Determination of oxidative stress-related surface damage to human sperm by atomic force microscopy.

Overview

Aim of the study:
Oxidative stress is considered to be one of the important etiological factors of male fertility disorders. Excessive production of oxygen radicals results in damage to the sperm cell membrane and its DNA. The aim of the study was to apply atomic force microscopy (AFM) to depict surface damage to sperm exposed to experimental oxidative stress.

Material and methods:
Fresh samples of semen from sperm donors were obtained and processed. The AFM system Ntegra Vita (NT-MDT, Moscow, Russia) was used to characterize spermatozoa morphology within a nanometer scale. Surface topography and spatial distribution of electrical potential gradient on the sample surface were measured and recorded simultaneously, providing more complex understanding of the surface morphology. After the initial scanning and imaging of the normal spermatozoa, the slides were exposed to hydrogen peroxide solution (50 mmol/l) for 10 minutes, properly rinsed with distilled water, air dried and re-scanned. The defects were detected and recorded.

Results:
The obtained images clearly show both normal sperm head and defects of the surface of spermatozoa exposed to hydrogen peroxide. It was possible to even clearly distinguish the ultrastructure of the top of the flagella and the acrosome surface. Moreover, elements of internal structure can be observed whenever plasmatic membrane is missing. The best images of both normal and damaged spermatozoa were selected for presentation.

Conclusion:
Collected AFM images clearly highlighted many details of normal spermatozoa and spermatozoa damaged by hydrogen peroxide. This technique could represent an important tool when researching oxidative stress and explaining its effect on male infertility.

Key words:
spermatozoon – oxidative stress – AFM – infertility