A comprehensive investigation of human endogenous retroviral syncytin proteins and their receptors in men with normozoospermia and impaired semen quality

Abstract

Purpose The study aims to investigate first the presence of Syncytin 2 and its receptor, MFSD2, in human sperm, and second whether the expressions of Syncytin 1, Syncytin 2, and their receptors, SLC1A5 and MFSD2, differ between normozoospermic, asthenozoospermic, oligozoospermic, and oligoasthenozoospermic human sperm samples. Methods The localization patterns and expression levels of syncytins and their receptors were evaluated in normozoospermic (concentration = 88.9 ± 5.5 × 10 6 , motility = 79.2 ± 3.15%, n = 30), asthenozoospermic (concentration = 51.7 ± 7.18 × 10 6 , motility = 24.0 ± 3.12%, n = 15), mild oligozoospermic (concentration = 13.5 ± 2.17 × 10 6 , motility = 72.1 ± 6.5%, n = 15), moderate oligozoospermic (concentration = 8.4 ± 3.21 × 10 6 , motility = 65.1 ± 8.9%, n = 15), severe oligozoospermic (concentration = 2.1 ± 1.01 × 10 6 , motility = 67.5 ± 3.2%, n = 15), and oligoasthenozoospermic (concentration = 5.5 ± 3.21 × 10 6 , motility = 18.5 ± 1.2%, n = 15) samples by immunofluorescence staining and western blot. Results Syncytins and their receptors visualized by immunofluorescence showed similar staining patterns with slight staining of the tail in all spermatozoa regardless of normozoospermia, asthenozoospermia, oligozoospermia, or oligoasthenozoospermia. The localization patterns were categorized as equatorial segment, midpiece region, acrosome, and post-acrosomal areas. The combined staining patterns were also detected as acrosomal cap plus post acrosomal region, the midpiece plus equatorial segment, and midpiece plus acrosomal region. However, some sperm cells were categorized as non-stained. Both syncytin proteins were most intensely localized in the midpiece region, while their receptors were predominantly present in the midpiece plus acrosomal region. Conspicuously, syncytins and their receptors showed decreased expression in asthenozospermic, oligozoospermic, and oligoasthenozoospermic samples compared to normozoospermic samples. Conclusion The expression patterns of HERV-derived syncytins and their receptors were identical regardless of the spermatozoa in men with normozoospermia versus impaired semen quality. Further, asthenozoospermia, oligozoospermia, and oligoasthenozoospermia as male fertility issues are associated with decreased expression of both syncytins and their receptors.

High-fat diet impairs male fertility by disrupting Divalent metal transporter 1 and miR-135b in the gut-testis axis

“…Phosphatidic acid (PA), a common phospholipid and a component of cell membranes, plays a very important role in the later stages of spermatogenesis, and phosphatidic acid levels have been associated with male infertility [53]. Glutamine and L-arginine have been proven to reduce sperm motility [54][55][56]. Thus, miR135b mainly affects sperm function in obese mice, including but not limited to sperm motility, sperm capacitation, sperm count and fertilization.…”

Molecular mechanisms of syncytin-1 in tumors and placental development related diseases

“…The abnormal expression of syncytin-1 is also associated with other placental developmental related diseases in addition to PE. Studies have found that the expression of syncytin-1 and its receptor SLC1A5 have significantly decreased in samples with asthenozoospermic, oligozoospermic and oligoasthenozoospermic than normozoospermic samples [ 90 ], suggesting that decreased expression of syncytin-1 and SLC1A5 could be a cause of infertility. So, it might be one way to treat infertility in the future by increasing their expression.…”