Angiogenesis, Arteriogenesis, and Physiological Perfusion: Review of Natural History and Concepts

Granulocyte-macrophage colony-stimulating factor as an arteriogenic factor in the treatment of ischaemic stroke

Granulocyte-macrophage colony-stimulating factor (GM-CSF) induces arteriogenic growth of collateral vessels after occlusion of cardiac or peripheral arteries. Recently, evidence has been provided that arteriogenesis also occurs in the brain under conditions of reduced arterial blood supply. Hemispheric hypoperfusion induced by unilateral carotid and bilateral vertebral artery occlusion (three-vessel occlusion, [3-VO]) led to the growth of the anterior and posterior segments of the circle of Willis, which is the main collateral pathway between the origins of the anterior, middle and posterior cerebral arteries. GM-CSF applied subcutaneously at daily doses of 40 microg.kg(-1) resulted in the marked acceleration of this process. Within one week after the onset of treatment, the diameter of the posterior segment of the circle of Willis enlarged to 170% of control, blood flow and the haemodynamic reserve capacity of the brain returned to normal, and haemodynamic stroke, induced after 3-VO by systemic hypotension, was greatly alleviated. GM-CSF-induced stimulation of arteriogenesis in the hypoperfused brain thus provides powerful protection against ischaemic stroke.

Modulation of collateral artery growth in a porcine hindlimb ligation model using MCP-1

For an appropriate extrapolation to patients with peripheral arterial obstructive disease, we tested the efficacy of monocyte chemoattractant protein 1 (MCP-1) treatment in a porcine hindlimb ligation model. In 40 minipigs, a femoral artery ligation was performed. Control animals were examined immediately after ligation (n = 4) or after 2 wk of intra-arterial infusion of PBS (n = 11). A second group of animals was evaluated after intra-arterial infusion of 2.0 microg/h of MCP-1 for 48 h (followed by 12 days of PBS; n = 13) or 2 wk continuously (n = 12). In the terminal experiment after 2 wk, resting flow to the leg and peripheral arterial pressures were assessed without vasodilatation. Subsequently, vascular conductance was determined by using a pump-driven extracorporal circulation during maximal vasodilatation. The results showed that resting blood flow to the hindlimb was 53% of the normal after 2 wk of infusion of PBS, compared with 81% in both MCP-1 treatment groups (P < 0.05). Collateral conductance was 645 +/- 346 ml x min(-1) x mmHg(-1) after 2 wk of infusion with PBS, compared with 1,070 +/- 530 and 1,158 +/- 535 ml x min(-1) x mmHg(-1) after 48 h and 2 wk treatment with MCP-1, respectively (P < 0.05). Modulation of the process of arteriogenesis is feasible in this large animal model via intra-arterial infusion of the Cys-Cys-chemokine MCP-1.

Exogenous application of transforming growth factor beta 1 stimulates arteriogenesis in the peripheral circulation

Increased expression of transforming growth factor beta1 (TGF-beta1) during collateral artery growth, as well as its numerous effects on monocytes/macrophages and the smooth muscle cell cycle and differentiation, suggest a modulating role for this growth factor during arteriogenesis. We studied the effects of exogenously applied TGF-beta1 on arteriogenesis as well as its interactions with monocytes, endothelial cells, and smooth muscle cells. In a New Zealand White (NZW) rabbit model of femoral artery ligation, increased expression of active TGF-beta1 was found around proliferating arteries in NZW rabbits. The exogenous application of TGF-beta1 led to an increase in both the number of visible collateral arteries as well as the conductance of the collateral circulation (4.0 +/- 0.5 ml/min/100 mmHg vs. 28.9 +/- 3.7 ml/min/100 mmHg, P<0.05). Fluorescence activated cell sorting analysis showed an increase in the expression of the MAC-1 receptor in both rabbit and human monocytes after treatment with TGF-beta1 (control: 91.2 +/- 4.2/482 +/- 21.7; TGF-beta1 200 ng/ml 193.9 +/- 6.7/ 675.5 +/- 25.7, P<0.05 for all differences). TGF-beta1 treated monocytes showed an increased endothelial adhesion and transmigration in transendothelial migration assays (5.75 +/- 0.63 x 10(5) vs. 10.11 +/- 0.04 x 10(5), P<0.05). TGF-beta1 had no direct pro-angiogenic effect on human umbilical vein endothelial cells in a spheroid model of angiogenesis and inhibited the angiogenic effects of vascular endothelial growth factor.

Time course of arteriogenesis following femoral artery occlusion in the rabbit

OBJECTIVE

We examined the time course of arteriogenesis (collateral artery growth) after femoral artery ligation and the effect of monocyte chemoattractant protein-1 (MCP-1).

METHODS

New Zealand White rabbits received MCP-1 or phosphate buffered saline (PBS) for a 1-week period, either directly or 3 weeks after femoral artery ligation (non-ischemic model). A control group was studied with intact femoral arteries and another 1 min after acute femoral artery ligation.

RESULTS

Collateral conductance index significantly increased when MCP-1 treatment started directly after femoral artery ligation (acute occlusion: 0.94+/-0.19; without occlusion: 168.56+/-15.99; PBS: 4.10+/-0.48; MCP-1: 33.96+/-1.76 ml/min/100 mmHg). However, delayed onset of treatment 3 weeks after ligation and final study of conductance at 4 weeks showed no significant difference against a 4-week control (PBS: 79.08+/-7.24; MCP-1: 90.03+/-8.73 ml/min/100 mmHg). In these groups increased conductance indices were accompanied by a decrease in the number of visible collateral vessels (from 18 to 36 identifiable vessels at day 7 to about four at 21 days).

CONCLUSION

We conclude that the chemokine MCP-1 markedly accelerated collateral artery growth but did not alter its final extent above that reached spontaneously as a function of time. We show thus for the first time that a narrow time window exists for the responsiveness to the arteriogenic actions of MCP-1, a feature that MCP-1 may share with other growth factors. We show furthermore that the spontaneous adaptation by arteriogenesis stops when only about 50% of the vasodilatory reserve of the arterial bed before occlusion are reached. The superiority of few large arterial collaterals in their ability to conduct large amounts of blood flow per unit of pressure as compared to the angiogenic response where large numbers of small vessels are produced with minimal ability to allow mass transport of bulk flow is stressed.