Vectors based on the adeno-associated virus (AAV) deliver therapeutic genes to muscle and heart
at high efficiency and maintain transgene expression for long periods of time. Here we report
about the synergistic effect on blood vessel formation of AAV vectors expressing the 165 aa
isoform of vascular endothelial growth factor (VEGF165), a powerful activator of endothelial cells,
and of angiopoietin-1 (Ang-1), which is required for vessel maturation. High titer AAV-VEGF165
and AAV-Ang-1 vector preparations were injected either alone or in combination in the normoperfused
tibialis anterior muscle of rats. Long term expression of VEGF165 determined massive
cellular infiltration of the muscle tissues over time, with the formation of a large set of new vessels.
Strikingly, some of the cells infiltrating the treated muscles were found positive for markers of
activated endothelial precursors (VEGFR-2/KDR and Tie-2) and for c-kit, an antigen expressed by
pluripotent bone marrow stem cells. Expression of VEGF165 eventually resulted in the formation
of structured vessels surrounded by a layer of smooth muscle cells. Presence of these arteriolae
correlated with significantly increased blood perfusion in the injected areas. Co-expression of
VEGF165 with angiopoietin-1-which did not display angiogenic effect per se-remarkably reduced
leakage of vessels produced by VEGF165 alone.
