Curvature in the reproductive tract alters sperm-surface interactions

The fallopian tube is lined with a highly complex folded epithelium surrounding a lumen that progressively narrows. To study the influence of this labyrinthine complexity on sperm behavior, we use droplet microfluidics to create soft curved interfaces over a range of curvatures corresponding to the in vivo environment. We reveal a dynamic response mechanism in sperm, switching from a progressive surface-aligned motility mode at low curvatures (larger droplets), to an aggressive surface-attacking mode at high curvatures (smaller droplets of <50 mu m-radius). We show that sperm in the attacking mode swim similar to 33% slower, spend 1.66-fold longer at the interface and have a 66% lower beating amplitude than in the progressive mode. These findings demonstrate that surface curvature within the fallopian tube alters sperm motion from a faster surface aligned locomotion in distal regions to a prolonged physical contact with the epithelium near the site of fertilization, the latter being known to promote capacitation and fertilization competence. The effect of fallopian tube's curvature on sperm motion has not been studied in detail. Here, the authors use droplet microfluidics to create soft curved interfaces, revealing a dynamic switch in sperm motility from a progressive surface-aligned mode at low curvatures, to an aggressive surface-attacking mode at high curvatures.

Automated summary

The curvature of the fallopian tube influences sperm motion, switching the mode of movement from faster surface alignment to prolonged interaction with the epithelium to enhance sperm maturation and fertilization competence. This dynamic switch in sperm motility was revealed using droplet microfluidics technology.