PURPOSE: Survival of lung transplant recipients is limited by the development of bronchiolitis obliterans syndrome (BOS), which presents as progressive dyspnea from bronchiole inflammation, matrix degradation, and fibrosis. Our work has replicated this pathology in both transplant and toxicant animal models of BOS. We have shown correlation between immune progression in BOS models and MMP-9 in lung tissue. MMP-9 and its upstream phosphorylation proteins appear critical to BOS development. In this report, we hypothesize that MMP-9 in bronchoalveolar lavage (BAL) correlates with BOS progression and propose that BAL MMP-9 is a clinical marker for BOS development.
METHODS: BAL rarely contains protein levels to produce satisfactory zymography, the favored method to profile MMP-9. To test our hypothesis, BALs were concentrated (3000 kD cutoff) tenfold. Pro-, active-, and lipocalin-bound MMP-9 were identified in three groups: 1) Transplant BOS, inbred MHC mismatched rats (DA trachea, BBDR host), 2) Transplant BOS, outbred rats (DA trachea, SD host), 3) SD rats, non-transplanted, but infected with S. aureus. All BALs and lung homogenates were taken at 6 weeks. Zymography and histological staining were performed.
RESULTS: Tenfold concentrates of BAL (two 3-mL saline washes) provided protein adequate for zymography. Mean band intensity of active MMP-9 (17 +/- 15.2) in the inbred, MHC mismatched transplants were significantly elevated over the outbred transplants (6.1 +/- 0.42, p<0.04), suggesting that BAL active MMP-9 relates to the immune reactivity of the host. This finding correlated with histology, anti-MMP-9, and H&E. Infected controls without transplant also demonstrated both high active MMP-9 and high lipocalin, not significantly different from the inbred (BBDR) MHC mismatch transplants.
CONCLUSION: BAL MMP-9 effectively correlates with histological signs of BOS, but is elevated equally with infection.
CLINICAL IMPLICATIONS: Use of MMP-9, in combination with other markers such as TGF-β, may improve specificity.
DISCLOSURE: Jennifer Svetlecic, No Financial Disclosure Information; No Product/Research Disclosure Information