Very little about human sperm quality is settled science. No male can be diagnosed with infertility based solely on semen analysis unless he has no moving sperm cells in his ejaculate. As long as a male has a couple of motile sperm cells, irrespective of their morphology, he can father a child either naturally or using assisted reproduction. DNA fragmentation is an artifact, which does not exist in live sperm cells. It is induced by the methods used to measure DNA fragmentation. The amount of sperm-bound, oocyte activating factor may play an important role in embryo quality.
My friend, Dr. Joel Geslevich, a reproductive endocrinologist, was seeing a patient who several years back had visited a world-renowned professor of andrology. The professor examined her husband’s sperm and told the couple that there is no possibility they will ever have children and should consider a sperm donor. The couple traveled back home, and to their surprise, soon after that, the woman became pregnant. The husband threatened to kill her if the child was not his and requested paternity testing, which showed that he was indeed the biological father. The reason for her visit to Dr. Geslevich was a tubal ligation because after four children she decided that her reproductive life must be curtailed.
This case illustrates a problem with semen analysis. Unlike the vast majority of clinical tests that have clearly defined diagnostic cut-offs, abnormal semen analysis can’t be interpreted on its own merits as a diagnosis of male infertility (with some exceptions). Only if a male has no moving sperm cells in ejaculate, male infertility can be safely assumed. Rush to diagnose male infertility based on semen analysis is very common and very consequential. It can easily become a trap that sends the infertility workup into the wrong queue.
Everything about sperm, their ideal number in ejaculate, morphology, motility, DNA fragmentation is a subject of heated debate. Whatever point about semen analysis you want to prove, you can find a study that supports it.
World Health Organization, based on the studies its experts have chosen according to their criteria, recommends the following values of normal reference range:
In my opinion, the studies that look at the sperm quality before a vasectomy are the least biased and they suggest very different ranges for normal sperm. The participants in such studies are proven-fertile males. According to one of such studies, a staggering 87% of proven fertile males had sperm parameters below what would be considered “normal” range and almost no one had normal morphology. Curiously, no lifestyle habits, such as smoking or drinking had any correlation with sperm parameters. Another set of very creditable studies demonstrates the ranges for normal sperm parameters so large, that figuratively speaking you can run a truck through them: volume from 0.6 to 11 ml, concentration from 4 to 318 mil/ml, and motility from 10 to 95%.
Before diving deeper into the subject, let’s establish what sperm really is. It is a small moving cell with packed DNA. Packing the DNA is only necessary for delivering it into the egg. Just like a parachute, the packed DNA must unpack (decondense) once inside of the oocyte, otherwise it has no use. Along with this DNA, a spermatozoon also delivers an activating factor, which sets development into motion. This activating factor is a protein, which we were first to discover, and which was subsequently identified as pLC Zeta.
Sperm cell (insert) and its decondensed DNA after delivery into the oocyte
Yep, a parachute
There are cases when we can physiologically trace morphological (shape) abnormality to altered function. For example, misshaped erythrocytes have reduced surface area diminishing the cell’s ability to transport oxygen and producing the symptoms of thalassemia. At the same time, we can’t assign clear physiological significance to the shape of the sperm head, to the size of the acrosome, or so-called “vacuoles” in the sperm nucleus. It is just not clear how those features would interfere with the sperm function 0f delivering the male DNA into the egg. In fact, the sperm cells vary from man to man in their shapes and other subtle ways as much as people’s heads. It may be even possible to use biometrics on them.
In order to say with certainty whether a particular sperm morphology is abnormal, we would need to use this very sperm to fertilize an egg in vivo and see if a baby will be born. This has never been done and will never be done: it is technically impossible to scrape a sperm from the slide after analysis and use it for natural fertilization.
There are only three studies ever published that evaluated the chromosomal complement of spermatozoa in respect to their live morphology (this is not conventional sperm morphology in semen analysis) by Rybouchkin et al and by Lee et al. Those studies are so rare, because of the very high level of expertise and resources required to perform them. They show, for example, that the rate of chromosomal errors in grossly morphologically abnormal – globospermic samples are the same as in the sperm from a donor.
If you look at the bags with packed parachutes, each of them looks slightly different – they have a different “morphology”. Can you use this “morphology” to tell which one contains a parachute that has a higher chance to fail? No. That is the problem with sperm morphology: we do not know what if any features are relevant.
Sperm DNA fragmentation
There are literally thousands of publications describing the link between DNA fragmentation in spermatozoa and fertility. Many reproductive medicine insiders believe that sperm DNA fragmentation is not only relevant for the diagnosis of male infertility but is the most important sperm parameter that has to be investigated. The rationale behind this concern is free radicals or some other agents present in the semen plasma (or perhaps inside of the sperm cells) may disrupt DNA, rendering a sperm cell incompetent. Yet, nobody has ever shown that a live sperm cell has any intrinsic DNA damage, because, in order to demonstrate DNA fragmentation, the sperm cell must undergo treatments that themselves induce DNA damage.
This means that when such technique is applied to the sperm cell, it measures not a pre-existing (intrinsic or natural) damage, but the damage artificially induced by the technique itself! In essence, those tests are measuring how resistant sperm DNA is to an array of physical and chemical agents of which sperm has absolutely no chance to encounter in the male or female reproductive tract.
Imagine you are buying a parachute and its certificate says: “Tested for resistance to acids, solvents and electric current”. How is the test relevant for assuring that the parachute will open?
Since sperm DNA fragmentation has a strong correlation with sperm viability, we can conclude that the DNA of dead sperm cells is more vulnerable to methods of testing. In other words, the sperm DNA fragmentation test is merely an expensive method to measure the percentage of dead sperm cells, which can easily be measured by other methods.
Another important consideration is that as the sperm cell slowly moves from the testicle toward vas deference, it continues to “mature”, acquiring more disulfide bonds that pack DNA more and more tightly, and as a result, it is probably becoming “harder” to break. As the sperm cell awaits for ejaculation in vas difference, sometimes days, sometimes weeks it “hardens” further. Because the process of forming disulfide bonds is very imprecise (just like aging), no normal values can be established.
Therefore, less DNA fragmentation does not mean that the sperm is better. It simply means that it aged or there were other changes that made it more difficult to break. DNA “damage” in the testicular spermatozoa illustrates this point well. According to sperm DNA damage tests, testicular sperm is more immature and has more DNA breaks. However, studies demonstrate that spermatozoa from the testicle produce better quality embryos than spermatozoa from the epididymis.
The image below shows a fertilized human oocyte with a single pronucleus. When analyzed, a sperm cell that failed to form a pronucleus (DNA failed to decondense) was found alongside a normal female pronucleus. Perhaps this parachute was packed too tight and failed to open within the allowed time frame.
A DNA damage measuring technique was initially developed for farm animals and was shown to be predictive of pregnancy. However, farm animals are bred to be alike and are easily comparable.
Humans, on the other hand, display incredible diversity of genetic backgrounds and live under various conditions. Our “morphologies” are very different, but who can say that some of them predict a better fit to perform our human mission?
Once in a while, we have a google-educated couple requesting to fertilize half of their oocytes with donor sperm because the male partner had a high DNA fragmentation index on the test. Yet, to the couple’s surprise (not ours) embryos that develop after fertilization with the husband’s sperm are usually the same or better. But not always! My interpretation is that there is some sperm deficiency that our current tests are missing and it is not DNA integrity.
Sperm-bound activating factor – missing parameter of sperm quality
There is one parameter of sperm quality that is never evaluated – the amount of activating factor, which we first identified as responsible for oocyte activation and subsequently characterized as pLC zeta. It has been known for a long time that oocyte activation, one of the critical functions of the sperm cell, is not an all-or-nothing phenomenon. The mode of oocyte activation has a profound impact on embryo development. Therefore, it can be speculated that the amount of pLC zeta in sperm cells may in theory impact embryo development. One can imagine that if the amount of PLC zeta is not adequate it may negatively impact embryo development, even if the sperm cell is chromosomally normal and an oocyte is of superb quality. In theory, this can be considered when every other explanation for unexpectedly poor embryo development has been ruled out.
Abstinence duration and sperm quality
No one knows the optimal duration of abstinence for the optimal chance of conception. The recommended duration of abstinence for semen analysis is 3-5 days, but this is only to have some standard for testing. It does not imply that this will produce the most potent sperm sample for fertilization and pregnancy. The historical evidence, from Torah, points to about 14 days as optimal. At the same time, there are publications, that concur with my observations on embryo development, that very short abstinence of less than a day will produce a sample with fewer sperm cells, but better motility and, anecdotally, better-resulting embryos.