By Nita A. Farahany, Henry T. Greely, and Charles M. Giattino
Scientists have restored and preserved some cellular activities and structures in the brains of pigs that had been decapitated for food production four hours before. The researchers saw circulation in major arteries and small blood vessels, metabolism and responsiveness to drugs at the cellular level and even spontaneous synaptic activity in neurons, among other things. The team formulated a unique solution and circulated it through the isolated brains using a network of pumps and filters called BrainEx. The solution was cell-free, did not coagulate and contained a haemoglobin-based oxygen carrier and a wide range of pharmacological agents.
The remarkable study, published in this week’s Nature1, offers the promise of an animal or even human whole-brain model in which many cellular functions are intact. At present, cells from animal and human brains can be sustained in culture for weeks, but only so much can be gleaned from isolated cells. Tissue slices can provide snapshots of local structural organization, yet they are woefully inadequate for questions about function and global connectivity, because much of the 3D structure is lost during tissue preparation2.
The work also raises a host of ethical issues. There was no evidence of any global electrical activity — the kind of higher-order brain functioning associated with consciousness. Nor was there any sign of the capacity to perceive the environment and experience sensations. Even so, because of the possibilities it opens up, the BrainEx study highlights potential limitations in the current regulations for animals used in research.
Most fundamentally, in our view, it throws into question long-standing assumptions about what makes an animal — or a human — alive.
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