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

Abstract

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.