Blood Flow-Induced Remodeling of the Artery Wall

Mature vascular tissues exhibit little evidence of tissue synthesis. Thus, under normal conditions, replication rates for endothelial and smooth muscle cells are typically 0.01% to 1% per day, and synthesis rates for the major extracellular constituents, for example, elastin and collagen, are often extremely low. The half-life for collagen in human arteries is many months, and for elastin it is years to decades. These data argue that vascular structures are extremely stable. Nonetheless, vascular tissues in individual arteries undergo substantial remodeling whenever the blood flows they carry change for more than a few days. These long-term hemodynamic changes are not rare events; they accompany menstrual cycles, pregnancy, disuse, weight gain, and many disease states. How can these apparent contradictions be reconciled?