Tissue Inhibitor of Metalloproteinase-2 (TIMP-2) expression during cardiac neural crest cell migration and its role in ProMMP-2 activation

Matrix metalloproteinases (MMPs) are important mediators of neural crest (NC) cell migration. Here, we examine the distribution of tissue inhibitor of metalloproteinase (TIMP)-2 and TIMP-3 and test whether manipulating TIMP levels alters chicken cardiac NC cell migration. TIMP-2 mRNA is expressed at stage 11 in the neural epithelium and only in migrating cardiac NC cells. TIMP-3 mRNA is expressed only in the notochord at stage 8 and later in the outflow tract myocardium. Exogenous TIMP-2 increases NC motility in vitro at low concentrations but has no effect when concentrations are increased. In vitro, NC cells express membrane type-1 matrix metalloproteinase (MT1-MMP) and TIMP-2 and they secrete and activate proMMP-2. Antisense TIMP-2 oligonucleotides block proMMP-2 activation, decrease NC cell migration from explants, and perturb NC morphogenesis in ovo. Because TIMP-2 is required for activation of proPMP-2 by MT1-MMP, this finding suggests TIMP-2 expression by cardiac NC cells initiates proMMP-2 activation important for their migration.