© 2001 by European Society of Cardiology
Copyright © 2001, European Society of Cardiology
All-trans retinoic acid regulates proliferation, migration, differentiation, and extracellular matrix turnover of human arterial smooth muscle cells
aMedical Clinic III, Department of Cardiology, University of Tübingen, Otfried-Müller St. 10, D-72076 Tübingen, Germany
bDepartment of Surgery, University of Tübingen, Tübingen, Germany
cBristol Heart Institute, University of Bristol, Bristol, UK
* Corresponding author. Tel.: +49-7071-298-7338; fax: +49-7071-295-749 daaxel{at}med.uni-tuebingen.de
Objective: The vitamin-A derivative all-trans retinoic acid (atRA) is a potent regulator of cell growth, differentiation, and matrix formation of various cell types and plays an important role in embryogenesis. However, sparse data are available about its effects on human vessel diseases. Thus, we studied the effects of atRA on human arterial smooth muscle cell (haSMC) and endothelial cell (haEC) proliferation, migration, differentiation and extracellular matrix (ECM) turnover in mono- and transfilter cocultures. Methods: Effects of atRA on human arterial cells in monocultures were determined using cell counting assays, BrdU-ELISA and MTT-tests. In transfilter cocultures 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. Results: atRA caused a dose dependent inhibition of haSMC-growth in monocultures (IC50 at 0.022 µM) whereas haEC-growth was inhibited less potently (IC50 at 97 µM). In addition, proliferation and migration of haSMC through a porous membrane were inhibited dose dependently by micromolar atRA-doses after non-stop and single dose application of atRA on the endothelial side of the complex transfilter coculture system. Immunostainings and Northern blotting demonstrated an enhanced 
-smooth muscle actin and heavy chain myosin expression in haSMC after atRA-treatment. Whereas mRNA-expression of the glycoproteins thrombospondin-1 and fibronectin were decreased, collagen-1 mRNA expression was even slightly stimulated. Transcription of biglycan and TGF-β1 were not influenced in a specific manner. Finally, protein expression and activity of the matrix metalloproteinases MMP-2 and MMP-9 were inhibited significantly by atRA. Conclusions: atRA was found to be a potent inhibitor of both haSMC-proliferation and -migration, even in coculture with haEC releasing growth factors. In addition, redifferentiation, ECM synthesis and ECM degradation were regulated by atRA which also influence haSMC migration and intima formation. Thus, atRA-treatment seems to be a promising strategy for the inhibition of processes involved both in atherosclerosis and restenosis.
KEYWORDS Cell culture/isolation; Cell communication; Extracellular matrix; Smooth muscle; Restenosis