A few people have been asking about my experience as an embryologist, so I thought I’d take to the blog to write about it!
Caught in action! Performing IVF at a micromanipulation scope
When I was a wee undergraduate student, I began wondering what sorts of things one could do with a Bachelor’s degree in biomedical science. I knew I loved science, and I’ve always had an underlying goal to make the world a better place, so how could I bring those two things together? As fate would have it, the year that I graduated from Colorado State University was the very first year that CSU was offering a new Master’s program in Biomedical Sciences with an emphasis on assisted reproductive technologies. I had a particular affinity for the reproductive sciences thanks in huge part to a very wonderful elective professor (thanks, Dr. Nett!) and an interest in the subject of bioethics (you too, Dr. Hickey!), so I was naturally drawn to this new Master’s program.
I entered this inaugural Master’s program with the intention to get involved in wildlife conservation. One of my graduate advisers, Dr. Barfield, was doing some extraordinary work with the American bison. I need to devote an entire post to her amazing contributions to the world of science and conservation. In a sentence, she utilizes in-vitro fertilization (IVF) in and effort to eradicate disease from bison populations and reestablish healthy herds in Colorado. Some of my fondest memories from my first master’s program were the early mornings spent out in the foothills of the Rocky Mountains, herding bison.
As I progressed through the program, though, I found myself entranced by the technologies of in-vitro fertilization. I was fascinated by its relative novelty and drawn to its rapidly evolving practice. I wanted to be where the IVF action was. I wanted to be on the cutting edge of this exciting, relatively new scientific endeavor. So, upon graduation with my M.S., I accepted a job in Manhattan, NY as an embryologist in one of the country’s most prestigious human IVF clinics. My time in NYC was a whirlwind of fun, friends, a long commute, and a very, very intense job.
Some fun photos from my life in NYC
As an embryologist, I was responsible for the care of tens of thousands to hundreds of thousands of dollars worth of hopes and dreams every day. There was no room for error. Mistakes weren’t an option. In a way, it was the perfect job for me. I can be extremely careful, efficient, and meticulous, and those are three very important characteristics in every successful embryologist.
But what do embryologists actually do?
Following gametes through an IVF cycle:
1.) Gametes (sperm and eggs) are acquired. In male-female couples (I use this model as an example, but we did plenty of IVF with single parents or same-sex couples), that often means that the woman undergoes an oocyte (egg) retrieval procedure in which she is put under and a doctor aspirates (verb: sucks out) a woman’s eggs from her ovaries with a needle. The aspirate (now a noun: the fluid that was sucked from the woman’s ovaries) is then passed immediately to the embryologist who, through a microscope, searches for and isolates all of the oocytes.
The oocytes may look like this upon retrieval. The fuzzy, speckled fluff around each of the darker circles are the cumulus cells. The darker circles are the actual eggs.
It is an embryologists job to isolate the eggs and cut away, using hand-held needles, excess cumulus cells. Later eggs may be treated with an enzyme, hyaluronidase, to further strip the cumulus cells from the eggs.
2.) Sperm is processed. Often around the same time, the man in a male-female couple will produce sperm, which the embryologist has to “clean” by removing debris and then reduce to a concentration suitable for IVF.
Relatively “clean” sperm
3.) Eggs are treated based on IVF plan. There are two ways to fertilize an egg: ICSI (intracytoplasmic sperm injection) or conventional. With conventional fertilization, optimal sperm concentrations are calculated to reduce risk factors like polyspermy (when more than one sperm fertilizes an egg. This would be bad!) and the sperm is put into the dish with the eggs and hopefully nature will take its course. With ICSI, a single sperm cell is selected and physically injected into the egg. In both cases, only “mature” eggs, that is- eggs that have reached the Metaphase II (MII) stage, are fertilized.
(left) a “holding needle” holds the oocyte steady while (right) an “injection needle” pierces into the egg and deposits one sperm
1.) Fertilization is assessed. An embryologist looks at the zygotes (fertilized eggs) to assess whether or not fertilization was successful. Fertilization is assessed, in large part, based on the presence of two pronuclei. Below is a picture of a normally fertilized egg. The hazy, translucent ring around the whole thing is the zona pelucida, or ZP (it’s like the egg’s shell). The sharply defined circle inside the ZP encompasses the actual egg. Between the ZP and the egg on the left are the polar bodies (little tiny exclusions from the egg that bud off at the MII stage). Inside the egg, you can see two overlapping circles with little specks inside them. These overlapping circles are the pronuclei.
Nothing! We leave the embryos-to-be in their incubators and let them develop.
1.) Assess development. At this stage, all of the embryos that have arrested (stopped developing) are separated from the ongoing ones.
A poor Day 3 blastocyst. The dark coloration, granulation, and differently-sized cells indicate sub-optimal development.
A beautiful Day 3 embryo. We see 8 cells, which is exactly where you’d want an embryo at this stage to be. All the dark specks on the ZP are sperm cells, which tells us that this embryo was fertilized with conventional insemination, not ICSI.
2.) Laser-assisted hatching. Patients may decide to have their embryos biopsied to test for genetic abnormalities. The biopsies occur on Day 5 or Day 6, but in order for them to be possible, the embryos must be hatching out of their zona pellucida. That means that on Day 3, the embryologist will use a laser and zap a small hole into the ZP so as the embryo grows and expands, it can easily push out of the ZP.
Near the bottom of each embryo, you can see the lines going through the zonas. This is where the embryo was hatched with a laser.
Nothing! We leave the embryos undisturbed in their incubators to grow and develop.
Day 5 &6:
1.) Assess embryo quality. Embryo quality depends on the amount of cells in both the trophectoderm (what will become the placenta) and the inner cell mass (ICM) (what will develop into the fetus). Number of cells isn’t everything. Qualities like organization, shape, and constitution also portray whether or not an embryo is high quality.
A beautiful, fully hatched embryo. The embryo has completely hatched out of its zona pellucida. The darker mass near the right of the embryo is the ICM. A close look under a scope would show that there are many cells comprising the ICM, although they have clumped together and organized nicely, so it’s difficult to distinguish one cell from another. The rest of the cells are trophectoderm cells- they will become the placenta. There are a TON of troph cells here, another indicator of a high quality embryo.
This embryo is in the process of hatching out of its zona. The ICM is the mass of cells near the top of the embryo that’s still inside the zona.
This is a very low-quality embryo. No discernible ICM, and very few, necrotic trophectoderm cells. The chances that this embryo would develop further is slim to none.
2.) Biopsy. As mentioned earlier, embryos that will be tested for genetic abnormalities are biopsied on Day 5 or 6. A small sample of 5-10 cells is taken from the trophectoderm, and the cells are shipped off to a lab for analysis. Biopsies allow us to detect various genetic diseases, as well as know the gender of the embryo.
3.) My favorite- vitrification! Aka. freezing the embryos. A single IVF cycle is likely to produce more than one viable embryo. Good practice is generally to only implant one good embryo back into the woman’s uterus at a time, so excess embryos can be frozen in liquid nitrogen and stored for later use. There is also growing evidence that pregnancy rates increase with frozen cycles- that is to say, a woman is more likely to get pregnant if she has all her embryos frozen on Day 5 or 6 and then comes back in a month or two to have an embryo thawed and then implanted back into her uterus.
And there you have it! IVF!
… kind of. I left out A LOT and definitely over-generalized, so take this post with a grain of salt. But now all you inquiring minds out there have some idea of what I did in my capacity as an embryologist!