Expression of matrix metalloproteases by fibrocytes: possible role in migration and homing.
BACKGROUND
Fibrocytes are progenitor cells characterized by the simultaneous expression of mesenchymal, monocyte, and hematopoietic stem cell markers. We previously documented their presence in lungs of patients with idiopathic pulmonary fibrosis. However, the mechanisms involved in their migration, subsequent homing, and local role remain unclear. Matrix metalloproteinases (MMPs) facilitate cell migration and have been implicated in the pathogenesis of pulmonary fibrosis.


OBJECTIVE
To evaluate the expression and role of matrix metalloproteinases in human fibrocytes.


METHODS
Fibrocytes were purified from CD14(+) monocytes and cultured for 8 days; purity of fibrocyte cultures was 95% or greater as determined by flow cytometry. Conditioned media and total RNA were collected and the expression of MMP-1, MMP-2, MMP-7, MMP-8, and MMP-9 was evaluated by real-time polymerase chain reaction. Protein synthesis was examined using a Multiplex assay, Western blot, fluorescent immunocytochemistry, and confocal microscopy. MMP-2 and MMP-9 enzymatic activities were evaluated by gelatin zymography. Migration was assessed using collagen I-coated Boyden chambers. Stromal cell-derived factor-1α and platelet-derived growth factor-B were used as chemoattractant with or without a specific MMP-8 inhibitor.


RESULTS
Fibrocytes showed gene and protein expression of MMP-2, MMP-9, MMP-8, and MMP-7. MMP-2 and MMP-9 enzymatic activities were also demonstrated by gelatin zymography. Likewise, we found colocalization of MMP-8 and MMP-7 with type I collagen in fibrocytes. Fibrocyte migration toward platelet-derived growth factor-B or Stromal cell-derived factor-1α in collagen I-coated Boyden chambers was significantly reduced by a specific MMP-8 inhibitor.


CONCLUSIONS
Our findings reveal that fibrocytes express a variety of MMPs and that MMP-8 actively participates in the process of fibrocyte migration.
García-de-Alba
Carolina
C
Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas," Mexico DF, Mexico.
Becerril
Carina
C
Ruiz
Víctor
V
González
Yolanda
Y
Reyes
Silvia
S
García-Alvarez
Jorge
J
Selman
Moisés
M
Pardo
Annie
A
D015153:Blotting, Western; D054443:Cell Migration Assays; D002465:Cell Movement / Q000502:physiology*; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis; D005109:Extracellular Matrix / Q000502:physiology; D005347:Fibroblasts / Q000201:enzymology*; D006801:Humans; D016130:Immunophenotyping; D020783:Matrix Metalloproteinase 7 / Q000378:metabolism; D020784:Matrix Metalloproteinase 8 / Q000378:metabolism; D020782:Matrix Metalloproteinases / Q000378:metabolism / Q000502:physiology*; D018613:Microscopy, Confocal; D016133:Polymerase Chain Reaction; D011658:Pulmonary Fibrosis / Q000503:physiopathology; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
D053773:Transforming Growth Factor beta1; D003094:Collagen; D020782:Matrix Metalloproteinases; D020783:Matrix Metalloproteinase 7; D020784:Matrix Metalloproteinase 8