Dynamics of extracellular matrix production and turnover in tissue engineered cardiovascular structures

Appropriate matrix formation, turnover and remodeling in tissue-engineered small diameter vascular conduits are crucial requirements for their long-te rm patency and function. This complex process requires the deposition and a ccumulation of extracellular matrix molecules as well as the remodeling of this extracellular matrix (ECM) by matrix metalloproteinases (MMPs) and the ir endogenous inhibitors (TIMPs). In this study, we have investigated the d ynamics of ECM production and the activity of MMPs and TIMPs in long-term t issue-engineered vascular conduits using quantitative ECM analysis, substra te gel electrophoresis, radiometric enzyme assays and Western blot analyses . Over a time period of 169 days in vivo, levels of elastin and proteoglyca ns/glycosaminoglycans in tissue-engineered constructs came to approximate t hose of their native tissue counter parts. The kinetics of collagen deposit ion and remodeling, however, apparently require a much longer time period. Through the use of substrate gel electrophoresis, proteolytic bands whose m olecular weight was consistent with their identification as the active form of MMP-2 (approximate to 64-66 kDa) were detected in ail native and tissue -engineered samples. Additional proteolytic bands migrating at approximate to 72 kDa representing the latent form of MMP-2 were detected in tissue-eng ineered samples at time points from 5 throughout 55 days. Radiometric assay s of MMP-1 activity demonstrated no significant differences between the nat ive and tissue-engineered samples. This study determines the dynamics of EC M production and turnover in a long-term tissue-engineered vascular tissue and highlights the importance of ECM remodeling in the development of succe ssful tissue-engineered vascular structures. (C) 2001 Wiley-Liss, Inc.