GROWTH-FACTOR EXPRESSION OF HUMAN ARTERIAL SMOOTH-MUSCLE CELLS AND ENDOTHELIAL-CELLS IN A TRANSFILTER COCULTURE SYSTEM

By releasing growth factors, vascular cells can modulate proliferation and migration of neighboring cells in the arterial wall. Previous his tological studies in transfilter cocultures, a culture model aimed to simulate vessel wall architecture, indicated that human arterial endot helial cells (haEC) can influence human arterial smooth muscle cell (h aSMC) growth significantly. The aim of this study was to investigate t he expression and secretion of various growth factors in order to bett er define the functional interactions between haEC and haSMC. Protein levels of platelet-derived-growth factor-AB (PDGF-AB), transforming-gr owth factor-beta 1 (TGF-beta 1), and tumor-necrosis factor-alpha (TNF- alpha) in mono- and cocultures were determined by ELISA 6, 12, 24, 48, 72 h after serum reduction, Highest PDGF-AB levels were found in mono cultures with proliferative haEC, showing a peak after 24 h. In cocult ures of haEC and haSMC, PDGF-AB levels were significantly lower. In co ntrast, neither proliferative, nor confluent haSMC released PDGF-AB si gnificantly, Highest TGF-beta 1 concentrations were detected in cocult ures, followed by monocultures of haSMC and monocultures of haEC, In a ll cultures, TGF-beta 1 levels increased in parallel with cultivation time and cell numbers, showing a maximum after 72 h. TNF-alpha could n ot be detected in any culture. Northern blots demonstrated a strong ex pression of PDGF-B chain-mRNA in haEC, but not in haSMC. PDGF-A chain and TGF-beta 1-mRNA were expressed by haSMC and haEC. Addition of PDGF -AB to haSMC resulted in a potent growth stimulation, whereas TGF-beta 1 and TNF-alpha exerted only moderate, divergent effects on haSMC. Hi stological observations in transfilter cocultures demonstrated that pr oliferative haEC induce the formation of fibromuscular plaques, These results suggest that proliferative haEC act as potent growth stimulato rs for haSMC, predominantly by PDGF-AB or -BB release. (C) 1997 Academ ic Press Limited.