Feng Liu, Can Sun, Yong Zhu, Shan S. Wang, Wen B. Shi, Jing J. Zhu, Yong H. Huang, Zheng Li
Objective: To develop a new mirco-straw (named as LSL straw) for cryopreservation of few sperm retrieved from severe oligozoospermia and testicular biopsy samples.
Methods: We developed a new micro-straw with max volume of 50 µL. The same sperm samples were cryopreserved using new mirco-straw and conventional 0.2 and 0.5 mL straws and post thaw motility, acrosomal integrity and sperm DNA fragmentation were compared. Total of 32 semen samples were used in this study and each sample was diluted to sperm concentration 10×106/mL. The diluted semen was mixed with cryoprotectant in ratio of 1:1 before transferring to micro-straw and 0.5 and 0.25 mL straws. Then place all the three straws containing sperm directly to liquid nitrogen vapor at –140 for 3 hours before plunge it to liquid nitrogen for storage at –196 °C. In post thaw sample, total and progressive motility, sperm morphology, acrosome integrity (FITC-PSA) and DNA fragmentation index (sperm chromatin diffusion, SCD) were assessed in the same samples before and after freezing.
Results: While post thaw motility (25.6% vs. 27.4% vs. 38.5% vs. 54.4%, P<0.001) and acrosomal integrity (65.08% vs. 66.61% vs. 68.84% vs. 77.8%, P<0.001) were all significantly lower in all straws compared with fresh semen, new micro-straws had significantly higher motility recovery than conventional 0.5 and 0.25 mL straws (38.5%, 25.6%, 27.4%, P<0.003). There was significantly correlation between speed of temperature and motility recovery: the faster temperature declines, the better motility recovery in post thaw samples. However, there was no significantly different in morphology, acrosome integrity and DNA integrity between the three types of straws.
Conclusions: New micro-straw for sperm cryopreservation has significant higher motility recovery than conventional 0.5 and 0.25 mL straws. This micro-straw may be benefit for cryopreservation of few sperm storage and easy to be recovered for ICSI treatment in several male factor infertility.
