In asthma, the remodelling process involves the deposition of collagen and elastic fibres28; MMP-9 is one of the main metalloproteases involved in this process, as it is capable of degrading many types of collagen, gelatin, elastin proteins, fibronectin and other extracellular matrix components14, and MMP-9 is directly related to the severity of asthma29. Here, MMP9 is linked to asthma.