EXPRESSION OF GM-CSF RECEPTOR AND IN-VITRO EFFECTS OF GM-CSF ON HUMANFIBROBLASTS

In the present study the effects of Granulocyte-Macrophage Colony Stim ulating Factor ( GMCSF) on fibroblast growth and activity have been st udied. In this regard the AA have evaluated in primary cultures of hum an gengival normal fibroblasts (PG1 cells): a)-the expression of GM-CS F receptor (GM-CSFR) (alfa unit) on the cell surface; b)the in vitro e ffects of different doses of GM-CSF on the GM-CSFR expression and on t he proliferation and activity of fibroblasts. PG1 cells have been stim ulated in vitro with different concentrations of GM-CSF (10, 50, 80,10 0 and 150 ng/ml) using promonocytic cell line U937 as positive control for GM-CSFR expression. GM-CSFR was investigated by now cytometry, wi th mouse monoclonal antibody (mAb) against the alfa chain of the human GM-CSFR and fluorescein-conjugated goat antimouse immunoglobulin G (I gG). At high GM-CSF concentration (80 ng/ml) the AA observed: 1)-A mar ked increase of GM-CSFR expression evaluated as fluorescence intensity (about three fold in respect to the controls); 2)-Maximal increase of PG1 cells proliferation. Moreover immunofluorescence on fibroblasts o btained from culture plates showed increased actin stress fibers and f ibronectin production with low stimulation by GM-CSF, while higher con centration of this cytokine determined increased proliferation of cell s, but a decreased formation of actine fibers and vinculin plaques. Th ese results demonstrate: 1)-The presence of GM-CSFR on the surface of fibroblasts; 2)-The proliferation and the synthesis activity of these cells tin vitro) are modulated by different concentration of GM-CSF. W e hypothesize that GM-CSF until 80 ng/ml can upregulate the expression of the receptor. Therefore, on the basis of previous findings of high serum levels of GM-CSF in course of scleroderma, a disease characteri zed by fibroblast hyperactivity, a possible role of this cytokine in t he pathogenic process of this disease can be hypotesized.