EDC IMPACT: Chemical UV filters can affect human sperm function in a progesterone-like manner.

Human sperm cell function must be precisely regulated to achieve natural fertilization. Progesterone released by the cumulus cells surrounding the egg induces a Ca2+ influx into human sperm cells via the CatSper Ca2+-channel and thereby controls sperm function. Multiple chemical UV filters have been shown to induce a Ca2+ influx through CatSper, thus mimicking the effect of progesterone on Ca2+ signaling. We hypothesized that these UV filters could also mimic the effect of progesterone on sperm function. We examined 29 UV filters allowed in sunscreens in the US and/or EU for their ability to affect acrosome reaction, penetration, hyperactivation and viability in human sperm cells. We found that, similar to progesterone, the UV filters 4-MBC, 3-BC, Meradimate, Octisalate, BCSA, HMS and OD-PABA induced acrosome reaction and 3-BC increased sperm penetration into a viscous medium. The capacity of the UV filters to induce acrosome reaction and increase sperm penetration was positively associated with the ability of the UV filters to induce a Ca2+ influx. None of the UV filters induced significant changes in the proportion of hyperactivated cells. In conclusion, chemical UV filters that mimic the effect of progesterone on Ca2+ signaling in human sperm cells can similarly mimic the effect of progesterone on acrosome reaction and sperm penetration. Human exposure to these chemical UV filters may impair fertility by interfering with sperm function, e.g. through induction of premature acrosome reaction. Further studies are needed to confirm the results in vivo.

Image cytometer method for automated assessment of human spermatozoa concentration.

In the basic clinical work-up of infertile couples, a semen analysis is mandatory and the sperm concentration is one of the most essential variables to be determined. Sperm concentration is usually assessed by manual counting using a haemocytometer and is hence labour intensive and may be subjected to investigator bias. Here we show that image cytometry can be used to accurately measure the sperm concentration of human semen samples with great ease and reproducibility. The impact of several factors (pipetting, mixing, round cell content, sperm concentration), which can influence the read-out as well as inter-operator and -cytometer variation on two different image cytometers (NC-3000 and SP-100) were evaluated. Furthermore, 725 semen samples were assessed both by manual assessment (WHO recommended method) and by image cytometry and tight correlations between the measured concentrations were shown. Moreover, by evaluation of repeated measurements it appeared that image cytometry produced more consistent and accurate measurements than manual counting of human spermatozoa concentration. In conclusion, image cytometry provides an appealing substitute of manual counting by providing reliable, robust and easy measurement of human sperm concentration.

Expression of the vitamin D metabolizing enzyme CYP24A1 at the annulus of human spermatozoa may serve as a novel marker of semen quality.

Vitamin D (VD) is important for male reproduction in mammals and the VD receptor (VDR) and VD-metabolizing enzymes are expressed in human spermatozoa. The VD-inactivating enzyme CYP24A1 titrates the cellular responsiveness to VD, is transcriptionally regulated by VD, and has a distinct expression at the sperm annulus. Here, we investigated if CYP24A1 expression serves as a marker for VD metabolism in spermatozoa, and whether CYP24A1 expression was associated with semen quality. We included 130 men (53 healthy young volunteers and 77 subfertile men) for semen analysis and immunocytochemical (ICC) detection of CYP24A1. Another 40 men (22 young, 18 subfertile) were tested for in vitro effects of 1,25(OH)(2)D(3) on intracellular calcium concentration ([Ca(2+)](i)) and sperm motility. Double ICC staining showed that CYP24A1 and VDR were either concomitantly expressed or absent in 80% of the spermatozoa from young men. The median number of CYP24A1-expressing spermatozoa was 1% in subfertile men and thus significantly (p < 0.0005) lower than 25% in spermatozoa from young men. Moreover, CYP24A1 expression correlated positively with total sperm count, -concentration, -motility and -morphology (all p < 0.004), and the percentage of CYP24A1-positive spermatozoa increased (15 vs. 41%, p < 0.0005) after percoll-gradient-centrifugation. We noticed that the presence of >3% CYP24A1-positive spermatozoa distinguished young men from subfertile men with a sensitivity of 66.0%, a specificity of 77.9% and a positive predictive value of 98.3%. Functional studies revealed that 1,25(OH)(2)D(3) increased [Ca(2+)](i) and sperm motility in young healthy men, while 1,25(OH)(2)D(3) was unable to increase motility in subfertile patients. In conclusion, we suggest that CYP24A1 expression at the annulus may serve as a novel marker of semen quality and an objective proxy for sperm function.