Circulating fibrocytes define a new leukocyte subpopulation that mediates tissue repair.
BACKGROUND
The host response to tissue injury requires a complex interplay of diverse cellular, humoral, and connective tissue elements. Fibroblasts participate in this process by proliferating within injured sites and contributing to scar formation and the longterm remodeling of damaged tissue. Fibroblasts present in areas of tissue injury generally have been regarded to arise by recruitment from surrounding connective tissue; however this may not be the only source of these cells.


METHODS
Long-term culture of adherent, human, and murine leukocyte subpopulations was combined with a variety of immunofluorescence and functional analyses to identify a blood-borne cell type with fibroblast-like properties.


RESULTS
We describe for the first time a population of circulating cells with fibroblast properties that specifically enter sites of tissue injury. This novel cell type, termed a "fibrocyte," was characterized by its distinctive phenotype (collagen+/vimentin+/CD34+), by its rapid entry from blood into subcutaneously implanted wound chambers, and by its presence in connective tissue scars.


CONCLUSIONS
Blood-borne fibrocytes contribute to scar formation and may play an important role both in normal wound repair and in pathological fibrotic responses.
Bucala
R
R
Picower Institute for Medical Research, Manhasset, New York 11030, USA.
Spiegel
L A
LA
Chesney
J
J
Hogan
M
M
Cerami
A
A
D000818:Animals; D001483:Base Sequence; D001853:Bone Marrow / Q000528:radiation effects; D001854:Bone Marrow Cells; D015704:CD4 Antigens / Q000378:metabolism; D002448:Cell Adhesion; D002478:Cells, Cultured; D002498:Centrifugation; D002678:Chimera; D003094:Collagen / Q000737:chemistry / Q000378:metabolism; D003238:Connective Tissue / Q000098:blood supply / Q000502:physiology; D003599:Cytoskeleton; D004268:DNA-Binding Proteins / Q000235:genetics; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005347:Fibroblasts / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D005434:Flow Cytometry / Q000379:methods; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D007962:Leukocytes / Q000166:cytology* / Q000502:physiology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010641:Phenotype; D051876:Sex-Determining Region Y Protein; D013997:Time Factors; D014157:Transcription Factors; D014183:Transplantation, Heterologous; D014746:Vimentin / Q000737:chemistry; D014945:Wound Healing / Q000502:physiology*
D015704:CD4 Antigens; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors; D014746:Vimentin; D003094:Collagen