Seminal Plasma: Relevant for Fertility?

Abstract

Seminal plasma (SP), the non-cellular component of semen, is a heterogeneous composite fluid built by secretions of the testis, the epididymis and the accessory sexual glands. Its composition, despite species-specific anatomical peculiarities, consistently contains inorganic ions, specific hormones, proteins and peptides, including cytokines and enzymes, cholesterol, DNA and RNA—the latter often protected within epididymis- or prostate-derived extracellular vesicles. It is beyond question that the SP participates in diverse aspects of sperm function pre-fertilization events. The SP also interacts with the various compartments of the tubular genital tract, triggering changes in gene function that prepares for an eventual successful pregnancy; thus, it ultimately modulates fertility. Despite these concepts, it is imperative to remember that SP-free spermatozoa (epididymal or washed ejaculated) are still fertile, so this review shall focus on the differences between the in vivo roles of the SP following semen deposition in the female and those regarding additions of SP on spermatozoa handled for artificial reproduction, including cryopreservation, from artificial insemination to in vitro fertilization. This review attempts, including our own results on model animal species, to critically summarize the current knowledge of the reproductive roles played by SP components, particularly in our own species, which is increasingly affected by infertility. The ultimate goal is to reconcile the delicate balance between the SP molecular concentration and their concerted effects after temporal exposure in vivo. We aim to appraise the functions of the SP components, their relevance as diagnostic biomarkers and their value as eventual additives to refine reproductive strategies, including biotechnologies, in livestock models and humans.

Bos taurus and Cervus elaphus as Non-Seasonal/Seasonal Models for the Role of Melatonin Receptors in the Spermatozoon

“…However, they are quiescent in the epididymal environment, whose osmolality, pH, and overall composition differs from other reproductive fluids, and where they are tightly packed at a very high density [ 52 ]. In fact, the dilution and contact with seminal plasma, even if brief (as is typical in ruminants), produces a wide range of changes and the activation or modulation of intracellular pathways, together with the modification of the plasma membrane and a wide range of peripheral proteins [ 53 ].…”

Should All Fractions of the Boar Ejaculate Be Prepared for Insemination Rather Than Using the Sperm Rich Only?

“…However, PSPs seem to have a controversial effect, inducing a higher migration of leukocytes within the female reproductive tract [ 36 ]. For this reason, the poor fraction is supposed to exert a negative effect on the fertility outcome with respect to the sperm-rich fraction [ 37 ]. However, our data showed that the poor fraction combined with other ejaculate fractions (F3) leads to similar fertility outcomes compared with F1 and F2.…”

The Activated AMPK/mTORC2 Signaling Pathway Associated with Oxidative Stress in Seminal Plasma Contributes to Idiopathic Asthenozoospermia

“…However, the pathogenesis of asthenozoospermia is complex and not yet fully understood. Changes in seminal plasma, an important part of semen, can influence the metabolism, motility, and survival of spermatozoa [ 6 , 7 , 34 , 35 ]. Thus, this study investigated the pathogenesis of AST using seminal plasma from patients undergoing assisted reproductive techniques.…”