Carrie Radomski

The primary purposes of cryopreserving the human body are threefold: 1. For conditions that are currently incurable, such as terminal illnesses or severe injuries (in an era of immortality, the main causes of death would be accidents like traffic collisions, making cryonics a lifesaving solution for such incidents), individuals can be cryopreserved until technology advances enough to treat them. They can then be thawed, revived, and cured. 2. For aging, which currently cannot be reversed, individuals can be cryopreserved until technology develops the capability for rejuvenation. They can then be thawed, revived, and restored to youth. 3. Astronauts can suspend their lives, undergo journeys lasting thousands of years, and be thawed upon reaching their destination planets to begin cosmic colonization and exploration. The larger the body mass, the greater the difficulty of freezing and thawing. Currently, cryopreservation and thawing technologies are fundamentally incapable of reviving a human body weighing several tens of kilograms. Even a mouse weighing just over 10 grams cannot be revived. Therefore, cryonics technology requires a disruptive innovation. Both the cooling process during freezing and the warming process during thawing produce ice crystals. These ice crystals can puncture cell membranes and damage internal cellular structures, which is the cause of biological death. Thus, how to inhibit the formation of ice crystals during cooling and warming is a critical issue determining whether cryopreserved individuals can be revived. Some have proposed using nanomachines to repair cellular damage, but this is not feasible. The repair process requires identifying the location and type of damage, which demands sufficient intelligence. However, nanomachines are too small to accommodate microcircuits. Additionally, nanomachines cannot move through dense tissues and cells filled with proteins and other substances. As for the ice crystals formed during freezing and thawing, which may damage some of the synaptic connections in neurons related to memory, could this lead to memory loss? I believe that brain memory is holographic. Every day, some neurons in our brain die while new ones are generated, and synaptic connections are deleted and regenerated. Yet, memories are not entirely erased; only unimportant memories become increasingly vague. This is similar to a holographic photograph: tearing it into pieces does not make the entire image disappear. However, the smaller the fragments, the blurrier the image becomes. Therefore, the destruction of a small portion of neurons and synaptic connections by ice crystals during freezing and thawing would not result in the loss of existing memories. As for whether to preserve the entire human body or just the head, I believe preserving the entire body is best. For those who only preserve the head, during future thawing and revival, the head would need to be transplanted onto a body cloned from the head's own cells. However, we cannot guarantee that a body cloned from one's own cells would be entirely free of immune rejection. During the process of cell division and cloning, DNA mutations occur. The immune system can trigger rejection even with the slightest mutation. Evidence for this includes: 1. The 30th amino acid in the B chain of human insulin is threonine, while in pig insulin, it is alanine. This single amino acid difference can lead to the production of antibodies and rejection when humans use pig insulin over the long term. 2. An article published in *Nature* on May 13, 2011, titled "Immunogenicity of induced pluripotent stem cells" reported that researchers from the University of California, San Diego, transplanted adult cells differentiated from reprogrammed mouse somatic cells (iPS cells) back into the source mice. Although the genetic background was identical, the mice rapidly rejected the transplanted cells. 3. Currently, transplantation of adult cells differentiated from iPS cells is limited to immune-privileged organs, such as the eyes, primarily because the immune system rejects the grafts as foreign in non-immune-privileged organs. Hibernation involves lowering body temperature and metabolic rate to enter a prolonged sleep. Hibernation requires the coordinated expression of many genes. Humans may possess genes related to hibernation. However, due to the principle of "use it or lose it" and millions of years of natural selection, the hibernation gene cluster in humans has likely mutated and degenerated. Therefore, achieving human hibernation is highly unlikely. To survive hot and dry environments, some animals enter aestivation. During aestivation, body temperature may not necessarily decrease, but the metabolic rate still drops. While human hibernation is currently unattainable, future approaches may use gene editing or plasmid transfection technologies to enable human cells to produce hibernation-related substances, thereby achieving human hibernation. Dormancy is a process in which plants and animals completely halt their metabolism. Some species of moss can remain dried for centuries and revive immediately upon contact with water. However, the human body cannot be preserved through desiccation because drying causes the brain to shrink and disrupts its three-dimensional structure. Many microorganisms and spores possess the ability to enter dormancy. The fairy shrimp (Artemia) cannot be killed by boiling or freezing, and its eggs can survive desiccation for hundreds of years. The resurrection plant (Selaginella lepidophylla) is also resistant to drying, freezing, and boiling. In the summer of 1983, I cooked mung bean soup in a thermos flask at 80–90°C for half a day. While most of the mung beans softened, a few remained hard and were called "iron mung beans" or "mung bean ghosts." I washed these uncooked beans and placed them in a warm, humid environment, rinsing them with clean water daily. After a few days, they swelled and sprouted white buds. Although they eventually rotted, the emergence of white buds indicated that they retained some vitality. If cooling occurs at a very rapid rate, ice crystals do not form, resulting in a state known as vitreous ice. However, the human body is too large. While the exterior can be cooled rapidly, the interior cannot achieve the same speed. The same applies to the warming process.