Metalloproteinase increases in the injured rat spinal cord

Up-regulation of matrix metalloproteinases MMP-9 and MMP-2 after injury to the spinal cord (SCI) is demonstrated. MMP-9 activity maximized at 12-24 h, and MMP-2 rose at 5 days postinjury. MMP-3 was not detectable by zymograph ic analysis, so its level of expression was, at most, very low. The level o f tissue inhibitor of metalloproteinases in the spinal cord was not altered by injury, perhaps permitting increased MMP-9:and MMP-2 activities in situ . Ablating them with an antibody demonstrated that infiltrating neutrophils were the principal source of MMP-9 activity after spinal cord injury, sugg esting that neutrophils utilize that proteinase in responding to spinal cor d injury. MMP-9 and MMP-2 probably contribute to breakdown of the extracell ular matrix following SCI. NeuroReport 11:3551-3554 (C) 2000 Lippincott Wil liams & Wilkins.