Enzymes that remodel the structural scaffolding of tissue — essential for wound healing and follicle cycling, but potentially harmful if overactivated.A family of zinc-dependent endoproteases that degrade ECM components: collagen, gelatin, fibronectin, laminin. MMPs are required for tissue remodeling in wound healing (clearing damaged matrix) and in hair follicle cycling (enabling stem cell migration from the bulge). GHK-Cu upregulates MMP-2, facilitating ECM remodeling in wound contexts. Excessive MMP activity contributes to cartilage destruction in arthritis and tissue invasion in cancer. MMP regulation — not simple activation or suppression — is the therapeutic goal in most healing contexts.