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

Abstract

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.

Vitamin D and assisted reproduction: should vitamin D be routinely screened and repleted prior to ART? A systematic review

“…In vitro studies showed that VDR induction mediated increased intracytoplasmic calcium in spermatozoa, resulting in increased motility and concomitant induction of the acrosomal reaction in capacitated sperm [16]. Furthermore, expression of VDR and CYP24A1 (a cytochrome P450 hydroxylase enzyme) in the annulus of sperm have been linked to all semen parameters, with higher expression of CYP24A1 associated with increased sperm motility in fertile compared to subfertile men [17]. However, two separate cross-sectional studies performed 1 year later failed to show a significant association between low serum vitamin D levels and poor semen quality [18,19].…”

Vitamin D and assisted reproduction technologies: current concepts

“…The favourable effect of 25(OH) on human spermatozoa has been shown in vitro [26-28] and three cross-sectional association studies on serum 25(OH)D levels and semen quality have been conducted in young healthy men without infertility problems [27,29,30]. The results, however, were quite discordant (Table 1).…”

Interactions between oestrogen and 1α,25(OH)2-vitamin D3 signalling and their roles in spermatogenesis and spermatozoa functions

“…1b) [125, 127, 128]. Subcellular VDR expression may therefore depend on optimal spermatogenesis and maturation, because incomplete formation of the subcellular compartments may lead to an unusual localisation and, potentially, an unusual function of the receptor [132, 133]. …”

“…Moreover, 1,25-D 3 increased sperm motility and induced acrosome reaction [145]. 1,25-D 3 effect on motility was dependent on the characteristics of samples as 1,25-D 3 significantly increased spermatozoa motility in young men but was unable to do so in spermatozoa from sub-fertile men [133]. …”