The sperm chromatin structure assay: A review of clinical applications

The sperm chromatin structure assay (SCSA) was introduced by Evenson in 1980 as a method to determine the susceptibility of sperm DNA to denaturation and how those results related to fertility. This initial study used human sperm and was followed by studies in bulls [Ballachey, B.E., Hohenboken, W.D., Evenson, D.P., 1987. Heterogeniety of spermatozoa nuclear chromatin structure and its relationship to bull fertility. Biol. Reprod. 36, 915–925; Ballachey, B.E., Evenson, D.P., Saacke, R.G., 1988. The sperm chromatin structure assay: relationship with alternate tests of semen quality and heterospermic performance of bulls. J. Androl. 9, 109–115] and boars [Evenson, D.P., Thompson, L., Jost, L., 1994. Flow cytometric evaluation of boar semen by the sperm chromatin structure assay as related to cryopreservation and fertility. Theriogenology 41, 637–651]. This assay was one of the first to introduce the technique of flow cytometry, which has the ability to evaluate specific sperm compartments of large numbers of sperm in a short time, as a methodology to evaluate sperm quality and further define the relationship of sperm quality to fertility. y assay to be of use clinically, it must not only be validated and adapted for the species of interest, but guidelines that associate specific levels of fertility with assay results must be defined. This review will describe how our laboratory uses the SCSA for clinical diagnosis of reduced fertility in the stallion.