LUNG EPITHELIUM-DERIVED IL-10 STIMULATES LUNG FIBROBLAST PROLIFERATION IN VITRO: IMPLICATIONS FOR THE PATHOGENESIS OF OBLITERATIVE BRONCHIOLITIS AFTER LUNG TRANSPLANTATION

Abstract

141 Obliterative Bronchiolitis (OB) is one of the leading causes of morbidity and mortality following lung transplantation. On a cellular level OB is still poorly understood. Some studies indicate that initial injury to bronchial epithelium may lead to the overproliferation of lung fibroblasts and occlusion of the bronchioles. We hypothesized that in vitro, bronchial epithelial cells may produce factors, such as IL-10, that could stimulate the growth of lung fibroblasts. Methods: Normal human bronchial cells were grown to subconfluence in supplemented media. The media was changed to basal media after the cells were washed. The supernatant was collected at 48 hours (HBECM). Normal human lung fibroblasts were grown in the presence of basal media or HBECM. The pre-incubation of anti-IL10 blocking antibody with HBECM for 30 minutes was also completed. The comparative fibroblast proliferation in the presence of basal media, HBECM, and HBECM with anti-IL-10, was assessed using a MTT microtiter assay. The absolute concentration of IL-10 in HBECM was determined using an ELISA assay. The direct fibrogenic effect of IL-10 at 100, 200, and 500 pg/ml in basal media was determined. Results: The presence of HBECM caused a dramatic increase in fibroblast proliferation over the basal control (p<0.001). The addition of IL-10 directly to the cells enhanced the growth of the lung fibroblasts (p<.005). The pre-incubation of blocking antibody against IL-10 and HBECM decreased this effect significantly (p<0.01). The concentration of IL-10 was extremely high in all preparations of HBECM used, with a mean value of 3250 +/- 250 pg/ml. Conclusions: We show for the first time that cytokine IL-10: i) is produced in high concentrations by bronchial epithelial cells, ii) enhances lung fibroblast growth, and iii) lung fibroblasts grown in HBECM with anti-IL10 demonstrated decreased proliferation. Thus, IL-10 may be an important factor derived from bronchial epithelial cells in the stimulation of lung fibroblast growth and these results have implications for the pathogenesis of OB.