Survivable potential of germ cells after trehalose cryopreservation of bovine testicular tissues

Germplasm preservation of livestock or endangered animals and expansion of germline stem cells are important. The purpose of this study is to investigate whether supplementation of trehalose to the freezing medium (FM) reduces tissular damage and improves the quality of testicular cells in the cryopreserved bovine testicular tissues. We herein established an optimized protocol for the cryopreservation of bovine testicular tissues, and the isolation as well as culture of bovine germ cells containing spermatogonial stem cells (SSCs) from these tissues. The results showed that FM containing 10% dimethyl sulfoxide (Me₂SO/DMSO), 10% knockout serum replacement (KSR) and 20% trehalose (FM5) combined with the uncontrolled slow freezing (USF) procedures has the optimized cryoprotective effect on bovine testicular tissues. The FM5 + USF protocol reduced the cell apoptosis, maintained high cell viability, supported the structural integrity and seminiferous epithelial cohesion similar to that in the fresh tissues. Viable germ cells containing SSCs were effectively isolated from these tissues and they maintained germline marker expressions in the co-testicular cells and co-mouse embryonic fibroblasts (MEF) feeder culture systems respectively, during the short-term culture. Additionally, upregulated transcriptions of spermatogenic differentiation marker C-KIT and meiotic marker SYCP3 were detected in these cells after retinoic acid-induced differentiation. Together, FM5 + USF is suitable for the cryopreservation of bovine testicular tissues, with benefits of reducing the apoptosis, maintaining the cell viability, supporting the testicular structure integrity, and sustaining the survival and differentiation potential of bovine germ cells containing SSCs.