[Study of the incidence of anuclear oocytes in vitro in aged mice]

For investigating the relationship between maternal age and incidence of molar pregnancy, attempt was made to experiment in animal model. C57BL/6J strain mice were used for experimental animal model because the transition of reproductive age of these animals have a strong resemblance to those of human. It is proved that hydatidiform mole arises from fertilization of "an empty egg" resulting from either enucleation or inactivation of the female pronucleus. Therefore incidence of anuclear oocyte during in vitro maturation process was examined of oocytes obtained from aged mice's ovaries(403-503 days old) in comparison with those of young mice's(108-274d.o.). The results were as follows: 1) Timing of oocyte maturation and ooclasmic maturation rate were the same in aged mice as in mature (young) ones. 2) But incidence of abnormal oocytes such as having two polar bodies were significantly higher in aged than in young mice(9.2% versus 3.6%). (p less than 0.025) 3) Especially incidence of abnormal anuclear oocytes were also very high in aged mice(aged: young = 12.5%:3.6%). (p less than 0.05) This result suggest the increase of molar pregnancy during climacteric in human is due to increase of anuclear oocytes for oocyte maturation.