Bovine sperm-oviduct interactions are characterized by specific sperm behaviour, ultrastructure and tubal reactions which are impacted by sex sorting

Miguel Camara Pirez,Heather Steele,Sven Reese,Sabine Kölle

doi:10.1038/s41598-020-73592-1

Miguel Camara Pirez, Heather Steele + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-73592-1

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Abstract

To date sperm-oviduct interactions have largely been investigated under in vitro conditions. Therefore we set out to characterize the behaviour of bovine spermatozoa within the sperm reservoir under near in vivo conditions and in real-time using a novel live cell imaging technology and a newly established fluorescent sperm binding assay. Sperm structure and tubal reactions after sperm binding were analysed using scanning and transmission electron microscopy and histochemistry. As a model to specify the impact of stress on sperm-oviduct interactions, frozen-thawed conventional and sex-sorted spermatozoa from the same bulls (n = 7) were co-incubated with oviducts obtained from cows immediately after slaughter. Our studies revealed that within the oviductal sperm reservoir agile (bound at a tangential angle of about 30°, actively beating undulating tail), lagging (bound at a lower angle, reduced tail movement), immotile (absence of tail movement) and hyperactivated (whip-like movement of tail) spermatozoa occur, the prevalence of which changes in a time-dependent pattern. After formation of the sperm reservoir, tubal ciliary beat frequency is significantly increased (p = 0.022) and the epithelial cells show increased activity of endoplasmic reticula. After sex sorting, spermatozoa occasionally display abnormal movement patterns characterized by a 360° rotating head and tail. Sperm binding in the oviduct is significantly reduced (p = 0.008) following sexing. Sex-sorted spermatozoa reveal deformations in the head, sharp bends in the tail and a significantly increased prevalence of damaged mitochondria (p < 0.001). Our results imply that the oviductal cells specifically react to the binding of spermatozoa, maintaining sperm survival within the tubal reservoir. The sex-sorting process, which is associated with mechanical, chemical and time stress, impacts sperm binding to the oviduct and mitochondrial integrity affecting sperm motility and function.

Highlights

To date sperm-oviduct interactions have largely been investigated under in vitro conditions
Our study provides the first comprehensive documentation of sperm-oviduct interactions in real-time and under near in vivo conditions using the bovine as a model
It highlights for the first time how physical and chemical stress impact the formation of the physiological sperm reservoir and the communication of spermatozoa and tubal epithelium

Summary

Introduction

To date sperm-oviduct interactions have largely been investigated under in vitro conditions. Our results imply that the oviductal cells react to the binding of spermatozoa, maintaining sperm survival within the tubal reservoir. Sperm binding may induce sex-specific changes in gene expression of oviductal cells in vivo with 501 transcripts known to be differentially expressed between oviductal epithelia incubated with X or Y-bearing spermatozoa. The majority of these transcripts are involved in signal transduction and immune response and are down-regulated in oviductal epithelia following contact with X-bearing spermatozoa[23]. The changing concentrations of estrogen and progesterone are involved in the formation of the bovine sperm reservoir and the timely release of capacitated spermatozoa[28]. The spermatozoa are labelled with the fluorescent DNA-binding dye Hoechst 33,342, passed through a flow chamber, exposed to a UV laser and are separated using magnetic field e xposure[45]

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