Genetic polymorphisms in MMP7 and reduced serum levels associate with the development of bronchiolitis obliterans syndrome after lung transplantation

Background: Pulmonary epithelium is the primary target of injury in the development of bronchiolitis obliterans syndrome (BOS) after lung transplantation. Matrix metalloproteinases (MMP)-8 and -9 already have been implicated in the pathogenesis of BOS. MMP-7, which is involved in the repair of the lung epithelium, has not been studied in this respect. We hypothesized that genetic polymorphisms in MMP7 influence its expression and correlate with serum MMP-7 levels and the development of BOS.

Methods: DNA was collected from 110 lung transplant recipients, including 21 patients with BOS. We genotyped 7 single nucleotide polymorphisms in MMP7 and measured serum MMP-7 levels. The control group comprised 422 healthy individuals.

Results: BOS(pos) patients had lower levels of MMP-7 than BOS(neg) patients (7.87 vs 10.18 ng/ml). Significant differences in genotype and haplotype distribution between the BOS(pos) and BOS(neg) patients and controls were found. An increased risk for BOS development was found in patients homozygous for the major alleles of rs17098318, rs11568818, and rs12285347, and for the minor allele rs10502001 (odds ratio, 3.88-5.30). Haplotypes constructed with 3 or 4 risk alleles correlated with lower MMP-7 levels.

Conclusions: Genetic polymorphisms of MMP7 predispose to the development of BOS. Patients carrying these risk alleles express lower levels of MMP-7, which may contribute to aberrant tissue repair and culminate in the development of BOS.