**2. Extracellular matrices contribute to the viscoelastic properties of connective tissues including the dermis**

The viscoelastic properties of human tissues are principally governed by the nature of the extracellular matrix (ECM). The ECM comprises secreted proteins that are deposited into the extracellular space. Although cell-ECM interaction and growth factor-ECM interactions have recently been investigated, the ECM represents the fundamental architecture of tissue. Some ECM proteins supply the connective tissues with hydration and resiliency through their characteristic molecular properties and assembly. ECM proteins such as collagen, proteoglycans, and glycoproteins are classified by their biochemical properties rather than their physical properties. Numerous ECM proteins are currently known and have been well characterized biologically. However, the contribution of each ECM protein to the viscoelastic properties of tissues has not been fully investigated due to the lack of a proper experimental system. Therefore, the contribution of each ECM protein to viscoelasticity in human tissue should be determined based on biological, physical, and clinical studies.

© 2012 Nemoto et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
