Somatic cell apoptosis markers and pathways in human ejaculated sperm: potential utility as indicators of sperm quality

Abstract

In this study we extended earlier work to determine whether sperm respond to somatic cell apoptotic stimuli and whether apoptotic phenotypes are significant indicators of human sperm quality. We evaluated ejaculated sperm from fertile donors and subfertile patients following purification of fractions of high and low motility. In unstimulated conditions, caspase enzymatic activity was higher in motile fractions from subfertile patients than in donors, and was higher in low motility fractions from both groups. Staurosporine, but not a Fas ligand or H2O2, significantly increased caspase activity, but only in high motility fractions. Procaspase-3, -7 and -9 and low levels of active caspase-3, -7 and -9 were identified by immunoblot analysis. Apoptosis-inducing factor (AIF) was present in all samples but poly ADP-ribose polymerase-1 (PARP-1) was not detected. Phosphatidylserine translocation was significantly increased only with H2O2 treatment. In ejaculates of both subfertile and fertile men, we demonstrated the presence and activation of several proteins that are key constituents of apoptosis-related pathways in somatic cells, which may serve as markers for sperm quality.

Clinical outcome of magnetic activated cell sorting of non-apoptotic spermatozoa before density gradient centrifugation for assisted reproduction

“…Apoptosis is an ongoing physiological phenomenon that maintains the number of germ cells within the supportive capacity of the Sertoli cells [19]. Although ejaculated spermatozoa display several apoptosis-like characteristics, these apoptosis-related features do not necessarily indicate death functions [20]. Nevertheless, the apoptosis-like phenotype of ejaculated sperm has been associated with the presence of abnormal spermatozoa in semen [21][22][23].…”

“…Failure to eliminate these abnormal spermatozoa during spermatogenesis, known as "abortive apoptosis," may be the reason for their presence in semen [21,23]. Activation of caspases, disruption of the mitochondrial membrane potential (MMP), and increased DNA fragmentation are some of the apoptotic features that have been identified in ejaculated spermatozoa [20,[24][25][26].…”

Impact of caspase activation in human spermatozoa

“…could be demonstrated in human sperm by immunoblot studies Taylor et al, 2004;Wang et al, 2003;Wuendrich et al, 2006). However, due to the small cytoplasmic compartment the detection of caspases in human sperm might be quite difficult.…”

Evaluation of ubiquitin and annexin V in sperm population selected based on density gradient centrifugation and zeta potential (DGC-Zeta)

“…Furthermore, apoptosis and capacitation have an inverse relation, which suggests that sperm undergoing capacitation are non-apoptotic, consequently apoptotic sperm have a lower ability to undergo capacitation [30]. Therefore, not all the external apoptotic factors, like H 2 O 2 , can induce PE externalization while they activate the capases which suggests that PS externalization in sperm post-ejaculation is not directly associated with apoptosis [34]. With these in mind, it can be concluded that EPS in ejaculate before capacitation may be an indicator of abortive apoptosis, however, increase in EPS following exposure of sperm to capacitation medium and induction of an acrosome reaction are part of the physiological process to achieve fertilization [32].…”