IN-UTERO CARDIAC GENE-TRANSFER VIA INTRAPLACENTAL DELIVERY OF RECOMBINANT ADENOVIRUS

Background The relationship among the maternal, placental, and uniquel y shunted embryonic circulation was explored to provide access to the embryonic cardiovascular system in utero. Manipulation of gene express ion in the developing heart would be particularly useful for studying the effects of altered gene expression on cardiac development and in t he etiology of congenital cardiac anomalies. Methods and Results Dye s tudies demonstrated that intraplacental injection allows direct access to the embryonic cardiac and systemic circulation. To evaluate the ef ficacy of cardiac gene transfer using this approach, replication-defic ient recombinant adenoviral vectors encoding luciferase or beta-galact osidase as reporter genes were injected intraplacentally into embryoni c day (E)12.5 murine embryos, an age at which the mass of the heart wa s observed to be large compared with other organs. Embryos were assaye d for transgene expression at E15.5 and at birth. Survival rates at th ese times were similar among vector-injected and control groups. At E1 5.5 and at birth, luciferase activity within the heart was 9- and 23-f old higher, respectively, than in the remainder of the embryo, althoug h levels of expression were generally lower at birth than during embry onic life. beta-Galactosidase expression was observed within all regio ns of the embryonic heart and was localized to approximate to 15% of a trial and ventricular cells. Conclusions Intraplacental delivery of ad enovirus at embryonic day 12.5 results in somatic gene transfer to the murine embryonic heart, which persists at least until birth. The comb ination of intraplacental injection to directly access the fetal coron ary circulation and injection at E12.5 when the mass of the heart is l arge compared with other organs results in transgene expression in car diac cells. Intraplacental injections early in embryonic life may thus be useful to study the effects of temporal manipulation of gene expre ssion on cardiac development and disease.