A 3D-Printed Large Holding Capacity Device for Minimum Volume Cooling Vitrification of Embryos in Prolific Livestock Species

Abstract

Although many devices have been developed to reduce sample volume, with an explosion of methods appearing in the literature over the last decade, commercially available devices with simultaneous vitrification of a larger number of embryos are scarce, with the apparent gap for their use in prolific livestock species. In this study, we investigated the effectiveness of a new three-dimensional (3D)-printed device that combines minimum volume cooling vitrification with simultaneous vitrification of a larger number of rabbit embryos. Late morulae/early blastocysts were vitrified with the open Cryoeyelet® device (n = 175; 25 embryos per device), the open Cryotop® device (n = 175; 10 embryos per device), and the traditional closed French mini-straw device (n = 125; 25 embryos per straw) and compared in terms of in vitro development and reproductive performance after transfer to adoptive mothers. Fresh embryos constituted the control group (n = 125). In experiment 1, there was no difference in the development rate to the blastocyst hatching stage between the CryoEyelet® and the other devices. In experiment 2, the CryoEyelet® device showed a higher implantation rate compared with the Cryotop® (6.3% unit of SD, p = 0.87) and French mini-straw® (16.8% unit of SD, p = 1.00) devices. In terms of offspring rate, the CryoEyelet® device was similar to the Cryotop® device but superior to the French straw device. Regarding embryonic and fetal losses, the CryoEyelet® showed lower embryonic losses compared to other vitrification devices. The analysis of bodyweight showed that all devices showed a similar outcomes—a higher birthweight but a lower body weight at puberty than those in the fresh transfer embryos group. In summary, the CryoEyelet® device can be used for the vitrification of many late morulae or early blastocyst stage rabbit embryos per device. Further studies should be performed to evaluate the CryoEyelet® device in other polytocous species for the simultaneous vitrification of a large number of embryos.