Since time immemorial, humanity has always pondered the subject of life and death. While the concept of life beyond death remains a moot point, with no substantial proof, in general life and death are considered antithetical. Death is viewed as the complete cessation of life. However, a new study now suggests that life and death may not be polar opposites.
Neither Life Nor Death?
A group of biologists looking into the potential for repurposing cells have proposed that there might be a “third state,” which defies the traditional definitions of life and death. Scientists typically view death as the irreversible cessation of an organism’s overall functioning. Nonetheless, actions like organ donation demonstrate how tissues, organs, and cells can carry on indefinitely after an organism passes away. This toughness begs the question: What systems enable some cells to continue functioning even after an organism has perished?
In a piece featured in The Conversation, biologists Peter Noble and Alex Pozhitkov explored how the advent of new multicellular entities has enabled us to transcend the conventional limits of life and death. Noble and Pozhitkov investigate the processes that occur within organisms post-mortem, and since successful organ transplants have demonstrated that cells can persist in function after death, they have delved deeper into the processes that make this possible.
Their research revealed that skin cells taken from deceased frog embryos could adjust to the conditions of a laboratory petri dish, spontaneously. forming new multicellular structures known as xenobots. These xenobots displayed behaviors that go well beyond their original biological functions. Notably, these entities use their cilia—tiny, hair-like projections—to navigate and move through their environment, whereas, in a living frog embryo, cilia are generally used to propel mucus.
Xenobots possess the unique ability to undergo kinematic self-replication, meaning they can duplicate their physical form and functions without undergoing traditional growth. This process is distinct from more familiar replication methods, which involve the organism growing either within itself or on its surface.
Additionally, studies have shown that individual human lung cells can spontaneously assemble into tiny, multicellular entities capable of movement. These anthrobots exhibit novel behaviors and structures. They can not only maneuver through their environment but also repair themselves and fix nearby damaged neuron cells.
Overall, these discoveries highlight the remarkable adaptability of cellular systems and challenge the notion that cells and organisms evolve in only predetermined ways. The concept of a third state suggests that the process of organismal death may significantly influence how life evolves over time.
Can Life Sustain Post-Mortem?
The ability of cells and tissues to survive and function after the death of an organism is influenced by several factors, including environmental conditions, metabolic activity, and preservation methods.
Different types of cells exhibit varying survival durations. For instance, in humans, white blood cells typically perish within 60 to 86 hours after death. In contrast, skeletal muscle cells in mice can be regenerated up to 14 days postmortem, while fibroblast cells from sheep and goats can be cultured for approximately a month after death.
Metabolic activity is crucial in determining whether cells can persist and remain functional. Cells that need a constant and significant energy supply to perform their functions are more challenging to culture than those with lower energy demands. Techniques like cryopreservation can help tissue samples, such as bone marrow, maintain functionality similar to that of living donors.
Inherent survival mechanisms are also critical for the continued viability of cells and tissues. Researchers have noted a marked increase in the activity of genes related to stress and immunity after death, likely as a response to the loss of homeostasis. Additionally, factors such as trauma, infection, and the duration of time since death have a significant impact on the viability of tissues and cells.
Variables like age, health, gender, and species type also influence the conditions following death. This is particularly evident in the difficulties associated with culturing and transplanting metabolically active islet cells—cells responsible for insulin production in the pancreas—from donors to recipients. Scientists suspect that factors such as autoimmune responses, substantial energy demands, and the breakdown of protective mechanisms may contribute to the frequent failures of islet transplants.
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