TIMP1 and peripheral nerve injury: Because TIMP-1 and MMPs can be up-regulated simultaneously during tissue damage and repair, such as in peripheral nerve injury (Parkitna et al., 2006; Huang et al., 2011; Kim et al., 2012; Yokose et al., 2012), disentangling how TIMP-1 regulates tissue remodeling/repair from the induction of pain, per se, is challenging.