Regional heterogeneity in the mechanical environment of the arteriolar wall due to differences in adventitial matrix

Despite the role that extracellular matrix (ECM) plays in vascular signaling, little is known of the complex structural arrangement between specific ECM proteins and vascular smooth muscle cells (VSMCs). We hypothesized that adventitial elastin fibers are important in vessels subject to longitudinal stretch. Skeletal muscle (SM) arterioles were isolated and allowed to develop spontaneous tone and compared with small cerebral arteries. 3D confocal microscopy was used to visualize ECM within the vessel wall. Pressurized arterioles were fixed and stained with: Alexa 633 Hydrazide (non‐selective ECM marker), anti‐elastin or anti‐type 1 collagen antibody and a fluorescent nuclear stain. Exposure of SM arterioles to elastase for 5 min caused an irreversible lengthening of the vessel segment not observed in cerebral arteries. Longitudinal elastin fibers were demonstrated on cremaster arterioles using 3D imaging but were confirmed to be absent in cerebral vessels. The fibers were also distinct from the type I collagen fibers and were degraded by the elastase treatment. These results indicate the importance of elastin in bearing longitudinal stress in the arteriolar wall and that these fibers constrain VSMCs. Differences between SM arterioles and cerebral small arteries may reflect differences in the local mechanical environment such as exposure to longitudinal stretch. (Supp. P01HL095486)