Rheotaxis of sperm in fertile and infertile men

Abstract

Sperm rheotaxis refers to the ability of sperm cells to align their swimming direction with or against fluid flow. Positive rheotaxis (PR) is the tendency of sperm cells to swim against the flow. Herein, we describe sperm rheotaxis in fertile and infertile males, using a microfluidic platform and focus on rheotaxis as a potential marker of male fertility. A previously reported computer-assisted sperm analysis (CASA) plugin for Image-J was used to detect and analyze the motion of human sperm cells in microfluidic environments. The fabricated microchannels mimic the female reproductive tracts and use an image-processing program to monitor sperm swimming behavior in semen samples from fertile and infertile men. We have constructed an image-processing pipeline. The image-processing pipeline incorporated strengthens object detection and particle tracking to adapt to sperm that are out of focus while swimming on the same track. PR% was defined as the number of PR sperm cells over the number of motile sperm cells. The results showed that the percentage of PR correlates with fertility, wherein the fertile male specimens showed a higher PR% than the other groups (P < 0.05). There is no difference in progressive motility between the control group (fertile men with normal sperm analysis) and group 1 (G1; infertile men with normal sperm analysis). However, PR% was lower (P < 0.05) in the G1 group (13.5 ± 0.4%) compared to the control group (40.3 ± 3.3%) and group 2 (G2; infertile with reduced sperm motility) (15.3 ± 4.6%). Thus, PR% may be used as a novel parameter to explain infertility even in situations where basic sperm analysis following the World Health Organization (WHO) guidelines is unable to do so. We propose to use PR% as a novel parameter for sperm analysis and as a method of sperm selection in assisted reproductive technology.

Keywords: CASA; Sperm rheotaxis; fertility; microfluidics.