Page 345 - Advances in Biomechanics and Tissue Regeneration

344 17. SKIN MECHANOBIOLOGY AND BIOMECHANICS: FROM HOMEOSTASIS TO WOUND HEALING

FIG. 17.1 Overview of human skin mechanical properties and schema of external mechanical forces that are transmitted across the skin tissue.

in vivo but mainly in rodent animal models that fail to represent skin biomechanics [25–27] and in pigs [28]. Thus, a
better understanding of how healthy and wounded tissue deforms and how cells respond to this mechanical stress is
critical for the creation of new therapies for scarless wound regeneration.
This chapter aims to elucidate the reader about skin biomechanics by focusing on the overall mechanical properties
of the tissue and on its biomechanics. For this purpose, the main concepts and methodologies to measure skin mechan-
ics as well as the mechanisms underlying skin mechanobiology and biomechanics are described. An overall analysis of
this knowledge is presented, and a discussion on how it can be the basis to ameliorated wound healing approaches and
relieve scarring through new therapies is provided.

17.2 BIOMECHANICS IN THE CONTEXT OF THE SKIN

As already mentioned the skin tissue is composed of different structural components, such as the collagen fibers
(27%–39% by volume and 75%–80% of fat-free dry weight), elastin fibers (0.2%–0.6% by volume and 4% of the fat-
free dry mass), and glycosaminoglycans (0.03%–0.35% by volume), in different combinations. Hence the properties
of the skin are both dependent on the composition and their organizational direction [29]. Numerous studies were
conducted over the last 40years to characterize the mechanical behavior of the human skin. Most of them describe
skin as a nonhomogeneous and anisotropic tissue with nonlinear and time-dependent mechanical behavior that can
include viscoelastic response highly variable and sensitive to environmental conditions [4, 10, 30–32]. Accurate
acknowledge of the skin structure and its constituents are important for determining its response to the different
mechanical loads since each of these components has its own role in the mechanical properties of the skin tissue.
Collagen (types I and III as the most prominent in human skin), as the main load-bearing and stiff component of

II. MECHANOBIOLOGY AND TISSUE REGENERATION