Dynamical characteristics of microvascular networks with a myogenic response gradient

Purpose: Myogenic response is the ability of smooth muscle cells lining the vascu- lar wall to react to changing intravascular pressure: increasing pressure normally induces contraction whereas decreasing pressure leads to dilatation. Experimental studies show that the intensity of the myogenic response is dierent in arteriolar vessels of dierent radii: smaller arterioles react relatively more intensely, but over a more narrow range of pressures, than larger arterioles. In a network of vessels, this gives rise to a myogenic response gradient. The physiological significance of this gradient is, nonetheless, debated. Our purpose is to investigate the dynamical characteristics of microvascular networks with a myogenic response gradient by means of mathematical modeling. Methods: We present a mathematical vascular network model which includes a de- tailed description of vessel wall mechanics and the myogenic response gradient. We focus on the influence of this gradient on short-term network dynamics. We perform a series of numerical simulations in both symmetrical and asymmetrical vascular trees in which the individual vessel is given a realistic morphology, i.e., relative wall thickness is smaller in larger vessels. Results: Our main findings show that the presence of a myogenic response gradient: 1. adjusts flow and pressure in the capillary bed to an adequate level and dampens oscillations transmitted from upstream feeding vessels; 2. provides the network as a whole with a basal level of tone necessary for the operation of vasomotor mechanisms other than the myogenic response; and 3. provides the system with the overall ability to autoregulate network flow smoothly. Conclusion: The mathematical model shows that networks with a myogenic response gradient present advantages regarding the physiological function of regulating flow in a bifurcating network compared to networks without myogenic response and passive networks