But it’s not just the individual cells we have to worry about. In a frozen state, tissues are generally biologically stable. Biochemical reactions, including degeneration, are slowed at ultra-low temperatures to a point where they are effectively halted. Nonetheless, there is a risk that frozen structures can experience physical disruption, such as hairline cracks. Then, upon thawing, temperature fluctuation causes a series of problems. Tissues and cells can be damaged at this state. But it also has an effect on our overall “epigenetics” – how environmental factors and lifestyle choices influence our genes – by causing epigenetic reprogramming. However, antioxidants and other substances can help aid post-thaw recovery and prevent damage.
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.