Extracellular vesicles would be involved in the release and delivery of seminal TGF-ß isoforms in pigs

Abstract

INTRODUCTION: Pig seminal plasma (SP) is rich in active forms of all three isoforms (1-3) of transforming growth factor ? (TGF-?), a chemokine modulatory of the immune environment in the female genital tract once semen is delivered during mating or artificial insemination (AI). The present study aimed to examine how TGF-?s are secreted by the epithelium of the male reproductive tract and how they are transported in semen, emphasizing the interplay with seminal extracellular vesicles (sEVs). METHODS: Source of TGF-?s was examined by immunohistochemistry in testis, epididymis, and accessory sex glands, by immunocytochemistry in ejaculated spermatozoa, and by Luminex xMAP(®) technology in SP and sEVs retrieved from healthy, fertile male pigs used as breeders in AI programs. RESULTS: All three TGF-? isoforms were expressed in all reproductive tissues explored and would be released into ductal lumen either in soluble form or associated with sEVs. Ejaculated spermatozoa expressed all three TGF-? isoforms, both inside and outside, probably the outer one associated with membrane-bound sEVs. The results confirmed that pig SP contains all three TGF-? isoforms and demonstrated that a substantial portion of them is associated with sEVs. DISCUSSION: Seminal EVs would be involved in the cellular secretion of the active forms of seminal TGF-? isoforms and in their safe transport from the male to the female reproductive tract.