Study design: Retrospective descriptive study.
Objectives: To study the presence of cell-free DNA (cfDNA) and DNase activity in males with spinal cord injury (SCI) with elevated sperm DNA fragmentation.
Setting: Hospital in Toledo, Spain; University-based Genetics laboratory in Madrid, Spain.
Methods: Semen was collected from 15 males with spinal cord injury and elevated sperm DNA fragmentation (SDF). The presence and concentration of cfDNA was assessed using standard gel electrophoresis and microfluidic electrophoresis. DNase activity was evaluated in seminal plasma and under the presence of EDTA and EGTA to control the response of enzyme activity. cfDNA fragments were mapped on the sperm genome using FISH. All results were compared to 15 normozoospermic fertile donors.
Results: Standard gel electrophoresis revealed a cfDNA band of ~150 bp in all samples from males with SCI; this band was ocasionally accompanied by another band of ~90 bp. These bands were not observed in normozoospermic donors. Microfluidid electrophoresis only identified the equivalent band of 150 bp. No correlation was observed between the intensity of the two bands and the level of SDF in males with SCI. Although DNase activity was present in the seminal plasma of both normozoospermic donors and men with SCI it did not digest cfDNA. cfDNA fragments were found to be hybridized all over the sperm genome.
Conclusions: SCI patients with elevated sperm DNA fragmentation showed a 150 bp DNA band of cfDNA in the seminal plasma, which appeared resistant to DNase activity.