Increased gracilis artery medial volume and inner diameter following chronic reduction of blood flow

Abstract

Vascular networks respond to chronic alterations in blood supply by structural remodeling. A previous study showed that the inner diameter of the mouse gracilis artery increased transiently with a peak at 14 days following a permanent reduction in blood flow. Here, the objective was to investigate whether the diameter increase is accompanied by growth of medial tissue. Blood flow was reduced by removing a portion of the saphenous artery, one of the two blood supplies of the gracilis artery. After 7, 14, 21, 28 and 56 days, the vasculature was perfused with India ink for diameter measurements, and processed for immune cytochemistry to mark smooth muscle cells (SMC) and nuclei of SMC and endothelial cells (EC). In the two thirds of the vessel length closest to the injury, the inner diameter was significantly larger at days 7–28. The cross‐sectional medial area was significantly larger at days 21 and 28. The ratio of internal diameter to medial thickness (an index of circumferential wall stress) and the ratio of medial area to number of SMC nuclei were significantly higher only at day 14. The results are consistent with the concept that outward remodeling causes increased circumferential wall stress, which stimulates vessel wall adaptation by a combination of SMC hypertrophy and proliferation to restore circumferential stress to near its initial level. Supported by HL34555 and HL63732.