MOL classification: a novel meiotic spindle scoring system for predicting human embryo development and ploidy

Area of Science:

• Reproductive Biology
• Embryology
• Assisted Reproductive Technologies (ART)

Background:

• Assessing human oocyte quality is crucial for successful ART outcomes.
• The meiotic spindle (MS) is a key determinant of oocyte developmental potential.
• Predictive markers for embryological outcomes are needed for both fresh and cryopreserved oocytes.

Purpose of the Study:

• To develop and validate the Meiotic Spindle (MS) Morphology, Orientation, and Localization (MOL) scoring system.
• To assess the predictive value of the MOL system for embryological outcomes in fresh and cryopreserved human oocytes.
• To evaluate the impact of cryopreservation on MS characteristics and their predictive value.

Main Methods:

• Human oocytes were analyzed using polarized light microscopy.
• The MOL system, a three-digit code, was used to score MS Morphology, Orientation, and Localization.
• Oocytes were evaluated before and after cryopreservation, with changes recorded.
• Associations between MOL scores and fertilization/euploid blastocyst rates were analyzed.

Main Results:

• Cryopreservation induced alterations in MS morphology, orientation, and localization.
• Specific MOL scores strongly correlated with successful fertilization and chromosomally normal embryo development.
• Each MOL category variant demonstrated distinct predictive value for both fresh and cryopreserved oocytes.

Conclusions:

• The MOL scoring system offers a reliable method for predicting oocyte fertilization and embryo development potential.
• The MOL system is applicable to both fresh and cryopreserved oocytes, showing clinical value in ART.
• MOL data can support machine learning models for enhanced predictive accuracy in embryo selection.