Serum MMP-9 is elevated in children with asthma.

This study explored the association of matrix metalloproteinase-9 (MMP-9) serum concentration and gene polymorphism with childhood asthma. Serum levels of MMP-9 were determined by sandwich enzyme-linked immunosorbent assay (ELISA) in 65 children with asthma (cases) and 68 healthy children (controls), and the -1562C/T polymorphism in MMP-9 was detected by polymerase chain reaction and restriction fragment-length polymorphism (PCR-RFLP) analysis. The results showed that the mean serum levels of MMP-9 in the children with asthma (136.53 ± 29.96 ng/ml) were significantly higher than that in the healthy controls (45.08 ± 12.53 ng/ml; P<0.05). At MMP-9 base position -1562, the frequencies of the genotypes CC, CT and TT in cases were 67.7, 29.2 and 3.1% and in controls were 73.5, 25.0 and 1.5%. The allele frequencies of C and T in cases vs. controls were 82.3 and 17.7% vs. 86.0 and 14.0%, respectively. No statistically significant difference was detected in genotype or allele frequency between these groups. In addition, no significant difference in serum levels of MMP-9 was observed within groups among children with different genotypes (P>0.05). Therefore, whereas serum levels of MMP-9 are associated with the occurrence of childhood asthma, the MMP-9 -1562C/T gene polymorphism has no correlation with the pathogenesis of childhood asthma.