Abnormal sperm parameters in humans are indicative of an abortive apoptotic mechanism linked to the Fas mediated pathway

The life cycle of many cell types can hinge on the presence of death factors that can control programmed cell death. The Fas-mediated apoptotic pathway has been implicated in controlling apoptosis during spermatogenesis in a number of mammalian species. In the human, the presence of nuclear DNA damage in ejaculated spermatozoa has pointed to a possible role for apoptosis during spermatogenesis. The presence of other molecular markers of apoptosis has, however, not been shown. More importantly, differences in these markers have not been investigated in men with normal and abnormal sperm parameters. In this study we examine for the presence of the cell surface protein Fas in ejaculated human spermatozoa. Ejaculated spermatozoa (55 samples) were labeled with anti-human Fas antibody and the number of spermatozoa displaying Fas were counted using a fluorescence-activated cell sorter (FACS). In 30/31 (96.8%) normal males (>20 million sperm per milliliter), less than 10% of the spermatozoa were Fas positive. In contrast, 14/24 (58.3%) oligozoospermic samples (