Cryopreservation of calf testicular tissues with knockout serum replacement

To enrich bovine gonocytes from cryopreserved testicular tissues, the cryoprotection effects of the freezing media containing knockout serum replacement (KSR) were examined. Using Minimum essential medium (MEM) + 10% dimethyl sulfoxide (Me₂SO) as the basic medium, calf testicular tissues were cryopreserved in media containing 0, 5, 10, 20, 40, 90% KSR and 5% fetal bovine serum (FBS) respectively. Morphologically, the seminiferous cords and interstitium were well preserved in all groups. The gonocytes were all glial cell line-derived neurotrophic factor (GDNF) family receptor α-1 (GFRα-1) positive. The recovery rates in all KSR groups were higher than that of the 10% Me₂SO group, while comparable to the 5% FBS group. The enriched gonocytes expressed gonocyte marker GFRα-1 typically. Collectively, supplementation of 5–10% KSR can achieve comparable cryoprotective effects with using 5% FBS, which is useful in future study due to its defined formulation that is more consistent in quality and stable in supply.