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Enhancing sperm resilience : protective potential of the extremolyte ectoine on in vitro and in vivo fertility outcomes
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Date
2026-02
Abstract
Ectoine, a naturally occurring compatible solute produced by extremophilic bacteria, protects macromolecules and cell structures from extreme environmental stress, without disrupting essential cellular functions. The overall aim of this thesis was to evaluate the impact of multiple stress conditions on bovine sperm and to determine the protective potential of ectoine on sperm function and fertility through a series of in vitro and in vivo studies. Initial studies (Chapter 2) confirmed that ectoine is non-toxic to bull sperm and does not compromise fundamental sperm quality parameters such as motility, viability, acrosome integrity, or membrane fluidity. Under heat stress, ectoine-treated sperm maintained functional stability, while under osmotic stress, ectoine conferred protection in bulls with low osmotic resistance. Subsequent studies (Chapter 3) demonstrated that ectoine can be safely incorporated into commercial cryopreservation protocols without impairing post-thaw sperm quality or fertilisation outcomes. While ectoine did not mitigate osmotic stress-induced damage during thawing, it effectively preserved motility under heat stress, reinforcing its utility in safeguarding sperm during thermal fluctuations. In the context of the female reproductive tract (Chapter 4), ectoine did not alter baseline or stimulated inflammatory cytokine responses in cervical and uterine explants, nor did it affect sperm–neutrophil interactions or compromise sperm motility in the presence of immune cells. These findings support the immunological compatibility of ectoine within the female reproductive tract. Finally (Chapter 5), ectoine was shown to preserve sperm quality during extended liquid storage, maintaining motility, mitochondrial function, acrosome integrity and membrane fluidity over seven days, particularly at 25 mM ectoine. Ectoine did not significantly affect non-return rate up to Day 2 post-collection, indicating that ectoine did not adversely affect fertility outcomes. Collectively, this work positions ectoine as a biocompatible and functionally protective additive for bovine semen, with applications spanning cryopreservation, liquid storage and reproductive tract exposure. Its integration into semen processing protocols may offer a novel strategy to enhance sperm resilience and improve reproductive outcomes in cattle breeding programmes.
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Peer-reviewed
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University of Limerick
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Weldon_2026_Enhancing.pdf
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Sustainable Development Goals
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Attribution-NonCommercial-ShareAlike 4.0 International