Design and realization of high performance textured lead-free piezoelectric ceramics through human-AI collaboration.

Currently, one of the primary approaches to treating infertility is assisted reproductive technology (, ). The success of assisted reproductive technology depends on several factors (, , ), among which the quality and maturity of the oocytes selected for fertilization are especially critical (). The presence of oocyte polar body has traditionally been regarded as a marker of nuclear maturity and readiness for fertilization during IVF (, ). However, recent studies have demonstrated that the presence of a polar body does not necessarily indicate full oocyte maturity, even when it is observed in the perivitelline space (, , , , ). , (), (), () reported that the status of the meiotic spindle (MS) at the time of intracytoplasmic sperm injection (ICSI) is a more reliable predictor of fertilization success. MS is a key structure involved in accurate chromosome segregation, and its presence reflects maturity of the oocyte. A normal MS is a transient, bipolar microtubule-based structure that assembles between two opposing spindle poles during meiosis. It captures chromosomes via kinetochore–microtubule attachments, aligns them at the metaphase plate, and generates the forces required for accurate chromosome segregation. In meiosis I, the spindle mediates the separation of homologous chromosomes, whereas in meiosis II, MS promotes the segregation of sister chromatids, thereby ensuring proper haploid chromosome distribution. The MS is crucial for accurate chromosome segregation during oocyte maturation, and its presence, orientation, and birefringence (retardance) are closely associated with developmental competence, thereby influencing both fertilization outcomes and subsequent embryo development (, , , , ). Oocytes with normal spindle morphology show a significantly higher likelihood of achieving full maturation and reducing the risk of aneuploidy in resulting embryos compared with those lacking or displaying abnormal spindles (). Importantly, polarized light microscopy, a non-invasive imaging method, enables direct visualization of MS (, ). In our recent pilot study (), adjusting the timing of fertilization according to the position of MS relative to the polar body significantly increased (by 33%) the likelihood of successful fertilization in women over 35 years of age. Oocytes with MS evaluation were fertilized according to MS status either 5–6 h after ovum pickup (OPU) or 7–8 h after OPU. Extended incubation allowed a greater proportion of oocytes to reach full maturation and become optimally prepared for fertilization. Under these conditions, the status of MS served as a critical indicator of oocyte immaturity. In contrast, for patients younger than 35 years, the oocyte maturation was naturally synchronized and the modifying ICSI time according to MS status did not significantly influence the efficiency of human-assisted reproduction.