MMP12 and pulmonary emphysema: MMPs have also been implicated in tissue remodeling in asthmatic patients by human genetic studies,32, 33 murine emphysema models,34, 35, 36 and the findings of increased bronchoalveolar lavage MMP3 and MMP9 levels in patients with status asthmaticus37 and increased sputum MMP12 levels in asthmatic smokers.38