Altered balance between extracellular proteolysis and antiproteolysis is associated with adaptive coronary arteriogenesis

To study the role of extracellular proteolysis and antiproteolysis during a daptive arteriogenesis (collateral vessel growth) we took 58 collaterals at various developmental stages from 14 dogs with chronic occlusion of the le ft circumflex coronary artery (LCx) by ameroid constrictor. Immunofluoresce nce and quantitative immunofluorescence with antibodies against alpha-smoot h muscle actin, desmin, matrix metalloproteinases 2 (MMP-2), MMP-9, tissue inhibitor of metalloproteinases 1 (TIMP-1) and 2 (TIMP-2), urokinase-type p lasminogen activator (u-PA) and its inhibitor-1 (PAI-1) were studied with c onfocal microscopy. Additionally, SDS-PAGE zymography was employed. We foun d that in normal coronary arteries, MMP-2, MMP-9 and PAI-1 were present in all layers of the wall in small amounts. TIMP-1 was found only in smooth mu scle cells. In contrast, in growing collaterals, MMP-2 and MMP-9 were 3.4-f old and 4.1-fold higher in the neointima than in the media respectively. TI MP-1 was 4.4-fold higher in the media over the growing neointima. Zymograph y showed MMP-2 and MMP-9 activated. PAI-1 was increased. especially in the growing neointima where it was 1.4-fold higher. In mature collaterals, MMr- 2 and MMP-9 were downregulated in the neointima, 1.4-fold and 1.3-fold high er over the media. TIMP-1 was 1.4-fold increased in the neointima but PAI-1 was downregulated. Desmin and alpha-smooth muscle actin were significantly increased in the neointima compared to growing vessels. U-PA was moderatel y increased in growing vessels, TIMP-2 was not detectable in collaterals. W e conclude that expression of MMP-2 and 9, TIMP-1 and PAI-1 showed a spatia l and temporal pattern which is closely associated with the development of collateral vessels. The shift of the balance between proteolysis and antipr oteolysis is regulated not only by MMPs and TIMP-1, but also by the PA-PAI system. (C) 2000 Academic Press.