Life in the cryo-kennel: The 'exceptional' life of frozen pet DNA

The Cold Futures of Mouse Genetics: Modes of Strain Cryopreservation Since the 1970s

Cryopreservation, or the freezing of embryos or sperm, has become a routine part of many research projects involving laboratory mice. In this article, we combine historical and sociological methods to produce a cryopolitical analysis of this less explored aspect of animal research. We provide a longitudinal account of mouse embryo and semen storage and uses in the UK and show that cryopreservation enabled researchers to overcome particular challenges-fears of strain loss, societal disapproval, and genetic drift-in ways which enabled the continued existence of strains and contributed to the scaling up of mouse research since World War II. We use the theoretical lens of cryopolitics to explore three different, yet overlapping, cryopolitical strategies that we identify. All share the ability to ensure the continued maintenance of genetically defined strains without the need for continually breeding colonies of mice. We argue that, in contrast to more common imaginaries of species conservation, the cryopolitical rationale can best be understood as purposefully not letting the strain die without requiring animals to live. The ability to freeze mice, then, had the potential to unsettle who the objects of care are in mouse research, from individual animals to the concept of the strain itself.

Cryopreservation of Gametes and Embryos and Their Molecular Changes

The process of freezing cells or tissues and depositing them in liquid nitrogen at -196 °C is called cryopreservation. Sub-zero temperature is not a physiological condition for cells and water ice crystals represent the main problem since they induce cell death, principally in large cells like oocytes, which have a meiotic spindle that degenerates during this process. Significantly, cryopreservation represents an option for fertility preservation in patients who develop gonadal failure for any condition and those who want to freeze their germ cells for later use. The possibility of freezing sperm, oocytes, and embryos has been available for a long time, and in 1983 the first birth with thawed oocytes was achieved. From the mid-2000s forward, the use of egg vitrification through intracytoplasmic sperm injection has improved pregnancy rates. Births using assisted reproductive technologies (ART) have some adverse conditions and events. These risks could be associated with ART procedures or related to infertility. Cryopreservation generates changes in the epigenome of gametes and embryos, given that ART occurs when the epigenome is most vulnerable. Furthermore, cryoprotective agents induce alterations in the integrity of germ cells and embryos. Notably, cryopreservation extensively affects cell viability, generates proteomic profile changes, compromises crucial cellular functions, and alters sperm motility. This technique has been widely employed since the 1980s and there is a lack of knowledge about molecular changes. The emerging view is that molecular changes are associated with cryopreservation, affecting metabolism, cytoarchitecture, calcium homeostasis, epigenetic state, and cell survival, which compromise the fertilization in ART.

On Ice: The impact of vitrification on the use of eggs in fertility treatment

The possibility to freeze sperm and embryos has long been available to men and women facing infertility as a result of an illness or medical treatment. However, the ability to successfully cryopreserve human eggs is comparatively recent. The introduction and increasing use of egg vitrification from the mid-2000s onwards, alongside the use of intracytoplasmic sperm injection, has seen improved ongoing clinical pregnancy rates compared with slow freezing methods. Despite concerns, the technology has been widely embraced by the scientific community and in recent years has been applied in a greater variety of contexts. In this short perspective paper, we consider two specific applications for the vitrification of human eggs in routine assisted reproduction practice: social egg freezing and the use of frozen eggs in egg donation. We suggest that vitrification is transforming the reproductive landscape in novel and complex ways and that we must be alert to the challenges, complexities and ethics of such developments, especially for those who may be excluded or marginalised by these techniques.