Morphological study of boar sperm during their passage through the female genital tract

Abstract

Once deposited in the female tract, sperm face a series of challenges that must be overcome to ensure the presence of an adequate normal sperm population close to the site of fertilization. Our aim was to evaluate the influence of the uterine milieu on boar sperm morphology. In experiment 1, sperm morphology was evaluated in the backflow (60 min after insemination) and within the uterotubal junction (UTJ) (collected ~24 h after insemination) following intrauterine sperm deposition (n = 6) and compared with the morphology of the sperm in the insemination dose. In experiment 2, the influence of the uterine fluid (UF) on sperm morphological modifications was evaluated. For this purpose, ejaculated (n = 4) and epididymal (n = 4) sperm were in vitro incubated with or without UF for 2 and 24 h. In both experiments, sperm were classified as normal, having a cytoplasmic droplet (proximal or distal) or having tail defects. The results of experiment 1 pointed to an increase in morphologically abnormal sperm collected in the backflow (27.70%) and a reduction of the same in the UTJ (2.12%) compared with the insemination dose (17.75%) (P < 0.05). In experiment 2, incubation of ejaculated sperm with UF did not provoke any morphological modifications; however, when epididymal sperm were incubated with UF, a pronounced increase in the percentage of normal sperm was evident after 24 h compared with the initial dose (from 25.77% to 53.58%, P < 0.05), mainly due to distal cytoplasmatic droplet shedding (53.22 vs. 20.20%). In conclusion, almost all the sperm that colonize the UTJ had a normal morphology, with part of the abnormal sperm having been discarded in the backflow and part selected/modified on their way to the oviduct. UF seems to influence cytoplasmic distal droplet removal, as demonstrated previously in seminal plasma.

An update of the regulatory factors of sperm migration from the uterus into the oviduct by genetically manipulated mice

“…Sperm cells gain fertilizing ability after remaining in the female reproductive tract for a period of time (Austin, ; Chang, ). The process that renders sperm competent to fertilize an egg is known as sperm capacitation, and this process is only confined to mammalian sperm (Araki et al, ; Austin, ), which must travel a long distance and overcome various barriers in the female reproductive tract before reaching the egg at the ampulla of oviduct, where fertilization takes place (Garcia‐Vazquez et al, ; Ikawa et al, ). The most major obstacle for sperm that enters the uterus, however, is a passage through the uterotubal junction (UTJ).…”

Sperm Proteome after Interaction with Reproductive Fluids in Porcine: From the Ejaculation to the Fertilization Site

“…The spermatozoa concentration was calculated by a SpermaCue photometer to reach a concentration of 20 × 10 6 sperm/mL and six different groups were prepared: (1) SP group: spermatozoa with 20% of SP in PBS; (2) UF group: spermatozoa with 20% of UF in PBS; (3) OF group: spermatozoa with 20% of OF in PBS; (4) SP + UF group: spermatozoa with 20% of UF and 20% of SP in PBS; (5) SP + OF group: spermatozoa with 20% of OF and 20% of SP in PBS. The concentration of the different fluids used was based on previous studies performed in the pig [ 125 ] and other species [ 126 , 127 , 128 ]. Moreover, preliminary experiment tests were performed and indicated that a 20% or higher concentration has no evident impact on the sperm physiology (unpublished data).…”

Importance of sperm morphology during sperm transport and fertilization in mammals

“…Once in the oviduct, the epithelial cells appear to exert rigorous selection, being able to bind spermatozoa with particular characteristics such as normal chromatin,8 lack of capacitation, or morphological “normality”1112 among others. The failure of abnormal spermatozoa to reach the site of fertilization has also been demonstrated in various species 1314…”