Tobacco smoking increases the in vivo MMP-9 burden. Total MMP-9 concentrations in the serum of smokers (n = 19) and non-smokers (n = 20) matched for age and gender were measured by ELISA. Circulating total MMP-9 concentrations are significantly increased in smokers compared to non-smokers (* p < 0.05). Error bars represent the interquartile range.
Xu et al. BMC Cell Biology 2008 9:19 doi:10.1186/1471-2121-9-19