Effects of CXCL12/CXCR4/CXCR7 axis on human sperm motility and chemotaxis

Mammalian spermatozoa undergo a series of functional changes in the female genital tract before they can fertilize oocytes. Chemokines and their receptors are involved in these complex biological events. However, the detailed molecular mechanisms on the modulation of chemokines on spermatozoa still need to be elucidated. CXCL12, a chemokine, has been widely studied in leukocyte migration and. Here we found that CXCL12 was existent in human cumulus cells and follicular fluid and its receptors CXCR4 and CXCR7 were co-expressed on human spermatozoa. We investigated the effects of CXCL12 on various biological functions of human sperm and which receptor plays a dominant role in these processes. We found that CXCL12 could promote human sperm chemotaxis, motility, penetration in the mucus, acrosome reaction and Ca2+ influx through CXCR4 rather than CXCR7. In addition, the simplified physical model reasonably explained the change of sperm velocity under the influence of CXCL12 concentration gradient, which was identical to their physiological motion patterns.