Preliminary study of the cellular characteristics of primary bronchial fibroblasts in patients with asthma: expression of alpha-smooth muscle actin, fibronectin containing extra type III domain A, and smoothelin.

■ Abstract Background: The relationship between fi broblasts, myofi broblasts, and smooth muscle cells within the airway wall remains poorly understood. Objective: The cellular characteristics of primary bronchial fi broblasts from patients with asthma were investigated by evaluating the expression of 3 proteins: α‐smooth muscle actin (SMA), fi bronectin containing extra type III domain A (EDAcFN), and smoothelin. Methods: Expression of SMA, EDAcFN, and smoothelin was evaluated in primary fi broblasts from 3 patients with asthma of varying symptom severity, embryonic fi broblasts, and a healthy control. In addition, primary bronchial fi broblasts from patients with asthma were assessed for SMA at various incubation times (4 hours to 76 hours) and with different extracellular matrices (ECMs). Immunofl uorescence was assessed by manually counting cells that stained positively as fifi lamentous structures under a fl uorescence microscope. Results: Expression of fiSMA tended to increase with the length of incubation. The positive to total cell ratio for fi lamentous cells did not differ signifi cantly between the various kinds of ECMs onto which cells were plated (P>.05). Primary bronchial fi broblasts from asthma patients produced more prominent expression of EDAcFN than control fi broblasts. Smoothelin was not expressed in any fi broblasts. Conclusions: More than 50% of primary bronchial fi broblasts were defi ned as myofi broblasts. Primary bronchial fi broblasts in patients with asthma had more potential for tissue fi brosis than control fi broblasts. No mature smooth muscle cells were observed in primary bronchial fi broblasts in patients with asthma.