Matrix metalloproteinases and their inhibitors in human traumatic spinal cord injury

Matrix metalloproteinases (MMPs) are a family of extracellular zinc- and calcium-dependent endopeptidases that degrade the extracellular matrix and other extracellular proteins. In experimental spinal cord injury (SCI), recent studies have demonstrated an involvement of various MMPs in the early posttraumatic events. In particular the knock-out of MMP-9 and -12 demonstrated an improved recovery of lesioned animals, most likely due to a decreased permeability of the blood brain barrier and a reduced density of microglia/macrophages at the lesion. In the present investigation, the expression pattern of several MMPs and their inhibitors has been investigated in samples of post mortem human spinal cord, taken from 15 patients who died at a range of times following traumatic SCI. Our data reveals an induction of all four MMPs studied (MMP-1, -2, -9 and -12) with an individual profile for each protein. They are mainly expressed during the first weeks after injury and are most likely involved in the destructive and inflammatory reaction cascade. The comparison of our data to the partially known situation in experimental animals shows concordance as well as disagreement regarding the possible role of individual MMPs in the posttraumatic events after human SCI supporting the idea of further investigation in this direction.