The use of an in vitro sperm activation assay to detect chemically induced damage of human sperm nuclei.

A human sperm activation assay (HSAA) has recently been developed to assess sperm quality and functionality. The HSAA involves incubating lysolecithin-permeabilized sperm in Xenopus laevis ova cytoplasmic extract. Factors in the extract activate sperm nuclei; the activation involves sperm chromatin decondensation, DNA synthesis, and chromatin recondensation. We report that human sperm chemically damaged in vitro by treatment with a reversible crosslinker, ethylene glycolbis(sulfosuccinimidylsuccinate; SEGS), display abnormal chromatin decondensation when analyzed in the HSAA. Less than 20% of SEGS-treated sperm fully decondensed, vs. 97% of control sperm. Chemical reversal of the crosslinks by treatment with 5 microM hydroxylamine restored full decondensation in 76% of treated sperm. These results demonstrate that chemically damaged sperm respond abnormally in the HSAA, and that chemical damage to sperm nuclei can be detected using the HSAA. Thus, there is potential for the HSAA to be used to detect chemical alterations of sperm nuclei from men exposed to environmental toxicants.