Agarose capsules as new tools for protecting denuded mouse oocytes/embryos during handling and freezing-thawing and supporting embryonic development in vivo

Abstract

Oocytes without a zona pellucida (ZP) often occur as a result of congenital or operational effects, but they are difficult to handle, and embryonic survival is low. Such zona-free (ZF) oocytes are therefore not used in clinics or laboratories. Furthermore, in the laboratory, removal of the ZP is often necessary for genetic manipulation by viral infection or twin production by blastomere separation, but adverse effects on development have been reported. It would therefore be extremely valuable if the embryo could be covered with a structure similar to that of the ZP. In this study, we sought to determine whether an agarose capsule could serve as a substitute for the ZP. Our results indicate that embryos derived from these agarose capsules were able to develop normally, and could be transplanted to obtain viable offspring, without having to remove the agarose capsule. Furthermore, before compaction, the agarose capsule embryos exhibited good freezing tolerance, and survival rate was extremely high compared to ZF embryos. Thus, agarose capsules represent a valuable tool for utilizing oocytes and embryos that lack a ZP, both in a clinical and livestock setting.

Establishment of a novel method for the production of chimeric mouse embryos using oil droplets

“…There are two methods for reconstructing the embryonic zona pellucida, one using agarose capsules (20) and other using sodium alginate capsules (21). Both methods have disadvantages, in that they have complicated process of production or inhibition of embryonic development (22, 23).…”

Cloning in action: can embryo splitting, induced pluripotency and somatic cell nuclear transfer contribute to endangered species conservation?

“…However, some efforts have focused on developing alternative approaches that negate the need to generate empty zonae. Microencapsulation techniques to create artificial zonae have been attempted in the mouse, consisting of sodium alginate, calcium alginate, poly‐L‐lysine or agarose (Krentz et al ., 1993; Elsheikh et al ., 1997; Cosby & Dukelow, 1990; Nagatomo et al ., 2017) while other approaches have involved culturing embryos without a zona at all, using culture dish microwells as an alternative (Tagawa et al ., 2008). Further developments of zona alternatives using novel biomaterial approaches may significantly improve the efficiency of twinning by blastomere separation.…”

Multiplying embryos: experimental monozygotic polyembryony in mammals and its uses

“…Thus, although in vitro culture with or without ZP does not have any significant effect on postimplantation rates, cycles of freezing and thawing on embryos without ZP diminish the subsequent embryos' quality and viability (Sotomaru et al, 1998). An exemplary solution to this problem is the usage of agarose capsules, which were first tested in mouse, but which are also suggested as a suitable protection for livestock and human embryos (Nagatomo et al, 2017).…”