Sperm nuclear maturity in spinal cord-injured men: evaluation by acidic aniline blue stain

For many of the spinal cord-injured (SCI) men who are able to produce an ejaculate, infertility because of poor semen quality is a concern. Impaired spermatogenesis has been attributed as a possible reason for the poor semen quality. If so, events that occur during spermatogenesis may be used as a marker to evaluate the extent of spermatogenic alteration. During spermatogenesis, when the sperm nuclear condensation occurs, lysine-rich somatic histone are replaced by arginine-rich protamines in the DNA. Acidic aniline blue preferentially stains the immature sperm nucleus blue by binding to the lysine. Hence, each sperm can be individually evaluated for nuclear maturity. To test this concept, the nuclear maturity of sperm from 12 SCI men obtained by vibratory stimulation was compared with sperm samples obtained by self-masturbation from 104 non-SCI men. Sperm smears stained with acidic aniline blue were evaluated for nuclear maturity. The percent of unstained spermatozoa for non-SCI men (mean +/- SEM; 83.4 +/- 1.1%) was not statistically different from that of the SCI men (79.7 +/- 4.8%). However, the sperm motility (70.5 +/- 1.2%) and the percentage of normal sperm morphology (50.8 +/- 0.7%) of non-SCI men were significantly (P < .01) different from those of the SCI men (36.5 +/- 6.8% and 44.0 +/- 2.4%). It seems that the poor semen quality observed in SCI men is probably not caused by inadequate nuclear maturity of the spermatozoa.