Collagen-elastin matrix

The ideal aortic valve bioprosthesis would consist of a collagen-elastin matrix. Lack of success in achieving such a system has been attributed to factors such as calcification and degradation. Calcification may be due to the cell membrane and / or the glutaraldehyde treatment. It is important to be able to remove cellular remnants and maintain the structural integrity of this collagen-elastin matrix. To mimic the properties of the aortic valve, an extraction process was developed [40]. The authors [40] investigated the effect of sodium dodecyl sulphate (SDS) and Triton-X 100 and cholate on the structural parameters of this extracellular matrix. 

W. Haslik, L.-P. Kamolz, G. Nathschlager, H. Andel, G. Meissl, M. Frey, First experiences with the collagen-elastin matrix Matri-derm as a dermal substitute in severe burn injuries of the hand. Bums 33 (2007) 364-368. 

M. Keck, et al.. Adipose tissue engineering three different approaches to seed preadipocytes on a collagen-elastin matrix, Ann. Plast. Surg. 67 (2011) 484-488. 

The pleural tissue is a typical connective tissue that consists mostly of matrix the fibrous proteins (collagen, elastin), and mucopolysaccharides, and a few scattered mesothelial cells, capillaries, venules, and ducts. Anatomists have defined several layers (Fig. 3.4) for each of the pleura. Layers 3 and 5 in Fig. 3.4 contain an abundance of fibrous protein, especially elastin. Both the interstitial (Layer 4) and mesothelial (1 and 2) layers contain capillaries of the vascular system and lymphatic channels. The matrix (ground substance) gives the pleura structural integrity and is responsible for its mechanical properties such as elasticity and distensibility. 

The MMPs are a family of zinc-dependent neutral endopep-tidases that share structural domains but differ in substrate specificity, cellular sources, and inductivity (Table I). All the MMPs are important for remodeling of the extra cellular matrix and share the following functional features (/) they degrade extracellular matrix components, including fibronectin, collagen, elastin, proteoglycans, and laminin, (//) they are secreted in a latent proform and require activation for proteolytic activity, (///) they contain zinc at their active site and need calcium for stability, (/V) they function at neutral pH, and (v) they are inhibited by specific tissue inhibitors of metalloproteinases (TIMPs). 

AMINO ACID COMPOSITION (EXPRESSED AS RESIDUES PER 1000 TOTAL RESIDUES) OF TYPICAL MATURE ELASTIN, MATRIX COLLAGEN AND MICROFIBRILLAR PROTEIN PREPARATIONS. 

An increase in the extracellular matrix due to collagens, elastin, proteoglycans, glycoproteins, etc. also produces various degrees of hepatomegaly. 

Proteoglycan aggregates are typically found in the extracellular matrix of connective tissue. The noncovalent attachment of each proteoglycan to hyaluronic acid via the core protein is mediated by two linker proteins (not shown). Proteoglycans interact with numerous fibrous proteins in the extracellular matrix such as collagen, elastin, and fibronectin (a glycoprotein involved in cell adhesion). 

The skin is an excellent barrier to microbial and parasitic infections. The most superficial layer of the skin is composed of flattened squamous cells, which are highly keratinized. Beneath this is the epidermal layer composed of cells tightly interconnected by desmosomes and other intercellular structures. These, in turn, are attached to the basement membrane composed of covalently bound or interwoven macromolecules. Between the basement membrane and a target blood vessel is an extracellular matrix rich in type I collagen, elastin and proteoglycan. Elastin and type I collagen are both interwoven fibrillar molecules, whereas the carbohydrate-rich proteoglycan behaves like a hydrated gel. For details of these macromolecular interactions, the reader is referred to reviews on the structure of skin. 

Inflammatory processes in the liver increase production of cytokines, chemokines, and signaling molecules, which activate the stellate cells to produce a complex extracellular glycoprotein matrix (i.e., the development of fibrosis). The matrix formed includes collagen, elastin, fibronectin, and laminin. Several noninvasive tests can be used as nonspecific indicators of fibrosis, but these have not been widely applied in laboratory animals. These tests include the collagen markers type III procollagen, YKL-40, and hyaluronic acid however, these tests have not been widely evaluated in laboratory animals (Cho and Lee 1998 Tran et al. 2000 Ding et al. 2001 Mardini and Record 2005). 

The normal artery is composed of three distinct layers (Fig. 34.21). That which is closest to the lumen of the vessel, the intima, is lined by a monolayer of endothelial cells that are bathed by the circulating blood. Just beneath these specialized cells lies the subintimal extracellular matrix, in which some vascular smooth muscle cells are embedded (the subintimal space). The middle layer, known as the tunica media, is separated from the intima by the internal elastic lamina. The tunica media contains lamellae of smooth muscle cells surrounded by an elastin- and collagen-rich matrix. The external elastic lamina forms the border between the tunica media and the outermost layer, the adventitia. This layer contains nerve fibers and mast cells. It is the origin of the vasa vasorum, which supply blood to the outer two thirds of the tunica media. 

Natural polymers such as collagen, elastin, and fibrin make up much of the body s native extracellular matrix (ECM), and they were explored as platforms for tissue engineered constructs [34,47 9]. Polysaccharides such as chitosan, starch, alginate, and dextran were also studied for these purposes. Simultaneously, silk fibroin was widely explored for vascular applications due to its higher mechanical properties in comparison to other natural polymers, such as fibrin [48]. The utilization of natural polymers to create tissue-engineered scaffolds has yielded promising results, both in vitro and in vivo, due in part to the enhanced bioactivity provided by materials normally found within the human body [50]. However, their mechanical response is usually below the required values therefore, synthetic polymers have been explored to achieve the desired properties. 

The extracellular matrix of vascular wall cells, a complex array of collagen, elastin, adhesion proteins, and proteoglycans (see Chapter 13), mediates a variety of functions with significance for the development of atherosclerosis and cardiovascular disease. These include blood cell adhesion, lipoprotein binding, vascular wall... 

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