Collagen synthesis of human arterial smooth muscle cells: Effects of platelet‐derived growth factor, transforming growth factor‐β1 and interleukin‐1

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Abstract
The effects of platelet-derived growth factor (PDGF), transforming growth factor-beta 1 (TGF-beta 1) and interleukin-1 (IL-1) on collagen synthesis of cultured human arterial smooth muscle cells in a confluent state were investigated. Synthetic activity of collagenous protein was determined with [3H]-proline uptake, and subsequent analysis of collagen types by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by fluorography. Although PDGF (0.5 U/mL and 5.0 U/mL) enhanced total collagen synthesis per dish, it suppressed total collagen synthesis per DNA (DNA content in a dish). TGF-beta 1 (10 pmol/L and 100 pmol/L) enhanced total collagen synthesis both per dish and per DNA. IL-1 (0.1 U/mL and 1.0 U/mL) suppressed total collagen synthesis both per dish and per DNA. A fluorogram revealed that human arterial smooth muscle cells synthesize types I, III, IV and V collagen. Densitometric analysis showed PDGF suppressed the proportion of type IV collagen and increased that of type V collagen. TGF-beta 1 increased the proportions of types IV and V collagen. IL-1 elicited un- remarkable change in the proportion of collagen types. These results suggest that, in the event of human atherosclerosis, TGS-beta 1 is most effective in enhancing collagen synthesis, and PDGF modulates collagen metabolism by stimulating a cell division of smooth muscle cells with a resultant increase of collagenous protein, especially of type V collagen.