Tissue fibrocytes in patients with mild asthma: A possible link to thickness of reticular basement membrane?

Background: Myofibroblasts, proposed as being derived from circulating fibrocytes, are considered to be important cells in thickening of the basement membrane in patients with asthma. We have studied the correlation of tissue fibrocyte levels to basement membrane thickness and the presence of fibrocytes in bronchoalveolar lavage fluid (BALF) in steroid-naive patients with mild asthma and controls. Methods: Patients with mild asthma (n=9) were recruited and divided into two categories based on whether or not fibroblast-like cells could be established from BALF. Non-asthmatic healthy subjects (n=5) were used as controls. Colocalization of the fibrocyte markers CD34, CD45RO, procollagen I, and alpha-smooth muscle actin (alpha-SMA) were identified in bronchial biopsies from patients and controls by confocal microscopy. Kruskall-Wallis method was used to calculate statistical significance and Spearman coefficient of rank correlation was used to assess the degree of association. Results: In patients with BALF fibroblasts, a 14-fold increase of tissue cells expressing CD34/CD45RO/alpha-SMA and a 16-fold increase of tissue cells expressing CD34/procollagen I was observed when compared to controls (p<0.05). In contrast, patients without BALF fibroblasts displayed a 2-fold increase when compared to controls (p