Selection of high quality spermatozoa may be promoted by activated vitamin D in the woman

Context:The vitamin D receptor (VDR) and enzymes involved in activation (CYP2R1, CYP27B1) and inactivation (CYP24A1) of vitamin D are expressed in ovary, testes, and spermatozoa.Objective:Determine responsiveness to 1,25-dihydroxyvitamin D (1,25(OH)2D3) in spermatozoa from normal and infertile men, identify site of exposure and how 1,25(OH)2D3 influences sperm function.Design:Spermatozoa expressing VDR, CYP2R1, CYP27B1, and CYP24A1 were analyzed in normal and infertile men. 25-hydroxyvitamin D (25-OHD), 24,25-dihydroxyvitamin D (24,25(OH)2D3), and 1,25(OH)2D3 were measured in serum, seminal fluid, cervical secretions and ovarian follicular fluid. 1,25(OH)2D3 was tested on human spermatozoa.Setting:Tertiary centre for fertility.Participants:Protein expression in spermatozoa and semen quality were assessed in 230 infertile and 114 healthy men. Vitamin D metabolites were measured in fluids from 245 men and 13 women, while 74 oocytes and 17 semen donors were used for sperm-function tests.Main Outcome Measures:VDR and CYP24A1 expressions in spermatozoa, fluid concentrations of 25-OHD, 24,25(OH)2D3 and 1,25(OH)2D3, and 1,25(OH)2D3–induced effects on intracellular calcium concentration ([Ca2+]i) and sperm-oocyte binding in vitro.Results:VDR and CYP24A1 were expressed in >2 fold higher fraction of spermatozoa from normal than infertile men (p