Effect of oxidative damage to human sperm in vitro on mitochondrial tRNa LeuUUR gene

OBJECTIVE: To study the oxidative damage to human sperm mitochondrial tRNA LeuUUR gene by reactive oxygen species (ROS) in vitro. METHODS: Spermatozoa of normal physiological function selected from semen samples by Percoll gradient centrifugation technique were used as normal sperm models, which were divided into two groups of 20 cases each, a damage group and a control group, the former treated with hypoxanthine xanthine oxidase system and the latter left untreated, both incubated at 37 degrees C in aerobic environment for 60 minutes. Sperm DAN was extracted, and digestion by the enzymes fpg and ligation-mediated PCR ( LM-PCR) was performed to map the damage to mitochondrial tRNA LeuUUR gene. The spermatozoa were labeled with specific fluorescent probe of Rhodamine 123 to measure mitochondrial membrane potential ( MMP) by flow cytometry and observe sperm function. RESULTS: Compared with the control group, after the normal spermatozoa were incubated with ROS, MMP of the spermatozoa significantly decreased ( 116. 27+/-11.72 vs 64.00+/-4. 88) , P <0.05. Digestion by the enzymes fpg and LM-PCR showed damage to mitochondrial tRNA LeuUUR, gene. CONCLUSION: Reactive oxygen species may inflict oxidative damage on sperm mitochondrial tRNA LeuUUR gene and thus affect sperm function ( as shown by significant decrease in MMP), resulting in infertility.