Use of sensitivity-enhanced nuclear magnetic resonance spectroscopy equipped with a 1.7-mm cryogenically cooled micro-coil probe in identifying human sperm intracellular metabolites

Context: The clinical value of human sperm metabolites has not been established due to the technical complexity in detecting these metabolites when sperm numbers are low. Aims: To detect endogenous intracellular metabolites in fresh and post-thaw human spermatozoa using 800 MHz nuclear magnetic resonance (NMR) spectroscopy equipped with a 1.7-mm cryo-probe. Methods: Processed spermatozoa from 25 normozoospermic ejaculates were subjected to extraction of intracellular metabolites and then profiled by sensitivity-enhanced NMR spectroscopy equipped with a 1.7-mm cryogenically cooled micro-coil probe. In parallel, some of the processed sperm fractions were subjected to freeze-thawing and were then analysed for intracellular metabolites. Key results: Twenty-three metabolites were profiled from only 1.25 million sperm cells. Comparison of the metabolomic signature of pre-freeze and post-thaw sperm cells did not show significant changes in the levels of metabolites. Conclusions: Sensitivity-enhanced NMR spectroscopy equipped with a 1.7-mm cryogenically cooled micro-coil probe is a potential tool for identifying intracellular metabolites when sperm number is low. Implications: Use of sensitivity-enhanced NMR spectroscopy opens up the opportunity to test for endogenous metabolites in samples with a limited number of spermatozoa, to understand the patho-physiology of infertility.