| Popis: |
Arterioles are embedded in the extensive connective tissue matrix of the interstitium. Mechanical interactions with the interstitium may affect the length-tension characteristics of arterioles, and thus affect their reactivity. However, no studies have adequately characterized the coupling between arterioles and the interstitium or investigated how the interstitium might change the physiological expression of arterioles. Therefore, the goal of this project was to directly characterize the physical connections between arterioles and the interstitium, both mechanically and morphologically, and then to predict the physiological consequences of these interactions for the arteriole. We measured in situ the mechanical coupling of arterioles to the interstitium, the mechanical properties of the interstitium, and the structure of the interstitium in the hamster cheek pouch. This allowed us to develop a comprehensive model of the mechanical interactions between arterioles and the surrounding connective tissue based on measurements made at the scale of a single arteriole. We demonstrated that there is mechanical coupling between arterioles and the interstitium that is mediated both through direct connections and through the movement of extracellular fluid through the connective tissue network. We also found that the stiffness of the interstitium increases near the arteriole, but does not depend on the direction of measurement. Finally, both the mechanical coupling of arterioles to the interstitium, and the mechanical properties of the interstitium, are explained by the structure of the connective tissue matrix. The arteriole is connected to adjacent fibroblasts and fibrocytes by collagen fibrils. These cells are in turn connected to the fiber matrix of the interstitium. Furthermore, the presence of these cells may explain the heterogeneity in stiffness of the interstitium. We propose a model of interactions between arterioles and the interstitium in which the physiological role of the interstitium is to protect arterioles from stretching and deformation of the tissue while allowing arterioles to freely constrict. The interstitium may also decrease the apparent compliance of the arteriolar wall and limit slightly the constriction of the arteriole. Thus, the in vivo connective tissue environment of arterioles both alters and protects the ability of arterioles to respond to physiological stimuli. |
