TIME-COURSE OF INCREASED CELLULAR PROLIFERATION IN COLLATERAL ARTERIES AFTER ADMINISTRATION OF VASCULAR ENDOTHELIAL GROWTH-FACTOR IN A RABBIT MODEL OF LOWER-LIMB VASCULAR INSUFFICIENCY

Proliferation of vascular cells has been previously shown to contribut e to spontaneous development of coronary collaterals. Recent studies f rom several laboratories have established that collateral artery growt h in both the heart and limb can be enhanced by administration of angi ogenic growth factors, or therapeutic angiogenesis. In this study, we south (1) to define the extent and time course of endothelial cell (EC ) and smooth muscle cell (SMC) proliferation accompanying spontaneous collateral development during limb ischemia and (2) to determine the e xtent to which proliferative activity of ECs and SMCs is augmented dur ing therapeutic angiogenesis with vascular endothelial growth factor ( VEGF), a heparin-binding EC-specific mitogen. Ten days after induction of limb ischemia by surgically excising the femoral artery of rabbits , either VEGF (500 to 1000 mu g) or saline was administered as a bolus into the iliac artery of the ischemic limb. Cellular proliferation wa s evaluated by bromodeoxyuridine labeling for 24 hours at day 0 (immed iately before VEGF administration) and at days 3, 5, and 7 after VEGF. EC proliferation in the midzone collaterals of VEGF-treated animals i ncreased 2.8-fold at day 5 (p < 0.05 versus control), and returned to baseline levels by day 7. SMC proliferation in midzone collaterals als o increased 2.7-fold in response to VEGF (P < 0.05). No significant in crease in EC or SMC proliferation was observed in either the stem or r e-entry collaterals of VEGF-treated animals compared with untreated is chemic control animals. Reduction of hemodynamic deficit in the ischem ic limb measured by lower limb blood pressure was documented at day 7 after VEGF (P < 0.01 versus untreated, ischemic control). These data t hus (1) establish the contribution of cellular proliferation to collat eral vessel development in limb ischemia and (2) support the concept t hat augmented cellular proliferation concept that augmented cellular p roliferation contributes to the enhanced formation of collateral vesse ls after therapeutic angiogenesis with VEGF.