Glass wool filtration leads to a higher percentage of spermatozoa with intact acrosomes: an ultrastructural analysis

We investigated the possibility of ultrastructural damage to human spermatozoa induced by different sperm preparation techniques. Ejaculates from 20 normozoospermic men were divided into equal aliquots and processed by glass wool filtration, Percoll density gradient centrifugation, and a simple two-step centrifugation procedure which served as a control. The evaluation of 60 spermatozoa from each of 20 test subjects (in all, n = 1200) ensured that a sufficiently large number of spermatozoa were investigated. Ultrastructural damage was assessed by scanning electron microscopy. We investigated the state of the acrosome after sperm preparation and measured the percentage of intact spermatozoal structures compared with that of the control. Compared with Percoll density gradient centrifugation, glass wool filtration yielded a significantly increased proportion of intact acrosomes. However, both preparations gave significantly better results than the control. In conclusion, both glass wool filtration and Percoll centrifugation are efficient techniques for the accumulation of spermatozoa with intact acrosomes. Because of the significantly higher percentage of intact acrosomes, glass wool filtration appears to be the more appropriate method. The significance of the conspicuous bending of sperm tails after Percoll centrifugation is not yet known.