Cell-Free, Embryo-Specific sncRNA as a Molecular Biological Bridge between Patient Fertility and IVF Efficiency

Abstract

Small noncoding RNAs (sncRNAs) are key regulators of the majority of human reproduction events. Understanding their function in the context of gametogenesis and embryogenesis will allow insight into the possible causes of in vitro fertilization (IVF) implantation failure. The aim of this study was to analyze the sncRNA expression profile of the spent culture media on day 4 after fertilization and to reveal a relationship with the morphofunctional characteristics of gametes and resultant embryos, in particular, with the embryo development and implantation potential. Thereto, cell-free, embryo-specific sncRNAs were identified by next generation sequencing (NGS) and quantified by reverse transcription coupled with polymerase chain reaction (RT-PCR) in real-time. Significant differences in the expression level of let-7b-5p, let-7i-5p, piR020401, piR16735, piR19675, piR20326, and piR17716 were revealed between embryo groups of various morphological gradings. Statistically significant correlations were found between the expression profiles of piR16735 and piR020401 with the oocyte-cumulus complex number, let-7b-5p and piR020401 with metaphase II oocyte and two pronuclei embryo numbers, let-7i-5p and piR20497 with the spermatozoid count per milliliter of ejaculate, piR19675 with the percentage of linearly motile spermatozoids, let-7b-5p with the embryo development grade, and let-7i-5p with embryo implantation. According to partial least squares discriminant analysis (PLS-DA), the expression levels of let-7i-5p (Variable Importance in Projection score (VIP) = 1.6262), piR020401 (VIP = 1.45281), and piR20497 (VIP = 1.42765) have the strongest influences on the implantation outcome.

Small RNA-seq analysis of extracellular vesicles from porcine uterine flushing fluids during peri-implantation

“…Furthermore, The piRNAs have been found in spent culture media of embryo [59], our results shown that lots of piRNAs were present in porcine UFs-EVs. However, there are currently not enough studies on porcine piRNAs or effective methods that accurately predict their target genes in pigs, so this analysis of porcine UFs piRNAs is limited.…”

Effect of ovarian stimulation on the expression of piRNA pathway proteins

“…However, collectively, the administration of exogenous gonadotropin led to substantial changes in the expression of these genes that play a crucial role in piRNA functions and biogenesis (Fig 1A and 1B). piR-NAs have strong effects on the occurrence of embryo implantation and they mediate the formation of healthy gametogenesis, especially in terms of genome integrity [5]. In a study, the purpose of which was to analyze the sncRNA expression profile of the spent culture media after fertilization and to investigate the relationship between the sncRNA and morphofunctional properties of gametes and the resulting embryos, it was revealed that some piRNAs have a significant effect on the occurrence of implantation, oocyte-cumulus complex and two pronuclei embryo numbers [40].…”

“…piR-NAs have strong effects on the occurrence of embryo implantation and they mediate the formation of healthy gametogenesis, especially in terms of genome integrity [5]. In a study, the purpose of which was to analyze the sncRNA expression profile of the spent culture media after fertilization and to investigate the relationship between the sncRNA and morphofunctional properties of gametes and the resulting embryos, it was revealed that some piRNAs have a significant effect on the occurrence of implantation, oocyte-cumulus complex and two pronuclei embryo numbers [40]. In other studies, it has been shown that abnormal conditions that cause defects in piRNA functions can lead to some important negative effects on the reproductive system, such as increased embryonic lethality [41] and infertility [19].…”

“…In recent years, many studies have shown that small noncoding RNAs (sncRNAs), including microRNAs (miRNAs), small endogenous interfering RNAs (siRNAs), and piwi-interacting RNAs (piRNAs), have crucial roles in reproductive functions [5]. piRNAs have a special function in reproductive biology among these sncRNAs.…”

Cell-Free Nucleic Acids

“…This Special Issue contains eight original research studies [20,21,22,23,24,25,26,27], and five review papers [28,29,30,31,32]; the diversity of the papers demonstrates how many different topics are covered by cell-free nucleic acid research.…”