Disruption of bovine sperm functions in the presence of aplastic midpiece defect

Abstract

Background: Bulls are of great importance in the productive chain and for this reason they should have a good semen quality. There is no doubt that sperm morphology is very important to bull fertility, although little is known about how exactly the abnormal morphologies may affect sperm functions. Objectives: To detail the morphological description of the aplastic midpiece defect (AMD), as well as to understand its consequences for male fertility based on membrane and acrosome status, mitochondrial membrane potential and DNA integrity parameters. Materials and methods: The bulls were divided into two groups: control, consisting of satisfactory potential breeders (n = 3); and AMD, consisting of unsatisfactory potential breeders with a high percentage of AMD (n = 3). Bulls were evaluated by the breeding soundness evaluation; five ejaculates were collected from each animal and analyzed by flow cytometry. Results: Spermatozoa from AMD group exhibited lower sperm motility and vigor (p < 0.05). In addition, it also exhibited lower mitochondrial membrane potential (p < 0.05), a higher percentage of spermatozoa with DNA fragmentation (p < 0.05), lower acrosome and plasma membrane integrity (p < 0.05), and higher lipid bilayer sperm membrane disorganization (p < 0.05) in comparison with control bulls. Discussion: These findings may be due to oxidative stress and a reduction of the energy production capacity in addition to an alteration in the structural composition of the sperm cell. Moreover, semen with a high percentage of AMD may also be undergoing apoptosis. Conclusion: Bulls with a high percentage of AMD in their semen are not suitable for reproduction. Furthermore, it suggests there is a putative genetic basis for this sperm defect.

High percentage of midpiece defects in Brangus bull sperm with no reduction in sperm kinematics

“…Beyond midpiece issues, electron microscopy uncovered additional defects like plasma membrane irregularities in the head, vacuoles and chromatin decondensation, aligning with Díaz‐Miranda et al. (2020)'s findings of acrosome and midpiece‐linked abnormalities. The subtle morphological defects, particularly those affecting the midpiece, underscore the limitations of light microscopy in detecting such intricacies.…”

“…Díaz‐Miranda et al. (2020) linked midpiece morphological changes to decreased motility and vigour, while Silveira et al. (2023) tracked altered spermiogenesis in a semen donor bull over 11 months, suggesting a testicular origin.…”

Defeitos na peça intermediária e baixa congelabilidade do espermatozoide bovino: Relato de caso

“…Todavia, as mitocôndrias exercem um importante papel na função metabólica das células, com o objetivo de proporcionar energia para a motilidade celular (Silva & Gadella, 2006). Além disso, possíveis alterações na estrutura da bainha mitocondrial como aplasia, inchaço e lacunas podem causar danos estruturais maiores (Díaz-Miranda et al, 2020). As alterações na camada das mitocôndrias podem levar a disfunção na produção de ATP gerando maior estresse oxidativo celular (Amaral et al, 2013).…”

“…Os achados no sêmen deste touro Aberdeen Angus sugerem a hipótese de que as lesões na peça intermediária dos espermatozoides tenham origem testicular, pois ocorreu um aumento nas fraturas e na distribuição irregular das mitocôndrias ao longo da estrutura, ocasionando a perda da motilidade no processo de congelação (Díaz-Miranda et al, 2020).. Uma precisa relação causa/efeito destas anormalidades de estrutura da peça intermediária sobre a fertilidade ainda não pode ser determinada (Barth & Oko, 1989). Não foram encontradas citações na literatura associando claramente estes defeitos com a baixa congelação do sêmen (Lorton et al, 1983).…”

“…Rocha et al (2006) descreveram um detalhado estudo morfológico de defeitos de peça intermediária de origem desconhecida, sem qualquer efeito deletério aparente sobre a capacidade de fertilização. Díaz-Miranda et al (2020) relataram que touros com alta percentagem de defeitos na peça intermediária em seu sêmen são inadequados para reprodução. Além disso, sugerem que há uma suposta base genética para este defeito do espermatozoide.…”