Impact of extracellular vesicles isolated from seminal plasma upon Assisted Reproductive Technology (oocyte maturation, fertilization and embryo culture) in a mammalian model

In vitro embryo production (IVEP) is an assisted reproductive technology (ART) with an enormous potential in the biomedical and agricultural fields. In humans, IVEP is the most effective treatment to overcome infertility. In animals, IVEP is an important reality in cattle industry, and it is considered an essential tool for basic research, accelerate genetic progress in animal production and as model for human medicine. However, the IVEP-efficiency remains still relatively low.
In recent years, there have been growing research interest in extracellular vesicles (EVs), nanoparticles (30-to-1000 nm) released by most functional cells into the extracellular environment. Based on their size and biogenetic pathways, they are categorized into exosomes (small EVs) and microvesicles (large EVs). One of the greatest drawbacks that limits the EV-research field is the lack of standardization on the isolation of EVs and their subtypes. An accurate isolation of EV-subtypes is essential for better understating of the role played by each EV-subtype in physio- and pathological processes (including reproductive) and for its potential use as biomarkers.
The EVs have been postulated as crucial messengers for modulating gamete/embryo–maternal interactions in the maternal tract. Studies conducted in livestock species have reported that EVs isolated from female reproductive fluids improved IVEP efficiency. However, no study has addressed which EV-subtype could be involved in these beneficial effects. Seminal plasma (SP), a fluid composed by secretions from male accessory sex glands, play a key role for sperm-genital tract interaction. SP contains a heterogenous population of EVs, which modulate sperm physiological processes. The hypothesis of SPARTEVs was that SP-EVs could play a pivotal role in the successful of IVEP, tackling the problematic of IVEP efficiency from a novel point of view.
The main objectives of SPARTEVs were to (1) enhance the current knowledge of SP-EV subtypes, and (2) to evaluate whether these EVs may improve the efficiency of IVEP. The main conclusions achieved were that: (1) SP-EV-subtypes can be accurately isolated using a size-exclusion chromatography based-method according to its size (large and small); (2) SP-EV subtypes can be taken up by the cumulus cells of oocytes and by capacitated sperm, but not by the oocyte/presumptive zygote; (3) supplementation with SP-EV subtypes: (a) during oocyte in vitro maturation (IVM), modify the gene expression of cumulus cells but do not affect oocyte maturation rates and (b) during in vitro fertilization (IVF), impairs sperm-oocyte binding leading to a decrease on IVF-rates, modulating sperm function; (4) SP-EV subtypes differs in their proteomic profile, suggesting different biogenesis and biological function and source; (5) SP-EVs contains immunoregulatory molecules (transforming growth factor (TGF) -β1, -β2 and 3), which may be involved on modulating uterine immune environment.