Development of reproductive engineering techniques at the RIKEN BioResource Center

Comparison of the effect of two commercialized vitrification carriers on pregnancy outcomes in freeze-thaw cycles

OBJECTIVE

This study aimed to compare the effects of two brands of commercial vitrification carriers on pregnancy outcomes in freeze-thaw cycles.

METHODS

We included 4871 patients who underwent a "freeze all" strategy using the commercial carriers J.Y. straw and OYASHIPS straw in the Reproductive Center of the First Hospital of Jilin University. The pregnancy outcomes of cleavage-stage embryos and blastocysts were studied separately. Detailed data and the safety of children born from mothers with the two types of carriers were also compared.

RESULTS

Patients who used J.Y. straw had similar clinical pregnancy and live birth rates with one and two cleavage-stage embryo transplantation to those who used OYASHIPS straw. In patients who had blastocyst transplantation, the clinical pregnancy rate of one blastocyst transplanted in those who used OYASHIPS straw was significantly higher than that in those who used J.Y. straw (57.85% vs 47.09%). Among children born from mothers who used J.Y. straw, the congenital disability rate was significantly higher than that in those with OYASHIPS straw.

CONCLUSION

The OYASHIPS straw carrier is cheap and can achieve clinical pregnancy and live birth outcomes comparable to those of J.Y. straw. Therefore, OYASHIPS straw is a good alternative option.

Improvement of short straws for sperm cryopreservation: installing an air-permeable filter facilitates handling

Saving space for sperm cryopreservation would aid mouse genetics research. We previously developed the ST (sperm freezing in ShorT STraw to reduce STorage space) method for cryopreserving mouse sperm in a smaller storage space than conventional methods. However, our ST method has two drawbacks: difficulties during freeze-thaw procedures and the potential risk of sperm loss during storage. Here, we refine ST, terming the new method improved ST (iST). In iST, the straw has an air-permeable filter and the straw container (2-ml cryotube) is endowed with air vents. As in our ST method, iST frozen-thawed sperm showed good performance upon in vitro fertilization. Moreover, up to nine straws can be stored in one cryotube, occupying less storage space than conventional methods. This method provides an easy and space-saving cryopreservation method for mouse sperm, and thus will be valuable for mouse genetics researchers.

Freezing sperm in short straws reduces storage space and allows transport in dry ice

Efficient cryopreservation and transportation of mouse sperm are among the most desirable strategies for current and future research on mouse genetics. However, the current method for sperm cryopreservation uses an 11-cm plastic straw, which is a bulky and fragile container. Developing an alternative to overcome the limitations associated with this method would accelerate biomedical research. Here, we developed the ST (sperm-freezing in ShorT STraw to reduce STorage space) method for cryopreserving mouse sperm in short 3.8-cm plastic straws. Up to nine short straws can be stored in a cryotube, reducing storage space. We further show that sperm frozen by the ST method can be transported in liquid nitrogen or dry ice without any detrimental effects on subsequent fertilization and the birth rate. Our findings suggest that this sperm-freezing method is beneficial not only for individual laboratories but also for large-scale mutagenesis/knockout and phenotyping programs.