In this article, one of the scientists involved in our rejuvenation research community outlines a very reasonable view on cryonics and cryopreservation. Cryonics is the low-temperature preservation of at least the brain following death, done these days with the use of cryoprotectants and vitrifiction to minimize ice crystal formation. It offers an unknown chance at a future restoration to life: technology marches onwards year after year, and for so long as the structures that encode the data of the mind are preserved, there is the possibility of living again in a future age that has mastered the technologies needed for restoration. This would include, at a minimum, comprehensive control over cellular biology and some form of advanced molecular nanotechnology. Even in our present era, there is considerable interest in developing reversible vitrification for organ storage, to ease the logistics of tissue engineering and organ donation and transplantation, and early proof of concept experiments have taken place in that field. The types of technology that would be needed to restore a preserved cryonics patient can be envisaged by extrapolation from present efforts in that field and in the work being carried out on rejuvenation therapies.
A teenager who tragically died of cancer recently has become the latest among a tiny but growing number of people to be cryogenically frozen after death. These individuals were hoping that advances in science will one day allow them to be woken up and cured of the conditions that killed them. But how likely is it that such a day will ever come? Nature has shown us that it is possible to cryopreserve animals like reptiles, amphibians, worms and insects. Nematode worms trained to recognise certain smells retain this memory after being frozen. The wood frog (Rana sylvatica) freezes during winter into a block of ice and hops around the following spring. However, in human tissue each freeze-thaw process causes significant damage. Understanding and minimising this damage is one of the aims of cryobiology.
At the cellular level, these damages are still poorly understood, but can be controlled. Each innovation in the field relies on two aspects: improving preservation during freezing and advancing recovery after thawing. During freezing, damage can be avoided by carefully modulating temperatures and by relying on various types of cryoprotectants. One of the main objectives is to inhibit ice formation which can destroy cells and tissues by displacing and rupturing them. For that reason, a smooth transition to a "glassy stage" (vitrification) by rapid cooling, rather than "freezing", is the aim. Reviving whole bodies also poses its own challenges as organs need to commence function homogeneously. The challenges of restoring the flow of blood to organs and tissues are already well-known in emergency medicine. But it is perhaps encouraging that cooling itself does not only have negative effects - it can actually mitigate trauma. In fact, drowning victims who have been revived seem to have been protected by the cold water - something that has led to longstanding research into using low-temperature approaches during surgery.
The pacemakers of scientific innovation in cryobiology are both medical and economic. Many advances in cell preservation are driven by the infertility sector and an emerging regenerative medicine sector. Cryopreserved and vitrified cells and simple tissues (eggs, sperm, bone marrow, stem cells, cornea, skin) are already regularly thawed and transplanted. Work has also started on cryopreservation of "simple" body parts such as fingers and legs. Some complex organs (kidney, liver, intestines) have been cryopreserved, thawed, and successfully re-transplanted into an animal. While transplantation of human organs currently relies on chilled, not frozen, organs, there is a strengthening case for developing cryopreservation of whole organs for therapeutic purposes.
But there's another huge hurdle for cryonics: to not only repair the damage incurred due to the freezing process but also to reverse the damage that led to death - and in such a manner that the individual resumes conscious existence. So will it one day be possible to cryopreserve a human brain in such a manner that it can be revived intact? Success will depend on the quality of the cryopreservation as well as the quality of the revival technology. Where the former is flawed, as it would be with current technologies, the demands on the latter increase. This has led to the suggestion that effective repair must inevitably rely on highly advanced nanotechnology - a field once considered science fiction. The idea is that tiny, artificial molecular machines could one day repair all sorts of damage to our cells and tissues caused by cryonics extremely quickly, making revival possible. Given the rapid advances in this field, it may seem hasty to dismiss the entire scientific aim behind cryonics.