Sestan himself had publicly told the experimental technique  at a specialist conference.

Let’s make it clear, however, that for the time being, we are still far from the applications on human beings, so for now the ethical questions concern exclusively animals. If even for pigs it is conceivable to bring a specimen back to life after death, in the case of people today it is not even possible to replicate an experiment like the one told in Nature. One of the keys to success, in fact, was that the brains of the pigs were in excellent condition before their death, and that place and time of death had been established at the table based on slaughter time, in order to optimize all technical and logistic operations. It goes without saying that it is unthinkable to replicate this organization in the case of human beings. And no serious scientist is thinking about the possibility of performing a brain transplant.

Reasoning in the long term, however, all the issues mentioned deserve extreme attention, both from a moral and a normative point of view. What would happen, for example, if the brain activity of the ex vivo brain was reactivated also at a global level, ie if the electroencephalogram was no longer flat? Can we accept, for research purposes, the reactivation of higher functions in brains belonging to dead bodies? Will similar experiments be conducted on human beings? The debate is very open.