The Epididymis, Cytoplasmic Droplets, and Male Fertility
Written by Ben Bunting: BA(Hons), PGCert.
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Cytoplasmic droplets are the normal organelle of spermatozoa. Having excess cytoplasm on spermatozoa is associated with infertility, but it is important not to label these germ cells immature. Instead, these should be referred to as extra-residual cytoplasm-bearing spermatozoa.
Centrosomes
The multifunctional epididymis provides a favorable microenvironment for spermatozoa maturation and storage. It also contains a sperm-specific homeodomain protein known as HOXBES2. In rat epididymis, HOXBES2 was found in the cytoplasm of principal epithelial cells and exhibited maximum expression in the distal epididymis. When testicular androgens were withheld from the epididymis, immunoreactive HOXBES2 declined to 5 percent.
During the process of fertilization, sperm contribute centrioles, which are recruited by the maternal microtubule organizing center. The centrioles are then recruited by the maternal microtubule organizing centers and disassembled during gametogenesis. As the centrioles are removed during male gametogenesis, the centrioles lose the GFP-centrin signal. This loss of centrioles occurs in both male and female meiosis, but in mice, maternal inheritance of centrioles seems to be unique.
Centrosomes are found in epididymis cytoplasm, as evidenced by electron micrographs of caput epididymal tubules. They appear as cribriform, round, and hexagonal structures that show an irregular apical and basal structure. They also have a heterochromatic nucleus, a cell membrane, and a regular outline.
In isolated testicular sperm, centrosomes can be identified using anticentrin antibodies. However, in mature caput sperm, centrin levels are reduced or absent. However, in transgenic mice, GFP-centrin shows a pronounced presence of centrioles in the epididymis, while GFP-CETN2 shows centrioles in the implantation fossa region.
While most factors are unknown at this time, researchers are making strides toward understanding the underlying mechanisms of male infertility. Recent breakthroughs in small noncoding RNAs have uncovered some key elements of the disease. With further research, more key elements of male infertility will be identified.
Astral microtubule nucleation
The epididymis is a reproductive organ that plays an important role in male fertility. It contains a population of centrioles, which are critical for the development of sperm. These centrioles are acquired during the process of ICSI40 or sperm-zone-free oocyte fusion. Once acquired, these centrioles are responsible for a range of functions, including organization of pericentriolar material, assembly of microtubules in the aster, and initiation of genome apposition in activated cytoplasm. However, unlike the centrioles that recruit g-tubulin and participate in cytoplasmic events, epididymal centrioles do not recruit oocyte g-tubulin or engage in other cytoplasmic
The epididymis controls the timing of various events in male fertility. Different timing events must occur in the epididymis for a fertile spermatozoon to fertilize an egg. While several of these events originate in the epididymis, many of them require a specific response from the fertilizing spermatozoon.
As sperm age, they exhibit reduced expression of the gene centrin. Centrin is present in the caput of spermatozoa and caput epididymis, but its expression is decreased in the vas deferens. The resulting reduction in sperm expression is statistically significant. Males with less expression of the gene seem to be less efficient at dissolving centrioles as they age.
The epididymis cytoplasm contains MTOCs that assemble the microtubule asters. The microtubule asters are a key part of male fertility and microtubule organization. The cytoplasmic MTOCs are found in all testis cells.
Studies have shown that the epididymis regulates osmolyte loading, a factor necessary for proper sperm function. When CDs are low, the sperms become swollen and lose flagellar angulation, which leads to infertility. The epididymis does not retain CDs in hypotonic conditions.
Testicular spermatozoa
There are several factors that contribute to the low number of testicular spermatozoa. Some of these factors include genetic abnormalities, such as deletions on the Y chromosome, infection, or exposure to chemicals. Other factors, such as varicocele, may also cause low sperm counts. In other cases, low testosterone levels or frequent use of hot tubs may be responsible for testicular hyperthermia.
Although there are still some questions about the role of testicular sperm in male fertility, most studies show that these sperm improve the odds of conceiving. Surgical sperm retrieval, for example, may benefit men with certain types of male infertility.
One study, Martinez-Soto JC, showed that dietary supplementation with DHA improved the seminal antioxidant status and decreased fragmentation of sperm DNA. This study was published in the N Engl J Med. It also showed that collagenase degraded the cell surface proteins, which could affect the viability of sperm during ART.
The testicles are the primary site for the production of sperm. Males produce millions of sperm cells every day at puberty. These sperm cells are 0.002 inches (0.05 millimeters) long and are housed in seminiferous tubules. Testosterone causes these germ cells to mature into sperm, which are then released into the epididymis tube. Sperm then move to the vas deferens.
Despite the fact that testicular sperm are significantly higher in quality and more viable than ejaculated sperm, studies have shown that damage to the DNA of sperm cells reduces the chances of pregnancy. In some cases, this damage can result in low-quality embryos, implantation failure, and recurrent pregnancy loss.
Sperm morphology
In an experiment, we examined sperm morphology and epididymial cytoplasmic droplets in male volunteers, before and after heat exposure. We found that, after heat exposure, the morphology of sperm was altered, resulting in a higher percentage of spermatozoa with abnormally thin heads and abnormal acrosomal regions. This effect was more pronounced on Day 165, when the heat exposure stopped.
Sperm morphology is important in determining male fertility. Sperms are organized schematically, with a long, thin midpiece, head, and cytoplasmic ring. The sperm head and midpiece are polygonal and contain tightly packed mitochondria. The cytoplasmic ring of the principal piece is thick and has a fibrous sheath.
The CD is a common element of mammalian spermatozoa and is part of a normal morphological process. However, excessive residual cytoplasm can impair sperm function and generate high levels of reactive oxygen species, leading to male infertility. Despite the importance of CD in sperm health, some studies have failed to distinguish between cytoplasmic droplets and excess residual cytoplasm. Therefore, in this review, we will discuss how CDs affect male fertility, examine the enzymes responsible for CD, and suggest a new test for detecting it in sperm.
The study also examined the relationship between mild temperature changes and sperm morphology. Researchers found that a mild increase in testicular temperature affected sperm morphology, epididymis transit, and sperm morphology. However, despite these findings, no human study has investigated the effect of scrotal temperature on sperm morphology. In addition, this type of study is limited by a limited number of volunteers.
The present study used a boar with a high incidence of abnormal spermatozoa. The morphology of these spermatozoa was assessed using a modified David classification and Shorr staining technique. Sperm morphology defects were further classified into three categories: tail, midpiece, and head defects. A multiple anomalies index (MAI) was calculated based on the number of defects per abnormal spermatozoon.
Conclusion
The epididymis is one of the least understood of man's organs, despite its role in male reproduction and the largest journey for sperm. While its functions include the management of reactive oxygen stress, they also suggest a site for transgenerational inheritance and vital modification. This may make epididymal transmission of epigenetic information of vital importance.
Cytoplasmic droplets from the epididymis are believed to regulate sperm osmolytes and the RVD at ejaculation. While the precise mechanism behind this is still unclear, it appears that it is achieved by repeated centrifugation. The loss of these sperm droplets may result in the inability to reach the egg. Hence, the loss of these droplets would be an early indication of male infertility.
Cytoplasmic droplets contain centrin, a protein that coalesces adjacent to centriole pairs. As sperm age, the expression of centrin is reduced. As a result, most spermatozoa lose their GFP CETN2 expression at the implantation fossa. Centrin is also found in the caput spermatozoa and axoneme basal body region.
Although cytoplasmic droplets in the epididymis are a normal organelle, their retention in the semen is associated with infertility. This is not to say that these spermatozoa are immature, but rather that they are not able to develop properly.
