The expression of matrix metalloproteinase-11 protein in various types of glomerulonephritis

Background. Matrix metalloproteinases (MMPs) have been implicated to play important roles in a number of pathological processes such as inflammation. In human glomeruli, the mesangial matrix turnover is controlled by a dynamic equilibrium between synthesis and degradation to which metalloproteinases are known to contribute. Metalloproteinase-11 (MMP-11) was originally discovered as a gene whose expression was associated with tissue remodelling. The aim of this study was to investigate whether MMP-11 protein is expressed in various types of glomerulonephritis and to elucidate the role of this expression. Methods. Using standard immunohistochemistry, we analysed MMP-11 expression in renal biopsies from 95 patients with primary glomerulonephritis (n ¼ 44) and secondary, either lupus-associated glomerulonephritis (n ¼ 22) or pauci-immune, ANCA-associated glomerulonephritis due to small vessel vasculitis (n ¼ 23) or Wegener’s granulomatosis (n ¼ 6). The examined cases were divided into two groups (proliferative and nonproliferative). Anti-Ki67 and -CD68 immunostaining was also performed in order to estimate cell proliferation and number of macrophages, respectively. Results. MMP-11 immunopositivity was detected in the glomeruli of the majority of pathological samples. The highest incidence of MMP-11 immunopositivity (26.3%) was noticed in glomerulonephritides associated with microscopic polyangiitis and Wegener’s granulomatosis. Generally, MMP-11 was often expressed in segmental areas of sclerosis, microadhesions, cellular and fibrocellular crescents. Fibrotic crescents and fibrotic glomeruli were constantly MMP-11-immunonegative. In MMP-11 immunoreactive glomeruli, increased numbers of macrophages were often detected in the mesangium (P ¼ 0.001), while no such observation could be made with regard to proliferating cells (P ¼ 0.170). Conclusions. MMP-11, like an inflammatory mediator, may exert a chemotactic influence on macrophages which aggregate in the mesangium; MMP-11 is not likely to have a parallel mitogenic or antifibrotic effect in diseased glomeruli.