Label-Free Detection of Acrosome Reaction of Human Sperm Based on Diffraction Phase Microscopy

Area of Science:

• Reproductive Biology
• Biomedical Imaging
• Sperm Analysis

Background:

• The acrosome reaction (AR) is critical for fertilization and assessing sperm's fertilization potential in clinical settings.
• Label-free methods for determining AR status in sperm remain a significant challenge in reproductive medicine.

Purpose of the Study:

• To develop and validate a label-free multimodal imaging system for assessing sperm acrosome reaction (AR) status.
• To evaluate the efficacy of phase imaging metrics in distinguishing AR status in live sperm.

Main Methods:

• A multimodal imaging system integrating fluorescence, phase, and bright-field imaging was developed to observe the same sperm.
• Sperm phase characteristics, specifically three phase metrics ($\stackrel{\circledR }{{\phi }_{acr}}$, $\stackrel{\circledR }{\Delta \phi }$, $\stackrel{\circledR }{R_{\phi }}$), were analyzed to assess AR status.
• A classification model based on the $\stackrel{\circledR }{R_{\phi }}$ metric was developed and validated using ROC analysis.

Main Results:

• The $\stackrel{\circledR }{R_{\phi }}$ metric demonstrated the highest accuracy in distinguishing AR status compared to other phase metrics.
• The classification model based on $\stackrel{\circledR }{R_{\phi }}$ achieved a high performance with an AUC of 0.907.
• Excluding sperm heads with vacuoles further improved the classification accuracy of $\stackrel{\circledR }{R_{\phi }}$ to 95.5%.

Conclusions:

• Label-free diffractive phase microscopy provides a quantitative method for detecting AR status in live sperm.
• The developed multimodal imaging system and phase metrics show significant promise for clinical applications in fertility assessment.