<P> Collagens are the most abundant protein in the ECM . In fact, collagen is the most abundant protein in the human body and accounts for 90% of bone matrix protein content . Collagens are present in the ECM as fibrillar proteins and give structural support to resident cells . Collagen is exocytosed in precursor form (procollagen), which is then cleaved by procollagen proteases to allow extracellular assembly . Disorders such as Ehlers Danlos Syndrome, osteogenesis imperfecta, and epidermolysis bullosa are linked with genetic defects in collagen - encoding genes . The collagen can be divided into several families according to the types of structure they form: </P> <Ol> <Li> Fibrillar (Type I, II, III, V, XI) </Li> <Li> Facit (Type IX, XII, XIV) </Li> <Li> Short chain (Type VIII, X) </Li> <Li> Basement membrane (Type IV) </Li> <Li> Other (Type VI, VII, XIII) </Li> </Ol> <Li> Fibrillar (Type I, II, III, V, XI) </Li> <Li> Facit (Type IX, XII, XIV) </Li>

Factors that are necessary for extracellular matrix formation