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Hi Dr Smith

Can you please provide your insights and advice. It looks like my post may have been overlooked

Thank you so very much

Sorry for the delay. I got busy in the lab and then I wanted to catch up on the topic before posting.

The 59% maturity is not really that far out of the expected 70-80%. However, the number of mature eggs becomes a critical factor when fewer eggs are retrieved. Yes, genetically normal eggs may have been among the immature eggs. We will never know. You are right, when advanced maternal age is a significant factor, it boils down to a numbers game (of chance).

As you pointed out, there are several groups working on in vitro maturation (IVM) of eggs. Although promising, it is being applied to "left over" eggs and/or eggs from certain specific populations of patients (i.e. PCOS). An important point to make: reasonable maturation rates (as judged by nuclear maturity, not cytoplasmic maturity - more about that later) and reasonable fertilization rates are not the whole story. Embryo development to the blastocyst stage, that is, reaching the stage where they are capable of implantation, and live birth rates would have to be equivalent or better than stimulated cycles for IVM to catch on.

There are two aspects of egg maturity. The first, and easiest to evaluate, is nuclear maturity. Nuclear maturity is determined by visual inspection. When mature, the egg has reached metaphase II and is capable of fertilization as evidenced by the ejection of the first polar body. The second aspect of maturity is cytoplasmic maturity. It is much more difficult to measure. While developing in the follicle, the egg makes and stores everything it will need to get through the first two division cycles and some of the things it will need to reach the blastocyst stage. Conditions during IVM are very simplistic when compared to the complex, dynamic conditions in the follicle. IVM can result in a reasonable number of eggs exhibiting nuclear maturity, but adequate cytoplasmic maturity remains the Holy Grail of IVM. Conclusion - not ready for prime time just yet in all patient populations.

With respect to the application of IVM to patients of advanced maternal age, there is one important thing to consider. At the begining of a cycle, the number of antral follicles is the number of antral follicles - natural cycle or stimulated cycle. The stimulation medications do not alter the number of antral follicles/eggs that are available for growth on that particular cycle. So, IVM may result in a predicted 60-70% nuclear maturation rate (cytoplasmic is another story) and stimulation may result in 70-80% nuclear maturation rate. Its basically a wash in terms of nuclear maturation and IVM, at present, does not provide all of the environmental factors required for adequate cyctoplasmic maturation.

The exception to this is in PCOS patients where nuclear and cytoplasmic maturation is compromised. In these patients, IVM may actually provide a better environment tha in the follicle.

Thank you for such a great explanation relative to egg maturity and its implications on the effectiveness of IVM. I did not realize that there were two levels of oocyte maturity. Interesting. I get the nuclear aspect.. that;s pretty clear... but the cytoplasmic is still a bit over my head. I thought I recalled reading something pertaining to cytoplasmic transfers which was outlawed in the US, wherein docs were extracting the fluid from a young woman's follicles and injecting into the follicle of older women, to help "engergize" the younger women's follicles. Does the cytoplasmic maturity have to do with the fluid within the egg? I guess I need a bit more explanation to fully grasp this one.

Also, you're comments pertaining to antral follicles were also a suprise for me. See quote. Are you saying that the antrals on CD3 are all there is.. and what;s there is there.. and stim meds DO NOT recruit more follicles at the beginning of a cycle? If, so, are some of the resting antrals just too small on CD3 just too small to be seen on ultrasound? For example, I had 10-12 antral follciles, on CD 3. There were supposed to be 12 (confirmed from u/s 1 week earlier), but he could only see 10 on VD3. On CD9, all 12 were showing. On CD 10, there were 15 visible and on CD12, there wer 17.

Am I to understand that there were always 17 antral follicles, and that theywere just small and not yet visible by ultrasound until they had been stimualted sufficiently to be able to be seen and large enough for retrieval?

Thanks, this is getting real interesting. You are awesome,... what a wonderful wonderful well of knowledge and kindness

Big Blessings to You This Holiday


{Quote} - At the begining of a cycle, the number of antral follicles is the number of antral follicles - natural cycle or stimulated cycle. The stimulation medications do not alter the number of antral follicles/eggs that are available for growth on that particular cycle. So, IVM may result in a predicted 60-70% nuclear maturation rate (cytoplasmic is another story) and stimulation may result in 70-80% nuclear maturation rate. Its basically a wash in terms of nuclear maturation and IVM, at present, does not provide all of the environmental factors required for adequate cyctoplasmic maturation.
{End Quote}

A1. Cytoplasm is the "fluid" inside the egg. It's not really a fluid, but more like a gel. While maturing in the follicle, the egg has to make and store all the "food" it needs to carry it through the first two division cycles (1 to 2 cell, 2 cell to 4 cell). This "food" is stored in the cytoplasm. The cytoplasmic "pantry" has to be stocked up, otherwise the embryo prematurely runs out of food and stops growing before it can make more food. The end.

What you are referring to is an experimental procedure called "cytoplasmic transfer" and, yes, its been banned in the US (Whew! and for good reason too). The cytoplasm that was transferred from the younger women's egg to the older women's egg contained mitochondria. Mitochondria are organelles (equivalent to the organs in the body) that are responsible for generating the energy "currency" of the cell, a molecule called ATP. In aging eggs, the mitochondria are tired and do not produce as much ATP as when they were young. Accordingly the developmental potential of the egg is compromised. Part of the cytoplasmic matuartion involves making and storing adequate reserves of ATP for development. Hence, transferring "young" mitochondria can improve cytoplasmic maturation. The downside to cytoplasmic transfer, and the reason it was banned, is because mitochondria also contain DNA which is specific to our family lineage. A mismatch of mitochondrial DNA can cause problems in future generations.

A2. Yes, thats exactly right. Some follicles are not clearly visible by ultrasound on cycle day 3. As the grow, they become clear on the ultrasound.

On a NATURAL cycle, some antral folicles "wake up" and become responsive to FSH. What causes some to "wake up" while others continue to "sleep" is a mystery. All of the antral follicles that "woke up" on that cycle (the actual number will depend on age and other factors) will begin to grow in response to FSH released from the pituitary gland. In a NATURAL cycle, the pitutary makes only enough FSH to sustain the growth of one follicle. THis is the only follicle that will continue to grow, rupture and release the egg (ovulation). The other follicles stop growing and "die off". In a STIMULATED cycle, the medications that contain FSH (Follistim, Gonal F, Menopur, etc) increase the available FSH and sustain the growth of all the follicles that "woke up" on that cycle. Some follicles grow faster than others, but the number of antral follicles that "woke up" on that cycle does not change in response to the stimulation medications.

The term "poor responder" is incorrect since the follicles are responding to the FSH containing stimulation medications, its just that there were just fewer antral follicles to stimulate. This is usually a result of advanced maternal age because there are fewer follicles left in the ovary. Giving more FSH will not alter the number of antral follicles that begin each cycle, just modulate their rate of growth. If it was as simple as just giving women more stimulating medication to make more follicles, every woman would have a gazillion follicles on every cycle.