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Where Do New Arterioles Come From? Mechanical Forces and Microvessel Adaptation

Although the origin of new capillaries and the remodeling of existing large blood vessels have been investigated extensively, the events that lead to the formation of new arterioles are only just beginning to be understood (13). Recent work provides evidence that mesenchymal fibroblasts are recruited to existing capillaries and that important controls on cell recruitment and differentiation are exerted by intravascular stresses. Why is this important? The formation of new arterioles is critical in a variety of normal physiological adaptations, such as wound healing in many tissues, exercise hypertrophy of skeletal muscle, and collateralization of infarcted myocardium. In such adaptations, the formation of capillaries alone is unlikely to provide the reduction in local flow resistance needed to perfuse the tissue adequately. New arteriolar channels are essential to reduce the flow resistance and deliver adequate overall flow.