Abstract: Objective To investigate the effect of improving human sperm quality by novel selection approach based on progressive motility and thermotaxis. Methods The capacitated spermatozoa were placed on one end of strip droplets with different length (2, 5, 8 cm) and different temperature conditions(32 ℃, 37 ℃ or 32 ℃~37 ℃) after density gradient centrifugation. The spermatozoa were collected from the other end of the droplets after swimming for 60 min. The concentration, motility rate, normal morphology rate and DNA fragment rate of sperm were compared among different distance-temperature-combined selection conditions. Results Under the same tempera-ture condition, the spermatozoa selected by long distance (5, 8 cm) had higher rate of normal morphology picture than the initial one (P＜0.05).With the increase of distance, the sperm motility rate increased slightly, while the concentration of sperm decreased significantly (P＜0.01).The sperm concentration in temperature gradient(32 ℃~37 ℃) was higher than that in no-gradient control groups (32 ℃ and 37 ℃,P＜0.01), while the sperm DNA fragment rate was lower (P＜0.05). Conclusions Through long distance swimming, a tremendous amount of sperm with abnormal morphology were eliminated, but long distance selection would also lead to a sharp drop in sperm concentration. The temperature gradients enrich more sperm with better DNA integrity and normal thermotaxis. Under the condition of 5 cm, 32 ℃~37 ℃, the effect of sperm selection is better, which may reduce the risk of genetic defective sperm combining with oocytes during IVF.

Key words: spermatozoa, swimming distance, thermotaxis, normal morphology, DNA fragment