A life under pressure: circumferential stress in the microvascular wall.

Microvessels live 'a life under pressure' in several ways. In a literal sense, vessels of the microcirculation are exposed to high levels of stress caused primarily by the intravascular pressure head. In a figurative sense, the individual vessel and the microvascular network as a whole must continuously strive to meet the changing demands of the surrounding tissue. The 'principle of optimal operation' as formulated by Y. C. Fung states that living tissues adapts structurally through remodelling and growth until a level of tensile and compressive stresses is reached at which tissue performance is optimal. This behaviour is characteristic for the microvascular wall. It is highly plastic by nature and meets sustained changes by structural adaptation so as to maintain functional optimality. Owing to the orientation of the vascular smooth muscle cell in the media, in particular, the circumferential stress component has a huge impact on the state of the vascular wall. It is involved as a unifying factor on vastly different timescales in processes as diverse as acute regulation of vessel diameter, structural vessel remodelling and growth or atrophy of the vascular wall. The aim of this MiniReview was to outline in brief this integrative role of circumferential wall stress in the microcirculation.