Mast Cells Induce Rat Pulmonary Fibroblast Proliferation and Differentiation <i>via</i> Direct Cell–Cell Contact

Abstract

SummaryWe investigated whether direct cell-cell contact between mast cells (MCs) and pulmonary fibroblasts (PFs) was important for PF proliferation, differentiation, and function, which are critically involved in the development of idiopathic pulmonary fibrosis. MCs and PFs were isolated from male Wistar rats for 3 experimental conditions: (1) PFs alone (Controls); (2) co-culture and contact (CC) between MCs and PFs; and (3) co-culture and no contact (NC) between MCs and PFs. We monitored PF proliferation using growth curves and MTT assays, evaluated PF expression of α-smooth muscle actin (α-SMA) by immunocytochemistry, and determined the concentrations of bFGF, TGF-β1, and Type I collagen in culture supernatants by ELISA. After 5 days in culture, CC conditions induced a significant increase in PF proliferation compared to the other 2 conditions. No significant difference was observed between the NC and control conditions. CC conditions also induced significantly higher PF expressions of α-SMA, and bFGF, TGF-β1, and Type I collagen production compared to the other 2 conditions. These results suggest that MCs promote both PF proliferation and their differentiation into myofibroblasts via direct cell-cell contact.Key words bFGF, Interstitial pulmonary fibrosis, Mast cells, Pulmonary fibroblasts, TGF-β1, Type I collagen.Idiopathic pulmonary fibrosis is a disease that progresses gradually and may be fatal under certain conditions. Pathologically, IPF is characterized by general interstitial pneumonia with damage to alveolar epithelial cells, fibroblast proliferation, and the deposition of large amounts of extracellular matrix (ECM) in the interstitium (Chilosi et al. 2006). There are currently no effective therapeutic strategies to restrain the development of IPF.Pulmonary fibroblasts play an important role in the synthesis of collagens and the ECM in the pulmonary interstitium. Thus, understanding the biological behaviors of pulmonary fibroblasts will aid in identifying the mechanisms underlying the formation of pulmonary fibrosis (Lawson et al. 2005). In idiopathic pulmonary fibrosis, there are numerous fibroblast foci in pulmonary connective tissues. These foci are primarily comprised of pulmonary fibroblasts and myofibroblasts, which differentiate from fibroblasts in the pulmonary interstitium. Both fibroblasts and myofibroblasts predominantly secrete Types I and III collagen, the major components of the ECM.Previous studies of pulmonary fibrosis have emphasized that mast cells (MCs) promoted the formation of tissue fibrosis via their interactions with pulmonary fibroblasts (Garbuzenko et al. 2004). In rats with pulmonary fibrosis, investigators have found that MCs aggregate in areas of pulmonary fibroblast hyperplasia. In IPF, it has been demonstrated that MCs produce large amounts of basic fibroblast growth factor (bFGF), and MC aggregates with high levels of bFGF expression have been found in regions with ECM deposition and proliferation of smooth muscle cells/myofi-

TGF-β1-Induced Pulmonary Fibroblasts Proliferation and Differentiation Are Inhibited by Antisense Oligodeoxynucleotide of Basic Fibroblast Growth Factor

“…Mast cells, a major source of bFGF, have been found to aggregate in areas of pulmonary fibroblast hyperplasia in the lungs of patients with chronic pulmonary fibrosis (Qu et al 1995, Reed et al 1995. Our previous study also found that mast cells which express high levels of bFGF induced rat pulmonary fibroblast proliferation and differentiation (Cheng et al 2012). These findings suggested that bFGF was closely related to the proliferation and differentiation of pulmonary fibroblasts.…”