Extracellular matrix mechanical properties

Multiple applications for resilin-like polypeptides have garnered renewed research interest since the report of the first recombinant resilin in 2005. The excellent mechanical properties of the resilin-like polypeptides has directed investigation toward their use as high-performance materials and in tissue engineering applications. It is widely acknowledged that cells interact and take cues from their microenvironment and, therefore, the development of polymeric scaffolds to mimic the extracellular matrix and drive desired cell or tissue responses has been of wide interest. To this end, our laboratories have developed a modular resilin-like polypeptide (RLP12) (see Fig. 20) that contains not only twelve repeats of the... 

The vitreous is a transparent extracellular matrix occupying the space between the posterior lens and the retina and, in the majority of vertebrate species, constitutes the major f)art of the volume of the eye. Embryo-logically it can be considered as the basement membrane of the retina. It provides a mechanical support for surrounding tissues and acts as a shock absorber by virtue of its viscoelastic properties (Balzas and Delinger, 1984). Vitreous consists mainly of water (98%) and colloids (0.1%) with ions and low molecular weight solutes making up the remainder. It is not fully developed at birth, and changes in both volume and chemical composition occur postnatally. 

The sole purpose of the filter support and any applied extracellular matrix is simply to provide a surface for cell attachment and thus to provide mechanical support to the monolayer. However, the filter and matrix also can act as serial barriers to solute movement after diffusion through the cell monolayer. The important variables are the chemical composition of the filter, porosity, pore size, and overall thickness. In some cases, pore tortuosity also can be important. It is desired that the filter, with or without an added matrix, provide a favorable surface to which the cells can attach. However, in some cases these properties can also result in an attractive surface for nonspecific adsorption of the transported solute. In these instances, the appearance of the solute in the receiver compartment of the diffusion cell will not be a true reflection of its movement across the mono-layer. Such problems must be examined on a case-by-case basis. 

Khatiwala, C.B., Peyton, S.R., and Putnam, A.J. (2006) Intrinsic mechanical properties of the extracellular matrix affect the behavior of pre-osteoblastic MC3T3-E1 cells. Am. J. Physiol. Cell Physiol. 290, C1640-C1650. 

The surface of the fibril provides the interface between the internal structural and mechanical properties of a fibril, and the rest of the extracellular matrix. The surface, therefore, is the most complex area of the fibril in terms of molecular heterogeneity and structure. Caution has to be taken in the comparison of structural and biochemical evidence from complementary techniques since the extraction, dehydration, and sample preparation can cause variation in observations of fibril surface properties (Raspanti et at, 1996). 

There are several important technical questions to be addressed. Very useful would be a deterministic study to examine the effect of collagenase treatment on channel properties and calcium regulation in isolated adult fibers. In particular, dystrophin links the intracellular cytoskeleton to the extracellular matrix through the DAG, and provides mechanical support for the sarcolemma through this linkage. Thus, removal of the extracellular matrix with enzymes might be predicted to alter the consequence of loss of dystrophin. To address this, fibers could be mechanically isolated and pinned out, then treated with collagenase. 

The development of parallel-plate perfusion chambers [67,68] made possible the study of platelet interaction with the extracellular matrix (ECM) generated by cells in culture or with isolated subendothelial components under defined experimental conditions. The use of the ECM produced by human umbilical vein endothelial cells (HUVEC) in culture as adhesive substrate has Su tated the understanding of the mechanisms involved in primary hemostasis [68]. HUVECs are immature and not subjected to flow conditions during their culture, two Ikctors which may influence the reactivity of their ECM towards platelets [69]. Interestingly, the properties and reactivity of the underlying ECM can be modified by exposure of HUVECs to different stimuli, an experimental approach which has fevored the investigation of basic mechanisms of thrombosis [33]. 

Owing to their stmctural similarity to the macromolecular-based components in the body (and their biocompatibility, permeability, and physical characteristics), hydrogels can also serve as a synthetic extracellular matrix (ECM) to organize cultured cells into a three-dimensional architecture and to present stimuli that direct the growth and formation of a desired tissue [33]. The balance between mechanical properties and controlled degradation of hydrogels mainly depends on the original... 

Hyaluronan is continuously synthesized and secreted by fibroblasts, keratino-cytes, chondrocytes and other specialized cells in the extracellular matrix (ECMs) throughout the body. It is synthesized by HA synthase (see also Chapter 9) at the inner face of the plasma membrane [98]. The level of HA synthesis is very high in skin and cartilage [99]. Hyaluronic acid is not one of the major components of the ECMs of the connective tissues, but it is found in various locations such as synovial fluid, vitreous humor, and umbilical cords [100]. Its biological functions include the maintenance of mechanical properties such as swelling in connective tissues and control of tissue hydration, providing lubricating properties in synovial fluid and heart valves. 

---