Long-term culture and transplantation of spermatogonial stem cells from BALB/c mice

Abstract

Objective To establish a long-term culture system for mouse spermatogonial stem cells(SSCs). Methods Testis cells from 4-6 days postpartum male transgenic BALB/C mice were collected by a modified two-step enzymatic digestion method.After three differential adherence selections,the enriched germ cells were finally suspended in StemPro-34 SFM medium supplemented with other nutrients factors and plated on mouse embryonic fibroblast(MEF)feeder layer.20 ng/ml Glial cell line-derived neurotrophic factor,10 ng/ml basic fibroblast growth factor and 200 ng/ml GDNF-family receptor al were added to the serum-free medium to promote SSCs proliferation.Aduh male BALB/C mice,4-5 weeks old,underwent intraperitoneal injection of 40 mg/kg busulfan as recipient mice.Cultured SSCs were also injected into the seminiferous tubules of the left recipient testis through micromanipulator and right testis as self-control.Testes of recipient mice were observed by a fluorescence stereomicroscope and HE stains at 2 months after transplantation. Results By improved digestion method,the vitality of isolated testis cells was more than 98%and the stem cells was enriched about 18.5 fold. 1-2 days after transferred to MEF feeder, the round germ cells started to proliferate and had the shape of paired or aligned undifferentiated spermatogonia connected by cytoplasmic bridges. After 3-4 days, SSCs proliferated continuously and formed typical colonies. SSCs from BALB/c mice could be cultured and passaged in a steady state for 3 months. Cryostat section through the transplanted testis showed that most of seminiferous tubules were filled with germ cells expressing EGFP.HE staining further showed clearly that seminiferous tubules contained complete spermatogenesis.Conclusions SSCs from BALB/c mice could be cultured in an improved culture system for 3 months.The culture system could facilitate understanding the regulatory mechanism that governs SSCs and might provide an opportunity for the cure of infertility. Key words: Spermatogonia; Stem cells; Cell culture techniques; Transplantation; Mice