Cryopreservation Freezing Methods: Dr Rama Sofat Hospital

Cryopreservation is the process of freezing biological material at extreme temperatures; most common -196 °C/-321 °F in liquid nitrogen (N2).

At these low temperatures, all biological activity stops, including the biochemical reactions that lead to cell death and DNA degradation. This preservation method in theory makes it possible to store living cells as well as other biological material unchanged for centuries as explained by Dr Rama Sofat.

The challenge of cryopreservation is to help cells to survive both cooling to extreme temperatures and thawing back to physiological conditions. Intracellular ice formation in particular is a critical issue that has to be controlled to keep the cell membrane intact and the cells alive.

The crucial elements to prevent this are the freezing rate (degrees per minute) and the composition of the freezing medium used. The freezing medium generally consists of a diluter, (sometimes) a protein source, as well as a cryoprotectant compound. The choice of most suitable cryoprotectant will influence the preservation result and will be different between different cells and different species.

TYPES OF CRYOPRESERVATION

There are 3 types of Cryopreservation in IVF spectrum:

1) Sperm Cryopreservation

2) Eggs Cryopreservation

3) Embryos Cryopreservation

Sperm Cryopreservation: Sperm are frozen to preserve because of a string of reasons: a) To develop sperm bank; b) To donate stored sperm; c) To use it during the treatment if the male partner is unable to ejaculate on the stipulated day; d) Before undergoing vasectomy; e) Prior to Cancer treatment which might adversely affect fertility; f) Retrieved sperms from epididymis (PESA) or testes (TESA) as explained by Dr Rama Sofat.

If sperm are frozen for the impending treatment of the donor, the storage period is usually 1 year. For the pre-chemotherapy storage, the duration is mostly of 10 years which can be extended in certain circumstances.

Eggs (oocytes) Cryopreservation: Dr Rama Sofat explains that Eggs Cryopreservation is for women who are about to undergo medical treatment for ailments such as cancer etc. which may affect her ability to produce eggs in the future. This technique is also useful for women who are career-oriented and does not want early motherhood.

Eggs are frozen within few hours of collection through the standard freezing process. Later, when women are ready to be pregnant, the frozen eggs are thawed, fertilised with the husbands’ sperms and resultant embryo is implanted in the uterus as described by Dr Rama Sofat.

Embryos Cryopreservation : During the treatments like IVF, ICSI the best embryos are selected and transferred during the first cycle, if any good quality ‘surplus’ embryos are left, they are frozen to preserve for the future use while curing infertile couples. It is to be noted that only the embryos of top-notch quality survive the freezing and thawing process.