Quantification and Topographical Distribution of Terminal and Linked Fucose Residues in Human Spermatozoa by Using Field Emission Scanning Electron Microscopy (FE-SEM).

Laura Robles-Gómez,Andrea López-Botella,Paula Sáez-Espinosa,Jon Aizpurua,Eliana Marina López-Viloria,María José Gómez-Torres

doi:10.3390/ijms222111947

Laura Robles-Gómez, Andrea López-Botella + Show 4 more

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https://doi.org/10.3390/ijms222111947

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Abstract

The modification of sperm glycocalyx is an essential process during sperm capacitation. The presence and redistribution of terminal and linked fucose have been described during in vitro capacitation in humans. However, the influence of the capacitation time on the quantification and localization of terminal and linked fucose is still unknown. In this study, the quantitative and qualitative changes in fucosyl residues during different in vitro capacitation times (1 and 4 h), are simultaneously characterized by using Aleuria aurantia (AAA) lectin–gold labelling and high-resolution field emission scanning electron microscopy (FE-SEM) in human sperm. A significant decrease was found in the number of terminal fucose registered in the whole sperm head during the in vitro capacitation. Nevertheless, the quantification of fucose residues after 1 h of in vitro capacitation was very similar to those found after 4 h. Therefore, the changes observed in terminal and linked fucose during capacitation were not time-dependent. Furthermore, the comprehensive analysis of the topographic distribution showed the preferential fucosyl location in the acrosomal region and the presence of distinct clusters distributed over the head in all the studied conditions. Overall, these findings corroborate the validity of FE-SEM combined with gold labelling to register changes in surface molecules during in vitro sperm capacitation.

Highlights

The mammalian sperm glycocalyx is a 20–60 nm thick coat composed of a wide variety of glycocomponents, which play an important role in the transport, recognition, and interaction of gametes [1,2]
Field emission scanning electron microscopy (FE-SEM) allowed the researchers to accurately localize and quantify the terminal and linked fucose recognized by AAA lectin in human sperm surface during in vitro capacitation
The methodology described in this study allowed the quantification of fucose residues in both acrosomal and postacrosomal regions due to the high resolution offered by field emission scanning electron microscopy (FE-SEM) [15]

Summary

Introduction

The mammalian sperm glycocalyx is a 20–60 nm thick coat composed of a wide variety of glycocomponents, which play an important role in the transport, recognition, and interaction of gametes [1,2]. The quantitative changes and the topographical distribution of terminal and linked fucose residues during in vitro capacitation are not completely understood. In this context, the authors of this paper previously used field emission scanning electron microscopy (FESEM) to accurately localize and quantify mannose residues in human sperm surface during in vitro capacitation. A significant and time-dependent decrease of mannose was registered during in vitro capacitation and a relocation mostly affecting acrosomal domain apical areas [14] These findings showed the efficacy of FE-SEM and gold labelling as a useful tool for studying sperm surface components

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