Abstract

Although matrix metalloproteinase (MMPs) and tissue inhibitor of metalloproteinase (TIMPs) play a vital role in tumour angiogenesis and TIMP-3 caused apoptosis, their role in cardiac angiogenesis is unknown. Interestingly, a disruption of co-ordinated cardiac hypertrophy and angiogenesis contributed to the transition to heart failure, however, the proteolytic and anti-angiogenic mechanisms of transition from compensatory hypertrophy to decompensatory heart failure were unclear. We hypothesized that after an aortic stenosis MMP-2 released angiogenic factors during compensatory hypertrophy and MMP-9/TIMP-3 released anti-angiogenic factors causing decompensatory heart failure. To verify this hypothesis, wild type (WT) mice were studied 3 and 8 weeks after aortic stenosis, created by banding the ascending aorta in WT and MMP-9-/- (MMP-9KO) mice. Cardiac function (echo, PV loops) was decreased at 8 weeks after stenosis. The levels of MMP-2 (western blot) increased at 3 weeks and returned to control level at 8 weeks, MMP-9 increased only at 8 weeks. TIMP-2 and -4 decreased at 3 and even more at 8 weeks. The angiogenic VEGF increased at 3 weeks and decreased at 8 weeks, the anti-angiogenic endostatin and angiostatin increased only at 8 weeks. CD-31 positive endothelial cells were more intensely labelled at 3 weeks than in sham operated or in 8 weeks banded mice. Vascularization, as estimated by x-ray angiography, was increased at 3 weeks and decreased at 8 weeks post-banding. Although the vast majority of studies were performed on control WT mice only, interestingly, MMP9-KO mice seemed to have increased vascular density 8 weeks after banding. These results suggested that there was increase in MMP-2, decrease in TIMP-2 and -4, increase in angiogenic factors and vascularization in compensatory hearts. However, in decompensatory hearts there was increase in MMP-9, TIMP-3, endostatin, angiostatin and vascular rarefaction.