Number, activation, and differentiation of circulating fibrocytes correlate with asthma severity.

BACKGROUND: A biomarker that predicts poor asthma control would be clinically useful. Fibrocytes are bone marrow-derived circulating progenitor cells that have been implicated in tissue fibrosis and T(H)2 responses in asthmatic patients. OBJECTIVE: We sought to test the hypothesis that the concentration and activation state of peripheral blood fibrocytes correlates with asthma severity. METHODS: By using fluorescence-activated cell sorting analysis, fibrocytes (CD45(+) and collagen 1 [Col1](+)) were enumerated and characterized in the buffy coats of fresh peripheral blood samples from 15 control subjects and 40 asthmatic patients. RESULTS: Concentrations of peripheral blood total (CD45(+)Col1(+)), activated (the TGF-ß transducing protein phosphorylated SMAD2/3 [p-SMAD2/3](+) or phosphorylated AKT [p-AKT](+)), and differentiated (α-smooth muscle actin [α-SMA](+)) fibrocytes were increased in asthmatic patients compared with control subjects. The increase in total and CD45(+)Col1(+)CXCR4(+) fibrocytes was primarily seen in patients with severe asthma (Global Initiative for Asthma steps 4-5) as opposed to those with milder asthma (Global Initiative for Asthma steps 1-3). In addition, numbers of circulating α-SMA(+) and α-SMA(+)CXCR4(+) fibrocytes were increased in asthmatic patients experiencing an asthma exacerbation in the preceding 12 months. A significant correlation (P < .05) was observed between CD45(+)Col1(+)CXCR4(+) fibrocytes and the activation phenotypes CD45(+)Col1(+)p-SMAD2/3(+) and CD45(+)Col1(+)p-AKT(+). CONCLUSION: There was correlation between circulating fibrocyte subsets and asthma severity, and there was an increased number of activated/differentiated fibrocytes in circulating blood of asthmatic patients experiencing an exacerbation in the preceding 12 months.

CXCR4, but not CXCR7, discriminates metastatic behavior in non-small cell lung cancer cells.

UNLABELLED: Chemokines have been implicated as key contributors of non-small cell lung cancer (NSCLC) metastasis. However, the role of CXCR7, a recently discovered receptor for CXCL12 ligand, in the pathogenesis of NSCLC is unknown. To define the relative contribution of chemokine receptors to migration and metastasis, we generated human lung A549 and H157 cell lines with stable knockdown of CXCR4, CXCR7, or both. Cancer cells exhibited chemotaxis to CXCL12 that was enhanced under hypoxic conditions, associated with a parallel induction of CXCR4, but not CXCR7. Interestingly, neither knockdown cell line differed in the rate of proliferation, apoptosis, or cell adherence; however, in both cell lines, CXCL12-induced migration was abolished when CXCR4 signaling was abrogated. In contrast, inhibition of CXCR7 signaling did not alter cellular migration to CXCL12. In an in vivo heterotropic xenograft model using A549 cells, expression of CXCR4, but not CXCR7, on cancer cells was necessary for the development of metastases. In addition, cancer cells knocked down for CXCR4 (or both CXCR4 and CXCR7) produced larger and more vascular tumors as compared with wild-type or CXCR7 knockdown tumors, an effect that was attributable to cancer cell-derived CXCR4 out competing endothelial cells for available CXCL12 in the tumor microenvironment. These results indicate that CXCR4, not CXCR7, expression engages CXCL12 to mediate NSCLC metastatic behavior. IMPLICATIONS: Targeting CXCR4-mediated migration and metastasis may be a viable therapeutic option in NSCLC.

The role of fibrocytes in sickle cell lung disease.

BACKGROUND: Interstitial lung disease is a frequent complication in sickle cell disease and is characterized by vascular remodeling and interstitial fibrosis. Bone marrow-derived fibrocytes have been shown to contribute to the pathogenesis of other interstitial lung diseases. The goal of this study was to define the contribution of fibrocytes to the pathogenesis of sickle cell lung disease. METHODOLOGY/PRINCIPAL FINDINGS: Fibrocytes were quantified and characterized in subjects with sickle cell disease or healthy controls, and in a model of sickle cell disease, the NY1DD mouse. The role of the chemokine ligand CXCL12 in trafficking of fibrocytes and phenotype of lung disease was examined in the animal model. We found elevated concentration of activated fibrocytes in the peripheral blood of subjects with sickle cell disease, which increased further during vaso-occlusive crises. There was a similar elevations in the numbers and activation phenotype of fibrocytes in the bone marrow, blood, and lungs of the NY1DD mouse, both at baseline and under conditions of hypoxia/re-oxygenation. In both subjects with sickle cell disease and the mouse model, fibrocytes expressed a hierarchy of chemokine receptors, with CXCR4 expressed on most fibrocytes, and CCR2 and CCR7 expressed on a smaller subset of cells. Depletion of the CXCR4 ligand, CXCL12, in the mouse model resulted in a marked reduction of fibrocyte trafficking into the lungs, reduced lung collagen content and improved lung compliance and histology. CONCLUSIONS: These data support the notion that activated fibrocytes play a significant role in the pathogenesis of sickle cell lung disease.

Circulating fibrocytes correlate with bronchiolitis obliterans syndrome development after lung transplantation: a novel clinical biomarker.

BACKGROUND: Development of bronchiolitis obliterans syndrome (BOS) after lung transplantation confers increased patient morbidity and mortality. Fibrocytes are circulating bone marrow-derived mesenchymal cell progenitors that influence tissue repair and fibrosis. Fibrocytes have been implicated in chronic pulmonary inflammatory processes. We investigated the correlation of circulating fibrocyte number with BOS development in lung transplant patients. METHODS: We prospectively quantified circulating fibrocyte levels among lung transplant patients. Patients were stratified according to the development of BOS as indicated by predicted forced expiratory volume in 1 second. Fibrocyte activity was analyzed by flow cytometry (cluster of differentiation 45+, collagen 1+) in a blinded manner related to clinical presentation. RESULTS: Thirty-nine patients (61.5% men) underwent double (33.3%), left (25.6%), or right (41.0%) lung transplantation. Average patient age was similar between BOS and non-BOS patients (58.3±3.9 vs 60.3±2.0 years, p=0.67). Chronic obstructive lung disease was the most common indication for lung transplantation (41.0%). Median forced expiratory volume in 1 second was lower among BOS patients compared with non-BOS patients (1.08 vs. 2.18 L/s, p=0.001). Importantly, circulating fibrocyte numbers were increased in BOS patients compared with non-BOS patients (8.91 vs 2.96×10(5) cells/mL, p=0.03) by flow cytometry and were incrementally increased with advancing BOS stage (p=0.02). CONCLUSIONS: Increased circulating fibrocyte levels correlate with the development of BOS after lung transplantation and positively correlate with advancing BOS stage. Quantification of circulating fibrocytes could serve as a novel biomarker and possible therapeutic target for BOS development in lung transplant patients.