Role of alpha5beta1 and alphavbeta3 integrins on smooth muscle cell spreading and migration in fibrin gels.

Fibrin is found at sites of vascular injury and is one of the major matrix ligands for beta3 integrins. Blocking the beta3 integrin on smooth muscle cell is hypothesized as a potential target to prevent restenosis because it could inhibit cell attachment and migration into fibrin provisional matrix. Human aortic smooth muscle cells (HNB18E6E7) spread stably in plasma gels within 24 h. Cell spreading was dramatically blocked by simultaneous use of alpha5beta1 and alphavbeta3 integrin antibodies (P <0.0001), however, blocking of either integrin alone failed to inhibit spreading. GPenGRGDSPCA, which has been considered a specific alphavbeta3 antagonist, inhibited spreading at 500 microM, suggesting that the peptide blocked both alpha5beta1 and alphavbeta3. Similarly, invasive migration into fibrin gels was blocked by simultaneous use of both alpha5beta1 and alphavbeta3 antibodies, however, blocking of either integrin alone failed to effect cell migration. Another migration assay using transwell indicated similar results. In conclusion, both alpha5beta1 and alphavbeta3 integrins are responsible for smooth muscle cell spreading and migration into fibrin gels. These data suggest that blocking beta3 integrin alone would not affect smooth muscle cell interaction with fibrin.