Cryopreservation is the process of freezing living tissues at extremely low temperatures for preservation. Properly preserved tissues can be revived without damage and function as they did in their original state. Cells can be stored in special deep freezers for short periods, but long-term storage requires liquid nitrogen, which can reach a temperature of 346 degrees Fahrenheit below zero. Cryopreservation already has several medical uses, and its potential increases with each new discovery in the cryonics field.
History
Biological cryopreservation began by accident in 1948. Scientists mislabeled a container of freezing agent containing avian sperm. The agent, glycerol, successfully preserved the sperm even at extremely low temperatures. When they discovered the mistake, the science of cryobiology developed. Seeing the implications for human fertilization, scientists improved the process and in 1978, the first in vitro fertilization, or IVF, baby was born. Cryopreservation allows embryos to be stored for several years.
Applications
Currently, the primary use of cryopreservation in humans is for fertility purposes. Young males who must undergo treatments or surgeries that may damage their ability to reproduce can choose to have their sperm cryogenically frozen. For example, the cryopreservation company Planer reports that a couple conceived a child with sperm that had been frozen for 21 years.
In another case, a couple produced viable embryos through in vitro fertilization. One of the implanted embryos produced a child in 1989. Years later, the mother was implanted with another embryo from the same batch that had been frozen for 16 years, producing a child born in 2005.
Risk Management
One risk of freezing cells is cellular damage due to ice crystal formation or dehydration. Cryopreservation scientists have found ways to minimize and even eliminate much of the risk by replacing the water found in cells with a different substance. This substance, usually glycerol or dimethyl sulfoxide, essentially acts as an antifreeze agent.
Potential
Cryopreservation can be used to store several types of tissue. The most common include blood, stem cells, semen, eggs, embryos and bone marrow. Scientists are currently working toward the goal of cryopreservation of organs for human transplants. Some success has been reported in the cryopreservation of mammalian organs. For example, a 2004 issue of "Cryobiology" reported that frozen rat ovaries were thawed and transplanted in a rat that subsequently gave birth.
Full-Body Preservation
For now, the revival of cryogenically frozen humans is relegated to the realm of science fiction. The Cryonics Institute and Alcor Life Extension Foundation, however, offer full-body and head-only freezing services. The bodies or heads are frozen through a special process as soon as possible after death to stop tissue decay. The hope is that future scientific advances will make revival possible.
References
- Purdue University: Cryopreservation of Cyanobacteria
- Genetics and IVF Institute: Human Embryo Cryopreservation (Embryo Freezing) and Frozen Embryo Transer Cycles
- Planer: Child Born After 21 Year Semen Storage Using Planer Controlled Rate Freezer
- "Cryobiology"; Cryopreservation of Organs by Vitrification; Gregory M. Fahy et al; February 2004
- Stranger than Fiction: Cryonics, Cryogenics --- Death in the Deep Freeze
