The history of sperm cryopreservation

While there have been several relatively recent comprehensive reviews of mammalian sperm cryopreservation (Watson, 2001; Leibo, 2004), this chapter is not meant to be a review of the literature of mammalian sperm cryopreservation. Instead, we intend to provide an understanding of the history, current status, and potential future direction of mammalian sperm cryobiology. There are many reasons why sperm cryopreservation is important, including: (1) maintenance of genetic diversity in domestic and wild species populations (Wildt, 1992; Critser & Russell, 2000); (2) facilitating the distribution of “genetically superior” domestic species lines; (3) treatment of iatrogenic infertility (Kuczynski et al., 2001; Ranganathan et al., 2002; Tash et al., 2003; Agarwal et al., 2004; Nalesnik et al., 2004); and (4) genetic banking of genetically modified animal models of human health and disease (Critser & Russell, 2000; Knight & Abbott, 2002). While actual references to sperm cryobiology and cryopreservation date as far back as the 1600s (Sherman, 1964), it was not until the development of artificial insemination (AI) in the late 1950s and early 1960s, when the dairy industry needed longer-term storage methods for bull sperm, that sperm cryopreservation became a major area of scientific investigation. Polge et al. (1949) made a pivotal discovery that showed that the use of glycerol (a permeating solute) could provide protection to cells at low temperatures. This is often cited as the defining moment in the establishment of modern sperm cryobiology. However, there is actually a very important body of literature which predates it, some of which established the scientific basis upon which their work was interpreted and further developed (Lovelock, 1953a; Lovelock & Polge, 1954; Menz & Luyet, 1965; Luyet, 1966; MacKenzie & Luyet, 1967a; 1967b; Luyet & Rapatz, 1970; Luyet, 1971; Rasmussen & Luyet, 1972; Rapatz & Luyet, 1973), and some of which was parallel literature that was not incorporated into the main pathway of sperm cryobiology mainly because it was published in Russian (Katkov, 2005). Based upon this scientific history, the development of “successful” mammalian sperm cryopresveration methods was established. It is critical to realize, however, that even today only a very few mammalian species’ sperm can be effectively cryopreserved. Even in those cases, the “success,” as measured by postthaw motility, routinely is 50 percent or less than that of the prefreeze motility. Successful cryopreservation varies highly among species, individuals within species, and even within ejaculates of individuals, which is largely attributed to the differences in biophysical characteristics among cell types (Gao et al., 1997; Thurston et al., 2002; Walters et al., 2005). Chapter