Beneficial effects of hypotaurine supplementation in preparation and freezing media on human sperm cryo-capacitation and DNA quality

Hanae Pons-Rejraji,Cyril Bouche,Sandra Dollet,Joël R Drevet,Solène Vorilhon,Florence Brugnon,Marc Berger,Céline Bourgne,Asmaa Difrane,Laure Chaput,Bruno Pereira

doi:10.1186/s12610-021-00144-6

Abstract

BackgroundAlthough widely used, slow freezing considerably modifies the functions of human spermatozoa. Cryopreservation induces nuclear sperm alterations and cryo-capacitation, reducing the chances of pregnancy. Hypotaurine is naturally present in the male and female genital tracts and has capacitating, osmolytic and anti-oxidant properties. The analysis were performed on surplus semen of men with normal (n = 19) or abnormal (n = 14) sperm parameters. Spermatozoa were selected by density gradient centrifugation before slow freezing. For each sample, these steps were performed in parallel with (“H+” arm) or without (“H-” arm) hypotaurine supplementation. After thawing, we measured total and progressive mobility, vitality, acrosome integrity, markers of capacitation signaling pathway and nuclear quality. For the latter, we focused on sperm chromatin packaging, DNA fragmentation and the presence of vacuoles in the sperm nucleus.ResultsPost-thaw spermatozoa selected and frozen in the presence of hypotaurine had a higher vitality (+ 16.7%, p < 0.001), progressive and total motility (+ 39.9% and + 21.6% respectively, p < 0.005) than spermatozoa from the control “H-” arm. Hypotaurine also reduced the non-specific phosphorylation of the capacitation protein markers P110 and P80 (p < 0.01), indicating a decrease in cryo-capacitation. Hypotaurine supplementation reduced chromatin decondensation, measured by chromomycin A3 (− 16.1%, p < 0.05), DNA fragmentation (− 18.7%, p < 0.05) and nuclear vacuolization (− 20.8%, p < 0.05).ConclusionOur study is the first to demonstrate beneficial effects of hypotaurine supplementation in preparation and freezing procedures on human spermatozoa sperm fertilization capacity and nucleus quality. Hypotaurine supplementation limited cryo-capacitation, increased the proportion of live and progressively motile spermatozoa and reduces the percentage of spermatozoa showing chromatin decondensation, DNA fragmentation and nuclear vacuolation.Trial registrationClinical Trial, NCT04011813. Registered 19 May 2019 - Retrospectively registered.

Highlights

IntroductionSlow freezing considerably modifies the functions of human spermatozoa
Widely used, slow freezing considerably modifies the functions of human spermatozoa
Sperm vitality and motility improvement Sperm vitality, total and progressive motility were significantly reduced after thawing compared with fresh sperm values (Table 1) for both H- (p < 0.0001 for all three parameters) and H+ (p< 0.0001 for vitality, p

Summary

Introduction

Slow freezing considerably modifies the functions of human spermatozoa. Slow freezing remains the standard method of cryopreservation of human spermatozoa [1,2,3] This method considerably affects sperm integrity, decreasing vitality and motility, and inducing both structural and functional changes, resulting in decreased sperm fertilizing capacity [4,5,6,7]. Freeze-thaw cycles increase the production of reactive oxygen species (ROS) and reduce the amount and activity of antioxidant (AO) systems, leading to oxidative stress (OS, for reviews see [8,9,10]) The effects of the latter are well known: disruption of plasma, acrosomal and mitochondrial membranes; impaired motility and fertilisation capacity; and, sperm death, especially by apoptosis [1, 10,11,12]. These sperm alterations are associated with premature capacitation or acrosome reaction or both, with low fertilization capacity and limited survival time [6, 15,16,17]

Objectives

Methods

Results

Discussion

Conclusion