Electroporation of the Testis

The mature mammalian testis is a marvelous organ that produces numerous sperm cells during its reproductive phase. This biologically significant process consists of three steps: stem cell self-renewal and differentiation, meiosis and genetic recombination, and haploid cell morphogenesis into sperm (Russell et al., 1990). The first step provides a good model for investigating the molecular mechanism of stem cell regulation. Currently, the mechanism underlying sperm cell production is a very exciting topic in regenerative medicine (Lensch et al. 2007; Okita et al., 2007). The spermatogonial stem cell system has several advantages, including the easy histological identification of stem cells (Russell et al., 1990), a clear relationship between stem cells and the supporting Sertoli cells, which provide a stem cell niche (Tadokoro et al., 2002; Yomogida et al., 2003), and a transplantation assay for stem cell activity (Oatley & Brinster, 2006). Although germline stem (GS) cells derived from the gonocytes in newborn testis constitute a suitable in vitro system for investigating the properties of spermatogonial stem cells (Kanatsu-Shinohara et al., 2003, 2004), studies using living mammalian testes continue to provide information regarding the roles of the stem cell niche. In vivo electroporation of the supporting cells in the testis will expand our ability to study it.

The last two steps in sperm cell production are important for species preservation and evolution. In mammals, meiotic cells at all stages of division and haploid cells are found continuously only in the testis. Indeed, most of our knowledge of the molecular mechanisms underlying these two processes has been obtained using mutant and genetically engineered animals, such as transgenic or knockout mice, because there are currently no suitable in vitro systems (Lau & Chan, 2007). However, the use of such mice requires significant time, money, and labor. The in vivo electropora-tion of mammalian testes could reduce this burden because it would allow a gene of interest to be inserted into the cells, and their behavior could be followed directly.