Application of antisense oligodeoxynucleotides (ODNs) for the intervention of kidney disease. Antisense ODNs for transforming growth factor-beta-suppressed glomerulosclerosis in experimental glomerulonephritis

Role of aldose reductase in TGF-beta1-induced fibronectin synthesis in human mesangial cells

Accumulation of glomerular extracellular matrix (ECM) may result in glomerulosclerosis. Several lines of evidence indicate a key role for transforming growth factor-beta1 (TGF-beta1) in glomerular ECM synthesis and degradation, such as fibronectin (FN). Aldose reductase (AR) was proven to be one of the TGF-beta1 responsive genes in cultured rat mesangial cells using the SSH-PCR method and there were positive correlation between the AR and TGF-beta1 in our previous studies. So we assumed that AR could regulate FN synthesis. In this study, we explored the role of AR in FN production and possible mechanism involved. The expression of AR, FN and c-Jun proteins were analyzed by Western blot and the activity of activator protein-1 (AP-1) was assessed by electrophoretic mobility shift assay (EMSA). Our results showed that AR could mediate the TGF-beta1-induced FN production, which may associate with AP-1 activation.

A novel model to study renal myofibroblast formation in vitro

BACKGROUND

In chronic renal disease, the decrease of excretory renal function closely correlates with the extent of interstitial fibrosis. A common feature of interstitial fibrosis is the occurrence of myofibroblasts, which are regarded as the predominant cells in matrix synthesis. We studied the transformation of renal fibroblasts into myofibroblasts in vitro as a model to elucidate the mechanisms underlying this process.

METHODS

Primary cultures of freshly isolated rat inner medullary fibroblasts were established as reported previously. mRNA expression of myofibroblast markers and interstitial collagens was examined by Northern blot and reverse transcriptase-polymerase chain reaction (RT-PCR). Phenotypic expression was investigated by immunolabeling. Endogenous transforming growth factor-beta (TGF-beta) production was inhibited by addition of a neutralizing antibody or by TGF-beta 1 antisense oligodeoxynucleotides (ODNs).

RESULTS

Initially and during the first 36 hours, primary culture cells expressed neither alpha-smooth muscle actin nor desmin mRNA. From day 2 of primary culture, we observed a strong increase in these mRNAs, as evaluated by RT-PCR, followed by the phenotypic expression of these myofibroblast markers. Collagen type I mRNA was first detectable from day 4 of primary culture and showed a strong increase in its expression level during the following days, with phenotypic expression predominantly in myofibroblasts. The transformation rate of fibroblasts to myofibroblasts largely decreased in cocultures with collecting duct cells. This effect could be reversed by reducing the seeding density. We examined in this system the effect of TGF-beta 1 to define further its putative fibrogenic activity. However, neither the addition of exogenous TGF-beta 1 nor the inhibition of endogenous TGF-beta production showed any significant effect on fibroblast transformation, suggesting that this cytokine exerts its effects at other levels or requires a cofactor.

CONCLUSIONS

We present a novel model to examine the de novo expression of myofibroblast markers and collagen type I in freshly isolated fibroblasts under defined conditions in primary culture. This model could provide a strategy for the molecular characterization of myofibroblast formation and the phenomena associated with this process.