Spermatozoa selected by a discontinuous Percoll density gradient exhibit better motion characteristics, more hyperactivation, and longer survival than direct swim-up

Abstract

Objective: To determine if a discontinuous Percoll density gradient selects spermatozoa with different motion characteristics than direct swim-up.

Design: Controlled prospective study of the effect of two preparation techniques on spermatozoa from normal semen samples using computer-aided sperm analysis (CASA).

Setting: The Fertility laboratory, Queen Charlotte's Hospital, London, United Kingdom.

Patients: Eighteen male patients.

Interventions: Semen samples were divided into two equal parts. The first part was prepared by a direct swim-up whereas the other half was subjected to a three-layer discontinuous Percoll density gradient centrifugation. The separated samples were then examined at 30 minutes and 3, 6, and 24 hours by CASA.

Results: Although swim-up selected a higher proportion of motile spermatozoa, Percoll produced a greater yield of motile cells. Straight line velocity was similar for both methods throughout study. In contrast, spermatozoa isolated by Percoll exhibited a significantly higher curvilinear velocity and amplitude of lateral head displacement, which lasted for > or = 6 hours. These changes were accompanied by a significant reduction in linearity of progression. The most dramatic effect of Percoll was to produce significantly greater numbers of spermatozoa expressing hyperactivation. After both swim-up and Percoll there was a decline in progressive motility over the 24 hours, although this was only significant for swim-up.

Conclusions: In normal semen, a discontinuous Percoll density gradient selects spermatozoa with better motion characteristics, more hyperactivation, and improved longevity compared with direct swim-up. In view of the relationship between sperm motion characteristics and fertilizing ability, we conclude that the three-layer discontinuous Percoll density gradient be adopted as the preferred method for the preparation of spermatozoa for assisted reproduction.