Tung Chih-kuan, Hu Lian, Fiore Alyssa G, Ardon Florencia, Hickman Dillon G, Gilbert Robert O, Suarez Susan S, Wu Mingming
Departments of Biological and Environmental Engineering.
Biomedical Sciences, and Family Planning Research Institute, Center of Reproductive Medicine, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, China.
Proc Natl Acad Sci U S A. 2015 Apr 28;112(17):5431-6. doi: 10.1073/pnas.1500541112. Epub 2015 Apr 13.
Successful mammalian reproduction requires that sperm migrate through a long and convoluted female reproductive tract before reaching oocytes. For many years, fertility studies have focused on biochemical and physiological requirements of sperm. Here we show that the biophysical environment of the female reproductive tract critically guides sperm migration, while at the same time preventing the invasion of sexually transmitted pathogens. Using a microfluidic model, we demonstrate that a gentle fluid flow and microgrooves, typically found in the female reproductive tract, synergistically facilitate bull sperm migration toward the site of fertilization. In contrast, a flagellated sexually transmitted bovine pathogen, Tritrichomonas foetus, is swept downstream under the same conditions. We attribute the differential ability of sperm and T. foetus to swim against flow to the distinct motility types of sperm and T. foetus; specifically, sperm swim using a posterior flagellum and are near-surface swimmers, whereas T. foetus swims primarily via three anterior flagella and demonstrates much lower attraction to surfaces. This work highlights the importance of biophysical cues within the female reproductive tract in the reproductive process and provides insight into coevolution of males and females to promote fertilization while suppressing infection. Furthermore, the results provide previously unidentified directions for the development of in vitro fertilization devices and contraceptives.
成功的哺乳动物繁殖需要精子在到达卵母细胞之前，穿过漫长而曲折的雌性生殖道。多年来，生育力研究一直聚焦于精子的生化和生理需求。在此我们表明，雌性生殖道的生物物理环境对精子迁移起着关键的引导作用，同时防止性传播病原体的侵入。我们使用微流控模型证明，雌性生殖道中常见的平缓液流和微槽协同促进公牛精子向受精部位迁移。相比之下，一种具鞭毛的性传播牛病原体——胎儿三毛滴虫，在相同条件下会被冲向下游。我们将精子和胎儿三毛滴虫逆流游动能力的差异归因于它们不同的运动类型；具体而言，精子利用后鞭毛游动，是近表面游动者，而胎儿三毛滴虫主要通过三根前鞭毛游动，对表面的吸引力低得多。这项工作突出了雌性生殖道内生物物理信号在生殖过程中的重要性，并为雄性和雌性共同进化以促进受精同时抑制感染提供了见解。此外，这些结果为体外受精装置和避孕药具的开发提供了此前未被发现的方向。
