Differences in mitochondrial and nuclear DNA status of high-density and low-density sperm fractions after density centrifugation preparation.

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.