CD34 and Hepatic fibrosis: Interstitial collagenase (i.e., MMP13) is an important enzyme for collagenolysis in liver fibrosis and type-1 collagen, that increased predominantly in liver fibrosis, can be mainly degraded by MMP13.28 In the present study, the active form of MMP13 was upregulated in the livers of fresh and expanded PB-CD34+ cell-transplanted livers compared to nontreated livers, although a nonexpanded/expanded effect was observed and no significant dose–response relationship was observed.