Matrix metalloprotease-2 and -9 concentration and activity in serum and culture medium samples: a methodological reappraisal

Background: Matrix metalloproteases (MMPs) play an important role in cardiovascular remodeling by degrading the extracellular matrix. The aim of this study was to compare two different methods for MMP-2 and MMP-9 concentration and activity determination. Methods: MMP-2 and -9 levels were measured by immunometric and enzymatic assays to determine total and active levels. The two procedures differ in assay principle and in the extent of cross-reactions with interfering substances present in biological samples. Both human serum and culture medium from an ex vivo human model of intimal hyperplasia were checked. Results: All methods were able to detect MMP-2 and -9 with similar levels of sensitivity, reproducibility and accuracy, and furnished positively related results, although significantly different, in both types of sample. Both systems were able to detect changes in MMP production such as the time-course of MMP-2 and -9 release by cultured saphenous vein associated with intima hyperplasia progression. Conclusions: Our data indicate that different values for MMP concentrations can be obtained using different analytical methods, even if they are intrinsically reliable. This suggests that methodological differences should be taken into account when comparing MMP results from different studies.