The effects of leukocyte reduction on matrix metalloproteinase release in cardiopulmonary bypass

Matrix metalloproteinases (MMPs) are a family of enzymes responsible for degrading the extracellular matrix, a process that likely contributes to the development of altered vascular permeability. Past studies in patients undergoing cardiopulmonary bypass (CPB) have documented increased levels of MMPs with CPB. The purpose of this study was to evaluate the effect of leukocyte reduction on MMP release during CPB. Patients (n = 17) undergoing elective coronary revascularization requiring CPB were randomly assigned to either a leukocyte-reducing filter (LRF) group (n = 9) or the standard CPB circuit with no LRF (n = 8). White blood cell (WBC) counts, MMP-2, and MMP-9 levels were serially measured at baseline and up to 12 hours post CPB. MMP levels were measured by enzyme-linked immunoassay. ProMMP-2 levels increased in both the non-LRF and LRF groups but to a higher degree in the LRF group. ProMMP-9 levels increased by 40% in the non-LRF group. In contrast, proMMP-9 decreased by 30% in the LRF group. The addition of leukocyte-reducing filters in the CPB circuit attenuated the release of MMP-9 but increased release of MMP-2 post-CPB. Because MMPs can degrade the extracellular matrix, leading to increased vascular permeability, attenuation of MMPs may have decreased the local tissue injury known to occur as a result of these enzymes. However, future prospective studies to test this hypothesis directly are warranted.