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. Author manuscript; available in PMC: 2009 Mar 16.
Published in final edited form as: Physiol Rev. 2007 Jan;87(1):69–98. doi: 10.1152/physrev.00022.2006

FIG. 2.

FIG. 2

MMP expression in mouse lung development. MMP2, MMP14, and an MMP inducer, CD147, are constitutively expressed in all five distinct stages of lung development: primary budding (E9.5−11.5), pseudoglandular (E12−16.5), canalicular (E17−18), saccular (E19-P5), and alveolar (P5-P21). Expression of these MMPs and their inducer tapers off with the completion of lung development. Expression of most other MMPs occurs following the postnatal period and in adult lungs. In inflammatory lung diseases, cells of the hematopoetic origin (e.g., macrophages, neutrophils, eosinophils, lymphocytes) home to the lung and express MMP8, MMP9, and MMP12. Alternatively, many MMPs are induced in the alveolar epithelial cells in response to exposure to environmental agents. For example, alveolar and bronchial epithelial cells express MMP7 and MMP9 induced by exposure to pathogens or toxins, respectively (see Refs. 3, 33, 34, 66, 122, 160, 165, 229).