**1. Introduction**

The extracellular matrix (ECM) is present within all tissues and organs. It constitutes the noncellular microenvironment around the cells that plays an important role in modulating their behavior and functions [1]. This elaborated milieu is very dynamic and extremely adaptable [2– 4]. ECM is composed of several components that include proteoglycans, as well as collagen proteins and noncollagenous glycoproteins. Each component has several subcategories of molecules that influence the ECM physical and biochemical properties [5].

#### **1.1. ECM deposition and assembly**

The homeostasis of epithelial tissues depends on a dynamic interaction of the stroma compo‐ nents, such as fibroblasts, adipocytes, and nonactivated immune players [6]. In fact, fibroblasts were reported to secrete and organize type I and type III collagens, elastin, fibronectin, tenascin, and a repertoire of proteoglycans (hyaluronic acid (HA) and decorin), that maintains interstitial ECM integrity [7]. The ECM is constantly remodeled to allow the healthy tissue to resist to a wide range of tensile pressures [8, 9]. This remodeling occurs through the synthesis of elastin, which originates secreted tropoelastin, the precursor of elastin, that assembles into fibers and becomes cross-linked on lysine residues by members of the lysyl oxidase (LOX) enzymes and lysyl oxidase homologues (LOXL) molecules [10]. LOX and LOXL catalyze the first step in the formation of collagens and elastins, a very conserved process that plays an important role in cell growth, chemotaxis, or sprouting of new blood vessels [11, 12]. On the one hand, coordinated secretion of matrix metalloproteinases (MMPs) by fibroblasts mediates ECM remodeling [13]. On the other hand, the mesh networks are counterbalanced by tissue inhibitors of metalloproteinases (TIMPs) [14] or by other enzymes such as LOX molecules and transglutaminases that stiffen the ECM [10].
