Gamete-specific DNA fragmentation in unfertilized XXXX oocytes after intracytoplasmic sperm injection.

@entity1 @entity4810 @entity1885 @entity12179 @entity14939
The objective of the present study was to assess the integrity of maternal and/or paternal chromatin in injected oocytes that remained unfertilized after intracytoplasmic sperm injection (ICSI). The study was performed on 102 oocytes that failed to show pronuclear formation 18-20 h after ICSI. We used chromatin labelling with @entity14939 ( @entity14939 ) to identify maternal and paternal chromatin, coupled with @entity1885 -mediated end-labelling to assess DNA fragmentation in each gamete. It was shown that 50% of oocytes without pronuclear formation following ICSI contained chromatin with damaged DNA, and that the source of the DNA fragmentation was equally divided between the spermatozoon (25.8%) and the oocyte (24.4%). A significantly greater proportion of condensed @entity12179 in @entity1 oocytes had damaged DNA, compared to decondensed @entity12179 (24.7 compared to 5.9%, P=0.002). There was a significant increase in the incidence of DNA fragmentation in oocytes from @entity1 older than 35 years (65+/-1.2%) compared to those from younger @entity1 (36+/-1.0%) (P < 0.05). Further, 17% of unfertilized oocytes contained no paternal chromatin. Thus, DNA fragmentation in both @entity12179 and oocytes is associated with failure of fertilization in ICSI. In some cases of severe @entity4810 , a significant proportion of @entity12179 injected into oocytes may contain fragmented DNA. Injection of oocytes with @entity12179 containing abnormal chromatin will probably result in failure of sperm decondensation and fertilization. In older @entity1 , a significant proportion of oocytes injected may contain fragmented DNA. These observations may explain the consistent inability of most clinics to achieve fertilization rates higher than 65% with ICSI.
