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Human papillomavirus and blastocyst apoptosis
Joan H Calinisan1, Steven R Chan, Alan King
1Department of Gynecology and Obstetrics, Loma Linda University School of Medicine, California 92350, USA.
Purpose:
The effect of human papillomavirus (HPV) DNA from the E6-E7 region on the integrity of DNA in blastocyst stage embryonic cells was studied. The study design paralleled the event whereby HPV DNA from the infecting virus would target host cell DNA. The objectives were (a) to determine if the DNA of blastocysts were disrupted by the presence of HPV DNA and (b) to determine if the intensity of DNA damage was associated with the type of HPV.
Methods:
This study involved superovulating female mice, mating, collecting one-cell embryos, and culturing to the expanded blastocyst stage. The blastocysts were infected with PCR-synthesized DNA fragments from either HPV type 16, 18, 31, or 33. The blastocyst DNA were analyzed by comet assay after 24 h of incubation. The fluorescent images were digitized and the pixel intensity of each blastocyst was measured.
Results:
Only the DNA of HPV type 16 was associated with significant DNA fragmentation in comparison with the other HPV types. There was no relationship between HPV DNA fragment size and the intensity of DNA fragmentation.
Conclusions:
The data suggested that one mode of action of HPV type 16 was to initiate apoptosis of embryonic cells through DNA fragmentation. The effect of HPV 16 occurred rapidly within 24 h. The intensity of DNA damage was not linked to the specific type of HPV. However, the results do not rule out the other HPV types affecting embryos under conditions different from this study.