Embryo Cryopreservation

Physical responses of mouse embryos under treatments with cryoprotectants (required before rapid-freezing) and rehydration (required in the recovery processes) (Siva Tsang).

One session of services includes:
  • Superovulation of donor females (if applicable)
  • Harvesting embryos from up to 8 donor females
  • Cryopreserving all harvested embryos by vitrification

Fee: HKD 2,000 / session (+HKD 500 per 5 years  storage per strain)

Notes: Transgenic strains may have variable mating performance and productivity of embryos. No. of embryos to be cryopreserved per service can vary.

FAQ: How many embryos I need?

It depends. One may consider the following factors.

  • The availability of backup supply of the strain.  If a strain is not available elsewhere from a reliable reposition, and no other similar strains available, more embryos may be stocked to manage the risk of losing the strain from the planet.
  • Plan to redistribute the strain. If one is prepared to redistribute the strains to collaborators or other requesters, more embryos may be stocked in advance.
  • Predicted genotype distribution among the thawed embryos. In a Hetero x WT cross to produce embryos for cryopreservation, one may expect half of the embryos are hetero. One will therefore double the number of embryos when comparing with a Homo x WT strategy.

One may also consider the following practical factors.

  • We put max 25 embryos in one container, thus thawing 25 embryos at a time.
  • More than 95% of embryos can be recovered in vitro and half of the embryos can develop to term after surgical transfer (similar to non-cryopreserved, fresh embryos).
  • Surrogates occupationally fail to maintain pregnancy, naturally, after surgical transfer of embryos.
  • One may want the revived animals be males to speed up the expansion of the colony.

Please contact us for further advise.


Dr. Siva WH Tsang (email: tsangwh@ust.hk; tel: 3469 2418)

Miss Joy HM Pan (email: joypan@ust.hk; tel: 23585947)


Tsang WH and Chow KL (2009). Mouse embryo cryopreservation utilizing a novel high-capacity vitrification spatula. Biotechniques. 2009 Jun;46(7):550-2. doi: 10.2144/000113125.

Tsang WH and Chow KL (2012). Cryopreservation of Embryos from Model Animals and Human, Current Frontiers in Cryobiology, InTech, DOI: 10.5772/32803.