Arterial smooth muscle cells synthesize matrix macromolecules in response to mechanical stimulation. Exposure to serum lipids also stimulates connective tissue fiber accumulation. To assess the effect of serum lipids on the biosynthetic response to tensile stress, we subjected rabbit aortic smooth muscle cells that were cultured on purified elastin membranes to cyclic stretching and relaxation 50 times per minute in the presence of serum-free medium (SFM), normolipemic serum (NLS), or hyperlipemic serum (HLS). Incorporation of 14C-proline into proline and into hydroxyproline was taken as a measure of protein and collagen synthesis. When cells were grown in plastic Petri dishes, exposure to NLS or HLS increased both protein and collagen production to the same extent compared to synthesis in SFM (1.7 times for NLS and 1.6 times for HLS; p < 0.001 compared to SFM). For cells grown on stationary elastin membranes, NLS and HLS also increased protein and collagen synthesis compared to SFM. The effect of NLS was 1.35 times that of HLS for protein and 1.43 times greater for collagen (p < 0.03). Cyclic stretching in SFM doubled synthesis for both protein (p < 0.002) and collagen (p < 0.002) compared to stationary controls, but had no effect on synthesis in NLS. In HLS, however, cyclic stretching elevated synthesis to the same level as was found in NLS (p < 0.003). We conclude that the relative inhibition of synthesis on stationary membranes by HSL was not due to a toxic effect, since HLS increased synthesis both in Petri dishes and on elastin membranes, and the amplifying effect of cyclic stretching in HLS was similar to that seen in SFM. The interactive effects of mechanical stimulation and hyperlipemia may help to account for individual differences in wall and plaque composition during atherogenesis.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine