Cryopreservation Flashcards
Typical sperm donor age
20-39
Typical egg donor age
19-30
What testing is undergone for sperm and egg donation?
- Psychological
- Genetic
- Medical
Donor sperm is frozen and quarantined for how long?
6 months to permit re-testing for STDs
Cryopreservation
Process where cells or whole tissues are preserved by cooling them from body temp (37C) to low temperatures in liquid nitrogen (-196C)
How does cryopreservation not cause cell death?
At low sub-zero temps biological activity, including biochemical reactions, are effectively stopped
Cells are protected from freezing injury by…
- Controlled cooling and thawing rate
- Cryoprotectants
Causes of damage to cells during slow freezing
- Extracellular ice formation
- Extracellular fluid becomes hypertonic to intracellular fluid due to extracellular ice formation
- Cells become dehydrated due to hypertonicity
- Intracellular ice formation
Optimal rate of cooling is not universal
Optimal rate differs for cells based on size, water permeability, and use of cryoprotectant
Sperm size
- 5 um by 6 um
- Head is approximately 5 um x 3 um
Embryo size
- Single cell from early embryo (day 3)
- 40 um diameter
Oocyte size
-130 um diameter
Permeating cryoprotectants
- small molecules that can diffuse across membranes
- form hydrogen bonds w/ water to slow ice crystallization
- protect cell from solution effects by diluting electrolytes which are toxic to cell
Examples of permeating cryoprotectants
- Propylene glycol
- Glycerol
- DMSO
Non-permeating cryoprotectants
- larger molecules that remain extracellular
- slow or prevent extracellular ice formation
- can assist in controlled dehydration of cells
- often used in combination w/ permeating cryoprotectants
