Summary
Vein grafts are used to bypass coronary arterial stenosis, but many grafts thrombose
soon after surgery. A model was developed in the pig to allow continuous measurement
of blood flow and production of flow-restricting thrombi (cyclic flow reductions;
CFRs). Saphenous vein lumen was exposed to adenovirus ex vivo, to over-express human tissue plasminogen activator (h-tPA), with β-galactosidase
adenovirus as a control. The vein segmen ts were engrafted into carotid arteries and
examined 0,1 or 3 days later (4–7 animals/group). Untransduced grafts examined on
the day of surgery developed repeated CFRs at both normal and restricted flow, but
their frequency declined in grafts examined after 3 days. Adenovirus transduction
was evident as β-galactosidase or h-tPA expression 1 day after engraftment. Blood
flow was increased 1.4-fold in h-tPA transduced grafts after 1 day [control 390 (280–510),
h-tPA 550 (450–660) ml/min; p=0.02 (expressed as mean (95% confidence intervals)].
CFRs were less severe (p=0.002) in the h-tPA transduced grafts than β-galactosidase-transduced
grafts. CFRs were also less frequent in unstenosed undamaged h-tPA grafts [control
17 (6.1–29), h-tPA 7.6 (1.7–14) CFR/hr; p=0.02], but this difference was reduced after
damage or stenosis. CFRs formed faster in h-tPA than in β-galactosidase-transduced
grafts [control 14 (11–17), h-tPA 23 (19–27) ml/min2; p<0.001], and resolved twofold faster [control 25 (22–30), h-tPA 48 (39–60) ml/min2;
p<0.001]. Hence, in this model, local gene therapy with h-tPA increased graft blood
flow and decreased measures of early graft thrombosis, namely quicker CFR resolution
and decreased frequency and severity.
Keywords
Vein graft - tissue plasminogen activator - acute thrombosis - gene therapy - animal
model