Inhibitory effects of dexamethasone on proliferation of fibroblasts derived by idiopathic orbital inflammatory pseudotumor

Background

Idiopathic orbital inflammatory pseudotumor (IOIP) is a common orbital disease, but its etiology is still unclear, so the effect of glucocorticoid treatment is unsatisfied.

Objective

This study was to investigate the effects of dexamethasone on orbital fibroblasts from IOIP patients and explore the action machanism.

Methods

Six pieces of IOIP tissues from 6 IOIP patients and 3 pieces of normal orbital connective tissues from lacrimal gland prolapse patients were obtained during the surgery in Beijing Tongren Hospital from November 2011 to January 2012.The orbital fibroblasts were cultured using explant culture method.The morphology of the cells were observed under the optical microscope, and biomarks of the cells were detected by immunochemistry.The growth and proliferation of the cells were assayed using WST-8.The expression of ICAM-1 in the cells in both the control group and the IOIP group was detected by immunochemistry.The fibroblasts were incubated in 96-well plates, and different concentrations of dexamethasone (0, 1×10^-3, 1×10^-4, 1×10^-5 and 1×10^-6 mol/L) were respectively added into the medium for 24, 48 and 72 hours, and then the proliferation of the cells was detected by WST-8 assay.The contents of ICAM-1 in different concentrations of dexamethasone groups were assayed by ELISA.

Results

The characteristics of the cells were similar between the control group and the IOIP group with the spindle shape and long protructions.The cells showed the positive response for vimentin and absent response for desmin, S-100, cytokeratin (CK). Compared with the control group, the growth speed of fibroblasts was fast in the IOIP group.The proliferative values of the cells (absorbancy) were gradually reduced with the increase of dexamethasone concentrations (F_{concentration}=36.27, P=0.00) and the lapse of acting time (F_time=3.69, P=0.00). In cultured cells without dexamethasone for 24, 48 and 72 hours, the mean expression levels of ICAM-1 were 0.298±0.008, 0.312±0.003 and 0.319±0.011, showing a gradually increasing trend.However, the expression of ICAM-1 was gradually reduced with the increases of concentrations and the lapse of acting time of dexamethasone (F_{concentration}=75.17, P=0.00; F_time=3.11, P=0.00).

Conclusions

Occurrence and development of IOIP is probably associated with the over-expression of ICAM-1 in orbital fibroblasts.Dexamethasone plays anti-inflammation and treating effects on IOIP by down-regulating the expression of ICAM-1 and inhibiting the proliferation of orbital fibroblasts.

Orbital pseudotumor/drug therapy; Fibroblasts/drug effects; Glucocorticoids/pharmacology; Dexamethasone; Intercellular adhesion molecule-1; Down-regulation; Cell culture