Circulating fibrocytes traffic to the lungs in response to CXCL12 and mediate fibrosis

J Clin Invest. 2004 Aug;114(3):438-46. doi: 10.1172/JCI20997.


Previous reports have identified a circulating pool of CD45(+) collagen I(+) CXCR4(+) (CD45(+)Col I(+)CXCR4(+)) cells, termed fibrocytes, that traffic to areas of fibrosis. No studies have demonstrated that these cells actually contribute to fibrosis, however. Pulmonary fibrosis was originally thought to be mediated solely by resident lung fibroblasts. Here we show that a population of human CD45(+)Col I(+)CXCR4(+) circulating fibrocytes migrates in response to CXCL12 and traffics to the lungs in a murine model of bleomycin-induced pulmonary fibrosis. Next, we demonstrated that murine CD45(+)Col I(+)CXCR4(+) fibrocytes also traffic to the lungs in response to a bleomycin challenge. Maximal intrapulmonary recruitment of CD45(+)Col I(+)CXCR4(+) fibrocytes directly correlated with increased collagen deposition in the lungs. Treatment of bleomycin-exposed animals with specific neutralizing anti-CXCL12 Ab's inhibited intrapulmonary recruitment of CD45(+)Col I(+)CXCR4(+) circulating fibrocytes and attenuated lung fibrosis. Thus, our results demonstrate, we believe for the first time, that circulating fibrocytes contribute to the pathogenesis of pulmonary fibrosis.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / metabolism
  • Animals
  • Bleomycin / toxicity
  • Chemokine CXCL12
  • Chemokines, CXC / metabolism*
  • Chemotaxis / immunology
  • Collagen Type I / metabolism
  • Disease Models, Animal
  • Fibroblasts / chemistry
  • Fibroblasts / immunology
  • Fibroblasts / metabolism*
  • Humans
  • Kinetics
  • Leukocyte Common Antigens / immunology
  • Lung Injury*
  • Mice
  • Mice, SCID
  • Muscle, Smooth / metabolism
  • Pulmonary Fibrosis / chemically induced
  • Pulmonary Fibrosis / genetics
  • Pulmonary Fibrosis / metabolism*
  • Pulmonary Fibrosis / pathology
  • Pulmonary Fibrosis / physiopathology*
  • Receptors, CXCR4 / metabolism
  • Receptors, Complement 3b / immunology


  • Actins
  • CXCL12 protein, human
  • Chemokine CXCL12
  • Chemokines, CXC
  • Collagen Type I
  • Cxcl12 protein, mouse
  • Receptors, CXCR4
  • Receptors, Complement 3b
  • Bleomycin
  • Leukocyte Common Antigens