High-efficiency, long-term cardiac expression of foreign genes in living mouse embryos and neonates

Background-The development of improved strategies for efficient and reprodu cible in vivo gene transfer into the murine heart will ultimately allow the intersection of somatic and germline gene transfer strategies to study com plex features of cardiac biology and diseases. Methods and Results-For embryonic gene transfer, an adenovirus vector expre ssing beta-galactosidase was injected in utero into the ventricular cavity of living embryos via microsurgical approaches. The injected embryos were d eveloped to term, and efficient expression of the transgene was detected in all cell types in the heart. For postnatal cardiac gene transfer, adenovir us was injected into the cardiac ventricle of neonatal mice, resulting in e fficient expression of the transgene in the outer layer of the myocardium a s well as cardiomyocytes in the middle and inner layers of the cardiac wall . Mice examined after 3 weeks displayed a pattern of expression that comple tely mimicked the pattern seen after 3 days, and gene expression was also f ound after 6 months. The infected myocytes can be identified by coinfection of an adenovirus expressing green fluorescent protein without affecting th eir normal physiological function. Conclusions-We have developed a new strategy to achieve efficient and long- term foreign gene expression in both embryonic and postnatal mouse myocardi um via direct intracardiac injection of recombinant adenovirus. The strateg y should allow the functional assessment of the expression of dominantly ac ting exogenous genes, overexpression of wild-type genes, and Cre recombinas e-mediated gene ablations at the single-cell level in the context of the in tact adult mouse myocardium.