Response of matrix metalloproteinase-9 to olfactory nerve injury.

Matrix metalloproteinases function in the remodeling of the extracellular matrix during growth and development as well as in injury and disease processes. We examined the role of matrix metalloproteinase-9 in a model of olfactory nerve injury in mice. We measured changes in matrix metalloproteinase-9 protein levels for up to 60 days following olfactory nerve transection. Matrix metalloproteinase-9 levels increased within hours after injury, peaked at day 1 and were elevated for approximately 2 weeks before returning to control levels over the 60-day time period. The increase in matrix metalloproteinase-9 was temporally associated with the degeneration of olfactory neurons that follows nerve transection and with increased gliosis. Our results demonstrate a temporal relationship between matrix metalloproteinase-9 elevation, degeneration of olfactory neurons and gliosis.