Objectives: The integration of a proviral plasmid into the host genome could be a good approach for fetal somatic gene transfer. The goal of this study was to assess the integration and transcription of a proviral marker gene injected intraperitoneally into rat fetuses as well as the risks of maternal contamination and germ-line transmission.
Methods: On day 17 post-coitus, each fetus was injected intraperitoneally with 10 microg plasmid DNA through the uterine wall. Twenty-one days after spontaneous delivery, integration and transcription of the plasmid in gonad, gut, liver, spleen, lung and brain tissue from 10 pups were determined by PCR and RT-PCR.
Results: 14 of 60 organs exhibited integration of the plasmid. Four samples of gut (40%), 3 samples of liver and spleen (30%), 2 samples of brain (20%) and no sample of lung were transfected. Two testicular samples were transfected and study of F1 rats from 2 brothers of one of the positive rats revealed transgenic pups from 1 of these 2 animals. No transfection of maternal tissues was detected.
Conclusion: Integration and transcription of a marker gene injected intraperitoneally into rat fetuses appear efficient, especially in intraperitoneal organs. The risk of maternal contamination appears very low when using a naked DNA plasmid injected directly into fetuses. However, germ-line contamination can occasionally occur even with injection late during pregnancy, suggesting further studies are necessary to assess this risk in direct gene transfer experiments.
Copyright 2002 S. Karger AG, Basel