IVI Sevilla SL

Proper chromosome segregation is essential to avoid aneuploidy, yet in mammalian oocytes it progressively fails in an age-dependent manner. The ageing population and the increasing age of parenthood are leading to a declined fertility. Proteins contributing to correct chromosome segregation and oocyte ageing are therefore of central interest. Mouse oocytes deficient in CENP-V are strongly impaired in meiosis I. The spindle assembly checkpoint (SAC)-dependent arrest of about half of the Cenp-V -/- oocytes at metaphase I is only found in oocytes from young adults, not in oocytes >12 months. This suggests SAC weakening in ageing oocytes allowing them to proceed despite continuous presence of mis-aligned chromosomes and present CENP-V depleted oocytes as a model for age dependent weakening of the SAC. Sporadic cases of very-low oocyte survival rate have been observed after vitrification and thawing protocols in the clinical practice. However, no diagnostic tools are currently available to detect these cases. The relevance of this problem has led to a demand on the scientific community to obtain specific and early biomarkers to predict decreased oocyte survival rates after thawing. The main goal of this project is to establish the expression levels of the CENP-V protein in human oocytes as a diagnostic tool for the aging of a cohort of oocytes. With this purpose, the immature oocytes from the oocytes cohort recovered from women with advanced maternal age (AMA) and control, will be matured in vitro in order to compare the CENP-V expression levels between both populations. In addition, in patients with AMA, these expression levels will be correlated with the aneuploidy rate from the blastocyst of the same oocyte cohort. CENP-V-deleted mouse oocytes show higher rate of aneuploidy and spindle aberrations after cold treatment compared to control oocytes. We hypothesize that alterations in the expression level of CENP-V could be responsible of the decrease in oocyte survival rate after thawing. The main objective of this project is to establish the expression levels of the CENP-V protein in human oocytes as a diagnostic tool to assess the damage of a cohort of oocytes. For this purpose, oocytes retrieved from advanced maternal age (AMA) and control patients, as well as oocytes undergoing vitrification / thawing procedures and controls oocytes, will be analyzed. In this study, only the immature oocytes of the patients, which are destined to be discarded and not used in their treatment, will be analyzed.

Sperm undergo complex selection processes and physiological changes as they move through the female reproductive tract. Ejaculated-sperm must undergo a set of molecular and biochemical changes globally named as capacitation in order to acquire the ability to fertilize the oocyte. These changes include post-translational modifications of sperm proteins, with phosphorylation of tyrosine residues being one of the most outstanding characteristics of the capacitation process. In the laboratory, the capacitation process is recreated artificially before performing artificial insemination or in vitro fertilization treatments. The sample is then incubated until it is used in the treatment. Reproductive success rates can be affected by differences in incubation times and levels of capacitation of the sample. In this study, the investigators intend to study the capacitation state of the sample by measuring the levels of phosphorylation of the tyrosine residues of the proteins contained in the sperm that have already been subjected to the capacitation process in vitro.

Identifying modifiable factors that contribute to preeclampsia risk associated with assisted reproduction can improve maternal health. Recent studies have shown an increased risk for hypertensive disorders of pregnancy after in vitro fertilization, particularly for pregnancies occurring during a hormone replacement therapy such a donor egg recipient and a frozen embryo transfer. This risk may be partly attributable to the degree by which the assisted reproductive treatment affects the maternal hormonal environment, when the corpus luteum is a major source of reproductive hormones. On the other hand, cryopreserved embryos are usually thawed and replaced in in a natural or hormonally manipulated cycle; on this point, frozen embryo transfer is associated with better perinatal outcome regarding preterm birth and low birth weight yet higher risk of large for gestational age and macrosomia compared to fresh transfer. The objective of our study is to investigate whether the absence of corpus luteum adversely affects pregnancy and to analyse if there are differences in the perinatal outcomes due to differences in the endometrial preparation protocol for a frozen embryo transfer.