International Journal of Animal Biology Vol. 1, No. 3, 2015, pp. 61-68 http://www.aiscience.org/journal/ijab * Corresponding author E-mail address: ban_heidari@yahoo.com (B. Heidari) Transplantation of Goat Spermatogonial Stem Cells into the Mouse Rete Testis Mohammad Sadra Shirazi 1 , Banafsheh Heidari 1, * , Mohammad Mehdi Naderi 1 , Bahareh Behzadi 1 , Ali Sarvari 1 , Sara Borjian-Boroujeni 1 , Morteza Farab 1 , Abolfazl Shirazi 1, 2 1 Reproductive Biotechnology Research Center, Avicenna Research Institute (ACECR), Tehran, Iran 2 Research Institute of Animal Embryo Technology, Shahrekord University, Shahrekord, Iran Abstract Assisted reproductive techniques involving isolation, culture, and transplantation of spermatogonial stem cells offer unique approach to manipulate the male germline. The application of these techniques in farm animals has been the subject of an increasing number of studies, mostly because of its potential as an alternative strategy in producing transgenic livestock with higher efficiency and less time and capital requirement than the current methods. The aim of this study was to assess the colonization and differentiation potentials of enriched goat spermatogonia into the mouse testes. Moreover, because stem cells may need to be preserved for several years before re-introduction to the recipient testes, we developed the efficient cryopreservation technique for type A spermatogonoa. The enzymatically isolated SSCs obtained from one month old goats’ testes were enriched by using discontinuous percoll density, and followed by cryopreservation protocol. After xenotransplantation of prepared goat testicular cells into the mouse rete testis, the proliferative activity and stemness potential of SSCs were evaluated and compared with in vitro culture condition. We demonstrated that the viability of testicular cells after cryopreservation was significantly lower than fresh cells, although these cells had normal structural and functional characteristics (P <0.001). Donor goat spermatogonia were able to survive and colonize in depleted recipient’s testis at 80 days after transplantation, but later stages of donor-derived spermatogenesis were not observed at this time. Although cross-species spermatogonial transplantation did not have the envisioned immediate practical application, it nonetheless provides a bioassay for stem cell potential of germ cells isolated from other species. Keywords Cryopreservation, Goat, Mouse, PGP9.5, Spermatogonial Stem Cells, Transplantation Received: April 4, 2015 / Accepted: April 25, 2015 / Published online: May 15, 2015 @ 2015 The Authors. Published by American Institute of Science. This Open Access article is under the CC BY-NC license. http://creativecommons.org/licenses/by-nc/4.0/ 1. Introduction Studies of spermatogenesis were long hampered because of a lack of powerful in vitro and in vivo assay systems until a method for the transplantation of germ cells (GCs) from one animal to another was established (Brinster and Zimmermann, 1994). Spermatogonial stem cell transplantation (SSCT), a procedure in which testis cells are harvested from a fertile male and microinjected into seminiferous tubules of an infertile recipient, offers unique approaches to explore basic biological aspects of male germ line stem cells, examine defects in spermatogenesis and treat male infertility (Dobrinski et al., 2006; Kim et al., 2008). This technique could enhance our understanding of developmental potential of Spermatogonial stem cell (SSCs) and increase the ability of male fertility preservation in both humane and animals. In cancer patients, GCs could be frozen prior to irradiation or chemotherapy treatment and subsequent re-introduction of