In vitro development of spontaneously activated bovine oocytes

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Abstract
Purpose: The aim of this study was to compare the development of bovine parthenogenetic and in vitro fertilization-derived (IVF) embryos. Oocytes were matured, fertilized, or allowed to activate spontaneously by aging and then cultured for up to 14 days in vitro. Cleavage and development rates, morphology, ultrastructure, and transcriptional activity were compared. Results: Very few parthenogenotes (7.5% of aged oocytes) were obtained and none developed to the hatched blastocyst stage. The pattern of3H-uridine incorporation at the two-, four-, and eight-cell stages was similar in both types of embryos. Morphological study, however, revealed that none of the parthenogenotes showed features associated with long-term development: they were developmentally delayed and usually arrested before reaching the blastocyst stage (only 0.5% of aged oocytes developed to the blastocyst stage). Structural differences between parthenogenotes and the IVF-derived embryos were observed at all stages of development. Conclusions: Structural observation suggested that failure of long-term development of bovine parthenogenotes may have a metabolic basis. Some functional changes appeared to coincide with chronological age rather than developmental age. Even though development of parthenogenotes was limited, some features of nuclear maturation and activation of the embryonic genome occur without contribution of the paternal genome.