Testis Tissue Explant Culture Supports Survival and Proliferation of Bovine Spermatogonial Stem Cells

The present study was designed to evaluate the survival and proliferation of bovine spermatogonial stem cells in an explant culture system over a 2-wk period. Explants of calf testicular parenchyma were placed on 0.45-μm pore membranes in culture and maintained for 1–2 wk. Histological examinations of fresh (t0) and cultured tissues revealed morphologically normal seminiferous tubules. Germ cell numbers/tubule increased ( P ≤ 0.05) during culture when compared with t0, yet germ cell differentiation was not observed. Testosterone was present in medium throughout the culture period, indicating functional Leydig cells. Sertoli, spermatogonial, and spermatogonial stem cell viability was evaluated by reverse transcription-polymerase chain reaction for cell-specific gene expression of stem cell factor, protein gene product 9.5, and glial cell line-derived neurotrophic factor family receptor-α1, respectively. Results demonstrated the expression of all genes at t0, 1 wk, and 2 wk of culture. Single-cell suspensions were prepared from the testicular tissues at t0 and during culture and transplanted into nude mouse testes to investigate spermatogonial stem cell viability. One month after transplantation, colonies of round bovine cells were identified in all mouse testes analyzed, indicating survival of spermatogonial stem cells. The average number of resulting colonies in recipient testes was significantly ( P ≤ 0.05) higher following 1 wk of culture compared with t0 and was numerically higher at 2 wk of culture compared with t0. This increase in colony numbers over time in culture indicates spermatogonial stem cell proliferation in vitro. This explant culture system appears to provide an environment that supports survival and proliferation of bovine spermatogonial stem cells.