All-trans retinoic acid regulates proliferation, migration, differentiation, and extracellular matrix turnover of human arterial smooth muscle cells

Objective: The vitamin-A derivative all-trans retinoic acid (atRA) is a pot ent regulator of cell growth, differentiation, and matrix formation of vari ous cell types and plays an important role in embryogenesis. However, spars e data are available about its effects on human vessel diseases. Thus, we s tudied the effects of atRA on human arterial smooth muscle cell (haSMC) and endothelial cell (haEC) proliferation, migration, differentiation and extr acellular matrix (ECM) turnover in mono- and transfilter cocultures. Method s: Effects of atRA on human arterial cells in monocultures were determined using cell counting assays, BrdU-ELISA and MTT-tests. In transfilter cocult ures haSMC-growth was studied under the stimulatory effect of proliferating haEC. Using Northern blot analysis, effects of atRA on mRNA expression of ECM-proteins were examined while protein expression and activity of matrix metalloproteinases were determined by Western blotting and zymography. Resu lts: atRA caused a dose dependent inhibition of haSMC-growth in monoculture s (IC50 at 0.022 muM) whereas haEC-growth was inhibited less potently (IC50 at 97 muM). In addition, proliferation and migration of haSMC through a po rous membrane were inhibited dose dependently by micromolar atRA-doses afte r non-stop and single dose application of atRA on the endothelial side of t he complex transfilter coculture system. Immunostainings and Northern blott ing demonstrated an enhanced a-smooth muscle actin and heavy chain myosin e xpression in haSMC after atRA-treatment. Whereas mRNA-expression of the gly coproteins thrombospondin-1 and fibronectin were decreased, collagen-1 mRNA expression was even slightly stimulated. Transcription of biglycan and TGF -beta1 were not influenced in a specific manner. Finally, protein expressio n and activity of the matrix metalloproteinases MMP-2 and MMP-9 were inhibi ted significantly by atRA. Conclusions: atRA was found to be a potent inhib itor of both haSMC-proliferation and migration, even in coculture with haEC releasing growth factors. In addition, redifferentiation, ECM synthesis an d ECM degradation were regulated by atRA which also influence haSMC migrati on and intima formation. Thus, atRA-treatment seems to be a promising strat egy for the inhibition of processes involved both in atherosclerosis and re stenosis. (C) 2001 Elsevier Science B.V. All rights reserved.