In CF, the overexpression of MMPs (MMP-8, MMP-9 and MMP-12) correlates with the impairment of lung function; in particular, MMP-9 expression has been shown to correlate with RBM degradation, the onset of bronchiectasis and a decline of lung function in pwCF [236,237,238,239]. Here, MMP9 is linked to bronchiectasis.