Cryopreservation involves preserving biological materials at extremely low temperatures, typically around -196°C, using liquid nitrogen. This halts biological activity and degradation, maintaining cell and tissue integrity. The public has long been fascinated by the concept of cryopreservation, particularly the idea of preserving humans for potential future revival. This raises a fundamental question about whether such preservation “works” in a way that allows for a return to life.
The Science of Cryopreservation
Cryopreservation reduces biological activity by lowering temperature to ultra-cold states. At these temperatures, cellular metabolism ceases. A primary challenge is preventing ice crystal formation, which damages cell membranes and structures.
To mitigate this, cryoprotectants are introduced. These are chemical compounds, such as glycerol or dimethyl sulfoxide (DMSO), that penetrate cells and lower the freezing point of water. They replace water molecules within cells, preventing damaging ice formation. This allows the biological material to solidify into a glassy, amorphous state known as vitrification, rather than freezing with ice crystals. Vitrification avoids mechanical injury from ice, a major benefit for cell preservation.
Current State of Human Cryopreservation
While cryopreservation has advanced for individual cells and some tissues, its application to whole human bodies remains speculative regarding revival. It is routinely used to store biological materials, including sperm, eggs, embryos, and blood cells. These simpler structures can be cryopreserved and later revived with high viability.
However, preserving and successfully reviving complex organs, let alone an entire human body, is not currently possible. Bodies can be preserved at cryogenic temperatures after legal death, but revival technology does not yet exist. The process aims to maintain cellular integrity, hoping future medical advancements enable revival. Despite success vitrifying and reviving a rabbit kidney that regained function, and a rabbit brain maintaining structural integrity, these breakthroughs have not translated to whole human bodies.
Major Hurdles to Revival
Scientific and technical obstacles prevent the successful revival of cryopreserved humans. One major hurdle is cryoprotectant toxicity. While essential for preventing ice formation, the high concentrations required for vitrification in large biological systems can be damaging to cells and tissues. Researchers are working to develop less toxic cryoprotectant mixtures.
Another challenge is the rewarming process. Achieving uniform rewarming of a large, complex structure like a human body without thermal stress or ice recrystallization is extremely difficult. Uneven rewarming can lead to new ice crystal formation and cellular damage. Furthermore, even with successful vitrification, there is concern about the preservation of delicate neural connections in the brain that encode memories and identity, as these can be vulnerable to molecular damage during the process.
Ethical and Societal Implications
Human cryopreservation raises ethical and societal questions beyond scientific feasibility. One consideration is the legal and moral status of a cryopreserved individual, legally deceased but preserved with intent of future life. This creates ambiguities regarding identity and personhood.
Future societal integration also presents complex issues, such as individuals waking up in a vastly different world. Concerns also exist about resource allocation, with critics questioning if significant financial investment in cryopreservation could be better utilized for current medical needs. The practice sparks philosophical debates about life, death, and the implications of extending human existence indefinitely.