Determination of live human sperm metabolism during post-ejaculation life using 13C-Magnetic Resonance Spectroscopy

The journey sperm make through the female reproductive tract (FRT) has two possible outcomes: fertilisation or death. During their journey three key events occur: (i) capacitation; (ii) hyperactivation; and (iii) the acrosome reaction. Whilst capacitation is a prerequisite for fertilisation to occur and the acrosome reaction allows sperm to penetrate the egg, the exact role of hyperactivation is debated. These key events likely use ATP generated by glycolysis or oxidative phosphorylation, but it is unclear what the exact ATP demands are. The aim of this research is to investigate live sperm metabolism during capacitation, hyperactivation, the acrosome reaction and apoptosis. Capacitation was successfully stimulated by HSA and bicarbonate in human and boar sperm, hyperactivation by caffeine, the acrosome reaction by progesterone, PGE1 and NH4Cl, and apoptosis by staurosporine. Hyperactivation was detected by CASA, capacitation, acrosome reaction and apoptosis by fluorescent staining; tyrosine phosphorylation, FITC-PSA and TUNEL assay respectively. Metabolism was investigated using 13C-NMR. There was a significant increase in lactate production during capacitation, hyperactivation and the acrosome reaction in human sperm and during capacitation and the acrosome reaction in boar sperm. A simultaneous decrease in bicarbonate production was observed during capacitation in human sperm and during the acrosome reaction in human and boar sperm. These results suggest that local glycolytic ATP generation in the head and principal piece support the capacitation, hyperactivation and acrosome reaction- associated events that occur in the head and tail, without a reliance on oxidative phosphorylation. An increased understanding of these essential events, and their underlying metabolic pathways, could lead to developments in assisted reproduction procedures, which could potentially impact the clinical outcome.