Embryo Cryopreservation

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


Services include:
  • Preparation of pseudopregnant surrogates
  • Superovulation of donor females (if applicable)
  • Harvesting zygotes from at least 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.  If the first operation produced few or no embryos for further proceedings, the fee for the next one operation will be adjusted to 50%.

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)


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, Prof. Igor Katkov (Ed.), InTech, DOI: 10.5772/32803.