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Creating males is costly, why parthenogenetic species are producing them? Most animals have female and male genders. Considering the investment of energy required for sexual reproduction, it is interesting to know why this strategy has been conserved during evolution in some species. The effort that goes into mating result in less reproduction. Moreover, meiotic recombination entails important inherent risks in terms of genomic instability, and the creation/production of separate sex, with specific genetic and physiological features distinct from the female, may be regarded as a burden for the evolutionary success of the species.

Biologically speaking, human development begins after the joining of a sperm and an egg. Around 100 years ago, the German biologist Theodor Boveri brilliantly summarised the unique contributions of each gamete, stating: “The ripe egg possesses all of the elements necessary for development save an active division-center. The sperm, on the other hand, possesses such a center, but lacks the protoplasmic substratum in which to operate. In this respect the egg and the sperm are complementary structures; their union in syngamy thus restores…

One of the challenges of modern society is being able to synchronize our own socio-economic context with the biological clock in order to find the most appropriate moment to become parents. Reproductive medicine professionals have been warning about the importance of women awareness about the acute decrease of fertility right before their mid-30s. Should they be fully aware, it would be possible for them to better plan their motherhood by preserving oocytes at young age. However, there are news on…

The ability of sperm to pass through both the uterus and the Fallopian tube and fertilise an egg depends on sperm motility and progression. The flagellum confers motility on the sperm but, sometimes, spermatozoa present an abnormal axoneme ultrastructure and so they cannot swim (asthenozoospermia). The axoneme, the “scaffolding” of the flagellum, is composed of 9+2 microtubules pairs and provided with dynein arms, which conforms the major motor protein and provides flagella with movement. Certain autosomal recessive genetic disorders affect the structure (hence function) of specific motor proteins and, therefore, they result in the impaired action of cilia and flagella.Kartagener syndrome (KS) is caused by different mutations in various genes that encode proteins necessary for ciliary structure and function. Not only these patients suffer from respiratory tract diseases, but also their sperm exhibit an abnormal structure of the axoneme that makes it impossible for the flagellum to beat. Consequently, these patients areinfertile.Motility in a sperm sample is one of the markers for viability

Currently, there are many research lines focused on the improvement of assisted reproduction technologies (ART) and the development of new ones that guarantee new reproductive options for patients. Among the most recent investigated topics there are some worth to mention, like 3D-printed ovaries, stem cells-derived gametes or the use of CRISPR-Cas9 technology for embryos. All these promising approaches have opened new paths of research in ART, too. Recently, a paper has been published reporting functional human eggs grown in the laboratory for the first time.The study was carried out by McLaughlin and colleagues from University of Edinburgh (UK), whose research focuses on the mechanisms of follicle development. As part of the procedure, ovarian samples were collected from 10 women, aged between 25 and 39, who were undergoing elective caesarean section. Tissue pieces that showed no damage or abundant stromal tissue were dissected in the laboratory. A total of 87 fragments with follicles of a mean diameter of 40 μm were cultured for 8 days at 37°C in humidified air with 5% CO2 and renewing half the media every two days. Secondly, the growing follicles (presumably secondary follicles) were mechanically dissected and cultured indiv

Human reproduction has benefited from the possibilities offered by cryopreservation as much as any other discipline, in particular with the latest use of vitrification as opposed to slow freezing techniques (1). The increased efficiency of different techniques has progressively led to a “freeze-all” strategy within last years, which supports an improvement in clinical outcomes. Current social trends imply a significant delay in the age of motherhood. There are a variety of factors to explain such shifts in demographic charts. However, not only social freezing has popularised the use of vitrification for female gametes; the reality is that research on oocytes, donor banks, or fertility preservation treatments in cases of cancer are possible thanks to cryopreservation. Considering the efficiency of vitrification over slow-rat

Figure 1. Schematic representation depicting one of the possibilities of Klinefelter syndrome development during meiosis in the mammalian testis. Modified from (1). The common sex chromosome dosage in mammals is XX for females and XY for males. This implies that under normal circumstances each one of the X chromosomes in XX females comes from one of the parents, whereas in XY males the only X chromosome is always maternal, because the Y chromosome always comes from the father. Even though both X chromosomes in an XX…

Figure 1. Different stages of human embryos treated with CRISPR-Cas9 technology (1). Genetic modifications are still seen with both excitement and reticence by the general population. This poses a challenge, being scientists and media responsible for the information available to the public. Besides GMOs (genetically modified organisms) for industry or food, the last decade has witnessed a growing interest in genetic modifications and genome-editing techniques applicable to humans. So, it is important to note that people who are not specialists in the…

Figure 1. A scientist holds a bioprosthetic mouse ovary made of gelatin with tweezers.(1) One of the scientific advances made in recent years is 3D printing of human organs. The creation of an organ from a suitable material often allows medical doctors to decide on the best way to perform a surgical procedure. In addition, it opens up new possibilities for the use of 3D printing technologies in organ transplant programs. Now, researchers from Northwestern University Feinberg School of Medicine and McCormick…

Sources: OvaScience, http://ovascience.com/ Since 2015, the fertility-related company OvaScience from Canada has recently launched a new technique called AUGMENT, which has resulted in a high controversy around the world. WHAT IS AUGMENT? It is a new IVF technique designed to improve women’s oocyte quality. How does it work? Through this technique, doctors have to biopsy tissue from the lining ovaries of a woman normally under general anesthesia, the entire procedure is performed via laparoscopic surgery. Then, samples are transported to the…