OBJECTIVETo observe the relative activity of sperm mitochondria and the proportion of ROS-positive sperm before and after capacitation and progesterone (Pg)-induced hyperactivation, and investigate the functional characteristics of sperm mitochondria.

METHODSWe collected 20 samples of normal human spermatozoa that met the criteria of WHO Laboratory Manual for the Examination and Processing of Human Semen (5th ed) and cultured them with the swim-up method in a CO2 incubator at 37 degrees C for 1 hour. We divided the sperm into a pre-capacitation and a capacitated group, and further incubated the capacitated sperm in an upright tube with (Pg-induced group) or without (control group) slow-releasing Pg at 37 degrees C for another hour. Then we determined the relative activity of mitochondria and the percentage of ROS-positive cells in the sperm samples using JC-1 and DCF staining.

RESULTSThe relative activities of mitochondria were significantly increased in the capacitated, control and Pg-induced groups (6.23, 14.36 and 12.33) as compared with the pre-capacitation group (1.42) (P < 0.05), while the percentages of balanced mitochondria (mitochondria with equal amount of high and low electric potentials) remarkably reduced (4.27%, 5.03% and 8.57% vs 21.64%, P < 0.05). The percentages of ROS-positive sperm in the pre-capacitation, capacitated, control and Pg-induced groups were 2.89%, 0.70%, 4.25% and 1.90%, respectively, significantly lower in the capacitated than in the pre-capacitation group (P < 0.01), but dramatically increased in the control group after another hour of swim-up incubation and markedly higher than in the Pg-induced group (P < 0.01).

CONCLUSIONProgesterone induction can hyperactive human sperm motility, inhibit the relative activity of mitochondria, keep mitochondria potential at a more balanced level, and reduce the production of ROS, which may help to raise the rate of in vitro fertilization and improve the quality of embryos.