In 2019, a study published in Nature by scientists at Yale University highlighted that they had managed to revive pig brains hours after the animals had been slaughtered. The breakthrough challenged the belief that brain death is irreversible and also raised ethical concerns and raised deeper questions about what really defines death. Now a team of Chinese scientists has gone further.
Led by Xiaoshun He, a team of Chinese scientists has managed to reactivate the brain activity of pigs almost an hour after circulation ceased, thanks to the surprising participation of the liver. The results have been published in EMBO Molecular Medicine.
If it can be transferred to humans, this finding could have significant implications for expanding the critical window in which doctors can resuscitate patients after cardiac arrest. He’s team experimented on the brains of 17 Tibetan dwarf pigs to investigate how the liver might influence brain recovery.
When the heart stops, blood flow to the brain stops, leading to ischemia, oxygen and nutrient deprivation. In just a few minutes, brain cells begin to die, making resuscitation time-sensitive.
Current medical knowledge limits successful resuscitation to a very brief windowbut this new research suggests that by integrating the liver into the life support system, that window could be expanded.
In the first set of experiments, scientists subjected pigs to 30 minutes of brain ischemia, and one group also experienced liver ischemia (the deprivation of oxygen and nutrients to the liver). The group with intact liver function performed much bettershowing significantly less brain damage than those without liver support.
The key to the experiment’s success lies in incorporating the liver into a life support system known as a liver-assisted normothermic brain perfusion (NMP) machine. This system imitates natural body functionspumping fluids through the brain and aiding recovery.
When a pig liver was included in the setup, the researchers They observed that the electrical activity of the brain returned and remained up to six hours. Surprisingly, even when oxygen was deprived for up to 50 minutes, brain activity restarted and was maintained.
Without the liver’s assistance, the brains deteriorated rapidly, showing inflammation, cellular damage, and decreased electrical activity. In contrast, liver-assisted brains showed less inflammation, healthier neurons and restored brain waveswhich are critical markers of functional brain activity.
The protective effect of the liver is based on its ability to produce crucial metabolic molecules and regulate inflammation: by generating ketone bodies, the liver provides an alternative energy source for the brain during lack of oxygen. Additionally, the presence of the liver reduced harmful immune responses that often exacerbate brain injury after blood flow is restored.
He’s team also measured lower levels of the S100-β protein, a known marker of neuronal injury, in liver-assisted brains. Furthermore, genetic analysis revealed that brains with liver support exhibited more favorable conditions for recoverywith less activation of genes linked to cell death and inflammation.
The study results challenge long-held views about the brain’s vulnerability to oxygen deprivation. Traditionally, medical professionals have assumed that irreversible damage occurs after 5 to 8 minutes of ischemia. However, with liver-assisted resuscitation, brain function was restored even after 50 to 60 minutes without blood flow.
This advance could one day lead to the development of liver support systems specifically designed to protect the brain during and after cardiac arrest. Although The heart and brain have always been the focal points of resuscitation effortsthis research highlights the critical role of the liver in ensuring better outcomes for patients.