Cryobiology is the branch of biology that studies the effects of low temperatures on living things within Earth's cryosphere or in science.
At least six major areas of cryobiology can be identified: 1) study of cold-adaptation of microorganisms, plants (cold hardiness), and animals, both invertebrates and vertebrates (including hibernation), 2) cryopreservation of cells, tissues, gametes, and embryos of animal and human origin for (medical) purposes of long-term storage by cooling to temperatures below the freezing point of water.
This usually requires the addition of substances which protect the cells during freezing and thawing (cryoprotectants), 3) preservation of organs under hypothermic conditions for transplantation, 4) lyophilization (freeze-drying) of pharmaceuticals, 5) cryosurgery, a (minimally) invasive approach for the destruction of unhealthy tissue using cryogenic gases/fluids, and 6) physics of supercooling, ice nucleation/growth and mechanical engineering aspects of heat transfer during cooling and warming, as applied to biological systems.
Most living organisms accumulate cryoprotectants such as antinucleating proteins, polyols, and glucose to protect themselves against frost damage by sharp ice crystals.
Three species of bacteria, Carnobacterium pleistocenium, Chryseobacterium greenlandensis, and Herminiimonas glaciei, have reportedly been revived after surviving for thousands of years frozen in ice.
[6] The fungus gnat Exechia nugatoria can survive after being frozen to -50 °C, by a unique mechanism whereby ice crystals form in the body but not the head.
Other vertebrates that survive at body temperatures below 0 °C include painted turtles (Chrysemys picta), gray tree frogs (Hyla versicolor), moor frogs (Rana arvalis), box turtles (Terrapene carolina - 48 hours at -2 °C), spring peeper (Pseudacris crucifer), garter snakes (Thamnophis sirtalis- 24 hours at -1.5 °C), the chorus frog (Pseudacris triseriata), Siberian salamander (Salamandrella keyserlingii - 24 hours at -15.3 °C),[10] European common lizard (Lacerta vivipara) and Antarctic fish such as Pagothenia borchgrevinki.
Cell suspensions (like blood and semen) and thin tissue sections can sometimes be stored almost indefinitely in liquid nitrogen temperature (cryopreservation).
Controlled-rate and slow freezing are well established techniques pioneered in the early 1970s which enabled the first human embryo frozen birth (Zoe Leyland) in 1984.
Such machines are used for freezing oocytes, skin, blood products, embryo, sperm, stem cells, and general tissue preservation in hospitals, veterinary practices, and research labs.
Dr Christopher Chen, Australia, reported the world’s first pregnancy using slow-frozen oocytes from a British controlled-rate freezer in 1986.
[citation needed] Cryosurgery (intended and controlled tissue destruction by ice formation) was carried out by James Arnott in 1845 in an operation on a patient with cancer.
[15] Although hibernating animals have adapted mechanisms to avoid metabolic imbalances associated with hypothermia, hypothermic organs, and tissues being maintained for transplantation require special preservation solutions to counter acidosis, depressed sodium pump activity.
Some cryobiologists are seeking mixtures of cryoprotectants for full vitrification (zero ice formation) in preservation of cells, tissues, and organs.
Human gametes and two-, four- and eight-cell embryos can survive cryopreservation at -196 °C for 10 years under well-controlled laboratory conditions.
In 1997, samples of ovarian cortex were taken from a woman with Hodgkin's lymphoma and cryopreserved in a (Planer, UK) controlled-rate freezer and then stored in liquid nitrogen.
In 2003, after freeze-thawing, orthotopic autotransplantation of ovarian cortical tissue was done by laparoscopy and after five months, reimplantation signs indicated recovery of regular ovulatory cycles.
Eleven months after reimplantation, a viable intrauterine pregnancy was confirmed, which resulted in the first such live birth – a girl named Tamara.
This international meeting offers opportunities for presentation and discussion of the most up-to-date research in cryobiology, as well as reviewing specific aspects through symposia and workshops.
Articles concern any aspect of low-temperature biology and medicine (e.g. freezing, freeze-drying, hibernation, cold tolerance and adaptation, cryoprotective compounds, medical applications of reduced temperature, cryosurgery, hypothermia, and perfusion of organs).
Cell Preservation Technology has been renamed Biopreservation and Biobanking and is the official journal of International Society for Biological and Environmental Repositories.