Expression of brain-derived neurotrophic factor in mature spermatozoa from fertile and infertile men.

Neurotrophins, a family of growth factor, are not only required for the survival and differentiation of the nervous system but also important for the development of reproductive tissues. We identified the expression of brain-derived neurotrophic factor (BDNF) transcript and protein in human spermatozoa. The presence of BDNF in human spermatozoa was investigated using RT-PCR, immunofluorescence and Western blotting. Real-time PCR and ELISA were employed to determine expression levels of BDNF. BDNF mRNA and protein were detected in human spermatozoa. Immunofluorescence staining showed that BDNF protein was localized in the head, neck, and tail of human spermatozoa. The amount of BDNF mRNA expressed in spermatozoa of oligoasthenozoospermic group was lower than that of fertile group (P < 0.05). The concentration of BDNF in seminal plasma from oligoasthenozoospermic group (2.8 ± 0.7 ng/ml) was both lower than that from fertile group (3.6 ± 0.4 ng/ml) and asthenozoospermic group (3.4 ± 0.5 ng/ml) (P < 0.05). The data showed that the decrease in BDNF transcript and protein in oligoasthenozoospermic group may be associated with pathogenesis in some types of male infertility.