Follicular Fluid

The assessment of oocyte quality in human in vitro fertilization (IVF) is getting increasing attention from embryologists. Oocyte selection and the identification of the best oocytes, in fact, would help to limit embryo overproduction and to improve the results of oocyte cryostorage programs. Follicular fluid (FF) is easily available during oocyte pick-up and theorically represents an optimal source on non-invasive biochemical predictors of oocyte quality. Unfortunately, however, the studies aiming to find a good molecular predictor of oocyte quality in FF were not able to identify substances that could be used as reliable markers of oocyte competence to fertilization, embryo development and pregnancy. In the last years, a well definite trend toward passing from the research of single molecular markers to more complex techniques that study all metabolites of FF has been observed. The metabolomic approach is a powerful tool to study biochemical predictors of oocyte quality in FF, but its application in this area is still at the beginning. This review provides an overview of the current knowledge about the biochemical predictors of oocyte quality in FF, describing both the results coming from studies on single biochemical markers and those deriving from the most recent studies of metabolomics.

Circulating or "extracellular" microRNAs (miRNAs) detected in biological fluids, could be used as potential diagnostic and prognostic biomarkers of several disease, such as cancer, gynecological and pregnancy disorders. However, their contributions in female infertility and in vitro fertilization (IVF) remain unknown. This study investigated the expression profiles of five circulating miRNAs (let-7b, miR-29a, miR-30a, miR-140 and miR-320a) in human follicular fluid from 91 women with normal ovarian reserve and 30 with polycystic ovary syndrome (PCOS) and their ability to predict IVF outcomes. The combination of FF miR-30a, miR-140 and let-7b expression levels discriminated between PCOS and normal ovarian reserve with a specificity of 83.8% and a sensitivity of 70% (area under the ROC curve, AUC = 0.83 [0.73-0.92]; p 2 (p = 0.04). Moreover, FF let-7b predicted the development of expanded blastocysts with 70% sensitivity and 64.3% specificity (AUC = 0.67 [0.54-0.79]; p = 0.02) and FF miR-29a potential to predict clinical pregnancy outcome reached 0.68 [0.55-0.79] with a sensitivity of 83.3% and a specificity of 53.5% (p = 0.01). Therefore, these miRNAs could provide new helpful biomarkers to facilitate personalized medical care during IVF.

The oviductal fluid is the first environment experienced by mammalian embryos at the very beginning of life. However, it has long been believed that the oviductal environment was not essential for proper embryonic development. Successful establishment of in vitro embryo production techniques (which completely bypass the oviduct) have reinforced this idea. Yet, it became evident that in vitro produced embryos differ markedly from their in vivo counterparts, and these differences are associated with lower pregnancy outcomes and more health issues after birth. Nowadays, researchers consider the oviduct as the most suitable microenvironment for early embryonic development and a substantial effort is made to understand its dynamic, species-specific functions. In this review, we touch on the origin and molecular components of the oviductal fluid in mammals, where recent progress has been made thanks to the wider use of mass spectrometry techniques. Some of the factors and processes known to regulate oviductal secretions, including the embryo itself, as well as ovulation, insemination, endogenous and exogenous hormones, and metabolic and heat stress, are summarized. Special emphasis is laid on farm animals because, owing to the availability of sample material and the economic importance of fertility in livestock husbandry, a large part of the work on this topic has been carried out in domestic animals used for dairy and/or meat production.

Polycystic ovarian syndrome (PCOS) is a common endocrine disorder characterized by ovulatory dysfunction. Fertility outcomes in PCOS patients are often suboptimal, potentially owing to alterations in the follicular fluid (FF) microenvironment. However, the differences in FF hormone levels between PCOS and non-PCOS patients, as well as their correlation with assisted reproductive technology (ART) outcomes, remain unclear. This prospective study included 18 PCOS patients and 18 infertile women without PCOS (control group) undergoing intracytoplasmic sperm injection at the Division of Reproductive Medicine, Ramathibodi Hospital. The primary objective was to compare ART outcomes between the groups. Furthermore, FF testosterone, dehydroepiandrosterone sulfate, and luteinizing hormone levels were evaluated to assess their correlation with these outcomes. The number of retrieved oocytes was significantly higher in the PCOS group; however, the rates of metaphase II oocyte formation, fertilization, blastocyst formation, and high-quality blastocyst formation were comparable between the groups. Although FF testosterone and FF luteinizing hormone levels were higher in the PCOS group than in the control group, the differences were not statistically significant. Spearman correlation analysis showed that FF testosterone levels were negatively correlated with fertilization rate (r = -0.3496, p = 0.0366). These findings suggest that increased FF testosterone levels may negatively correlation with fertilization rates, which may reflect one of the contributing factors to the suboptimal ART outcomes observed in PCOS patients.