The sperm chromatin structure assay (SCSA) was used to measure over 500 human semen samples from two independent studies: Study I, 402 samples from 165 presumably fertile couples wishing to achieve pregnancy over 12 menstrual cycles; Study II, samples from 115 patients seeking fertility counselling. The SCSA measures susceptibility to DNA denaturation in situ in spermatozoa exposed to acid for 30 s, followed by acridine orange staining. SCSA data from the male partners of 73 couples (group 1) achieving pregnancy during months 1-3 of Study I were used as the standard of 'sperm chromatin compatible with high fertility' and were significantly different from those of 40 couples (group 3) achieving pregnancy in months 4-12 (P < 0.01) and those of male partners of 31 couples (group 4) not achieving pregnancy (P < 0.001). Group 2 contained couples who had a miscarriage. SCSA values for Study II were almost twice that of the Study I fertility standards. Within-couple repeatability tended to be less for group 3 than for groups 1, 2 or 4. Based on logistic regression, spermatozoa with denatured DNA (cells outside the main population, COMP alpha t) were the best predictor for whether a couple would not achieve pregnancy. Some 84% of males in group 1 had COMP alpha t < 15%, while no couples achieved pregnancy in group 1 with > or = 30% COMP alpha t, a threshold level considered not compatible with good fertility. Using selected cut-off values for chromatin integrity, the SCSA data predicted seven of 18 miscarriages (39%).

The Sperm Chromatin Structure Assay (SCSA) was first described in the December 5, 1980 issue of Science (Evenson et al, 1980a). The data described in that article showed a significant difference between proven fertile and subfertility or infertility in men and bulls and the susceptibility to denaturation of their sperm nuclear DNA. A subsequent study (Evenson et al, 1984) described SCSA data obtained from men with testicular cancer. The data were heterogeneous, and begged the question, what was SCSA measuring? Great effort has been spent over the past 15 years on animal model systems, mostly related to dose-response toxicology experiments and large animal fertility trials. The results from these studies showed that SCSA was highly dose-responsive to toxicants, highly repeatable, and provided meaningful biological information on sperm nuclear DNA defects. The extensive data from nonhumans (Evenson et al, 1985(Evenson et al, , 1989a(Evenson et al, ,b, 1993a(Evenson et al, ,b,c, 1994Ballachey et al, 1987Ballachey et al, , 1988Evenson and Jost, 1993; Sailer et al, 1995a,b;Evenson, 1999a), and human toxicology and fertility studies (Evenson et al, 1978(Evenson et al, , 1980a(Evenson et al, ,b, 1984(Evenson et al, , 1991Evenson and Melamed, 1983;Evenson, 1999b;Larson et al, 1999Larson et al, , 2000Larson et al, , 2001 provide This work was supported in part by grant R827019 from the US Environmental Protection Agency, grants EPS-9720642 and OSR-9452894 from the National Science Foundation, and by SCSA Diagnostics, Inc. This is South Dakota Agricultural Experiment Station publication 3273 of the journal series.Correspondence to: Donald P. Evenson, Olson Biochemistry Laboratories, ASC 136, South Dakota State University, Brookings, SD 57006 (e-mail: donald evenson@sdstate.edu).Received for publication September 20, 2001; accepted for publication September 20, 2001. compelling evidence that SCSA will be useful in clinical human semen analysis (Figure 1).After reviewing current infertility center sites on the World Wide Web and approximately a dozen lay-oriented books on infertility and assisted reproductive technology (ART), it was amazing that not a single reference contained any information about the negative influence of fragmented sperm nuclear DNA on successful pregnancy outcome. Furthermore, few physicians are aware of scientific literature on this subject. Currently, if a spermatozoon has some motility as seen under a light microscope, and reasonable morphology, then many ART clinics assume that the sperm DNA must be fine. However, a number of cases have been documented in which couples have had multiple failed attempts at intracytoplasmic sperm injection (ICSI), even using donor eggs, and we found that the fragmentation of sperm DNA was above our threshold for less than 1% probability of achieving a successful pregnancy. Spermatozoa with defective DNA can fertilize an oocyte, produce high-quality early stage embryos, and then, in relationship to the extent of DNA damage, fail in producing a successful term ...

Flow cytometry of heated sperm nuclei revealed a significant decrease in resistance to in situ denaturation of spermatozoal DNA in samples from bulls, mice, and humans of low or questionable fertility when compared with others of high fertility. Since thermal denaturation of DNA in situ depends on chromatin structure, it is assumed that changes in sperm chromatin conformation may be related to the diminished fertility. Flow cytometry of heated sperm nuclei may provide a new and independent determinant of male fertility.

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Despite advances in the field of male reproductive health, idiopathic male infertility, in which a man has altered semen characteristics without an identifiable cause and there is no female factor infertility, remains a challenging condition to diagnose and manage. Increasing evidence suggests that oxidative stress (OS) plays an independent role in the etiology of male infertility, with 30% to 80% of infertile men having elevated seminal reactive oxygen species levels. OS can negatively affect fertility via a number of pathways, including interference with capacitation and possible damage to sperm membrane and DNA, which may impair the sperm's potential to fertilize an egg and develop into a healthy embryo. Adequate evaluation of male reproductive potential should therefore include an assessment of sperm OS. We propose the term Male Oxidative Stress Infertility, or MOSI, as a novel descriptor for infertile men with abnormal semen characteristics and OS, including many patients who were previously classified as having idiopathic male infertility. Oxidation-reduction potential (ORP) can be a useful clinical biomarker for the classification of MOSI, as it takes into account the levels of both oxidants and reductants (antioxidants). Current treatment protocols for OS, including the use of antioxidants, are not evidence-based and have the potential for complications and increased healthcare-related expenditures. Utilizing an easy, reproducible, and cost-effective test to measure ORP may provide a more targeted, reliable approach for administering antioxidant therapy while minimizing the risk of antioxidant overdose. With the increasing awareness and understanding of MOSI as a distinct male infertility diagnosis, future research endeavors can facilitate the development of evidence-based treatments that target its underlying cause.