PurposeTo investigate the relationship between the meiotic spindle size in human metaphase II oocytes and embryo developmental potential after intracytoplasmic sperm injection (ICSI).MethodsAnalyzed were 1302 oocytes with a visible meiotic spindle from 281 patients aged under 40 years undergoing ICSI cycles. The meiotic spindle was imaged by using PolScope before ICSI. The oocytes were classified into three groups, according to spindle size: group A (<90 μm2), group B (90‐120 μm2), and group C (>120 μm2).ResultsOverall, 389 (29.9%) oocytes were classified into group A, 662 (50.8%) into group B, and 251 (19.3%) into group C. The fertilization rate of the group B oocytes was significantly higher than for the A and C oocytes. The blastocyst formation rate in group B was significantly higher than in group A. In addition, the pregnancy rate in group B was significantly higher than in the other two groups.ConclusionThe oocytes with a spindle size of 90‐120 μm2 showed higher fertilization, blastocyst formation, and clinical pregnancy rates than those with larger or smaller spindles. The measurement of the meiotic spindle size thus has a positive predictive value for identifying human embryo developmental potential clinically.

Successful assisted reproductive technology pregnancy depends on the viability of embryos and endometrial receptivity. However, the literature has neglected effects of the endometrial environment during the proliferative phase on implantation success or failure. Human endometrial stromal cells (hESCs) were isolated from endometrial tissues sampled at oocyte retrieval during the proliferative phase from women undergoing infertility treatment. Primary hESC cultures were used to investigate the relationship between stemness and senescence induction in this population and embryo receptivity. Patients were classified as receptive or non-receptive based on their pregnancy diagnosis after embryo transfer. Biomarkers of cellular senescence and somatic stem cells were compared between each sample. hESCs from non-receptive patients exhibited significantly higher (P &lt; 0.01) proportions of senescent cells, mRNA expressions of CDKN2A and CDKN1A transcripts (P &lt; 0.01), and expressions of genes encoding the senescence-associated secretory phenotype (P &lt; 0.05). hESCs from receptive patients had significantly higher (P &lt; 0.01) mRNA expressions of ABCG2 and ALDH1A1 transcripts. Our findings suggest that stemness is inversely associated with senescence induction in hESCs and, by extension, that implantation failure in infertility treatment may be attributable to a combination of senescence promotion and disruption of this maintenance function in this population during the proliferative phase of the menstrual cycle. This is a promising step towards potentially improving the embryo receptivity of endometrium. The specific mechanism by which implantation failure is prefigured by a loss of stemness among endometrial stem cells, and cellular senescence induction among hESCs, should be elucidated in detail in the future.

Purpose To investigate the relationship between meiotic spindle characteristics in human oocytes and the timing of the first zygotic cleavage after intracytoplasmic sperm injection (ICSI). Methods Zygotes that had cleaved to two-cell stage by 27 h post-ICSI were classified as early cleaving and the remainder as late cleaving. Meiotic spindle parameters previously imaged using the PolScope were compared between the two groups. Results Of 384 embryos, 163 were classed as early cleaving and 221 as late cleaving. The rate of blastocyst formation or pregnancy by Day 2 embryo transfer was significantly higher following early cleavage than after late cleavage (52.4% vs. 24.4% or 32.6% vs. 11.4%). Spindle areas (108.0 vs. 89.8 μm 2 ), lengths (14.7 vs. 13.4 μm) and PolScope retardance were also significantly greater in the early cleaving group. Conclusions Meiotic spindle parameters determine the timing of the first zygotic cleavage and are strong indicators of human embryo developmental potential.

Aging of the uterine endometrium is a critical factor that affects reproductive success, but the mechanisms associated with uterine aging are unclear. In this study, we conducted a qualitative examination of age-related changes in endometrial tissues and identified candidate genes as markers for uterine aging. Gene expression patterns were assessed by two RNA sequencing experiments using uterine tissues from wild type (WT) C57BL/6 mice. Gene expression data obtained by RNA-sequencing were validated by real-time PCR. Genes expressing the pro-inflammatory cytokines Il17rb and chemokines Cxcl12 and Cxcl14 showed differential expression between aged WT mice and a group of mice composed of 5 and 8 week-old WT (young) animals. Protein expression levels of the above-mentioned genes and of IL8, which functions downstream of IL17RB, were analysed by quantitative immunohistochemistry of unaffected human endometrium tissue samples from patients in their 20 s and 40 s (10 cases each). In the secretory phase samples, 3,3’- diaminobenzidine (DAB) staining intensities of IL17RB, CXCL12 and CXCL14 for patients in their 40 s were significantly higher than that for patients in their 20 s, as detected by a Mann Whitney U test. These results suggest that these genes are candidate markers for endometrial aging and for prediction of age-related infertility, although confirmation of these findings is needed in larger studies involving fertile and infertile women.

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