Expression of Cu/Zn and Mn superoxide dismutases during bovine embryo development: influence of in vitro culture.

Temporal pattern of expression of Cu/Zn and Mn superoxide dismutases (SODs) was investigated in bovine oocytes and embryos produced in vitro in two different culture conditions and in vivo after superovulation. SODs were examined at a transcriptional level in single oocytes and embryos by reverse transcriptase-polymerase chain reaction (RT-PCR) and, at a protein level, by Western blotting on pools of embryos. mRNA encoding Cu/Zn SOD were detected in in vitro bovine embryos throughout preattachment development as well as in in vivo derived morulae and blastocysts. Transcripts for Mn SOD gene were detected in most immature and in vitro matured oocytes as well as in some zygotes and 5- to 8-cell embryos while no transcript was found at the 9-to 16-cell stage in both culture conditions. In vitro embryonic expression of Mn SOD was detected earlier in the presence of serum. Half of the morulae showed the transcript if cultured with 5% serum while none without serum. At the blastocyst stage Mn SOD could be detected independently of culture conditions. For in vivo-derived embryos Mn SOD transcripts were detected both in morulae and blastocysts. Immunoblotting analyses revealed that Cu/Zn SOD and Mn SOD were also present at a protein level in in vitro-derived zygotes and blastocysts. Together these data demonstrate, for the first time, that Mn SOD is transcribed and that Cu/Zn and Mn SOD proteins are expressed in preimplantation bovine embryos. Finally, they suggest that Mn SOD transcription is altered by in vitro culture conditions.

Presence of integrated DNA sequences of adeno-associated virus type 2 in four cell lines of human embryonic origin.

The human helper virus-dependent parvovirus adeno-associated virus (AAV) has been found in human female genital tissues including material from first trimester miscarriage. In the latter case, AAV type 2 (AAV-2) DNA and viral proteins were detected mainly in the trophoblast cell layer of placenta. In this report, we present evidence that AAV DNA is also present in established human trophoblast cell lines (JEG-3, JAr, BeWo) and in the human amnion cell line FL. In cells of these lines, AAV-2 DNA could be detected both by PCR and Southern blot analysis. Restriction enzyme analysis indicated that AAV DNA was integrated into the host cell genome. Although the cell lines supported AAV replication when infected with AAV-2 and adenovirus type 2 (Ad2) as a helper virus, superinfection with Ad2 alone did not induce replication of AAV DNA, i.e. it failed to rescue AAV from its integrated state. This is probably due to rearrangements within the integrated AAV genome. The presence of AAV DNA in cells derived from human embryonic tissue corroborates the suggestion that human embryonic tissue may be one of the targets of AAV infection.

Human genital tissues containing DNA of adeno-associated virus lack DNA sequences of the helper viruses adenovirus, herpes simplex virus or cytomegalovirus but frequently contain human papillomavirus DNA.

The detection of DNA of the helper virus-dependent adeno-associated virus type 2 (AAV-2) in biopsies of material from spontaneous abortion and in tissue samples from the uterus raises the question of whether sequences of known helper viruses can be detected simultaneously within the same specimen despite the lack of histological evidence for the presence of lytic viruses. Therefore, we performed PCR analyses with primers detecting DNA sequences of viruses (adenovirus, herpes simplex virus and human cytomegalovirus) known for their helper activity in the replication of adeno-associated viruses. In addition, PCR was performed to detect DNA of human papillomaviruses (HPV), which were recently shown to be able to help AAV replication in vitro. In no cases were sequences of the known helper viruses found. However, HPV DNA was detected in approximately 60% of paraffin sections from uterus biopsies and cervical lesions containing AAV DNA and in approximately 70% of material from early miscarriage. This finding suggests that HPV may be a helper virus for AAV.