Mammalian sperm chemokinesis

The effect of chemicals on mammalian sperm navigation within the female reproductive tract (FRT) is poorly understood. In this study, our aim was to investigate the impact of chemical cues on sperm behavior and their navigational mechanisms within the FRT using microfluidic experimentation as well as theoretical modeling. Specifically, we explored the chiral and hyperactive behaviors of bovine sperm induced by chemokinetic agonists and the subsequent modulation of sperm-side-wall interactions and pseudo-chemotaxis. We first discovered distinct motion patterns characterized by circular swimming (chiral behavior) and random reorientation events (hyperactive behavior), which were found to be influenced by the rheological properties of the surrounding media. Subsequently, we examined how chemokinesis affects sperm-side-wall interactions and navigation along physical boundaries in the FRT. Notably, we observed that sperm initially exhibited sidewall swimming until hyperactivation-induced curvature surpassed a critical value, leading to a reduction in their sidewall preference and the emergence of intriguing "Run-Stop" motion. This modulation of sperm-side-wall interaction induced a pseudo-chemotaxis behavior, wherein sperm exhibited a prolonged stay in regions with higher agonist concentrations. These novel findings shed light on the intricate interplay between chemical cues, sperm behavior, and the physical boundaries within the FRT, contributing to our understanding of successful sperm migration and fertilization in this complex setting.