Radiation-induced alteration of rat mesangial cell transforming growth factor-beta and expression of the genes associated with the extracellular matrix.

We hypothesized that the altered mesangial cell phenotype observed in radiation nephropathy reflects, at least partly, radiation-induced changes in expression of the genes associated with transforming growth factor-beta (TGF-beta) and extracellular matrix (ECM). To test this hypothesis, rat mesangial cells were used between passages 7 and 11 after primary isolation from glomeruli. Cells were placed in serum-free medium 24 h prior to irradiation and irradiated with single doses of 5-20 Gy 137Cs gamma rays; control cells received sham irradiation. After irradiation, the cells were maintained in serum-free medium for up to 48 h postirradiation. Total RNA was isolated, and Northern analysis was performed using cDNA probes for TGF-beta 1, beta 2 and beta 3 and several ECM genes. Irradiation resulted in isoform-specific alterations in TGF-beta mRNA; TGF-beta 1 levels showed a dose-independent increase 24-48 h postirradiation; TGF-beta 3 mRNA levels showed a progressive dose-independent decrease over the same period, decreasing to levels approximately 25% of those seen in controls. These changes were associated with a concomitant increase in levels of mRNA expressed by genes for the components of the ECM; no changes were observed in TGF-beta 2, collagen I, collagen III or decorin. Thus radiation can alter mesangial cell TGF-beta and the expression of the genes involved in ECM, although the nature of this alteration varies for the TGF-beta isoforms and specific ECM genes.