HEMATOPOIETIC COLONY STIMULATORY FACTOR FORMATION BY MURINE MESANGIALCELLS - GENE-EXPRESSION AND BIOLOGICAL-ACTIVITY

This study examined the ability of mesangial cells to synthesize colon y-stimulating factors (CSF), cytoregulatory peptides associated with t he differentiation and proliferation of hematopoietic cells. Condition ed media obtained from SV-40 transformed murine mesangial cells stimul ated the growth of murine bone marrow progenitor cells of the myeloid series. Differential analysis of these cells showed the presence of bo th macrophages and granulocytes. Cellular identification of bone marro w colonies stimulated in response to mesangial cell conditioned media was examined by flow cytometric analysis and revealed the presence of F4/80 antigen positive macrophages (67%) and Gran-1 antigen positive g ranulocytes (21%). Neutralizing antibodies to macrophage colony-stimul ating factor (M-CSF) and granulocyte-macrophage colony-stimulating fac tor (GM-CSF) but not antibody to interleukin-3 (IL-3), or stem cell fa ctor (SCF) significantly inhibited the growth of the progenitor cells induced by mesangial cell conditioned media. Utilizing Northern blot a nalysis, murine mesangial cells expressed mRNA transcripts for M-CSF, GM-CSF, and granulocyte colony-stimulating factor (G-CSF). Further stu dies were performed to determine optimal incubation conditions for mes angial cell CSF gene expression. These studies revealed that both GM-C SF and G-CSF mRNA were maximally expressed at early time points (4 and 8 h of incubation), while M-CSF mRNA expression remained unchanged du ring the incubation of mesangial cells from 4-48 h. Incubation of mesa ngial cells with various concentrations of fetal bovine serum (FBS, 0. 5-15%) markedly increased the mRNA expression of M-CSF, GM-CSF and G-C SF in a dose-dependent manner. These studies indicated that transforme d murine mesangial cells are able to synthesize and secrete biological ly active CSF that are associated with the migration and proliferation of circulating mononuclear cells in the glomerulus. Furthermore, obse rvations regarding the role of duration of incubation and the media co ncentration of FBS on mesangial cell CSF mRNA expression may provide u seful data to understand the optimal conditions for studies that exami ne the gene expression of basal or inducible CSF in mesangial cells.