The human respiratory system appears as an outgrowth from the ventral wall of the primary
foregut and its development includes a series of subsequent processes, dependent on
the interactions between endothelial cells, respiratory epithelium and extracellular matrix
(ECM). These interactions determine the acquisition of normal structural and functional
features of the newly created tissues. The essential role in the morphogenesis of the respiratory
system is performed by matrix metalloproteinases (MMPs). MMPs are endopeptidases
containing zinc ion in their active center, necessary for the processes of hydrolysis of
peptide bonds of substrates. The production of MMPs takes place in most connective tissue
cells, leukocytes, macrophages, vascular endothelial cells as well as in neurons, glial cells
and in tumor cells. Like other proteolytic enzymes, MMPs are produced and secreted in the
form of inactive pro-enzymes, and their activation occurs in the extracellular space. MMPs
perform both physiological and pathological functions during tissue modeling and their
role in embryogenesis is based on the regulation of angiogenesis processes, stroma formation
and cells migration. This article aims to characterize, discuss and demonstrate the
activity and the role of MMPs in the subsequent stages of respiratory development.