Fig. 1. Elastin inhibits proliferation of vascular smooth muscle cells. (A) RT-PCR experiments confirm that murine vascular smooth muscle cells lines express cell specific markers. The elastin gene product is detected in Eln^+/+ and not Eln^-/- cells. Immunofluorescence analysis with elastin antibodies and accompanying phase photomicrographs demonstrate that Eln^+/+ vascular smooth muscle cells (B) synthesize and secrete elastin matrix, whereas Eln^-/- vascular smooth muscle cells (C) do not produce elastin. (D) Assay measuring cell numbers demonstrates that Eln^-/- vascular smooth muscle cells proliferate at a much higher rate than do Eln^+/+ vascular smooth muscle cells (P<0.0001, ANOVA). This difference is eliminated by the addition of recombinant elastin gene product or tropoelastin (tEln). (E) Assay measuring [³H]thymidine incorporation assay demonstrates that Eln^-/- vascular smooth muscle cells proliferate at a rate over twofold greater than that for Eln^+/+ cells. This difference is eliminated by the inhibition of Eln^-/- cells proliferation by tropoelastin (P<0.0001, ANOVA).