Fertilization and embryo development to blastocysts after intracytoplasmicsperm injection in the rhesus monkey

Notwithstanding the thousands of seemingly healthy children born after intr acytoplasmic sperm injection (ICSI), it is not yet possible to conclude abs olutely that the ICSI procedure might induce some altered development or th at the ICSI protocol might not be improved even further To address this in a clinically relevant system, the developmental potential of rhesus monkey embryos produced by ICSI is reported. Oocytes collected by laparoscopy from gonadotrophin-stimulated fertile females were fertilized by ICSI using spe rmatozoa obtained from fertile males by electro-ejaculation. Neither sperm immobilization prior to injection nor an additional chemical stimulus were necessary to achieve oocyte activation and pronuclear formation. Survival a nd activation of the injected oocytes were judged by the extrusion of the s econd polar body. Successful fertilization was confirmed by the presence of two pronuclei within 12 h post-ICSI. Some oocytes were fixed and processed for the detection of microtubules and chromatin. Fluorescent labelling rev ealed that by 12 h post-ICSI the male and female pronuclei were closely app osed and eccentrically positioned within a large microtubule aster ICSI res ulted in a 76.6 +/- 14.9% fertilization rate. First cleavage was completed within 24 h post-ICSI. Two-cell ICSI embryos were co-cultured in CMRL mediu m on a buffalo rat liver cell monolayer until the hatched blastocyst stage. Oocytes collected laparoscopically from stimulated monkeys can be fertiliz ed by ICSI and will complete preimplantation embryo development in vitro de monstrating that the rhesus monkey is an excellent preclinical model for ex amining and understanding many aspects of human ICSI.