Purpose  

Cryopreservation of sperm is a widely used technique to maintain and protect the fertility in various occasions such as infertility and malignancy treatments. This study aims to reveal the effects of freezing and thawing on human spermatozoa.

Materials and methods  

To evaluate the effects of freeze–thawing, semen samples were evaluated by light microscopy by means of morphology, motility and viability, by scanning and transmission electron microscopy for detailed ultrastructural changes.

Results  

After cryopreservation, a significant decrease in spermatozoa viability was observed (p < 0.01). Group a, b and c motility according to World Health Organization criteria decreased considerably (p < 0.05, p < 0.01, p < 0.05, respectively), whereas there was a substantial increase in group d motility. A strong correlation between rise in number of immotile spermatozoa and decrease in viability was also noted (r = −0.848, p < 0.01). Post-thaw light microscopic studies revealed a considerable decrease in rate of normal spermatozoa (p < 0.05). A considerable decline in the rate of normal sperm was also observed by TEM (p < 0.05). Statistically, acrosomal changes and subacrosomal swelling were found to be significantly increased (both p < 0.05), where the latter appears to be a novel finding in literature.

Conclusion  

Cryopreservation has deleterious effects on spermatozoa, especially on plasmalemma, acrosomes and tails. Electron microscopy is the ultimate modality to investigate spermatogenic cells.