In our Study of the Day feature series, we highlight a research publication related to a John Templeton Foundation-supported project, connecting the fascinating and unique research we fund to important conversations happening around the world.
When an organism dies, it almost never dies all at once. Living cells tend to stay living, and under the right circumstances can persist for a very long time. So what does the experience of organismal death look like, from the perspective of an individual cell? Does the cell receive and respond to stress signals that something is deeply awry? Does it run off the rails, engage in a flurry of futile last-ditch attempts at self-preservation, attempt to strike off on its own in a solo existence, or simply keep plugging along obliviously until it shuts down or is subsumed by decay?
Recently a group of scientists gathered at the National Institutes of Health in Bethesda, Md. for a two-day workshop to share ideas and discoveries around key open questions (both biological and philosophical) that arise around the so-called “twilight of death.” They identified a list of pertinent questions — ranging from What are the underlying mechanisms of slow (prolonged) and fast (traumatic) death? to What is death of a multicellular organism when some of its individual cells are still alive? — and discussed how their own research and others’ recent findings might offer answers, or hint at further mysteries to be investigated.
Cellular life after bodily death
Recent research has shown that some cells in recently dead organisms may be more genetically active than those in living ones. As the report from the workshop put it, “the demise of vertebrates is much more complicated than originally envisioned, as controlled experiments showed that thousands of transcripts significantly increased in abundance several hours/days postmortem relative to live samples.” Studies of dying Catholic nuns have shown that pre-mortem fever, infection and unconsciousness are associated with changes in gene expression regulating the brain’s immune response system, even after death.
Other work shows that, in certain cases, the death of a host organism can liberate individual cells to strike out on their own, at least for a little while. One participant in the workshop, Michael Levin of Tufts University, has been examining such cellular dispersions. His team has found that frog embryo cells, when separated, can do surprising things: “These cells re-assemble, utilize cilia for movement, repair damage, interact with their environment, and display spontaneous behavior while repurposing some of their original functions.”
Organ transplantation offers a more familiar example of keeping parts of an organism alive indefinitely; open questions remain about which types of cells can remain viable post-mortem, and for how long. Erik J. Woods, co-founder of Ossium Health, shared his company’s advances in harvesting and cryogenically preserving bone marrow cells from cadavers to be banked for stem cell transplants for patients with blood diseases.
Our cells can live beyond what is typically thought of the moment of death — but what about our sense of self? The workshop discussed recent studies that suggest that aspects of consciousness may be retained far longer after the human brain loses its oxygen supply, with delta, alpha and theta waves detected for up to 80 minutes — well beyond the usual 5-to-10 minute threshold for declaring “brain death.” Cardiac arrest survivors often report memories suggestive of consciousness during the state of clinical death, and researchers have been able to stimulate circulation and cellular activity (although not signs of consciousness) in pigs’ brains four hours after death
What Remains
Even when decay truly sets in, the twilight of life continues, as many of the cells from an organism’s microbiome consume their former host. It’s a process that tends to follow a predictable pattern — in humans, for some reason, the prostate and uterus are the last internal organs to decay. As the workshop participants noted, it may be a result of an evolutionary optimization to facilitate decomposition or influence ecological interactions — the twilight of one form of life giving way to the dawn of others. As Walt Whitman put it, “Behold this compost! behold it well! / Perhaps every mite has once form’d part of a sick person—Yet behold! / The grass of spring covers the prairies.”
Still Curious?
Read “Unraveling the Enigma of Organismal Death: Insights, Implications, and Frontiers”
Learn more about xenobots and anthrobots, the artificial living organisms created with post-death cells in Michael Levin’s lab at Tufts.
