Up-regulation of MMP-2 and MMP-9 leads to degradation of type IV collagen during skeletal muscle reperfusion injury; Protection by the MMP inhibitor, doxycycline

Objectives: to determine the role of matrix metalloproteinascs, MMP-2 and MMP-9, in reperfusion injury following skeletal muscle ischaemia and whether inhibition of MMI's by doxycycline protects against tissue damage. Methods: rats were anaesthetised and a tourniquet applied to the proximal thigh to occlude blood flow. Four, how's of ischaemia was followed by reperfusion for 0, 4, 24 or 72 h. Two further groups received doxycycline for 7 days prior to bilateral ischaemia and 24 It reperfusion. Skeletal muscle from both limbs, kidneys and lungs were harvested for zymography and immunohistochemical staining for type IV collagen. Results: upregulation of MMP-2 and MMP-9 was detected by zymography in the ischaemic leg and lung but not ill the kidney. Quantitative immunohistochemical analysis showed marked degradation of type TV collagen in reperfused muscle, lung and kidney. Doxycycline-treated rats showed significant preservation of type IV collagen in skeletal muscle and a trend towards preservation ill kidney and hing. Conclusions: MMP-2 and MMP-9 are strongly upregulated in skeletal muscle ischaemia/reperfusion injury and are also upregulated in remote organs, leading to degradation of basement membranes. Inhibition of MMP activity may therefore be potentially therapeutically useful in reducing the severity of reperfusion injury.