Background MicroRNAs (miRNAs) are a class of noncoding small RNAs that play important roles in many physiological processes by regulating gene expression. Previous studies have shown that the expression levels of total miRNAs increase during mouse embryonic development, and some miRNAs control the regulatory network in development progression. However, few studies have focused on the effects of miRNAs on early human embryonic development. The relationship between miRNAs and early human embryogenesis is still unknown. Results In this study, RNA-seq data collected from sperm samples from 102 patients with a normal sperm index but treated with assisted reproductive technology (ART) were analyzed for the relationships between differentially expressed small RNAs and the fertilization rate (FR), blastocyst rate and high-quality embryo rate (HQER). The sperm samples with high hsa-mir-191 expression had a higher FR, effective embryo rate (EER) and HQER. hsa-mir-191 was used as a single indicator to predict the HQER. The receiver operating characteristic (ROC) curve had an area under the ROC curve (AUC) of 0.686. We also found that hsa-mir-191 expression is correlated with an abnormal sperm rate (cor = 0.29, p < 0.01). We also evaluated the relationship between hsa-mir-34c and early human embryo development in these 102 sperm samples and obtained negative results. Conclusions These findings suggest that high hsa-mir-191-5p expression in sperm is associated with early human embryonic quality and that hsa-mir-191-5p could be used as a potential marker to screen high-quality sperm to improve the success rates of in vitro fertilization (IVF).

Basal generation of reactive oxygen species (ROS) was essential for male reproductive function, whereas high ROS levels may be linked to low quality of sperm and male infertility. We examined the associations between ROS levels in whole ejaculates and sperm quality among 1092 male factor infertility (MFI) patients and 50 donors with normal semen characteristics. ROS levels were significantly positively correlated with abnormal morphology rate, head defect, and sperm deformity index. Further, we investigated whether seminal plasma from MFI patients with high ROS levels affects sperm motility from donors with normal semen characteristics. After cross-culturing fresh human sperm from donors possessing normal semen characteristics with seminal plasma from infertitle men, sperm motility was measured at different ROS levels. Seminal plasma from MFI patients significantly reduced motility of sperm and the reduction rate increased with increasing ROS levels in seminal plasma. On the other hand, we found MFI patients with the ROS levels in the lowest 25th percentile had similar ROS levels to donors with normal semen characteristics. Collectively, our observations lead to the hypothesis that oxidative stress plays a critical role in the development of MFI among those with high ROS levels, but not those with low ROS levels.

Aims: To establish reference values of semen parameters in a residential, geographic, and age representative sample of healthy Chinese men. Methods: From a national study of 1,191 healthy Chinese men, semen samples were analyzed from 105 subjects whose wives or partners were pregnant within the 12 months prior to the date when the semen sample was taken. Results: The means, fifth percentiles, and percentages lower than the WHO criteria for semen parameters were, respectively: 75.8 × 10⁶/ml, 17.8 × 10⁶/ml, and 6.7% for sperm concentration; 206.9 × 10⁶/ejection, 26.3 × 10⁶/ejection, and 6.7% for total sperm count; 18.9, 3.0, and 79.1% for rapid progressive motility; 49.1, 25.3, and 52.4% for sperm progressive motility; 73.8, 49.3, and 45.7% for sperm viability, and 49.5, 25.2, and 9.5% for normal morphology. Conclusion: The values of semen parameters for Chinese men are lower than the WHO criteria, especially for rapid progressive motility, progressive motility, and sperm viability, and a different standard for Chinese may be needed.