Sperm cryopreservation is a fundamental reproductive biotechnology, enabling the long-term storage of genetic material and supporting assisted reproduction programs. Despite its widespread application, the process is associated with significant limitations due to the cryo-induced cellular damage that occurs during freezing and thawing. These injuries primarily affect the plasma membrane, nuclear DNA, and motility, thereby compromising the fertilizing potential of spermatozoa. Furthermore, interspecies variability in terms of cryo-sensitivity poses a major challenge to the development of standardized cryopreservation protocols. Recent advances have focused on mitigating cryodamage through the use of various strategies. The inclusion of antioxidants in cryopreservation media has proven effective in reducing oxidative stress, thereby enhancing cellular protection. Similarly, the addition of lipid-based supplements contributes to membrane stabilization, improving post-thaw sperm viability and functionality. Moreover, the application of omics technologies, such as transcriptomics and proteomics, has facilitated a deeper understanding of molecular damage and protective responses, paving the way for the development of tailored, species-specific protocols. These integrated approaches optimize cryopreservation conditions, maximizing post-thaw survival and the fertilizing capacity of sperm. Enhancing cryopreservation techniques not only improves the outcomes of assisted reproductive technologies, but also plays a crucial role in the conservation of genetically valuable livestock species. In conclusion, the integration of biotechnological and molecular tools holds significant promise for overcoming the current limitations and advancing the efficacy of sperm cryopreservation.

Reproductive failure in dogs is often due to unknown causes, and correct diagnosis and treatment are not always achieved. This condition is associated with various congenital and acquired etiologies that develop inflammatory processes, causing an increase in the number of leukocytes within the female reproductive tract (FRT). An encounter between polymorphonuclear neutrophils (PMNs) and infectious agents or inflammation in the FRT could trigger neutrophil extracellular traps (NETs), which are associated with significantly decreased motility and damage to sperm functional parameters in other species, including humans. This study describes the interaction between canine PMNs and spermatozoa and characterizes the release of NETs, in addition to evaluating the consequences of these structures on canine sperm function. To identify and visualize NETs, May–Grünwald Giemsa staining and immunofluorescence for neutrophil elastase (NE) were performed on canine semen samples and sperm/PMN co-cultures. Sperm viability was assessed using SYBR/PI and acrosome integrity was assessed using PNA-FITC/PI by flow cytometry. The results demonstrate NETs release in native semen samples and PMN/sperm co-cultures. In addition, NETs negatively affect canine sperm function parameters. This is the first report on the ability of NETs to efficiently entrap canine spermatozoa, and to provide additional data on the adverse effects of NETs on male gametes. Therefore, NETs formation should be considered in future studies of canine reproductive failure, as these extracellular fibers and NET-derived pro-inflammatory capacities will impede proper oocyte fertilization and embryo implantation. These data will serve as a basis to explain certain reproductive failures of dogs and provide new information about triggers and molecules involved in adverse effects of NETosis for domestic pet animals.

In swine reproduction, immune-mediated mechanisms such as neutrophil extracellular trap (NET) formation can affect sperm function and reduce fertility outcomes. This study evaluated the capacity of antioxidant and reproductive compounds—butylated hydroxytoluene (BHT), prostaglandin E₂ (PGE₂), bovine serum albumin (BSA), and seminal plasma (SP)—to modulate NETosis in co-cultures of swine neutrophils and cryopreserved spermatozoa. NET formation was quantified by nuclear area expansion and validated by digital cytometry and immunofluorescence. BHT (0.5 mM) and PGE₂ (10 µM) produced the most significant inhibitory effects, reducing NETotic cell percentages from 34.5 ± 2.7% (sperm-exposed controls) to 12.2 ± 1.3% and 14.5 ± 2.1%, respectively (p < 0.01). SP at 20% decreased NETosis to 16.8 ± 1.8%, while BSA (0.5%) achieved a moderate reduction to 21.3 ± 2.5%. Flow cytometry revealed reduced peroxynitrite levels in sperm treated with SP and BSA. Two NET phenotypes (aggNETs and sprNETs) were identified. BTS medium enhanced NET formation, whereas DNase I degraded NETs effectively. These findings identify porcine NETosis as a redox-sensitive pathway modulated in vitro, suggesting an immunological role in enhancing sperm preservation for swine artificial insemination.