Rabbit Embryo Vitrification Using Cryogenic Straw: An Ultra-Rapid Cooling Technique to Preserve Rabbit Embryos for Long-term Storage

Published: April 30, 2023

Abstract

Source: Garcia-Dominguez, X. et al. Minimally Invasive Embryo Transfer and Embryo Vitrification at the Optimal Embryo Stage in Rabbit Model. J. Vis. Exp. (2019)

In this video, we describe the procedure for vitrification of harvested rabbit embryos at desired development stage using ethylene glycol and dimethyl sulfoxide as cryoprotectants and cryogenic straw as the carrier system. The vitrified embryos have high survival rate and can be stored for an extended period until use.

Protocol

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.

1. Embryo Vitrification

  1. Perform all the manipulations at room temperature (around 22 °C) to reduce the vitrification solution toxicity at warmer temperatures.
    NOTE: Embryos can be moved using 0.1–2 µL automatic pipette in this protocol, but other similar devices to move the embryos dragging the minimum volume can be suitable.
  2. Vitrify the embryos in a two-step addition procedure:
    1. Place the embryos for 2 minutes in equilibrating solution consisting of 10% (v/v) ethylene glycol and 10% (v/v) dimethyl sulfoxide dissolved in base medium (BM). (Composition of BM: Dulbecco's Phosphate-Buffered Saline (DPBS) supplemented with 0.2% (w/v) of Bovine Serum Albumin)
    2. Move the embryos (from step 1.2.1) for 1 minute into vitrification solution consisting of 20% (v/v) ethylene glycol and 20% (v/v) dimethyl sulfoxide dissolved in BM.
  3. Load the embryos into a 0.25 mL plastic ministraw (which contains one closed end with a cotton plug and one open extreme). The process is schematized in Figure 1.
    1. Couple the closed end of 0.25 mL ministraw with the appropriate microdispenser (e.g. Captroll III®).
    2. Aspirate BM until 1/3 of the straw length, following by a small air bubble.
    3. Aspirate the embryos in a volume of 40 µL of vitrification solution, followed by another small air bubble.
    4. Aspirate BM until the first liquid fraction (step 1.3.2) reaches the cotton.
    5. Close the open end with a straw plug.
  4. Perform step 1.2.2 while step 1.3 is being done to ensure that no more than one-minute elapses, which would be toxic to embryos.
  5. Plunge the ministraw directly into liquid nitrogen to achieve vitrification.
  6. Store the ministraw in a dewar for nitrogen for the desired time.

Representative Results

Figure 1
Figure 1: Schematization of correctly loaded straw. A) BM refers to the embryo manipulating media employed during vitrification. Embryos must be loaded in vitrification solution. B) Macroscopic appearance of the loaded straw with a magnified detail of the embryo position. This large-volume device allows us to vitrify large number of embryos, unlike minimum volume devices. Furthermore, the handling of this device is easier compared with minimum volume devices.

Disclosures

The authors have nothing to disclose.

Materials

Bovine Serum Albumin (BSA) VWR 332
Dimethyl Sulfoxide Sigma Aldrich W387509
Dulbecco's phosphate-buffered saline (DPBS) Sigma Aldrich D5773 Without calcium chloride.
Ethylene Glycol Sigma Aldrich 102466-M
Liquid Nitrogen Air Liquide P1505XXX
Plastic Straw 0.25 mL IMV – technologies 6431
Stereomicroscope Leica MZ16F There are cheaper options such as Leica MZ8 or Nikon SMZ-10 or SMZ-2B, to name a few.
Straw Plug IMV – technologies 6431

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Cite This Article
Rabbit Embryo Vitrification Using Cryogenic Straw: An Ultra-Rapid Cooling Technique to Preserve Rabbit Embryos for Long-term Storage. J. Vis. Exp. (Pending Publication), e20935, doi: (2023).

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