Light Retardance of Oocyte Components as Biomarkers for Predicting Embryo Developmental Potential

Award-Winning Paper at the 2025 Taiwan Society for Reproductive Medicine #3rd Place – Basic Research Category

Authors:
Chun-I Lee^*1,2,3, Chien-Hong Chen¹, Chun-Chia Huang^1, Hsiu-Hui Chen¹, Pin-Yao Lin¹,Ming-Jer Chen¹, Tsung-Hsien Lee^1,2,3, Maw-Sheng Lee^1,2,3,
Affiliations:
Division of Infertility, Lee Women’s Hospital [1], Department of Obstetrics and Gynecology, Chung-Shan Medical University Hospital [2], Institute of Medicine, Chung Shan Medical University [3]

Study Question:

Can the light retardance of oocyte components, assessed via polarized light imaging, predict embryo developmental potential?

Study Design, Size, Duration:

A prospective cohort study at Lee Women’s Hospital (IRB: CS2-23192) investigated whether polarized light imaging of oocyte components (581 mature oocytes) predicts embryo developmental potential. This study enrolled 36 IVF patients from August 2024 to May 2025.

Materials, Setting, Methods:

Oocyte birefringence was classified into four groups based on zona pellucida (ZP) and spindle birefringence: (1) low ZP/low spindle (LZB/LSB), (2) high ZP/low spindle (HZB/LSB), (3) low ZP/high spindle (LZB/HSB), and (4) high ZP/high spindle (HZB/HSB). Spindle area, position, and retardance values were measured  by the LC-PolScopeTM software. Primary outcomes included embryo development and morphokinetics, secondary outcomes were associations with usable blastocyst formation. Statistical analyses included Fisher’s exact, chi-square, and generalized estimating equation models.

Main Results:

Oocytes with MII spindle birefringence had significantly higher fertilization rates (80.9% vs. 46.9%), blastocyst formation (57.9% vs. 18.8%), and usable blastocyst rates (46.1% vs. 15.6%) than those without. The HZB/HSB group achieved the highest blastocyst (63.5%) and usable blastocyst rates (53.7%), outperforming LZB/LSB (36.8%, 15.8%) and HZB/LSB (43.8%, 32.1%). HZB/HSB embryos developed faster, with 75.7% and 50.9% achieving high-quality inner cell mass (ICM) and trophectoderm (TE) grades (≥ B). ZP retardance was higher in HZB vs. LZB oocytes (62,696–63,366 nm vs. 47,237–47,377 nm). Spindle retardance (564–665 nm vs. 335–362 nm) and area (287–297 μm2 vs. 216–241 μm2) were elevated in HSB vs. LSB. In contrast to oocyte retardance (OR = 0.977), spindle retardance (OR = 3.889) and area (OR = 1.003) positively correlated with usable blastocyst formation. The spindle-to-oocyte retardance ratio (SORR) was strongly predictive (adjusted OR = 1.151, AUC = 0.63) for usable blastocyst formation. Oocytes with SORR ≥ 0.01127 had superior fertilization (87.6%), blastocyst (71.0%), and usable blastocyst rates (61.8%). 

Conclusion:

Birefringence intensities of the ZP and meiotic spindle are robust indicators of oocyte quality. The SORR serves as a novel biomarker for identifying oocytes with high potential to develop into usable blastocysts.