Successful transplantation of transfected enriched buffalo (Bubalus bubalis) spermatogonial stem cells to homologous recipients

Spermatogenesis regeneration by transfected spermatogonial stem cells in infertile roosters through testicular transplantation

Investigations pertaining to spermatogonial stem cells (SSCs) have led to the use of these cells in a variety of fields including infertility treatments, production of transgenic animals, and genome editing. The aim of the present study was to investigate the plausibility of regenerating spermatogenesis in infertile roosters by transplanting transfected SSCs into testes. Spermatogonial stem cells were isolated and cultured for seven days. Afterward, pDB2, a plasmid vector carrying a reporter gene, GFP, was transfected into the SSCs. Transfected SSCs were transplanted into the left testis of infertile roosters. Tissue samples from the recipients' testes were obtained six weeks after the transplantation and transplanted SSCs were observed in the basement membrane. After eight weeks, GFP-positive spermatozoa were observed in collected semen from the recipient roosters and GFP gene in spermatozoa was confirmed using PCR. The recipient roosters were mated with hens. Hatchlings were visually checked and their tissue samples were tested by PCR to identify transgenesis but both of them were negative. Overall, it seems that regeneration of spermatogenesis in roosters via transfected SSCs is possible but more studies are need to produce recombinant proteins by this way.

Production of Transgenic Handmade Cloned Goat (Capra hircus) Embryos by Targeted Integration into Rosa 26 Locus Using Transcription Activator-like Effector Nucleases

Transgenic goats are ideal bioreactors for the production of therapeutic proteins in their mammary glands. However, random integration of the transgene within-host genome often culminates in unstable expression and unpredictable phenotypes. Targeting desired genes to a safe locus in the goat genome using advanced targeted genome-editing tools, such as transcription activator-like effector nucleases (TALENs) might assist in overcoming these hurdles. We identified Rosa 26 locus, a safe harbor for transgene integration, on chromosome 22 in the goat genome for the first time. We further demonstrate that TALEN-mediated targeting of GFP gene cassette at Rosa 26 locus exhibited stable and ubiquitous expression of GFP gene in goat fetal fibroblasts (GFFs) and after that, transgenic cloned embryos generated by handmade cloning (HMC). The transfection of GFFs by the TALEN pair resulted in 13.30% indel frequency at the target site. Upon cotransfection with TALEN and donor vectors, four correctly targeted cell colonies were obtained and all of them showed monoallelic gene insertions. The blastocyst rate for transgenic cloned embryos (3.92% ± 1.12%) was significantly (p < 0.05) lower than cloned embryos (7.84% ± 0.68%) used as control. Concomitantly, 2 out of 15 embryos of morulae and blastocyst stage (13.30%) exhibited site-specific integration. In conclusion, the present study demonstrates TALEN-mediated transgene integration at Rosa 26 locus in caprine fetal fibroblasts and the generation of transgenic cloned embryos using HMC.

Persistence of undifferentiated spermatogonia in aged Japanese Black cattle

Aging is a major risk factor for spermatogenesis deterioration. However, the influence of age on spermatogenic stem cells and their progenitors in bulls is largely unknown. Here, we report age‐related changes in undifferentiated and differentiating spermatogonia in Japanese Black cattle with nearly constant sperm output, by using spermatogonial markers. The numbers of differentiating spermatogonia and more differentiated spermatogenic cells were significantly decreased in aged bovine testes compared with those in young testes. In contrast, the number of undifferentiated spermatogonia was maintained, and their proliferative activity did not differ significantly between young and aged bovine testes. Although severe calcification was only observed to a small extent in aged testes, fewer Sertoli cells and interstitial fibrosis were observed in noncalcified testicular regions. These results suggest that, even in old bulls with nearly constant sperm output, testicular spermatogenic activity declined whereas undifferentiated spermatogonia numbers were maintained. Thus, we propose that undifferentiated spermatogonia may be resistant to age‐related changes in bovine testes. Because undifferentiated spermatogonia may contain stem cell activity, our findings highlight the potential utility of undifferentiated spermatogonia as an agricultural resource to produce spermatozoa beyond the natural bovine lifetime through transplantation and in vitro spermatogenesis in future animal production.

The effect of regulating the Wnt signaling pathway on the proliferation and differentiation of spermatogonial stem cells

Background

Spermatogonial stem cells and organ engineering research has raised new hope in infertility treatment. Spermatogenesis is a complex physiological process. To observe the proliferation ability and differentiation tendency of mice spermatogonial stem cells (SSCs), to study the effect of regulating the Wnt signaling pathway on the proliferation and differentiation of SSCs, and to provide a valuable basis for the clinical application of SSCs.

Methods

SSCs were isolated and cultured by immunomagnetic separation. Cell surface markers were identified by flow cytometry. Axin1 was chosen as the target gene to inhibit fibrosis of SSCs by inhibiting the activity of Wnt signaling pathway. Axin-siRNA interference vector was constructed and transfected into spermatogonial stem cells. Cultured SSCs were randomly divided into six groups: control group, SSCs + TGF-β group, SSCs + DKK1 group, SSCs + Axin-RNAi group, SSCs + TGF-β + DKK1 group, SSCs + TGF-β + Axin-RNAi group. Proliferation of SSCs in each group was detected by MTT assay. Immunofluorescence, western blot and real time polymerase chain reaction analysis were used to detect protein expression in the Wnt/β catenin signaling pathways and the molecular markers of fibroblasts in SSCs.

Results

Flow cytometry analysis confirmed that the cultured SSCs were of high purity. MTT assay showed there was no significant difference between Axin-siRNA transfected and non-transfected cells. The proliferation ability was significantly increased in the SSCs + TGF-β group, however, it was retarded in SSCs + Axin-RNAi group. The results of immunofluorescence and western blot analysis showed that the expression levels of the Wnt signaling pathway proteins were relatively inhibited after Axin-siRNA was applied. Real-time polymerase chain reaction showed that the expression levels of the molecular markers of fibroblasts were close to the normal control group.

Conclusions

The Axin-siRNA constructed in this study specifically inhibited Wnt/β-catenin signal pathway activation, then inhibited the differentiation of SSCs into fibroblasts, which provides a valuable basis for the clinical application of SSCs.