Background: The relationship between fibroblasts, myofibroblasts, and smooth muscle cells within the airway wall remains poorly understood.
Objective: The cellular characteristics of primary bronchial fibroblasts from patients with asthma were investigated by evaluating the expression of 3 proteins: alpha-smooth muscle actin (SMA), fibronectin containing extra type III domain A (EDAcFN), and smoothelin.
Methods: Expression of SMA, EDAcFN, and smoothelin was evaluated in primary fibroblasts from 3 patients with asthma of varying symptom severity, embryonic fibroblasts, and a healthy control. In addition, primary bronchial fibroblasts from patients with asthma were assessed for SMA at various incubation times (4 hours to 76 hours) and with different extracellular matrices (ECMs). Immunofluorescence was assessed by manually counting cells that stained positively as fine filamentous structures under a fluorescence microscope.
Results: Expression of filamentous SMA tended to increase with the length of incubation. The positive to total cell ratio for filamentous cells did not differ significantly between the various kinds of ECMs onto which cells were plated (P > .05). Primary bronchial fibroblasts from asthma patients produced more prominent expression of EDAcFN than control fibroblasts. Smoothelin was not expressed in any fibroblasts.
Conclusions: More than 50% of primary bronchial fibroblasts were defined as myofibroblasts. Primary bronchial fibroblasts in patients with asthma had more potential for tissue fibrosis than control fibroblasts. No mature smooth muscle cells were observed in primary bronchial fibroblasts in patients with asthma.