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A recent collaborative research jointly conducted by the Epithelial Cell Biology Research Center of The Chinese University of Hong Kong (CUHK) and Shenzhen Second People’s Hospital revealed that deficient human b-defensin-1 (DEFB1) underlies male infertility associated with poor sperm motility and genital tract infection. The finding has recently been published in an international leading scientific journal, Science Translational Medicine. 

Infertility affects around 10-15% of couples worldwide, and male infertility contributes to approximately 50% of these infertile cases. Male infertility is attributed to multiple factors. Sperm motility is considered one of the most important sperm functions that affect natural conception, and reduced sperm motility is a common cause of infertility and accounts for approximately 18% of the male subfertility and infertility cases. On the other hand, seminal tract infection is another common cause of infertility, which is observed in approximately 11% of infertile male patients. Interestingly, sperm with reduced motility is often associated with genital tract infection; however, the underlying cause and possible association between the two disorders remain largely unexplored. 

The research led by Prof. CHAN Hsiao Chang, Director of Epithelial Cell Biology Research Center and Professor of Physiology, found that the amount of DEFB1 in sperm from infertile men exhibiting either genital tract infection or reduced sperm motility is much lower compared to that in normal fertile sperm. Interference with DEFB1 function also decreases both motility and bactericidal activity in normal sperm. 

The study further demonstrates that treatment with recombinant DEFB1 markedly restores DEFB1 expression, bactericidal activity, sperm quality, and egg-penetrating ability in sperm from infertile patients exhibiting poor sperm motility and genital tract infection, suggesting a feasible therapeutic approach for related male infertility. 

A previous work by Prof. Chan’s team published ten years ago in Nature Cell Biology was the global first study to demonstrate the role of b-defensin in initiating sperm motility.