Abstract

In order to understand the effect of chronic exposure to low-dose-rate radiation on female fertilities and the risk of heritable genetic effects on domestic animals after the Fukushima Daiichi Nuclear Power Plant (FNPP) accident, we assessed the developmental ability of oocytes, and examined the histological characters and structure of ovaries. We showed that potentially viable oocytes could be collected from the ovary of abandoned cattle in the ex-evacuation zone set within a 20-km radius from FNPP, resulting in production of the morphologically normal calves following in vitro culture and embryo transfer. The proliferation of cattle ovarian granulosa cells was confirmed by expression of Ki-67. Apoptosis of oocytes and granulosa cells was few determined by the TUNEL assay. In addition, porcine and inobuta oocytes had the abilities of in vitro maturation. These results suggest that chronic radiation exposure associated with the FNPP accident may have little effect, if any, on the female fertilities of domestic animals.

Highlights

  • Female reproductive organs such as the ovary, oviduct and uterus are essential organs to produce the generation in mammals

  • After culture for In vitro maturation (IVM), cumulus expansion with cell proliferation, which is known as an index of oocyte maturation, was observed in almost all cumulus-oocyte complexes (COCs)

  • We showed that potentially viable oocytes were obtainable from the ovaries of abandoned cattle, resulting in production of offspring

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Summary

Introduction

Female reproductive organs such as the ovary, oviduct and uterus are essential organs to produce the generation in mammals. Female germ cells, are contained in the ovary. Oocyte production begins in the fetal ovary. The ovaries at the time of birth contain a large amount of oocytes, and oogenesis in the adult does not increase the number of germ cells. Oocytes form the ovarian follicles along with somatic cells such as granulosa cells which support the growth of oocytes. A primordial follicle, consisting of an oocyte surrounded by a single layer of follicular cells (pregranulosa cells), is the most immature stage of an ovarian follicle’s development and can remain in this state for many years. After puberty (sexual maturation), some primordial follicles resume development into the primary, secondary and antral follicles with proliferation of granulosa cells and an increase in the oocyte diameter, and ovulate following development to the fully mature state. Damage to oocytes and follicular cells may lead to apoptosis, mutants and chromosomal changes, resulting in infertility and hereditary diseases

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