RESUMEN

Plasminogen activator inhibitor 1 (PAI-1) is believed to control proteolytic activity and cell migration during angiogenesis. We previously demonstrated in vivo that this inhibitor is necessary for optimal tumor invasion and vascularization. We also showed that PAI-1 angiogenic activity is associated with its control of plasminogen activation but not with the regulation of cell-matrix interaction. To dissect the role of the various components of the plasminogen activation system during angiogenesis, we have adapted the aortic ring assay to use vessels from gene-inactivated mice. The single deficiency of tPA, uPA, or uPAR, as well as combined deficiencies of uPA and tPA, did not dramatically affect microvessel formation. Deficiency of plasminogen delayed microvessel outgrowth. Lack of PAI-1 completely abolished angiogenesis, demonstrating its importance in the control of plasmin-mediated proteolysis. Microvessel outgrowth from PAI-1-/- aortic rings could be restored by adding exogenous PAI-1 (wild-type serum or purified recombinant PAI-1). Addition of recombinant PAI-1 led to a bell-shaped angiogenic response clearly showing that PAI-1 is proangiogenic at physiological concentrations and antiangiogenic at higher levels. Using specific PAI-1 mutants, we could demonstrate that PAI-1 promotes angiogenesis at physiological (nanomolar) concentrations through its antiproteolytic activity rather than by interacting with vitronectin.

Asunto(s)

Neovascularización Fisiológica/efectos de los fármacos , Inhibidor 1 de Activador Plasminogénico/farmacología , Animales , Aorta/efectos de los fármacos , Aorta/crecimiento & desarrollo , Vasos Sanguíneos/efectos de los fármacos , Vasos Sanguíneos/crecimiento & desarrollo , Técnicas de Cultivo , Relación Dosis-Respuesta a Droga , Femenino , Genotipo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos , Ratones Noqueados , Plasminógeno/genética , Inhibidor 1 de Activador Plasminogénico/genética , Inhibidor 1 de Activador Plasminogénico/fisiología , Receptores de Superficie Celular/genética , Receptores del Activador de Plasminógeno Tipo Uroquinasa , Activador de Tejido Plasminógeno/genética , Activador de Plasminógeno de Tipo Uroquinasa/genética

RESUMEN

Angiogenesis, a key step in many physiological and pathological processes, involves proteolysis of the extracellular matrix. To study the role of two enzymatic families, serine-proteases and matrix metalloproteases in angiogenesis, we have adapted to the mouse, the aortic ring assay initially developed in the rat. The use of deficient mice allowed us to demonstrate that PAI-1 is essential for angiogenesis while the absence of an MMP, MMP-11, did not affect vessel sprouting. We report here that this model is attractive to elucidate the cellular and molecular mechanisms of angiogenesis, to identify, characterise or screen "pro- or anti-angiogenic agents that could be used for the treatment of angiogenesis-dependent diseases. Approaches include using recombinant proteins, synthetic molecules and adenovirus-mediated gene transfer.