Establishment of Etv5 gene knockout mice as a recipient model for spermatogonial stem cell transplantation.

Spermatogonial stem cell (SSC) transplantation is an alternative reproductive method to achieve conservation and production of elite animals in livestock production. Creating a recipient animal without endogenous germ cells is important for effective SSC transplantation. However, natural mutants with depletion of SSCs are difficult to obtain, and drug ablation of endogenous germ cells is arduous to perform for practical use. In this study, we used mouse models to study the preparation of recipients with congenital germ cell ablation. We knocked out (KO) Ets-variant gene 5 (Etv5) in mice using the CRISPR/Cas9 system. The testicular weight of Etv5-/- mice was significantly lower than that of wild-type (WT) mice. The germ cell layer of the seminiferous tubules gradually receded with age in Etv5-/- mice. At 12 weeks of age, the tubules of Etv5-/- mice lacked almost all spermatogenic cells with a Sertoli cell-only phenotype, and sperm were completely absent in the epididymis. We subsequently transplanted allogeneic SSCs with enhanced green fluorescent protein (EGFP) into 3- (immature) or 7-week-old (mature) Etv5-/- mice. Partial restoration of germ cell layers in the seminiferous tubules and spermatogenesis was observed in all immature testes but not in mature adult testes at 2 months post-transplantation. The presence of heterologous genes Etv5 and EGFP in recipient testicular tissue and epididymal sperm by PCR indicated that sperm originated from the transplanted donor cells. Our study demonstrates that, although Etv5-/- mice could accommodate and support foreign germ cell transplantation, this process occurs in a quite low efficiency to support a full spermatogenesis of transplanted SSCs. However, using Etv5-/- mice as a recipient model for SSC transplantation is feasible, and still needs further investigation to establish an optimized transplantation process.

Zhang X ，Zhao X ，Li G ，Zhang M ，Xing P ，Li Z ，Chen B ，Yang H ，Wu Z ... -  《Biology Open》

Loss of Etv5 decreases proliferation and RET levels in neonatal mouse testicular germ cells and causes an abnormal first wave of spermatogenesis.

Tyagi G ，Carnes K ，Morrow C ，Kostereva NV ，Ekman GC ，Meling DD ，Hostetler C ，Griswold M ，Murphy KM ，Hess RA ，Hofmann MC ，Cooke PS ... -  《-》

Effects of ETV5 (ets variant gene 5) on testis and body growth, time course of spermatogonial stem cell loss, and fertility in mice.

Schlesser HN ，Simon L ，Hofmann MC ，Murphy KM ，Murphy T ，Hess RA ，Cooke PS ... -  《-》

ETV5 is required for continuous spermatogenesis in adult mice and may mediate blood testes barrier function and testicular immune privilege.

Morrow CM ，Hostetler CE ，Griswold MD ，Hofmann MC ，Murphy KM ，Cooke PS ，Hess RA ... -  《-》

Germ cell transplantation into mouse testes procedure.

To illustrate the step-by-step protocol followed to assay germ cell transplantation into the seminiferous epithelium of mouse testes. Video presentation of an animal model for research in reproductive and regenerative medicine. Research laboratory. Male nude mice (NU-Foxn1(nu)). Mice were chemically sterilized with alkylant compounds (busulfan) followed by gonadal microsurgery to inject donor germ cells. Donor cells should be labeled with reporter genes, such as green fluorescent protein (GFP), lactose operon (LacZ), or alternatively design an effective strategy with specific antibodies to track them within the recipient testes. Sperm detection in the ejaculate can also be used as a read out. However, in this case detection of the donor genotype in the sperm is mandatory to elucidate their origin. In the present study we describe the complete protocol for germ cell transplant by efferent duct injection, including the preparation of recipient mice, surgery for the germ cell transplant, and analysis of recipient testes. The main strength of this technique is that it constitutes the gold standard for a functional test of the germ cell potential as only spermatogonial stem cells are able to properly colonize the seminal lumen. Both fresh and frozen/thawed testicular cells are suitable for this technique as donor germ cells. Also, enrichment of living spermatogonial stem cells, previous to the transplant, seems to improve the efficiency of colonization. For proper colonization of germ cells, the niche should be available and thus mouse strains that lack endogenous spermatogenesis such as W/W(v) mutant mice are usually used. In the case of nonmatched donor cells, seminiferous epithelium of immune-suppressed recipient mice should be germ cell depleted before the transplant. One limitation of this technique is that the procedure can take up to 3 months. Also, in contrast to the full recovery of spermatogenesis in mouse-to-mouse transplants, xenotransplantation of germ cells from phylogenetically distant species, such as humans into mouse recipients, results in colonization of donor cells and spermatogonial expansion, but fail in their spermatogenic progression due to evolutive incompatibilities with the recipient niche. Xenografting of pieces of donor testis tissue under the skin of mouse hosts is an alternative approach that is currently being investigated to try to solve this limitation. Transplantation of spermatogonial stem cells into the seminal lumen of mouse testes is a functional assay that defines this cellular subpopulation by its ability to colonize it. This technique can be used as a model to elucidate the insights of spermatogonial stem cells, to produce transgenic animals by genetically manipulating donor cells before transplantation, but also it has potential applications in fertility preservation in cattle and humans as it is feasible in large animals, as recent reports have demonstrated with rhesus monkeys, that recovered spermatogenesis after allogenic transplantation, and even from human cadaver testes. Therefore spermatogonial stem cells isolated from prepuberal boys, who are treated with alkylant chemotherapy, could be returned to their testis to regenerate spermatogenesis in the future.

Medrano JV ，Martínez-Arroyo AM ，Sukhwani M ，Noguera I ，Quiñonero A ，Martínez-Jabaloyas JM ，Pellicer A ，Remohí J ，Orwig KE ，Simón C ... -  《-》