Differences between species in the role of seminal plasma in sperm transport

Jessica P. Rickard¹, Sophie Warr¹, Taylor Pini², Simon P. de Graaf¹

1. The University of Sydney, Faculty of Science, School of Life and Environmental Sciences, NSW 2006, Australia

2. School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia

Abstract Text:

Spermatozoa are faced with a host of physical, biochemical and immunological female selection barriers when inside the reproductive tract, many of which differ depending on whether deposition occurs in the vagina or uterus, like that of the ram or boar respectively.  Understanding the mechanisms behind these critical sperm-female interactions are key for optimising reproductive technologies in animal production industries, which often involves using spermatozoa following storage or in vitro processing, as well as insemination techniques which bypass the physiologically normal pathway to the site of fertilisation.  Consequently, the influence of seminal plasma on sperm transport, survival and pregnancy success following artificial insemination specifically, varies depending on species and type of spermatozoa used, identifying it as a highly complex medium likely contributing to immune tolerance of allogenic sperm and developing embryos in the female.

Considerable research has focused on the diverse role of seminal plasma both on sperm function and survival within the female over recent decades.   Seminal plasma has been shown to promote implantation in pigs, horses and cattle by modulating uterine endometrial immune responses, while in sheep, it facilitates cervical transit but also exacerbates sperm clearance.  The use of advanced molecular techniques such as transcriptomics, proteomics, cell culture, cytokine expression and neutrophil binding assays have increased our understanding of the relationship between sperm- immune recognition, and how this can be manipulated in the presence of seminal plasma in vitro.  Here, we use the sheep model as an example, assessing the role of seminal plasma in sperm transport and immune interactions, comparing with findings in cattle, pig and horse to identify potential trends in seminal plasma function and reproductive strategy.  Isolating immune pathways and seminal plasma components could ultimately lead to the development of strategies to restore the balance between immune tolerance and sperm survival, improving outcomes following artificial reproductive technologies.