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

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.

We sought to test the hypothesis that the concentration and activation state of peripheral blood fibrocytes correlates with asthma severity.

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.

Concentrations of peripheral blood total (CD45(+)Col1(+)), activated (the TGF-β 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(+).

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.