Table 1.

Factors influencing ECM stiffness and their regulating processes.

Factor	Regulation Process
Kind of ECM protein	Different types of proteins have different basic stiffnesses. Different composition and mixing ratios of different types affect the stiffness. ECM proteins elicit specific signaling events.
Concentration/density/elasticity (local)	Concentration rise increases stiffness and mechanical barrier. Local changes lead to stiffness gradient.
Crosslinking	Increased crosslinking increases stiffness.
Intrinsic tension	A tensioned network has an increased fiber stiffness.
Degradability	Increased degradability provides reduced resistance to proteolysis resulting in faster reduction of stiffness.
Synthesis	Incorporation of additional ECM proteins increases stiffness.
Remodeling	Change of architecture increases tension and stiffness of the ECM network.