RESUMO
OBJECTIVE: To determine the mitochondrial DNA and nuclear DNA fragmentation of sperm populations separated by using discontinuous density gradient. DESIGN: Analysis of mitochondrial and nuclear DNA status of sperm from high and low density layers. SETTING: Regional fertility center. PATIENT(S): Twenty-eight men who presented for an initial infertility investigation. MAIN OUTCOME MEASURE(S): Semen was prepared by using discontinuous density gradient (90.0%:45.0%) and subjected to a modified long polymerase chain reaction to assess mitochondrial DNA deletions and to a modified single-cell alkaline gel electrophoresis assay to determine nuclear DNA fragmentation. RESULT(S): The high-density fraction displayed significantly more wild-type mitochondrial DNA (75% of samples) than did the low-density fraction (25% of samples). In the high-density fraction, the incidence of single deletions was higher than that of double or multiple deletions, and the deletions were predominantly small. A strong correlation was observed between nuclear DNA fragmentation and the number and size of mitochondrial DNA deletions. CONCLUSION(S): Density centrifugation isolates a population of sperm with high-quality mitochondrial DNA and nuclear DNA.
