Abstract
Although matrix metalloproteinases (MMPs) are increasingly being implicated in several pathologies of the nervous system, it is not yet clear what role they play in normal neurobiological processes. We review the expression of extracellular matrix (ECM) components as well as MMPs and tissue inhibitors of metalloproteinases (TIMPs) in the peripheral nervous system. We explore the expression of certain MMPs and the four TIMPs at the mRNA level in the postnatal mouse sciatic nerve. In addition, we have used substrate gel and in situ zymography to determine levels of MMPโ2 and โ9 and TIMP activity in rat sciatic nerve after crush and during regeneration. A rapid and transient increase in MMPโ9 localised at and immediately distal to the site of injury was observed, whereas an increase in MMPโ2 activity was delayed, prolonged, and extended proximal and distal to the injury site. This activity coincides with periods of axonal elongation, suggesting that it could act to facilitate axonal extension along the nerve matrix. We also detected multiple species of gelatinolytic inhibitory activity, including TIMPโ1 and โ3 in control and injured nerve. These activities probably act to prevent uncontrolled gelatinolytic activity, maintaining nerve integrity at the level essential for axonal regrowth. ยฉ 2003 WileyโLiss, Inc.