Hypo-osmotic Swelling Test and Sperm Motility after Swim-up and Two-layer Percoll Gradient Preparation of Frozen-Thawed Sperm

Abstract

Objective To evaluate the percentage of motility and hypo-osmotic swelling test (HOST) for frozen-thawed sperm, compare between sperm preparation by washing and swim-up and two-layer Percoll gradient techniques.

Subjects and methods Semen samples from 35 men were cryopreserved by the liquid nitrogen vapor method for six months. Then the frozen-thawed samples were divided into two aliquots, which were separated by washing and swim-up, and two-layer Percoll gradient techniques. The percentage of sperm motility and HOST were evaluated before and after sperm separation by both techniques.

Results Both sperm separation techniques resulted in a significant increase in sperm motility. However, washing and swim-up separated far better sperm motility than two-layer Percoll gradient (80.7 + 13.1 versus 41.7 + 19.7 ; p < 0.001). The HOST results after washing and swim-up also showed significantly higher percentage than two-layer Percoll gradient techniques (37.4 + 22.4 versus 19.9 + 15.7 ; p < 0.001), and the percentage of swollen sperm tail after the latter separation technique was lower than initial post-thaw sperm (19.9 † 15.7 versus 21.4 + 6.7 ; p < 0.05).

Conclusion Preparation of cryopreserved sperm by washing and swim-up procedure improves sperm motility and sperm tail hypo-osmotic swelling test better than that preparation by two-layer Percoll gradient procedure. However, the HOST do not provide significant information in evaluating the viability of cryopreserved sperm.