Arteriogenesis in hypoperfused rat brain.

Experimental and clinical studies have provided evidence for spontaneous and therapeutically induced arteriogenesis after occlusion of major peripheral or cardiac vessels. Such evidence is lacking for the cerebrovascular system. In halothane-anesthetized rats, different degrees of brain hypoperfusion were induced by one- to four-vessel occlusion, that is, one or both common carotid arteries in combination with or without bilateral vertebral artery occlusion. The flow decline was monitored by laser Doppler flowmetry, the residual hemodynamic reserve by testing flow reactivity to ventilation with 6% CO(2) and arteriogenesis by intravascular latex infusion and immunohistochemistry of vascular proliferation and monocyte adhesion. The optimum condition for induction of arteriogenesis was three-vessel (one carotid plus both vertebral arteries) occlusion, which led to reduction of blood flow to about 50% and complete suppression of CO(2) reactivity, but no histologic injury. One week after three-vessel occlusion, the ipsilateral posterior cerebral artery significantly enlarged by 39%, and after 3 weeks by 72%, paralleled by the partial return of CO(2) reactivity and the appearance of immunohistochemical markers of arteriogenesis. Three-vessel occlusion is a reliable model for the induction of arteriogenesis in the adult brain and is a new approach for exploring the potentials of arteriogenesis for the prevention of progressing brain ischemia.