Objective: To investigate the effects of interferon-gamma (IFN-gamma) on tubular epithelial-myofibroblast transdifferentiation (TEMT) induced by transforming growth factor (TGF-beta1).
Methods: The normal rat kidney tubular epithelial cells (NRK52E) were cultured and divided into blank (NRK52E cells only) control group, TGF-beta1 (3 ng/mL) treated group, IFN-gamma (1000 IU/mL) treated group, and IFN-gamma inhibition group (TGF-beta1 3 ng/mL + IFN-gamma 200, 400, 600, 1000, 2000, 3000 IU/mL). After 72 hours of treatment, the morphology of cells was observed under phase-contrast microscopy and scanning electron microscopy. The expressions of a-smooth muscle actin (alpha-SMA) and connective tissue growth factor (CTGF) were detected by immunocytochemistry. Flowcytometry was employed to measure the percentage of alpha-SMA+ cells and the mean channel fluorescence (MCF). The expressions of alpha-SMA mRNA and CTGF mRNA were examined by reverse transcription-polymerase chain reaction analyses (RT-PCR). The level of collagen in the culture supernatant was measured by Enzyme-linked immunoadsordent assay (ELISA).
Results: NRK52E cells cultured in the control group showed a classic cobblestone morphology. TGF-beta1 induced NRK52E cells to transdifferentiate into myofibroblast-like cells, which showed strong alpha-SMA immunostaining. The TGF-beta1 treated cells had higher percentage of a-SMA+ cells, MCF and alpha-SMA mRNA, increased CTGF mRNA expression, and ascended collagen III than the blank controls (P<0.05). IFN-gamma treated alone did not make any changes to the cell morphology, the expressions of alpha-SMA mRNA and CTGF mRNA and the level of collagen III (P>0.05). IFN-gamma exerted a strong inhibitory effect on the TEMT induced by TGF-beta1. With the increase of IFN-gamma, the percentage of alpha-SMA+ cells, the level of collagen III, and the expressions of alpha-SMA mRNA and CTGF mRNA decreased (P<0.05).
Conclusion: IFN-gamma inhibits the TEMT induced by TGF-beta1 and reduces the level of collagen III.