THE MECHANICS OF ARTERIOLE-TISSUE INTERACTION

Arterioles are embedded in the extensive connective tissue matrix of t he interstitium. Mechanical interactions with the interstitium may aff ect the length-tension characteristics of arterioles, and thus affect their reactivity. However, no studies have adequately characterized th e coupling between arterioles and the interstitium or investigated how the interstitium might change the physiological expression of arterio les. Therefore, the goal of this project was to investigate the mechan ical interactions between arterioles and the interstitium and then to predict the physiological consequences of these interactions. We measu red in situ the mechanical coupling of arterioles to the interstitium, the mechanical properties of the interstitium, and the structure of t he interstitium in the hamster cheek pouch. We demonstrated that there are mechanical interactions between arterioles and the interstitium t hat are mediated both through direct connections and through the movem ent of extracellular fluid through the connective tissue network. We a lso found that the elastic modulus of the interstitium increases in th e vicinity of the arteriole. Finally, both the mechanical coupling of arterioles to the interstitium and the mechanical properties of the in terstitium are explained by the structure of the connective tissue mat rix. The arterioles appear to be connected to adjacent fibroblasts and fibrocytes by collagen fibrils. These cells are in rum connected to t he fiber matrix of the interstitium. Furthermore, the presence of thes e cells may explain the mechanical heterogeneity of the interstitium. We propose that the physiological role of the interstitium surrounding arterioles is to protect arterioles from stretching and deformation o f the tissue while allowing these vessels to constrict freely. (C) 199 5 Academic Press, Inc.