Intracytoplasmic Sperm Injection (ICSI)

What is ICSI?

Intracytoplasmic sperm injection (ICSI) utilizes a procedure called transvaginal aspiration to harvest oocytes (unfertilized eggs) directly from the follicles within the ovary.  This technique can be performed in the live mare or with excised ovaries after euthanasia.  Once the oocytes are recovered, they are stored and/or transported in specialized holding media.  This is followed by an incubation period in maturation media to help oocytes fully mature. Those oocytes that properly mature will be injected with a single sperm from the stallion of choice.  Fresh, cooled or frozen semen can be used as long as it arrives in good condition and at the appropriate time.  One of the benefits of ICSI is that because you are only using a single sperm for the procedure, a small portion of sperm is all that is needed for processing.  A single straw of frozen semen may give up to 20 samples for ICSI use.  Following sperm injection, the oocyte is further incubated for over a week to determine if it develops into a viable embryo.  Any fully-developed embryos can then either be immediately transferred into a recipient or vitrified (frozen) for future use.

Why do this procedure?

The greatest application for this procedure is in those mares that no longer have a uterine environment conducive for allowing embryos to survive.  We see this mostly in mares with a compromised uterus that results in chronic fluid accumulation and infections.  Cervical damage can be another reason to choose this procedure over others.  Many owners of valuable frozen semen like to utilize ICSI procedures because of limited amounts of semen available.  Certain owners of show mares are in favor of using this technique because it is a potential method of getting offspring out of their competition horse with minimal time away from training and performance.

ERC’s Program

Our facility has established a program whereby mares are assessed for size and number of follicles within each ovary.  If there are a sufficient number of follicles to aspirate then we will undergo transvaginal aspiration.  This is a standing procedure that uses an ultrasound-guided transvaginal probe with a double-lumen needle.  Once a follicle is visualized, it is then punctured and repeatedly aspirated and refilled with media to help dislodge the oocyte from the follicular wall.  All notable follicles on both ovaries will be aspirated.  The fluid retrieved will then be cleaned and searched for the presence of oocytes.  All recovered oocytes will be packaged in holding media and sent to another facility for incubation and sperm injection.  Any resulting embryos will be shipped back to ERC for either direct transfer into a recipient or placed in a liquid nitrogen storage tank for future use.