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 ...

The predictive value of sperm chromatin integrity for pregnancy outcome following in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) was studied in 24 men attending a university-based assisted reproductive techniques laboratory using the flow cytometric sperm chromatin structure assay (SCSA). The SCSA is a measure of the susceptibility of sperm DNA to low pH-induced denaturation in situ. The mean percentage of spermatozoa in the neat sample demonstrating DNA denaturation was significantly lower in the seven men that initiated a pregnancy (15.4 +/- 4.6, P = 0.01) than in the 14 men who did not initiate a pregnancy (31.1 +/- 3.2). No pregnancies resulted if > or =27% of the spermatozoa in the neat semen sample showed DNA denaturation. These data demonstrate that SCSA parameters are independent of conventional semen parameters. Furthermore, the SCSA may allow physicians to identify male patients for whom IVF and ICSI will be unlikely to result in pregnancy initiation.

The integrity of mammalian sperm DNA is of prime importance for the paternal genetic contribution to normal offspring. Damaged DNA in the single sperm that fertilizes the female egg can have a dramatic negative impact on fetal development. This comprehensive and detailed unit presents a rapid, reliable, practical test for DNA integrity based on staining with acridine orange. SCSA data have been conclusively shown to predict sub/infertility. This assay is ideally suited to human and animal fertility clinics to assess male sperm DNA integrity as related to fertility potential and embryo development. The authors, who have decades of experience in studying sperm viability, provide extensive commentary and methodological tips, making this unit the most detailed method for this test published to date. Keywords: flow cytometry; sperm chromatin structure assay; SCSA; DNA denaturation; acridine orange;animal and human fertility; toxicology The integrity of mammalian sperm DNA is of prime importance for the paternal genetic contribution to normal offspring

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