Effects of Active Chronic Cigarette-Smoke Exposure on Circulating Fibrocytes

Purpose This study aimed to evaluate the hypothesis that active smoking impacts upon mediators and abundance of circulating fibrocyte cells in smoking-related disease characterised by fibrosis. Methods Flow cytometry and enzyme-linked immunosorbent assays were used to investigate blood from five patient groups: healthy never-smokers, healthy current smokers, stable chronic obstructive pulmonary disease (COPD) active smokers, idiopathic pulmonary fibrosis (IPF) never-smokers, and IPF active smokers. Results A significant inverse dose–response relationship was observed in healthy smokers among cumulative smoking burden (pack-years) and fibrocyte abundance ( p = 0.006, r = −0.86). Among serum profibrotic fibrocyte chemokines measured, CCL18 rose significantly alongside fibrocyte numbers in all five subject groups, while having an inverse dose–response relationship with pack-year burden in healthy smokers ( p = 0.003, r = −0.89). In IPF, CCL2 rose in direct proportion to fibrocyte abundance irrespective of smoking status but had lower serum levels in those currently smoking ( p =