Interstitial matrix

One intensively investigated feature of the inflammatory process in COPD is the release of proteases from neutrophils and monocytic cells that destroy elastin and other components of the interstitial matrix (Table 1). The best studied protease is neutrophil elastase. Independent of its elastolytic activity, neutrophil elastase is a potent secretagogue. More recently matrix metalloproteases (MMP) have received increasing attention, in particular MMP 12 (macrophages elastase). To which extent and how exactly these proteases become activated is not clear at present. 

In biology, extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. ECM is the defining feature of connective tissue in animals. ECM includes the interstitial matrix and the basement membrane. 

Although the precise role of MMPs in inducing VSMC migration is not fully understood, there are multiple proposed mechanisms of action, which include the removal of physical restraints by the severing of cell-matrix contacts via integrins or cell-cell contacts via adherins, Additionally, contact with interstitial matrix components may be facilitated and migration may be stimulated through exposure of cryptic extracellular... 

Table 6 Composition of interstitial matrix and matrix rims on chondrules in the CO3.0 chondrite, ALHA77307, and...

The proteoglycans in this family, which includes decorin, biglycan, lumican, and fibromodulin, are major components of the interstitial matrix produced by fibroblasts and other cells. The core proteins are small (37-45 kDa) and have several leucine-rich motifs [112] with similarity to the LH-CG receptor, thyrotropin receptor, and Drosophila proteins chaoptin and toll. Core proteins of this family characteristically undergo proteolytic processing following synthesis, with removal of an additional small peptide from the N-terminus. 

In addition to its role in surfactant production, the type II cell also has a progenitor function, acting as the stem cell of the alveolar epithelium. The alveolar type I cells are highly susceptible to injury by oxygen and a variety of noxious substances. In such situations, type II cells can differentiate into type I cells and thus regenerate the gas-exchanging alveolar surface. Other functions of the type II cell are also believed to be the metabolism of foreign compounds (xenobiotic metabolism) and fluid and electrolyte absorption from the alveolar sacs into the interstitial matrix that surrounds the alveoli. 

This fluid accumulation is called edema. This circumstance is important clinically since solute exchange (e.g., O2) decreases due to the increased diffusion distances produced when the accumulated fluid pushes the capillaries, tethered to the interstitial matrix, away from each other. 

As already outhned in Chap. 4, the interstitial compartment of tumors is significantly different from that of normal tissues. As a result of (a) vessel leakiness, (b) lack of functional lymphatics, (c) interstitial fibrosis and (d) contraction of the interstitial matrix mediated by stromal fibroblasts, most solid tumors have an... 

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