| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2005: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
To date, no modality has been approved for antifibrotic therapy of liver cirrhosis in humans, mainly due to insufficient specificity for particular target molecules or target cells. In the present study, we first confirmed substantial suppression of collagen secretion from normal rat kidney (NRK) fibroblasts by small interfering RNA (siRNA) for a 46-kDa collagen-binding glycoprotein-(gp46)(heat shock protein 47 of rat), a collagen-specific chaperon. Since hepatic stellate cells (HSC), which play a key role in fibrogenesis, are known to take up vitamin A (VA) through retinol-binding protein receptors (RBPRs), we then treated primary rat HSCs and a human HSC cell line (LI90) with carboxy-fluorescein (FAM)-labeled siRNA gp46 encapsulated in VA-coupled liposomes (VA-lip-siRNAgp46) in the presence of various concentrations of FBS, and affirmed that the fluorescence of these cells was appreciably suppressed by anti-RBP antibodies. Specific delivery of FAM-labeled VA-lip-siRNAgp46 to HSCs was also verified following i.v. injection in rats with liver cirrhosis induced by dimethylnitrosamine (DMN), since the fluorescence was mainly observed in HSC areas of the cirrhotic liver but scarcely in the liver parenchyma, lung, spleen or retina. When ^3H-VA-lip-siRNAgp46 was administered, radioactivity was seen mainly in the liver of DMN-treated rats, while in the normal rats, radioactivity in the liver was not prominent. Treatment of DMN rats with VA-lip-siRNAgp46 (i.v.) resulted in nearly complete histological resolution of liver cirrhosis, due to apoptosis of HSCs, and a 100% survival rate; in contrast, no untreated rats survived. This novel approach may be applicable not only to the therapy of liver cirrhosis, but also for treating fibrotic conditions in other organs, such as nephrosclerosis and chronic pancreatitis, in which stellate cells reportedly play an essential role.
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