COL1A2 and neoplasm: A growing body of research have identified that loss of structural integrity of ECM is considered to be the main cause of pathogenesis of skin photoaging, its main structural component is type I procollagen, and MMP-1 specifically degrades type I procollagen during photoaging; therefore, the generation of MMPs and debasement of type I procollagen in photoaging play profound roles (20, 21).