Chromatin condensation but not DNA integrity of pig sperm is greater in the sperm-rich fraction

Estel Viñolas-Vergés; Jordi Ribas-Maynou; Isabel Barranco; Camila Peres Rubio; Sergi Bonet; Jordi Roca; Marc Yeste

doi:10.1186/s40104-023-00938-w

Chromatin condensation but not DNA integrity of pig sperm is greater in the sperm-rich fraction

J Anim Sci Biotechnol. 2023 Nov 6;14(1):139. doi: 10.1186/s40104-023-00938-w.

Authors

Estel Viñolas-Vergés^#^{1

2}, Jordi Ribas-Maynou^#^{3

4}, Isabel Barranco⁵, Camila Peres Rubio⁵, Sergi Bonet^{1

2}, Jordi Roca⁵, Marc Yeste^{1

2

6}

Affiliations

¹ Unit of Cell Biology, Department of Biology, Faculty of Sciences, University of Girona, Girona, Spain.
² Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain.
³ Unit of Cell Biology, Department of Biology, Faculty of Sciences, University of Girona, Girona, Spain. jordi.ribasmaynou@udg.edu.
⁴ Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain. jordi.ribasmaynou@udg.edu.
⁵ Department of Medicine and Animal Surgery, Faculty of Veterinary Science, University of Murcia, Murcia, Spain.
⁶ Catalan Institution for Research and Advanced Studies (ICREA), S08010, Barcelona, Spain.

^# Contributed equally.

Abstract

Background: Protamination and condensation of sperm chromatin as well as DNA integrity play an essential role during fertilization and embryo development. In some mammals, like pigs, ejaculates are emitted in three separate fractions: pre-sperm, sperm-rich (SRF) and post sperm-rich (PSRF). These fractions are known to vary in volume, sperm concentration and quality, as well as in the origin and composition of seminal plasma (SP), with differences being also observed within the SRF one. Yet, whether disparities in the DNA integrity and chromatin condensation and protamination of their sperm exist has not been interrogated.

Results: This study determined chromatin protamination (Chromomycin A3 test, CMA₃), condensation (Dibromobimane test, DBB), and DNA integrity (Comet assay) in the pig sperm contained in the first 10 mL of the SRF (SRF-P1), the remaining portion of the sperm-rich fraction (SRF-P2), and the post sperm-rich fraction (PSRF). While chromatin protamination was found to be similar between the different ejaculate fractions (P > 0.05), chromatin condensation was seen to be greater in SRF-P1 and SRF-P2 than in the PSRF (P = 0.018 and P = 0.004, respectively). Regarding DNA integrity, no differences between fractions were observed (P > 0.05). As the SRF-P1 has the highest sperm concentration and ejaculate fractions are known to differ in antioxidant composition, the oxidative stress index (OSi) in SP, calculated as total oxidant activity divided by total antioxidant capacity, was tested and confirmed to be higher in the SRF-P1 than in SRF-P2 and PSRF (0.42 ± 0.06 vs. 0.23 ± 0.09 and 0.08 ± 0.00, respectively; P < 0.01); this index, in addition, was observed to be correlated to the sperm concentration of each fraction (Rs = 0.973; P < 0.001).

Conclusion: While sperm DNA integrity was not found to differ between ejaculate fractions, SRF-P1 and SRF-P2 were observed to exhibit greater chromatin condensation than the PSRF. This could be related to the OSi of each fraction.

Keywords: Chromatin; Condensation; DNA integrity; Ejaculate fractions; Pig; Protamination; Sperm.

Abstract

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