Cryobiology

Cryobiology is the study of living organisms, organs, biological tissues or biological cells at low temperatures. This knowledge is practically applied in three fields: cryonics, cryopreservation and cryosurgery.

Definitions/Distinctions
Cryobiology is the branch of biology that studies the effects of low temperatures on organisms (most often for the purpose of achieving cryopreservation). The word cryobiology (from the Greek words "cryo" = cold, "bios" = life, and "logos" = science) literally signifies the science of life at low temperatures. In practice, this field comprises the study of any biological material or system (e.g., proteins, cells, tissues, organs, or organisms) subjected to any temperature below normal (ranging from moderately hypothermic conditions to cryogenic temperatures). At least 6 major areas of cryobiology can be identified: 1) study of cold-adaptation of microorganisms, plants (= cold hardiness), invertebrates, and animals (= hibernation), 2) cryopreservation of cells, tissues, gametes, and embryos of animal and human origin for (medical) purposes of long-term storage. 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.


 * Cryogenics: The branch of physics (or engineering) that studies very low temperatures (or the production of very low temperatures). People often confuse "cryogenics" with "cryonics".


 * Cryonics: Cryonics is the low temperature preservation of humans and animals in a damaged state with the intention of future revival. Cryonics uses information from many fields, including cryobiology, to reduce damage during preservation and measure what preservation is achieved. . However no human has ever been revived from cryopreservation by cryonics, and proposed methods for revival are based on speculation concerning capabilities of future technology . Therefore cryonics is viewed with skepticism by most scientists and medical doctors today, although there are some scientists involved in cryonics.

Historical Background
Cryobiology history can be traced back to antiquity. As early as in 2500 BC low temperatures were used in Egypt in medicine. The use of cold was recommended by Hippocrates to stop bleeding and swelling. With the emergence of modern science, Robert Boyle studied the effects of low temperatures on animals.

In 1949 sperm was cryopreserved for the first time by a team of scientists led by Christopher Polge (1926-2006). This led to a much wider use of cryopreservation today, with many organs, tissues and cells routinely stored in low temperatures. Large organs such as hearts are usually stored and transported, for short times only, at cool but not freezing temperatures for transplantation. Cell suspensions (like blood and semen) and thin tissue sections can sometimes be stored almost indefinitely at liquid nitrogen temperature (cryopreservation). Human sperm, eggs and embryos are routinely stored in fertility research and treatments. In the early 2000s a baby was born from a cryopreserved egg fertilized by a cryopreserved sperm.

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. Although not very widespread, cryosurgery has its benefits. Hypothermia, e.g. during heart surgery on a "cold" heart (generated by cold perfusion without any ice formation) allows for much longer operations and improves recovery rates for patients.

Modern developments
Discussions of modern developments in cryobiology can be found under cryopreservation and vitrification.

Scientific Societies
One of the two leading scientific societies in the field of cryobiology is the Society for Cryobiology. This society was founded in 1964 to bring together those from the biological, medical and physical sciences who have a common interest in the effect of low temperatures on biological systems. As of November 2006 the Society for Cryobiology had approximately 300 members from around the world, and one half of them are US based. The purpose of the Society is to promote scientific research in low temperature biology, to improve scientific understanding in this field, and to disseminate and apply this knowledge to the benefit of mankind. The Society requires of all its members the highest ethical and scientific standards in the performance of their professional activities. '''According to the Society's Bylaws membership may be refused to applicants whose conduct is deemed detrimental to the Society, this includes explicitly any practice or application of freezing deceased persons in the anticipation of their reanimation. This is the characteristic difference between "cryobiology" (which is a scientific discipline) and "cryonics"'''. The Society organizes an annual scientific meeting dedicated to all aspects of low-temperature biology. 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. Members are also kept informed of news and forthcoming meetings through the Society newsletter, News Notes. The 2006-2007 President of the Society for Cryobiology is Andreas Sputtek.

The Society for Low Temperature Biology was founded in 1964 and became a Registered Charity in 2003 (Charity Commission for England & Wales No. 1099747) with the purpose of promoting research into the effects of low temperatures on all types of organisms and their constituent cells, tissues and organs. As of 2006 the Society for Low Temperature Biology had approximately 130 (mostly British and European) members and holds at least one Annual General Meeting. The program usually includes both a symposium on a topical subject and a session of free communications on any aspect of low temperature biology. Recent symposia have included long-term stability, preservation of aquatic organisms, cryopreservation of embryos and gametes, preservation of plants, low temperature microscopy, vitrification (glass formation of aqueous systems during cooling), freeze drying and tissue banking. Members are informed through the Society Newsletter, which is presently published 3 times a year. The 2005-2006 Chair of the Society for Low Temperature Biology has been Tiantian Zhang.

A list of additional scientific societies (mostly using "applied" cryobiology) can be found here.

Journals
CRYOBIOLOGY, (publisher: Elsevier) is the foremost scientific publication in this area, with approximately 60 refereed contributions published each year. 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).

There is an independent UK based rapid communication journal named CRYO LETTERS which publishes papers on the effects produced by low temperatures on a wide variety of biophysical and biological processes, or studies involving low temperature techniques in the investigation of biological and ecological topics.

CELL PRESERVATION TECHNOLOGY is a peer-reviewed quarterly scientific journal published by Mary Ann Liebert, Inc. dedicated to the diverse spectrum of preservation technologies including cryopreservation, dry-state (anhydrobiosis), glassy-state and hypothermic maintenance.