Life and death are commonly considered contrasting concepts. Nonetheless, the appearance of novel multicellular life forms from the cells of a deceased organism presents a " third state that exists beyond the conventional limits of life and death.
Generally, scientists view death as the permanent cessation of the operation of an organism Overall, though, procedures like organ donation demonstrate that organs, tissues, and cells can still operate effectively following an organism's death. This durability prompts the inquiry: What processes enable specific cells to remain functional post-mortem?
We are researchers who investigate what happens within organisms after they die . In our recently published review We explain how specific cells—when supplied with nourishment, oxygen, bioelectric signals, or chemical instructions—are capable of transform into multicellular organisms including new features post-mortem.
Existence, demise, and the arising of anew
The third state poses a challenge to the conventional understanding of cellular behavior among scientists. Although we are well acquainted with developmental changes such as those seen when caterpillars transform into butterflies or tadpoles turn into frogs, there are limited examples of organisms altering themselves in non-predestined manners. Tumors provide an example of this uncommon transformation. organoids , and cell lines capable of dividing endlessly in a Petri dish, such as HeLa cells , are not regarded as part of the third state since they do not acquire new functionalities.
Nevertheless, scientists discovered that skin cells taken from dead Xenopus laevis embryos were capable of adapting to the new environment within a laboratory petri dish, where they self-organized into multicellular structures. called xenobots These creatures displayed actions that go well beyond what would be expected from their initial biological functions. Notably, these xenobots utilize their cilia—tiny, hair-like projections—to explore and travel within their environment; however, in a developing frog embryo, cilia generally serve to circulate fluid.
Xenobots can also carry out kinematic self-replication This means they can duplicate their structure and functionality without increasing in size. Unlike many typical replication methods which include expansion inside or on the organism’s body.
Scientists have discovered that individual human lung cells are capable of spontaneously organizing themselves into small, multi-cellular structures that can navigate through their environment. These anthrobots They behave and are organized differently now. Not only can they move around their environment, but they can also fix themselves as well as mend damaged neuron cells nearby.
These discoveries collectively highlight the flexible nature of cellular systems and contradict the notion that evolution in cells and organisms occurs solely through predefined pathways. This third state implies that the process of an organism’s death might be crucial in understanding how life evolves over time.
Postmortem conditions
Several factors influence Whether specific cells and tissues remain viable and functional following an organism’s death depends on various factors such as environmental circumstances, levels of metabolism, and methods used for preservation.
Various cell types exhibit different lifespans. For instance, in humans, white blood cells expire within 60 to 86 hours following biological demise. In mice, skeletal muscle cells can be regrown after 14 days postmortem, while fibroblast cells from sheep and goats can be cultivated up to about a month after death.
Metabolic activity is crucial for the ongoing survival and functionality of cells. Active cells Those requiring an ongoing and significant amount of energy to sustain their functions are harder to cultivate compared to cells needing less energy. Preservation methods for these challenging cultures also pose additional difficulties. such as cryopreservation Can permit tissue samples like bone marrow to operate akin to living donor sources.
Inherent survival mechanisms Additionally, they play a crucial part in determining cell and tissue survival. For instance, scientists have noted a substantial rise in the activity level of genes linked to stress and genes associated with immunity following an organism's demise, potentially aimed at offsetting the reduction in homeostasis Furthermore, elements like trauma , infection , and the time elapsed since death substantially impact the health and survival of tissues and cells.
Elements like age, health, gender, and kind of organism also influence the postmortem environment. This becomes apparent in the difficulty associated with cultivating and transferring tissues. metabolically active islet cells , which produces insulin in the pancreas, from donors to recipients. Researchers think that autoimmune responses, high energy demands, and the deterioration of protective mechanisms might be responsible for many islet transplantation failures.
The way these factors interact to enable specific cells to keep operating following an organism’s death is not well understood. A proposed idea is that particular channels and pumps within the cell's exterior membranes might play a role in this process. intricate electrical circuits These channels and pumps create electrical impulses enabling cells to interact with one another and carry out particular tasks like proliferation and migration, thus contributing to the architecture of the organism they compose.
The degree to which various cell types can transform following their demise remains unclear. Past studies have identified certain genes associated with stress, immunity, and more. epigenetic regulation are activated after death in mice, zebrafish , and people , suggesting widespread potential for transformation among diverse cell types.
Implications for biology and medicine
Not only does the third state provide fresh perspectives on cell adaptability, but it also opens up possibilities for developing novel therapies.
For example, anthrobots could be sourced from an individual’s living tissue to deliver drugs without triggering an unwanted immune response. Engineered anthrobots injected into the body could potentially dissolve arterial plaque in atherosclerosis patients and remove excess mucus in cystic fibrosis patients.
Significantly, these multicellular organisms possess a limited lifespan, deteriorating over time as expected. four to six weeks This "kill switch" stops the development of possibly invasive cells.
Enhanced comprehension of how certain cells persist and transform into multicellular structures even after an organism has died could potentially advance personalized and preventative medical practices.
The article was initially posted on The Conversation by Peter A Noble from the University of Washington and Alex Pozhitkov from the Irell & Manella Graduate School of Biological Sciences at City of Hope. Read the original article here .
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