To investigate whether female fertility decreases with age due to poor
oocyte quality, we examined the presence of DNA fragmentation in ovul
ated oocytes from young, mature and aged mice, Oocytes from three age
groups of female mice (7-8, 20-24 and 40-48 weeks) were retrieved from
the oviducts 15 h after human chorionic gonadotrophin (HCG) injection
. Oocytes from each mouse were incubated in a CO2 incubator for 0-60 h
in human tubal fluid (HTF). After incubation, each oocyte was stained
with the terminal deoxynucleotidyl transferase-mediated dUDP nick-end
labelling (TUNEL) method, The rate of DNA fragmentation (interpreted
as apoptotic changes) was significantly higher for oocytes from aged m
ice, acid the fertilization rate was significantly lower, compared wit
h oocytes from young and mature mice, Our results suggest that DNA fra
gmentation of oocytes might be one of the reasons for poor oocyte qual
ity and lower fertility in the aged group.