Cryopreservation

Semen, oocytes, ovarian tissue, embryo cryopreservation

All biological activity is paused until it is thawed. Freezing needs cryopreserving agents that minimize damage to the cells during freezing and thawing process. Semen cryopreservation also called sperm banking is a procedure to preserve sperm cells. It is a method for men to preserve their  sperm and store in a bank for future treatment. Cryopreservation is freezing of cells to subzero temperature, typically –196oC.

 

Why cryopreservation?

  • Semen with very limited number of spermatozoa or abnormal semen parameters.
  • Cancer patients to preserve their fertility prior to gonadotoxic chemotherapy or radiation.
  • Patients undergoing certain types of pelvic or testicular surgeries.
  • Persons in occupation where significant risk of gonadotoxicity prevails.
  • Men undergoing surgical sterilization like vasectomy.
  • Allow donor semen samples to be guarantined while performing appropriate screening to prevent transmission of infectious pathogens during donor insemination.
  • In combination with ART technique.
  • Patient who suffer from degenerative illness like DM, multiple sclerosis, spinal cord, disease, etc.

 

Ovarian tissue cryopreservation for transplantation

With the newer aggressive treatment regimens, the number of cancer survivors are constantly growing and hence fertility preservation is of high priority. Previously only ovarian stimulation with oocytes or embryo cryopreservation was the only possible option for women to conceive after recovery from a sterilizing cancer treatment. But ovarian stimulation may be incompatible with an urgent cancer treatment cryopreservation.

Transplantation of ovarian tissue helps to overcome such short comings. This technique does not require pre-treatment. It can be performed any day independently of where the patient is in the menstrual cycle. Ovarian tissue banking is a promising clinical technique because it avoids ovarian stimulation and provides opportunity for preserving gonadal function in pre-pubertal as well as adult patient.

 

Oocyte and embryo cryopreservation

Oocyte cryopreservation or vitrification is a rapidly advancing breakthrough technology in ART where women’s eggs (oocytes) are extracted, frozen and stored.  Later when pregnancy is desired, the eggs can be thawed, fertilized and transferred to the uterus.

Fertility and fecundity decreases with age. So women who would like to preserve their future ability to have children, either because they do not have a partner or for other personal or medical reasons. It is done as a part of ART treatment for couples who do not consider embryo freezing an option. It is also performed in those diagnosed with cancer and have not yet begun chemotherapy or radiotherapy.

The egg retrieval process for oocytes cryopreservation is same as that for IVF. The women undergo several weeks of hormonal injection for stimulation. Once the eggs are of adequate size, final maturation induction is performed and eggs are subsequently removed from the body under ultrasound guidance and are frozen using cryoprotectants which replace most of the water within the cells and inhibit formation of ice crystals. The percentage of transfer of cycles is lower in frozen cycles when compared with fresh cycle.

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